Statement by Scientists and Engineers Concerning Fukushima Daiichi Nuclear Power Plant (no.3)
May 19, 2011
Our Views of the Accidents at the Fukushima Nuclear Plants after the Earthquake
From: The Group of Concerned Scientists and Engineers Calling for the Closure of the Kashiwazaki-Kariwa Nuclear Power Plant
Toda Building, 4th Floor, 1-21 Yotsuya, Shinjuku, Tokyo 160-0004
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Following an unprecedented request from Prime Minister Kan, all the reactors at the Hamaoka Nuclear Power Plant (NPP) were stopped on May 14. The Prime Minister has also vowed that the national policy to promote nuclear power plants will be dropped and that Japan’s energy policy be subject to review. We welcome this progressive decision. It implies that the heartfelt voices of many people were heard by the Prime Minister. It is important that we keep working towards building a society in which people can live without fear. We should not succumb to the pressure from groups and individuals who have vested interests in the nuclear power industry, including those in political, bureaucratic, business and academic circles. Now that the Hamaoka Nuclear Power Plant is stopped, we ask next that the Kashiwazaki-Kariwa Nuclear Power Plant, which has been proven to be vulnerable to earthquakes, be decommissioned. After Kashiwazaki-Kariwa, we suggest that high-risk nuclear plants be stopped one by one, beginning with those considered to pose the highest risk.
Although more than two months have passed since March 11, the condition of the Fukushima Daiichi Nuclear Power Plant (NPP) remains critical. Last month, the severity rating of the nuclear plant accident at Fukushima was raised to a Level 7 nuclear crisis, the same category as Chernobyl. In the same month, the Tokyo Electric Power Company (TEPCO) announced a work schedule (‘roadmap’) for stabilizing the critical situation at Fukushima Daiichi NPP. Soon after, however, we learned that the damage to the reactors was worse than previously reported, which implies that this schedule needs to be revised. The strenuous efforts of workers to stabilize the situation at Fukushima Daiichi NPP continue with no end in sight, and a worker who was engaged in decontamination work suddenly died on May 14.
On the basis of the data published by the Japanese government and TEPCO, we have presumed that the earthquake must have damaged reactors at Fukushima Daiichi NPP before the tsunami waves struck the plant. This point is discussed in detail in 1.1-1.5 below.
We have also had repeated discussions about how we should deal with the contamination of food and water as a result of the continuing release of radioactive materials. The issue of contamination in general is examined in 2.1-2.3, and the contamination of food is discussed in 2.3. Some of us believe that we should not eat contaminated food at all in order to avoid potential risks. Others suggest that maintaining ties with food producers near Fukushima Daiichi NPP is extremely important, and that one way to support them is to eat their products while being aware of certain risks. Given that contamination of the air, water and soil is very widespread, these are questions that everybody has to face. We have recently learned that the contamination level of green tea leaves harvested even in the western part of Kanagawa Prefecture (300 km away from Fukushima Daiichi NPP) exceeded the Japanese government’s safety standard.
The concluding section of this statement, Section 3, argues that the Kashiwazaki-Kariwa NPP must be stopped immediately.
This statement is based primarily on comments from the individuals listed below. Hiromitsu INO (Professor Emeritus, University of Tokyo, Metallurgy), the Head of The Group of Concerned Scientists and Engineers Calling for the Closure of the Kashiwazaki-Kariwa Nuclear Power Plant, and Tamotsu SUGENAMI, the Secretary, are responsible for finalizing the statement. For each section, the name of the individual who acted as the primary author is listed. In addition to the names listed below, many other people have helped us compile this statement. Nos. 1 and 2 of “Our Views of the Accidents at the Fukushima Nuclear Plants after the Earthquake” are available at our website.
List of Collaborators: Yoshinori ITO (lawyer), Shiro OGURA (former nuclear power plant engineer), Chihiro KAMISAWA (Citizens’ Nuclear Information Center [CNIC]), Masashi GOTO (former designer of reactor containment vessels), Hisako SAKIYAMA (former Chief of the National Institute of Radiological Sciences; Takagi School for Alternative Scientists), Mitsuhiko TANAKA (science writer and former designer of reactor containment vessels), Makoto NAITO (electronic engineer; Society for the History of Modern Technology), Eisuke NARAMOTO (Professor, Hosei University), Yukio YAMAGUCHI (Co-director of CNIC, physics), and Yoshichika YUASA (Professor Emeritus of Tokyo Metropolitan University, civil engineering).
1. What Happened at the Fukushima Daiichi Nuclear Power Plant?
By Mitsuhiko TANAKA
The ongoing calamity at the Fukushima Daiichi NPP was recently rated as Level 7, the highest possible level on the International Nuclear Event Scale (INES). Reactor Units 1, 2, and 3 have experienced meltdowns. Although two months have passed since the earthquake, there is no indication that stabilized cooling of Reactor Units 1 through 3 and of the fuel storage pools of Units 1 through 4 is being achieved.
In April, TEPCO announced a two-tiered “roadmap” towards stabilization of the reactors. However, there are many potential problems to be overcome in the realization of their plans. Even if they manage to keep to the schedule, it will take at least six months before Reactor Units 1 and 3 can be stabilized and cooled. Moreover, in the case of Reactