This Google knol discusses each of the three major nuclear-reactor accidents, ending up with comparisons of each.
There is no clinical proof that any member of the public has died solely as a result of the Chernobyl or Three-Mile Island accidents. The same can be said of the nuclear-reactor accidents in Japan, so far.
Human beings have done some remarkable things to overcome nature’s adversities and shortcomings. One can’t help but be impressed by a century of human achievements in application of nuclear radioactivity and fission; no other complex technology that has been so successful and reliable. In contrast, hydroelectric dams have breached, mines have caved in, air pollution has increased, bridges have collapsed, world and regional wars have been fought, infectious pandemics have spread, humans have starved, and other calamities have occurred. Yet, nuclear accidents have resulted in comparatively few fatalities.
This knol examines relevant factors of each of the three nuclear-power station accidents.
One must also keep in mind that Japan rebounded from the devastation it suffered as a result of World War II, including the atomic bombings of Hiroshima and Nagasaki.
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The nuclear accident at Chernobyl Reactor #4 took place on 26 April 1986, now 25 years ago.
The accident was directly a result of operational tests that were poorly planned, supervised, and carried out.
When emergency reactor shutdown was attempted as a result of a sudden, unexpected power-output surge, a more extreme spike in power output followed, leading to reactor-vessel rupture and a series of explosions. This event exposed graphite moderator components of the reactor to air, causing them to ignite. The resulting fire sent a plume of radioactive fallout into the atmosphere and over an extensive geographical area, including the neighboring town of Pripyat.
Staff at the plant had been running tests to find out how well they could cope with a temporary shutdown of the reactor’s cooling system. The test went wrong and there was a power surge. The operators tried to shut the reactor down, but instead the nuclear reaction accelerated rapidly.
The extreme heat from the nuclear reaction triggered an explosion which blew the roof off both the reactor vessel and the building surrounding it – exposing the reactor core to the outside world – and sending radioactive material hurtling into the atmosphere.
Fires then started. While most were put out within hours, the fire in the damaged reactor burned for many days, spreading even more radioactive material.
Classified as a Level 7 event on an international scale, Ukraine and Belarus were burdened for the most part with the continuing and substantial decontamination and health care costs.
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Early estimates of the total number of deaths attributable to the accident varied enormously, from close to a million on down to tens or hundreds of thousands.
The actual number of provable fatalities is about 50. When the reactor self-destructed, 31 people were killed – 28 of them from radiation exposure and 3 of them scalded to death by escaping steam.
In addition, 134 people gradually received high radiation doses. While several dozen of these have subsequently died, it was mostly of causes unrelated to the radiation exposure.
Even though the much-larger publicized numbers of extrapolated general-population deaths have long been scientifically discredited, some nuclear-power opponents continue to use their media platforms and contacts to perpetrate fraudulent information about the accident.
The 50 or so direct Chernobyl fatalities were limited to the reactor staff and emergency workers.
It is possible that up to 15 children in the general population might have prematurely died from radiation-induced thyroid cancer, but that’s difficult to validate because of the substantially larger rate of juvenile fatalities resulting from chronic poor health care in the former Soviet Union.
There’s no post-mortem data to prove that any member of the public died of Chernobyl radiation-induced fallout. An international study, 20 years after the accident, estimated through statistical-based calculations that the number of delayed fatalities could be somewhere between 0 and 4000.
Those, as well as all other public-death fatality forecasts have been derived from questionable calculations, not based corroborative medical examinations. The confirmed public death toll – 25 years after the Chernobyl nuclear accident – remains near zero.
While some people may die prematurely in years to come, it is becoming clear that original assessments were wildly pessimistic. Moreover, there have been none of prematurely predicted and feared gruesome birth defects, terrible radiation burns, or public radiation sickness.
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No other reactors of the Chernobyl type have since been built. Their design had been based on Cold War USSR plutonium-production requirements, not civilian-power standards.
The reactor had no external containment building, a safety feature now mandatory for civil power reactors worldwide. If reinforced-concrete containment had surrounded the reactor, the amount of personal and property damage and risk would have been greatly reduced.
The four RBMK 1000 MWe reactors at the site produced about 10% of Ukraine’s electricity at the time of the accident. The destroyed #4 Reactor had been in operation for only three years.
Reactor #1 at the Chernobyl Nuclear Station suffered a previously undisclosed partial core meltdown in 1982, but it was repaired and put back in operation reportedly within months. One reactor lasted 22 years; a fifth nearly-complete reactor was abandoned incomplete.
The Nuclear Station utilized one large, open turbine hall for all four reactors, two turbines per reactor. In 1991 a fire broke out in one of the turbines, causing repairable damage to the turbine and the reactor hall.
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Chernobyl Reactor #4 remains “mothballed” in a sarcophagus-type containment that must be permanently monitored.
The other three reactors at the Chernobyl site continued to be operated and produced power until 1999.
The most nonsensical, expensive and harmful action, however, was the evacuation of over 300,000 people from contaminated regions of the former Soviet Union, where the radiation dose from Chernobyl fallout was about twice the natural dose. The evacuation caused great harm to the populations of Belarus, Russia, and Ukraine. It led to mass psychosomatic disturbances, great economic loss, and traumatic social consequences.
It was a serious sociological and economic mistake to permanently evacuate much of the surrounding population. The massive and permanent evacuation can be attributed to a public and bureaucratic overaction to radiation hysteria.
After dissolution of the USSR, Russia has rebounded and prospers. Even though the Ukraine, where the Chernobyl reactors are located, does not have the natural resources that Russia has discovered and extracted, the new nation is progressing.
Chernobyl is the only event ever to be given the maximum rating of 7 on the International Nuclear and Radiological Event Scale, which measures the severity of nuclear accidents. This means it released a major amount of radioactive material that covered a wide area.
Summarizing the impact of the Chernobyl accident:
• About 50 emergency workers died from site-related injuries and acute radiation.
• No physical public-health impact is explicitly attributable to radiation exposure.
• No unambiguous evidence has surface for increased cancer incidence, although an international study in 2006 had estimated that as many as 4000 adults (out of 600,000 persons) exposed to radiation fallout might die prematurely because of Chernobyl radiation-induced cancer.
• No excess radiation-induced leukemia has been detected.
• No birth defects are attributable to radiation exposure.
• Up to a dozen thyroid-cancer juvenile fatalities were diagnosed, not necessarily caused by Chernobyl radiation.
• No genetic damage to humans has been detected .
As everywhere else, better medical attention, diagnosis, and treatment have resulted in significantly improved detection of latent thyroid cancers at early (and often treatable) stages. In the Soviet Union, especially in rural areas prior to the Chernobyl accident, preventative, diagnostic, and curative treatments for abnormal thyroid conditions were not as common as in the West. After the accident, considerable diagnostic and medical treatment (and media attention) was focused on possible occurrence of thyroid cancer in children. Iodine deficiency was common for children during the Soviet era.
No other fatalities from the otherwise-disastrous reactor explosion were confirmed, and none were linked by medical diagnosis or post-mortem examination to radiation exposure. Partly because of net improvements in post-accident remedial action and health care, actual premature fatalities could turn out to be much less than the 4000 estimated upper limit — in fact, even down to zero.
For more information, especially about health effects from the Chernobyl accident, see my Google knol, Chernobyl Nuclear Accident Minimal Radiation Effects: Update 2010 Based on Recent Assessments:
Also, for more about radiophobia, see my Google knol: ETHICS IN SCIENCE: The Exaggeration of Radiation Hazards
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On March 11, 2011 the Province of Fukushima in Japan was the nearest land site to a 9.0-magnitude earthquake. It triggered a powerful tsunami that swallowed urban areas and farmland across the northern part of the country. Much air and train traffic has shut down. Power outages and cell phone service cutoff hampered communication in affected areas.
The Fukushima Dai-Ichi nuclear-reactor facility (Fukushima I Nuclear Power Station) caught fire, prompting government shutdown of the facility as well as 11 other nuclear power plants, including nearby Fukushima II Nuclear Power Station (Fukushima Dai-Ni).
The earthquake ranks about the fifth strongest registered in the world and the strongest in Japan’s recorded history.
When the earthquake exceeded seismic-alarm limits, the reactors were automatically “scrammed” (control rods inserted to halt the nuclear chain reaction). Residents nearby were soon evacuated.
The evacuation zone was extended on 12 March to 20 km, affecting 170,000–200,000 people, and the government advised residents within a further 10 km to stay indoors. The release of fission products from the damaged reactor core, notably radioactive iodine, led Japanese officials to distribute prophylactic iodine to people living around both Fukushima I and Fukushima II but only one worker was confirmed to be ill.
This 2011 Tohoku earthquake and tsunami was centered off the northeast coast of Japan. On that day, Fukushima I Reactor units 1, 2, and 3 were operating, but units 4, 5, and 6 had already been shut down for periodic inspection. When the earthquake was detected, units 1, 2 and 3 underwent an automatic shutdown.
All reactors at Fukushima I are of the Boiling-Water type. Boiling-water reactors are installed within a steel pressure vessel through which water and steam lines penetrate; the reactor core is within the pressure vessel. The reactor and its pressure vessel are secure inside their primary containment, designed to act as a barrier to prevent the escape of radioactive fluids or gases. Surrounding the primary containment is a reactor building, not built to contain high pressures. Only those external reactor buildings were breached by excessive pressure or explosion of volatile gases.
Following is a summary of major nuclear-related events at each of the two Fukushima power stations.
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Fukushim Dai-Ichi (#1) nuclear-power station is located in the town of Okuma of Fukushima Prefecture, Japan, about 130 miles north of Tokyo. The facility consists of six boiling-water reactors (BWR) designed by General Electric driving electrical generators with a combined power of 4.7 gigawatts, making Fukushima I one of the largest nuclear power stations in the world.
Fukushima I was the first nuclear facility to be constructed and run entirely by the Tokyo Electric Power Company (TEPCO). The six reactors at the station range in power from 440 MWe to 1100 MWe.
The Fukushima I nuclear accident consisted of a series of equipment failures and releases of radiation at the Nuclear Power Plant, following the 2011 Tohoku earthquake and tsunami on 11 March 2011.
The plant comprises six separate boiling water reactors maintained by the Tokyo Electric Power Company (TEPCO). Reactors 4, 5, and 6 had been shut down prior to the earthquake for planned maintenance. The remaining reactors were shut down automatically after the earthquake, but the subsequent tsunami flooded the plant, knocking out emergency generators needed to run pumps which cool and control the reactors. The flooding and earthquake damage prevented assistance being brought from elsewhere.
Over the following days there was evidence of partial nuclear-fuel damage in reactors 1, 2, and 3; hydrogen explosions destroyed the upper structure of buildings housing reactors 1, 3, and 4; an explosion damaged Reactor 2’s containment; and multiple fires broke out at Reactor 4.
In addition, spent fuel rods stored in spent fuel pools of units 1-4 began to overheat as water levels in the pools dropped. Fears of radiation leaks led to a 20 km (12 mile) radius evacuation around the plant.
With the concurrent loss of electric power, the reactors needed an external power source to keep cooling going in order to dissipate decay heat. The backup diesel-powered generators kicked in; however, when the 40-foot tsunami exceeded the 30-foot sea wall, the generators drew in water, thereby becoming damaged and inoperable.
The working generators had only about eight hours of fuel on hand, and, they couldn’t be promptly re-supplied because of the earthquake and tsunami devastation.
Because of loss of reactor coolant, fuel-element fission-product decay heat rises quickly. In addition, hydrogen gas generated from reaction of air with zirconium clad builds up in the reactor vessels; from there it is vented to the containment buildings. The volatile gas usually ignites and explosions took place in the containment buildings – but the reactor vessels weren’t breached.
A hydrogen-driven explosion signifies that the zirconium-alloy tubes containing the uranium pellets reacted exothermically in contact with steam. The zirconium steals oxygen from the water vapor, thus releasing hydrogen gas and heat. Vented to the containment building, it ignited,
resulting in the loss of that structure.
Sea water was pumped into the reactors in order to cool them. This is an extraordinary measure that effectively abandons all hope of functional plant recovery.
Nuclear plant workers are decontaminated by the simple expedient of washing them down with soap and water.
There is essentially no potential for a Chernobyl-type explosion of any of the containment vessels.
A boiling water reactor is contained within a thick steel vessel (looking like an upside-down light bulb); it has reinforced-concrete building fully surrounding it.
Although considerable seismic precautions had been taken for the reactors, the tsunami breach of the sea wall exceeded design expectations. Failure of cooling pumps from tsunami damage was also not anticipated. Although the reactors were shut down, their cores still had residual heat, and their temperature continued to climb without external cooling.
After being shut down for one hour, the decay-heat power level typically drops by a factor of a hundred. After a day, it is down by about a factor of 1000, but it still needs cooling for at least another few days before being safe from fuel-element cladding failure.
At the time of the earthquake on 11 March, units 1, 2, and 3 were operating and units 4, 5, and 6 were out of service for scheduled maintenance and refueling. When the earthquake occurred, the three units in operation were shut down as a standard response to an earthquake, stopping on-site generation of electricity.
A few minutes later, incoming electrical supplies from the grid were also lost as a result of the earthquake. Initially on site diesel generators supplied power to the residual heat removal system, cooling the reactor cores as designed. The diesel generators failed shortly after the tsunami, and alternative power arrangements were insufficient to support the control systems for the normal or emergency cooling systems.
Had these systems continued to operate, the core temperature would have remained under control, with no damage to the reactors or its fuel. Even with some fuel damaged and reactor cladding partially melted, the reactors could have been brought under control. The first attempts to restore electrical connections to the grid to enable the cooling systems to be operated were reported on 17 March. This effort was impeded initially by the tsunami damage in the area of the plant and then by the damage caused by the explosions at the plant.
Merely pumping water into the reactor containment did not get water into the pressurized reactor vessel and pipework and into contact with the fuel. Fire trucks and water cannon could not achieve the required pressures. The operators tried to fill the reactor containment with water.
To put the requirement for cooling water in context, a decay heat output of 10 MW (typical of a power reactor a few days after shutdown) has the capacity to boil off over three hundred tonnes of water per day.
Cooling is needed to remove decay heat even when a plant has been shut down. Nuclear fuel requires 1–3 years of constant active cooling (by flowing water that transfers heat to a another surface).
Boiling water reactors have steam-turbine driven emergency core cooling systems that can be directly operated by steam produced after a reactor shutdown and can inject water directly into the reactor. Using these pumps, boiling water reactors can provide water without electrically driven pumps, but only while the reactor is at pressure. This results in less dependence on emergency generators but only operates so long as the reactor is safely producing steam, and some power is still needed to operate the valves and monitoring systems.
When a reactor is shut down, decay heat is usually removed from the fuel by circulating water over it. High pressure systems circulate water through the reactor pressure vessel and pipework. The heated water is cooled in water-water heat exchangers, the heat passing to sea water circulated through the secondary side of the heat exchangers. In this way the decay heat is pumped out to sea and disperses. The systems which do this are typically called residual heat removal, for normal removal of decay heat during a planned shutdown, or emergency core cooling systems for core cooling after an accident.
After the reactors shut down, electricity generation stopped. Normally the plant could use the external electrical supply to power cooling and control systems, but the earthquake had caused major damage to the power grid. Emergency diesel generators started but stopped abruptly, ending all AC power supply to the reactors.
The entire plant was protected by a sea wall, but the tsunami topped this sea wall, flooding the low lying generator building.
After failure of the diesel generators, emergency power for control systems was supplied by batteries that would last about eight hours. Batteries from other nuclear plants were sent to the site and mobile generators arrived within 13 hours, but work to connect portable generating equipment to power water pumps was still continuing on 12 March.
Generators would normally be connected through switching equipment in a basement area of the buildings, but this basement area had been flooded. After subsequent efforts to bring water to the plant, plans shifted to a strategy of building a new power line and re-starting the pumps.
In the Fukushima I reactors the primary radiation-containment consists concrete structures immediately surrounding the reactor pressure vessel.
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Fukushima Unit 1 is 40 years old. It is an earlier-design, low-power, boiling-water reactor rated to produce about 1200 MW of thermal energy (460 MWe).
12 March: While evidence of partial meltdown of the fuel rods in Unit 1 was growing, a hydrogen explosion destroyed the upper section of the building. The explosion injured four workers, but the reactor containment inside the building remained intact.
Hydrogen and steam had been vented from the reactor to reduce pressure within the containment vessel and within the confinement building. Operators of the plant had to use sea water for emergency cooling.
The Japan Atomic Energy Agency announced that it was rating the situation at Unit 1 as level 4 (accident with local consequences) on the International Nuclear and Radiological Event Scale.
The upper shell of the reactor building was blown away leaving in place its steel frame. The outer building was designed to provide ordinary weather protection for the areas inside, but not to withstand the high pressure of an explosion or to act as containment for the reactor.
Experts soon agreed the cause was a hydrogen explosion. Exposed zircaloy metal-clad fuel rods become very hot and, when they do, react with steam oxidizing the metal and inducing the release of hydrogen. Almost certainly hydrogen gas was formed inside the reactor vessel because of falling water levels, and this volatile gas then leaked into the containment building.
Safety devices should have removed the hydrogen when it is vented before explosive concentrations are reached, but these systems failed, or could not be operated due to the shortage of electrical power.
Officials indicated the reactor container had remained intact and there had been no large leaks of radioactive material, although an increase in radiation levels was confirmed following the explosion. Radiation dose rates remained at a comparatively low level.
Four workers were reported to have been physically injured by the explosion at the Unit 1 reactor, and that three injuries were reported in other incidents at the site.
12 March: The Japanese government ordered seawater to be injected into Unit 1 in an ultimate effort to cool the degraded reactor core. TEPCO then announced they planned to cool the reactor with seawater, adding boric acid to act as a neutron absorber to prevent a criticality accident.
The water was to take five to ten hours to refill the reactor core, after which it would be contaminated with corrosive salts (mainly NaCl) and suspended particles, meaning the reactor would have to be decommissioned anyway.
13 March: Injection of seawater into the reactor pressure vessel through the fire-extinguisher system commenced.
14 March: Injection of seawater was halted because all available water in the plant pools had run out (similarly, water feed to Unit 3 was halted). Water supply was later restored.
16 March: It was stated that 70% of the fuel rods were estimated to be damaged.
18 March: Work was proceeding to install a new electrical distribution panel adjacent to Unit 1 which was to supply power from a transmission-grid transformer at Unit 2. It was anticipated power would be restored to units 1 and 2 by 19 March.
21 March: Injection of sea water for cooling was continuing but the unit seemed to be in a stable condition. Repairs to restore control instrumentation were proceeding.
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Unit two had been operating prior to the earthquake and experienced the same loss-of-coolant consequences directly after the earthquake (diesel engine power supply failed after about an hour). Nevertheless, stable water levels were reported. Some power was achieved by mobile power units, while preparations were made to perform pressure venting.
14 March: Cooling functions at Reactor Unit 2 stopped, and cooling-water levels in the reactor were falling. This happened when diesel fuel for the emergency pumps ran out.
Workers succeeded in refilling half the reactor with water. However, at that time, the upper part of the fuel rods were still exposed, and technicians could not rule out the possibility that some fuel rods had melted. Workers demolished parts of the walls of Reactor Building 2 to allow the escape of hydrogen and hopefully prevent another explosion.
15 March: Damage to temporary cooling systems on Unit 2 by the explosion in Unit 3 plus problems with its venting system meant that water could not be added. Unit 2 was in the most severe condition of the three reactors. An explosion in the “pressure suppression room” caused some damage to Unit 2’s containment system.
The measured radiation rates at the gate of the plant had reached the annual limit for non-nuclear workers in twenty minutes, but had fallen back later. It was believed that the 4m-long fuel rods in the reactor were fully exposed for the second time.
15 March: The utility said that the hydrogen explosion at Unit 3 might have caused a glitch in the cooling system of Unit 2. Four out of five water pumps being used to cool Unit 2 Reactor had failed after the explosion at Unit 3. In addition, the last pump had briefly stopped working. To replenish the water, the contained pressure would have to be lowered first by opening a valve of the vessel. The unit’s air-flow gauge was accidentally turned off and, with the gauge turned off. Flow of water into the reactor was blocked, leading to full exposure of the rods.
15 March: Water was being pumped into the reactor of Unit 2 again; water level was reported to be at 1.20 meters and rising.
An explosion was heard in Unit 2, possibly damaging the pressure-suppression system, which is at the bottom part of the containment vessel. The radiation level was reported to exceed the legal limit and the plant’s operator started to evacuate all non-essential workers from the plant. Only a minimum crew of 50 was left at the site. Soon after, radiation equivalent dose rates had risen.
While admitting that the suppression pool at the bottom of the containment vessel had been damaged in the explosion, causing a drop of pressure there, Japanese nuclear authorities emphasized that the containment had not been breached as a result of the explosion and contained no obvious holes.
In a news conference, the director general of the IAEA said that there was a “possibility of core damage” at the No. 2 Unit of the damaged Fukushima power plant. The Japan Nuclear and Industrial Safety Agency stated 33% of the fuel rods were damaged.
17 March: Work was to continue through the night aimed at reconnecting mains power to the reactor from the transmission grid once water spraying of Unit 3 ceased.
19 March: Grid power had been connected to the existing transformer at Unit 2 but work continued to connect the transformer to the new distribution panel installed in a nearby building.
20 March: power became available at Unit 2.
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Unlike the other five reactor units, Reactor 3 runs on mixed uranium and plutonium oxide, or MOX fuel.
On 13 March, it was considered that Unit 3 had possible core damage. Both reactors 1 and 3 were vented and re-filled with water and boric acid to reduce temperatures and inhibit further nuclear reactions.
An official told a news conference that the emergency cooling system of Unit 3 had failed, spurring an urgent search for a means to supply cooling water to the reactor vessel in order to prevent a meltdown of its reactor core. There was no immediate means of adding coolant to the reactor due to loss of the power grid. Work to restore power and vent pressure continued. At one point, the top three meters of fuel rods were not covered by coolant.
Manual venting took place and operators began injecting water containing boric acid into the primary containment vessel via a fire-truck pump. When water levels continued to fall and pressure increased, the injected water was switched to sea water. However, despite adding water, the level in the reactor did not rise and radiation had increased. A water-level rise was eventually recorded, but the level apparently stuck 2m below the top of reactor core. Other readings suggested that this could not be the case and the gauge was malfunctioning.
Hydrogen was building up inside the outer building of Unit 3 just as had occurred in Unit 1, threatening the same kind of explosion.
14 March: The reactor building for Unit 3 exploded, injuring eleven people. There was no release of radioactive material beyond that already being vented but blast damage affected water supply to Unit 2. Injection of sea water into the vessel was discontinued until supplies could be restored.
An explosion occurred in the building surrounding Reactor 3 after ignition of built-up hydrogen gas. The top section of the reactor building was blown apart, but the inner containment vessel was not breached. The explosion was larger than that in Unit 1. Pressure readings within the reactor remained steady. Water injection continued. Eleven people were reported injured in the blast.
15 March: At one location near Reactor units 3 and 4, high radiation levels were detected. This might have been due to debris from the explosion in Unit 4.
16 March: White fumes were rising from the facility. Officials suggested that the Unite 3 reactor building was the most likely source, and said that its containment systems may have been breached. The control room for Reactors 3 and 4 was evacuated but staff were cleared to return and resume water injection into Reactor 3. Chinook helicopters were preparing to pour water on Unit 3. White fumes rising from the building were believed to be water boiling away from the fuel rod cooling pond on the top floor of the reactor building, and on Unit 4 where the cooling pool was also short of water. The mission was cancelled when helicopter measurements reported radiation comparatively high levels. The government reported that major damage to Reactor 3 was unlikely, but that it nonetheless remained their highest priority. Four helicopter drops of seawater took place. Police used a water cannon to spray water onto the top of the reactor building.
17 March: Helicopters dropped water on the spent-fuel pools of units 3 and 4. In the afternoon it was reported that the Unit 4 spent fuel pool was full with water, and none of the fuel rods was exposed.
18 March: A crew of firemen took over the task with six fire engines each spraying 6 tons of water in 40 minutes.
20 March: TEPCO announced that pressure in containment vessel for Reactor 3 was rising, and that it might be necessary to vent air containing radioactive particles to relieve pressure.
21 March: Grey smoke was reported to be rising from the southeast corner of Reactor 3, where the spent fuel pool is located.
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At the time of the earthquake, Unit 4 had been shut down for a scheduled periodic inspection since 30 November 2010. All 548 fuel rods had been transferred in December 2010 from the reactor to the spent-fuel pool on an upper floor of the reactor building where they were held in racks containing boron to damp down any nuclear reaction.
The pool is used to store rods for some time after removal from the reactor and contained 1,479 rods. Recently-active fuel rods produce more decay heat than older ones
14 March: Water in the spent-fuel pool had reached a temperature of 84 °C compared to a normal value of 40-50 °C.
A fire broke out at Unit 4 involving spent-fuel rods from the reactor, which are normally kept in the water-filled spent-fuel pool to prevent overheating. Radiation levels at the plant rose significantly but subsequently fell back. Radiation dose rates at one location in the vicinity of Unit 3 were slightly higher in one hour than the average natural dose for a year.
15 March: An explosion – thought to have been caused by hydrogen accumulating near the spent fuel pond – damaged the 4th floor rooftop area of the Unit 4 reactor as well as part of the adjacent Unit 3.
The Unit 4 spent-fuel pool caught fire, likely releasing radioactive contamination from the fuel stored there. Workers extinguished the fire.
Radiation rates measured from the Reactor Unit 4 reached 100 mSv per hour. There was no continued release of “high radiation”.
Japan’s nuclear safety agency reported two holes, each 8 meters square in a wall of the outer building of the number 4 reactor after an explosion.
Further, it was reported that water in the spent-fuel pool might be boiling. Radiation inside Unit 4 had increased so much inside the control room that employees could not stay there any longer. Seventy staff remained on site, but 800 had been evacuated.
TEPCO was reported to be unable to pour water into No. 4 reactor’s spent-fuel storage pool. It was reported that TEPCO was considering using helicopters to drop water on the storage pool, but delayed using the option because of concerns over safety and effectiveness. The use of high-pressure fire hoses was considered instead.
16 March: TEPCO announced its belief that the fuel-rod storage pool of Unit 4 – located outside the containment area – may have begun boiling, raising the possibility that exposed rods could reach criticality.
TEPCO released a photograph of No.4 Reactor showing that “a large portion of the building’s outer wall has collapsed.” Technicians reportedly considered spraying boric acid on the building from a helicopter.
Water sprayed into the pool of Unit No. 4 was disappearing faster than evaporation could explain, leading to the suspicion water was leaking from that pool.
TEPCO announced its belief that the storage pool may have begun boiling, raising the possibility that the exposed rods would breach. However, helicopter observation indicated that the pool had not boiled off.
The spent-fuel pool in Unit 4 contained a large number of fuel assemblies. Unit 4 had been shut down a month before, and all fuel assemblies were transferred to the pool. Also, it contained assemblies discharged from the reactor last year.
Hydrogen explosions uncovered spent-fuel pools in Unit 3 and 4. Inability to pump water caused the water temperature in these pools to rise, and start boiling, which reduced the amount of water and speeded up oxidation of zircaloy cladding. It was the degradation of cladding that caused release of fission gases (Kr and Xe) as well as radioactive Cs, I, and Tl. These two pools were causes of high dose rates near the units, and further slowed down the cooling process.
It took them more than seven days to bring external power lines to the site, but destruction of external electric outlets further slowed down reconnection to the grid.
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Both Units 5 and 6 were off line at the time the earthquake struck (reactor 5 had been shut down on 3 January 2011 and Reactor 6 on 14 August 2010). Both were still fueled, unlike Reactor 4 where the fuel rods had been removed prior to the earthquake.
Reactors 5 and 6 were being closely monitored, as cooling processes were not functioning well. The removal of roof panels from Reactor buildings 5 and 6 was being considered in order to allow hydrogen build-up to escape.
15 March: Water levels in Unit 5 Reactor were reported to be 2m above fuel rods, but were falling at a rate of 8cm per hour.
17 March: Unit 6 was reported to have operational diesel-generated power and this was to be used to power pumps in Unit 5 to supply more water. Preparations were made to inject water into the reactor pressure vessel once main power could be restored to the plant, but water levels in the reactors were said to be declining.
It was estimated that grid power might be restored on 20 March through cables laid from a new temporary supply being constructed at units 1 and 2.
Storage pool temperatures at both Units 5 and 6 remained steady around 60–68 °C, rising slowly.
18 March: Reactor water levels remained around 2m above the top of fuel rods. It was confirmed that panels had been removed from the roofs of Units 5 and 6 to allow any hydrogen gas to escape.
19 March: The second unit of emergency generator A for Unit 6 was restarted and was being used to operate the residual heat-removal system in Unit 5 to cool the spent fuel storage pool.
Temperature at Unit 5 decreased to 48 °C.
20 March: Restored emergency power to the spent-fuel pond cooling systems for Units 5 and 6 brought the Unit 5 pond temperature down from 68.8 °C to 37 °C and the Unit 6 pond temperature down from 67.5 °C to 41 °C.
21 March: External power was partially restored.
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Fukushima Dai-Ni [#2] is located in the town of Naraha in Fukushima Prefecture. Like the Fukushima I, 7 miles to the north, it is run by the TEPCO.
After the March 11, 2011 earthquake and tsunami, all four units were automatically shut down, and diesel engines were started for cooling purposes.
The tsunami (23 feet in height) that followed the earthquake inundated the entire facility, which was designed to withstand a tsunami of 21 feet. This resulted in flooding of pump rooms that are used for heat transfer to the sea, the ultimate heat sink of the reactors.
All reactors in the Fukushima II Nuclear Plant are the more modern BWR-5 type with electric power of 1,100 MWe each. The reactors were supplied by Japanese companies.
12 March: Reactors shut down and reactor water level was stable; offsite power available; control rods fully inserted (reactors in subcritical status); main steam-isolation valves closed; water injected into the reactors by Make-up Water Condensate. An increase in reactor containment-vessel pressure was assumed to be due to leakage of reactor coolant; did not appear to be leakage of reactor coolant in the containment vessel. Temperature of the suppression chamber exceeded 100 degree and the reactor pressure-suppression function was unexpectedly lost; implementing measures were taken to reduce the pressure of the reactor containment vessel (by a partial discharge of air containing radioactive materials) in order to fully secure safety.
The loss of cooling water at the four reactors was classified a level 3 on the International Nuclear Event Scale (serious incident).
The plant operating company, TEPCO, announced that a worker operating in a crane on the exhaust stack had died.
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Onagawa is a nuclear power plant in the Miyagi Prefecture, Japan. It is managed by the Tohoku Electric Power Company. It was the most quickly constructed nuclear power plant in the world. All the reactors were constructed by Toshiba.
The site is also on the northeast side of Japan, along the coast, about 40 miles north of Sendai. While the community of Onagawa, suffered heavily in the earthquake, the nearby nuclear power plant rode out the earthquake and smaller tsunami.
There are three BWR reactors on the site, respectively 524 MWe starting in 1984, 825 MWe in 1995, and 825 MWe in 2002.
March 11: Tohoku earthquake damaged the turbines in Unit 3, and it was shut down after a fire broke out.
March 20: Eight reactors that furnish 9 GWe at Fukushima Dai-Ni, Onagawa, and Tokai remain in cold shutdown.
March 22: Spent-fuel pond of Unit 2 Fukushima Dai-Ichi being injected with seawater; Units 3 and 4 reactors being water-sprayed.
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The biggest threat that this incident has posed was the loss of 9 GWe electricity at a time when, in the aftermath of the highly destructive earthquake and tsunami, Japan was suffering from wintry weather, and electricity was needed to pump and purify water, to pump out waste, etc. The loss of electrical generating capacity was the true danger, not the inconsequential radiation leakage.
There were no public injuries or fatalities due to the nuclear reactors or due to radiation; there was no melt-through of any reactor cores. While some produce has been contaminated with low levels of radiation, it would not have been harmful if ingested in normal quantities.
Contrary to press reports stoked by alarmists, the mixed plutonium-uranium oxide (MOX) fuel at one of the Fukushima reactors added no additional risk to workers, the plant, or the public. Although a constuent in the fuel and in spent-fuel rods, there has been no official indication that plutonium has been detected outside the reactors. Officials at the International Atomic Energy Agency say the presence of MOX fuel does not add significantly to the dangers. In any event, uranium-fueled reactors produce plutonium as a byproduct during operation; so all spent-fuel rods contained a correspondingly small amount of plutonium.
Control rods correctly shut down the operating nuclear reactors when the earthquake occurred, but the fuel elements in all reactors still needed cooling. No internal or external electricity was available to run the cooling-system pumps, so water boiled away faster than the emergency backup could supply. When fuel elements became overheated, radioactive and hydrogen gases were released, the latter probably leading to an explosive buildup. It’s unknown if uranium fuel itself melted (which would be unlikely because the oxide has a high melt temperature). However, the loss of fuel-element cladding would allow fuel pellets to block cooling channels and even drop to the bottom of the reactor vessel, adding a small a risk of burning through the bottom of the pressure vessel.
When nuclear plants lose grid power, emergency on-site generators are supposed to furnish backup power. But some diesel generators at the Fukushima Daiichi plant failed a short time later due to damage from the tsunami that followed the earthquake. That forced the plant to resort to batteries to temporarily provide electricity to critical instrumentation and controls at the reactors.
The Tohoku earthquake and tsunami in Japan are anticipated to have caused tens-of-thousands of fatalities, huge personal losses, and infrastructure damage amounting to hundreds-of-billions of dollars for the population at large. The loss of the reactors, to whatever extent it remains, appears to be primarily monetary, perhaps some ten billion dollars.
Damage to the nuclear facilities highlighted a planning failure regarding the design-based assumptions for the magnitude of possible earthquakes and subsequent height of tsunami wave, especially in seismic-prone Japan.
Many reactor-specific improvements in the sturdiness of the plants are now more evident: for example, improved backup systems for emergency reactor core and spent-fuel pond cooling; portable generators compatible with electrical connections at the reactors; controlled and filtered venting after hydrogen buildup.
Better education for the public and emergency workers is needed to help allay unfounded long-term fears of low radiation levels. No amount of education, however, can replace resolute government action, which – of necessity – must be conservative and responsive in accordance with psychological circumstances at the time of stress, emergency, and uncertainty.
Radioactive isotopes of iodine and cesium released from the reactors have been detected as far away as Tokyo. These radioisotopes can have effects on health, but only if a substantial quantity were inhaled or ingested. Potassium-iodide pills could have be made available sooner, but in this case would have had no physically helpful effect.
The radioisotope cesium-137 behaves chemically like potassium and is absorbed by cells throughout the human body. Ingestion or inhalation allows the radioactive material to be distributed in the soft tissues, especially muscle, exposing these tissues to beta particles and gamma radiation and slightly increasing cancer risk. Strontium-90, another fission product, behaves like calcium, and tends to deposit in bone and blood-forming tissue (bone marrow).
However, it is unlikely that hazardous doses of any fission-product radiation reached the public.
As mentioned, psychological circumstances under stressful conditions are a challenge for governments and corporate spokespeople. Prudence dictates conservative responses until the full scope of danger can be assessed and improved.
It is relevant to mention that a little more than a week after the Tohoku earthquake, 52 miners were killed in Pakistan in a single coal-mine explosion. Coal is the main source of fuel for electricity and industrial processes in Japan.
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Almost reflexively after the news came out about the reactor problems, some alarmists were suggesting that the Fukushima could turn into a Chernobyl. The thing is, even Chernobyl did not do what is often blamed on Chernobyl. Although Chernobyl was, by far, the worst nuclear accident in history (a Category 7), it is astonishing how uncatastrophic it was, even as mega-disasters go.
In the days after the Tohoku megaquake rocked Japan and left many thousands dead, knowledgeable nuclear experts repeatedly stated that the Japanese situation could not get as bad as Chernobyl.
Following the magnitude-9 earthquake off the coast of Japan, the reactors at Fukushima Daiichi automatically shut down – as they were meant to. However cooling systems of the reactors and the spent-fuel ponds failed, causing the some reactor cores and spent fuel to overheat.
This led indirectly to explosions damaging both the outer buildings and parts of the containment systems intended to prevent radioactive material from escaping. Because of these breaches, some radioactive aerosols went into the atmosphere, and some was deposited on the ground at various distances.
What are some differences between Chernobyl and the Fukushima Daiichi accidents? First of all, the Chernobyl reactor was actually in operation – albeit at low power – at the time of its accident. By contrast the Fukushima reactors automatically shut down as soon as they felt the earthquake, inserting control rods such that the nuclear reactions in their cores began slowing within seconds. This means that, from the outset, the amount of heat being produced in the Japanese reactors was much less than at Chernobyl.
So why couldn’t a runaway reaction happen at Fukushima Daiichi? The Chernobyl reactor had a fundamentally different design to those at Fukushima Daiichi. Chernobyl ran on unenriched uranium, a fairly weak nuclear fuel. In order to use it, the reactor was designed in a way that made it easier for the nuclear reaction to internally accelerate. This allowed it to generate useful amounts of power, but it also left it vulnerable to running out of control.
Fukushima Daiichi reactors run mostly on slightly enriched uranium, a more powerful nuclear fuel than Chernobyl had. Thus, in contrast to the Ukrainian reactor, Fukushima design minimizes the nuclear reaction unless boosted by its operators.
Ordinarily the Fukushima reactor cores are surrounded by water. Heat from the nuclear reaction boils the water, creating steam that drives turbines which generate electricity. In doing so, the water also helps to cool the reactor. But importantly, the water is also a “moderator”: It helps keep the uranium fission reaction going by slowing down neutrons produced by the reaction as they escape from the fuel rods. Such “slow” neutrons sustain the reaction, liberating still more neutrons and heat from uranium atoms in the rods. If the water heats up too much, however, bubbles form within it, which allows neutrons to escape, automatically slowing down the nuclear reaction.
If the coolant overheats, it effectively starts shutting down the reaction without any human intervention. Nuclear engineers call this a “negative void coefficient,” because having voids in the coolant slows down the reaction. By contrast, Chernobyl had a positive void coefficient; so the reaction was more likely to accelerate.
Could Fukushima Daiichi catch fire like Chernobyl did? There have been some small fires on the site in Japan, all of which were put out rapidly. They apparently involved the diesel engines pumping water into the reactors. All fires were outside the pressure vessel that contains the core of radioactive fuel rods.
At Chernobyl, the reactor pressure vessel was breached, and the reactor had no external containment. In that case, the core itself burned fiercely, largely because it was made of graphite – which was used as the moderator. This did not make the accident more likely, but once the reactor exploded, the graphite made the situation worse because it burned so readily. The fires lofted radioactive material from the reactor core high into the atmosphere, where it spread far and wide. This could not happen at Fukushima Daiichi, as it does not use graphite as the moderator.
What was the worst-case scenario for Fukushima Daiichi? The reactors themselves now seem to be largely under control and are cooling rapidly. The control rods, which absorb neutrons and dampen down the nuclear reactions, had been immediately inserted, and the reactors have been saturated with seawater laced with boric acid – another neutron absorber. Because of the negative void coefficients, the nuclear reactions cannot now restart unless those actions are reversed.
There have been some leaks of radioactive material and might be more for a while, partly because secondary containment systems had been breached, and partly because radioactive steam had to be regularly vented to allow more water in. The fuel rods are likely to have been damaged, releasing fission gases into the reactor vessel and allowing fuel pellets to aggregate downward.
An inadequately engineered threat did occur at the spent-fuel ponds, where the water level fell and temperatures rose. That loss of coolant might have lead to fuel rods breaking open, releasing their radioactive contents inside the basin. That too could have contributed to some atmospheric release of fission gases.
Unlike the reactor cores, the spent-fuel ponds contain no high-pressure steam that make it difficult to pump in cooling water. The ponds are a standard feature of nuclear facilities, and are typically designed to ensure that nuclear reactions cannot restart in the fuel rods: Among other things, the rods are widely spaced from each other.
It is important to note that newer, more modern nuclear reactors may not have failed after the Tohoko earthquake. Passive cooling systems and other advanced designs should be more resilient to natural disasters.
The advanced reactor designs could help avoid the overheating and explosions that have occurred at the Fukushima Daiichi nuclear plant following the powerful earthquake and tsunami. Newer designs propose passive cooling systems that would not fail after a power outage, as happened in Japan, as well as other novel approaches in managing reactor heat.
The high temperatures at Fukushima enabled a chemical reaction to occur between zirconium in the fuel rods and water, a reaction which produces zirconium oxide and hydrogen. As pressure builds, plant operators have to release overpressure steam and hydrogen into the secondary containment structure. At Daiichi, the buildup of hydrogen caused explosions in these structures.
The Fukushima reactors, built in the early 1970s, rely on active cooling systems that require electricity. Newer plant designs would lessen or eliminate the need for active cooling, making use of natural convection or a “gravity feed” system to cool reactors in the event of an emergency.
In one design – for example, the relatively new Westinghouse AP1000 – water is suspended over the reactor housing. If pressure within the system drops, this allows the water to submerge the reactor to keep it cool.
Some advanced reactor designs use molten metals to cool the reactor; the heat-capacity of such systems is enough to provide cooling in an emergency. Another alternative is the “pebble bed reactor,” designed to prevent fuel from getting hot enough for meltdown.
The ability of Japan to supplant fossil-fuel electrical generation is important for energy independence, price stability, pollution control, and its economy. It’s important remember that a major factor driving Japan into aggression prior to the second World War was a shortage of natural resources, particularly oil.
Another perspective to keep in mind is that in order to help bring about the end of World War II, atomic bombs were dropped on Hiroshima and Nagasaki. Japan thus suffered the most terrible of all disasters. Since then, in less than a half century, Japan’s economy rebounded and its nuclear aversion turned to adoption of nuclear technology and power.
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In 1979, The Three Mile Island Unit-2 reactor core was destroyed. No physical trauma to the population, surrounding and distant, was ever detected; no property damage occurred outside the TMI reactor vessel, which maintained its integrity. No adverse physical effects on humans, animals, or plants were ever found to be correlated with the accident.
The internal structure (core) of the reactor was severely damaged, resulting in a financial calamity for the owners, a cost increase to regional ratepayers, generation of pollution when the lost power was made up by burning more coal, and an elaborate cleanup effort for the operator and the government.
The reactor was permanently shut down and defueled. Considerable emotional trauma was experienced by the nearby population, aggravated by hysterical press coverage. Litigious reactions also ensued, stirred in part by anti-nuclear-power activists.
After the 1979 TMI nuclear-reactor meltdown in Pennsylvania, unwarranted fears and exaggeration of its effects resulted in injury expectations that never materialized. Contrary to persisting overstatement, no palpable deaths or injuries were suffered by plant workers or nearby residents.
In more than 30 years that have followed, no consistent evidence has emerged that any radioactivity released during the TMI accident had a significant impact on a normal mortality experience.
On the other hand, medical experts have presented reasoned arguments that certain psychoneurological syndromes – not directly correlated to dose (absorbed radiation) nor level of contamination – have nevertheless resulted in chronic fatigue, sleep disturbances, and impaired memory attributable to radiophobia. Despite outlandish claims by anti-nuclear power interventionists and uninformed academics, no deaths or injuries occurred to operators or to the public.
One of the two TMI reactors is still operating.
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For future policy decisions, it is important to note the differences and similarities between the Japanese nuclear plant destruction, when compared with the TMI and Chernobyl accidents. It does little good in decision-making to look at the accident in isolation.
Compared with other energy sources, the Chernobyl reactor eruption resulted in far fewer human casualties than other types of industrial disasters.
Radiophobia, exacerbated by and after the accident, vastly and unnecessarily increased subsequent economic losses in the former Soviet Union and elsewhere in Europe. Morever, in the aftermath of the Chernobyl tragedy, radiophobia was stoked at the time by misguided arms-control advocates who used public fear of low-level radiation in order to encourage opposition to Cold War nuclear-weapons testing.
The former Cold War mix of military and peace-going nuclear issues has been modified by the passage of time and change of circumstances. With nuclear arms control and nonproliferation now progressing on their own pace, peaceful applications of nuclear technology can be judged on merit – free of the emotional military links once attributed to nuclear power, radioisotopes, spent-fuel storage, plutonium demilitarization, fuel recycle, and fast-reactors. While some “obdurates,” mostly academics, still try to link these together, they have found it increasingly difficult to stigmatize peaceful nuclear applications.
Chernobyl’s enormous political, economic, social, and psychological impact was mainly due to deeply rooted fear of radiation. Such radiophobia has been compounded by the still-unproven so-called linear non-threshold (LNT) assumption: to the effect that known effects from high, quantifiable doses could be linearly extrapolated to real effects at low, estimated doses.
That assumption remains – long past a half century – to be unproven and probably fallacious for the low dose levels encountered by the public in these three major reactor accidents.
What follows are a number of other relevant comparisons.
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Measured as early deaths per electricity unit produced by Chernobyl (9 years of operation, total electricity 36 GWe-years, 31 early deaths) provides an average rate of 0.86 death/GWe-year. This rate is lower than fatalities from a majority of other energy sources.
Normalized in terms of electricity units, the Chernobyl fatalities among operators and emergency workers were nearly 50 times lower than accidents caused by hydroelectric failures – breaches of dams (~40 deaths/GWe-year).
In terms of human losses (nearly 50 early deaths), the accident in the Chernobyl nuclear power plant was a minor event compared with other major industrial catastrophes.
In the 20th century more than ten such catastrophes occurred, with several hundreds to many thousands of fatalities in each. For example, coal smog killed approximately 12,000 people in London, UK, between December 1952 and February 1953. The annual death toll from accidents in Chinese coal mines reached 70,000 deaths in the 1950s.
In 1984 up to 20,000 people perished due to an eruption in a pesticide factory in Bhopal, India, and the collapse of a hydroelectric dam on the Banqiao river in China in 1975 caused 230,000 fatalities.
But the political, economic, social and psychological impact of Chernobyl was enormous.
Chernobyl reactors were inherently unsafe and the Soviet managers knew it. But it was cheaper and more expeditious to convert a bomb-factory reactor to a power reactor than to build a safe reactor for peaceful power generation. The British had pointed out this danger to the Soviets, who they thought they could handle the greater risk.. They failed, and nobody builds power reactors like that any more.
As mentioned, the Chernobyl reactor used graphite, rather than water as a neutron moderator; this resulted in a the graphite burn that released the volatile fission products. In contrast with TMI and the Japanese reactors; Chernobyl had no containment vessel surrounding the reactor core. Other differences include sturdier composition of BWR fuel and numerous designed safety measures. Although many safety features of the Japanese reactors failed under the extreme stress of the earthquake and tsunami, the engineered reactor defense-in-depth principle prevented excessive radiation exposure to the general population.
When a reactor starts to get out of control, its temperature rises. In a reactor using water, the rising temperature slows down the reaction (the negative temperature coefficient). If the water reaches the boiling point the nuclear reaction is completely turned off. The Chernoblyl used graphite as its moderator; Three-Mile Island and the Japanese reactors all use water.
In a reactor using graphite, raising the temperature speeds up the nuclear reaction (the positive temperature coefficient). When all the cooling water is boiled out the reaction gets speeded up even more until the Chernobyl graphite got so hot that it burned, sending clouds of radioactive smoke into the air, carried by winds for large distances.
The Japanese reactors still have serious problems. We will have to see whether the plant operators and managers have been successful like they were at Three-Mile Island, keeping harmful radioactive materials from getting outside the confines of the reactors. So far, very small, barely detectable, radiation has escaped. In any event, this situation is completely different from that of Chernobyl.
Although the replacement costs of the reactors is many billions of dollars, it overall cost compared with total disaster is comparatively small.
Future reactors in Japan and elsewhere will benefit from this experience, just as others have gained lessons from other reactor accidents. Higher seawalls, for example, will be one consideration. Elevation of backup pumps and other auxiliary systems will have to be implemented. Emergency equipment and supplies need to be better isolated. Many of these considerations had already been adopted for newer reactors.
Spent-fuel storage will need better fail-safe cooling methods. The role of water acting as coolant and shielding in spent-fuel ponds needs to be revisited.
Moreover, aged spent fuel should be moved to a national storage area, such as Yucca Mountain for the United States. Spent-fuel elements remain for up to seven years in cooling ponds; then they are stored in dry casks on site for now. By not having a secure destination for nuclear waste, spent-fuel is accumulating at reactor power plants.
Four nations – France, Japan, Russia, and the United Kingdom – have been reducing their nuclear-storage burden by reprocessing spent fuel, which significantly reduces the volume of waste to be stored and salvages the residual value of unspent fissile energy.
In Japan, there are many fewer nuclear-plant siting options, with so little available land, especially near sources of water for cooling. In fact, that’s one of the reasons why Japan chooses nuclear power, compared to coal plants that foul the environment. Moreover, Japan has been chronically short in oil and natural-gas resources.
In the meantime, new nuclear power plants of the proven PWR and BWR design are rated for a minimum functional lifetime of 60 years (50 years for the Russian-designed VVER-1200). Originally built and licensed for about half of that lifetime, their staying power has been remarkable. It is because of the approved extensions in lifetime that nuclear plants have generally been financially attractive, especially with the initial construction cost having been written off.
Generation IV reactors are a class of theoretical nuclear-reactor designs that had been researched.
Advanced reactor types that were to be evaluated included a very-high-temperature reactor, a supercritical-water-cooled reactor, a molten-salt-cooled reactor, and fast-spectrum reactors – sodium, lead, and gas-cooled.
Most of these Gen IV designs were generally not expected to be available for commercial construction before 2030, with the exception of a Very High Temperature Reactor version to be completed by 2021. Current reactors in operation around the world are generally considered second- or third-generation systems, with most of the first-generation systems having been retired some time ago. Research into new reactor types was officially started by an International Forum based on technology goals derived from operating experience. The primary objectives were to improve nuclear safety, amplify proliferation resistance, minimize waste and natural resource utilization, and decrease the cost to build and run such plants.
Gen IV advanced-reactor planning during the G.W. Bush administration became a victim of partisan politics.
Among other lessons learned for the recent reactor disruption in Japan are the following: keep backup diesel generators at a greater distance from the reactor building; place backup systems above ground level (especially their fuel tanks); design the nuclear plant for indefinite passive cooling; factor in the loss of all power or human interaction; avoid seismic zones; anticipate tsunami disruption and flooding; do better emergency preparation of responders and local population; have fail-safe designs for spent-fuel ponds; move spent fuel out of ponds earlier to fuel-processing facilities. Also to be included in backup design is greater reliance on passive (e.g., gravity) measures.
New supercomputer simulations of cataclysms should be run to see if sea walls are high enough to protect cities and important assets like nuclear reactors from tsunamis, earthquakes, hurricanes and other natural disasters.
The seawall protecting the nuclear reactors at Fukushima in Japanese was breached by the recent tsunami because its height was apparently calculated using outdated geologic information. If supercomputer simulations had been rerun, then the current nuclear disaster might have been averted with more technologically advanced sea walls.
Japan already leads the world in earthquake preparedness, which was mostly successful in protecting many large buildings. Tough building codes in Japan require that large structures take advantage of the latest earthquake-mitigation technologies.
Similar re-evaluations need to be done for earthquake-prone California, which is a major consumer of electricity imported from other states. Less than a decade ago, California suffered blackouts because of undependable out-of-state electric-power suppliers.
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Nuclear power, ship propulsion, and radioisotopes are important examples of modern uses of energy derived from nuclear fission.
Of approximately 1000 nuclear reactors in the world, nearly half are designed for production of electricity, steam, heating, and desalinization.
There are about 440 electrical-power producing reactors in the world, and about 200 reactors for naval-propulsion and icebreakers.
About 280 research, isotope-production, and training reactors are in operation around the world.
A decreasing number of nuclear reactors are used to produce weapons materials, including tritium.
About 13% of world electricity production in 2008 was nuclear (40% coal, 21% gas, and 16% hydro).
Many reactors are small university installations for research, education, or training. Another subset is used for commercial production of radioactive materials applied to medicine, quality control, and research.
As an example of ill-destined consequences resulting from anti-nuclear-power campaigns, one can point to nuclear-reactor radioisotope production. As an older person who has at least several times so far benefitted from medical isotopes, I have a personal stake in seeing that radioactive sources, including Mo-99, are maintained. Frankly, it is with some chagrin that anti-nuclear policies are impeding the commercial availability of radionuclides. Senseless U.S. emphasis on domestic reactor core-enrichment conversion is an example of misplaced nuclear priorities . More generally the medical-isotope shortage is a result of the many years in which anti-nuclear-power bias prevailed.
Food Sterilization is another potentially valuable application of radiation that is neither harmful nor problematic.
Commercial nuclear reactors are increasingly being used to destroy – to demilitarize – weapons-grade materials, an invaluable and irreversible measure of enduring consequence for nuclear-arms control. Moreover, burnup and conversion of former weapons materials has generated timely income for governments who have excess fissile stockpiles.
By moving beyond the theoretic objections of a few recalcitrant academics, the process of demilitarizing and denaturing weapons-grade uranium and plutonium has become a major and practical step in irreversible nuclear arms control and nonproliferation.
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One detrimental feature found in many anti-nuclear-power publications and statements is an unsubstantiated degree of alarmism. Some of it during the Cold War was characteristic of “worst-case” strategic assessments, the product of analysts such as Albert Wohlstetter and Herman Kahn who specialized in what was called operational analysis.
Alarmists avoid the four basic tenets of scientific methodology — peer review, replicability, documentation, and stated rates of error. By avoiding these criteria, they can publish just about anything without systematic scrutiny from the scientific community.
In post-Cold-War times, there is much less need for worst-case assessments; instead, probabilistic studies can be better used for planing guidance. Constructive analysis is based on experience-driven data.
In the absence of extreme alarmism and radiophobia, nuclear-energy policy would be determined more by these key observations:
> No victims of the Chernobyl accident have been identified with clinical certitude 25 years after the event.
> Low-level ambient radiation over eons has been mostly beneficial to human speciation and survival.
> Nuclear-electricity cost has been competitive with other industrial sources for more than half-a-century.
> Nuclear-electric base-station generation has been provided with close to 90% reliability.
> No measurable harm has been found from low doses of radiation from reactors.
> Radon found in home basements is much less harmful than feared.
> There has been a remarkable survival rate for Hiroshima-Nagasaki A-bomb survivors after more than half-a-century.
> The so-called China Syndrome meltdown through a reactor floor is largely a figment of Hollywood imagination.
> Nuclear reactors contribute nearly zero emissions of greenhouse-implicated gases, nor do the reactor plants emit other noxious or polluting substances.
> The recycling of plutonium is neither dangerous nor costly.
> Spent-fuel reprocessing is routine and economical.
> Nuclear-material safeguards are robust and successful to date.
> Nuclear waste can be and has been managed safely and effectively.
> Nuclear reactors have been remarkably safe compared to alternative energy sources.
> More than half-a-century of medical radiation applications have been beneficial and durable.
> Research and materials-testing reactors are safe, secure, and ubiquitous.
> Radiation-isotope-production reactors are needed and are cost-effective.
> Nuclear-ship propulsion has been efficient and competitive for their applications.
> Radioisotope batteries, especially for space missions, are useful and safe.
> Capital cost of reactor construction is high, but still competitive with alternative energy sources.
> Reactor lifetimes have exceeded their design standards, now headed for an extraordinary 60 years.
> Research applications for reactors and radioisotopes are increasing.
Looking over this list of achievements, one can’t help but be impressed by a century of human achievements in application of nuclear radioactivity and fission.
In the annals of human endeavor, there is probably no other complex technology that has been so successful and reliable. During the time period corresponding to modern nuclear development, many dams have breached, mines have caved in, air pollution has increased, bridges have collapsed, world and regional wars have been fought, infectious pandemics have spread, humans have starved, and other calamities have occurred. Yet, nuclear accidents have resulted in comparatively few fatalities.
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Although construction-price estimates for nuclear power plants have been increasing, so have levelized costs for other power sources, including coal, oil, gas, solar, and wind.
In 2007, estimates for nuclear-plant construction in the United States varied considerably in “overnight cost, from $3000/kWe (overnight cost) to between $5,000 and $6,000/kWe (final or “all-in” cost). Because of the subsequent rise in commodity prices, the final cost of installing new nuclear capacity in the U.S. might possibly exceed $7,000/kWe.
In comparison, similar reactors already under construction in China have been reported with substantially lower costs, dropping down to as low as $1000/kWe.
The lifetime cost of new generating capacity in the United States was estimated in 2006 by the U.S. government at 6 cents per kWh. However, nuclear plant life has been greatly extended, thus lowering the capital cost/year and the fuel cost/year. Nuclear fuel in extended-life power plants costs as little as 2 cents/kWh.
A 2008 study concluded that if carbon capture and storage was mandated, then nuclear power would be the cheapest source of electricity, even at $4,000/kWe in overnight capital cost.
Generally, a nuclear power plant is significantly more expensive to build than an equivalent coal-fueled or gas-fueled plant. However, bulk coal is much more expensive than nuclear fuel, and natural gas significantly had been more expensive than coal; thus, capital costs aside, natural gas-generated power was the most expensive. However, capital cost of nuclear plants is usually based on a 25-year lifetime, but the plants have experienced double that lifetime.
Most forms of electricity generation produce some form of negative externality – costs imposed on third parties that are not directly paid by the producer – such as pollution which negatively affects the health of those near and downwind of the power plant.
Another externality is environmental damage caused by (fossil or renewable) energy sources, both through land use (whether for mining fuels or for power generation) and through air and water pollution and solid waste
Wind power in the United Kingdom has been calculated to be more than twice as expensive as nuclear power. With a carbon tax added, coal costs came close to that of onshore wind (including back-up power costs).
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In considering the long-term consequences of the combined seismic, flooding, and nuclear disasters in Japan, one must keep in mind that Japan rebounded from the devastation it suffered as a result of World War II, including the atomic bombings of Hiroshima and Nagasaki. Because of the enduring tacit reluctance on the part of the Japanese to confront such matters, not much about that part of its past will be openly discussed.
Meanwhile, turmoil continues around the world, especially now in Arab countries around the entire crescent of the former Ottoman Empire.
Russia, which gained its independence from the former Soviet Union, is thriving after discarding the Soviet yoke. Moscow is home to more than 100 billionaires, many of them profiting from the wealth of oil and natural gas being exploited. As an aftermath of Chernobyl, Russia has modernized its design of nuclear reactors and competes on the world market for sale of nuclear plants.
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Remarkable survival rates have been experienced by the radiation-exposed survivors of the atomic bombing of Japan. The A-bomb survivors were flashed within less than a second by radiation doses at least 50,000 times higher than any U.S. inhabitants will ever receive over a period of 50 years from the Chernobyl fallout. Although cancer-risk factors based on epidemiological studies of the survivors are not directly relevant to much smaller doses received over a longer period of time, the survivors’ longevity is significant.
Radiophobia is an unwarranted fear of radiation, regardless of context. It was exacerbated by the Chernobyl accident. Radiophobia – stirred up by anti-nuclear alarmists – vastly and unnecessarily increased subsequent economic losses in the former Soviet Union and elsewhere in Europe.
Inasmuch as the average dose of any substance does not determine average risk, particular care should be taken not to make or give credibility to the “ecological” or “collective-dose” fallacy, a methodological flaw. Simply put, an ingested one-time dose of 100 aspirins to one individual can cause that individual’s death, but that does not mean that if you give each of 100 people one aspirin, there will then be one death in that group of 100 people. That fallacy in logic is common among those who have excessive fear of radiation.
Radiation has been with humankind long before life began. In fact, humans might have evolved as a dominant species because of, rather than despite, radiation-causing genetic changes.
In point of fact, no deaths in the general population can be proven to have occurred as a result of the Chernobyl nuclear accident. This remains the case, even though international organizations have statistically estimated approximately a dozen premature deaths among exposed juveniles in the former Soviet Union and up to 4000 premature cancer deaths among adults. The international-study committees have had to concede their estimates are so uncertain that, in fact, nobody might have died prematurely as a result of the extra radiation from Chernobyl. In any event, there is no palpable evidence of increased mortality from the spread of Chernobyl’s radiation.
Population-epidemiology surveys by scientists do not fully account for confounding factors and are usually reported without justifiable statistical confidence regarding harmful health consequences forecast from low doses of ionizing radiation.
In 1993 the U.S. Supreme Court revised the federal judicial standards for testimony regarding areas of science that required an explicit estimate of probabilistic error. In the federal case, Daubert v. Merrell Dow Pharmaceuticals, the Supreme Court ruled that quantifiable evidence should meet four “scientific method” standards, namely peer review, replicability, documentation, and stated rates of error. More specifically, the Daubert decision called for the admissibility of expert testimony to be based on those standards, key among them being whether the testimony is connected explicitly to a testable hypothesis, and whether there is a known or potential error associated with the evidence. Such reasonable standards could not be satisfied by claims in court of population casualties due to Chernobyl radiation.
Confusion about the impact of Chernobyl has arisen owing to the fact that many thousands of people in the affected radiation-fallout areas of the former Soviet Union have died of natural causes. Also, widespread expectations of ill health and a tendency to attribute all health problems to radiation exposure have led local residents to assume that Chernobyl related fatalities were much higher than they actually were.
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Because of the detailed technical and evaluational nature of this essay, here’s some information about the author’s credentials to address these issues.
I (Dr. Alexander DeVolpi) am the author/compiler of a three-volume book set Nuclear Insights: The Cold War Legacy, consolidated from a multi-authored pair of detailed citation-heavy volumes Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry, both sets listed and described on the web site www.NuclearShadowboxing.INFO.
The three-volumes of Nuclear Insights are as follows: Vol. 1, Nuclear Weaponry (An Insider History); Vol. 2, Nuclear Threats and Prospects (A Knowledgeable Assessment); Vol. 3, Nuclear Reductions (A Technically Informed Perspective). All three volumes of Nuclear Insights, published in 2009, are available on Amazon.Com. Except for the latest on the Japanese reactors, much of the information included in this Google knol is contained in or derived from Nuclear Insights.
I have had considerable education, training, exposure, and experience in nuclear physics, technology, reactors, and radiation.
My MS degree was in Nuclear Engineering Physics, followed by a PhD in Physics, both from the Virginia Polytechnic Institute. Also completed a two-year course and internship at the International School of Nuclear Science and Engineering at Argonne National Laboratory. The second (internship) year of the course involved working directly, hands-on, with zero-power nuclear reactors. Moreover, my MS thesis involved assembling a subcritical nuclear reactor.
Almost 40 years working as a physicist at Argonne National Laboratory gave me extraordinary and nearly unlimited access to nuclear reactors and related facilities and laboratories. At the Argonne Illinois site, we had many nuclear-fuel-cycle facilities, among them an experimental boiling water (EBWR), a research and training reactor (Juggernaut), and the research reactor CP-5.
I spent many hours and years doing nuclear experiments at CP-5 and elsewhere that involved or experienced controlled exposure to all forms of nuclear radiation. In those days, the standards for voluntary radiation exposure were far less stringent than they are today.
My U.S. Naval Reserve obligations gave me valuable research time at the Naval Research Laboratory in Washington, DC, and the Radiological Defense Laboratory in San Francisco, CA.
In connection with subsequent research, developments, and inventions, I engaged for about ten years in a project that used the TREAT transient reactor in Idaho for experiments. That also gave me familiarization with the EBR fast-reactor and fuel-handling facilities. In the course of time, I’ve seen dozen of nuclear reactors, and recall having been inside at least one civilian power reactor under construction.
During my second two decades at Argonne, I was involved in application of nuclear technology to arms-control and treaty verification. That led to opportunities to visit many research and power reactors throughout the world, as well as less-relevant, but more-imposing visits to nuclear-weapon storage facilities.
One key thing that came out of that experience was an appreciation for contributions of many engineering and scientific disciplines involved in nuclear power, including metallurgists, structural engineers, chemists, physicists, programmers, other specialists, and technical management.
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Had I been there at the time the reactors started to malfunction, I too would have been scared and perplexed. It must have been difficult to understand surrounding events or get meaningful data. It must have been especially problematic for responsible officials, particularly with the backdrop of casualties and destruction from the earthquake and tsunami. Members of the public would easily have been frightened by the added uncertainties and impressions derived from unfathomable events surrounding the nuclear plants and with the information then available.
No amount of experience or knowledge would have sufficed to prevent fear. Now, however, in the light of converging resolution, it is possible to place the Japanese reactor accidents within the context of other major nuclear accidents, and to rank nuclear accidents within the context of conventional industrial accidents and human endeavors.
It’s been 100+ years since the nuclear genie emerged, more than 70 years since both Nazi Germany and the United States governments became interested in uranium fission, nearly 70 years after the first reactor, and over 60 years since the first nuclear bombings of the Japanese cities of Hiroshima and Nagasaki. Since then, close to 1000 nuclear reactors have been built, and nuclear byproducts make major contributions to human progress.
Looking over the past, one can’t help but be impressed by a century of human achievements in application of nuclear radioactivity and fission. In the annals of human endeavor, no other complex technology that has been so successful and reliable. During the same time period, many dams have breached, mines have caved in, air pollution has increased, oil spills have occurred, bridges have collapsed, world and regional wars have been fought, infectious pandemics have spread, humans have starved, and other calamities have occurred. Yet, nuclear accidents have resulted in few fatalities compared to nature’s devastation or compared to other human constructs.
END OF “Chernobyl, Fukushima, and Three-Mile Island: Implications of Three Major Nuclear Reactor Accidents”
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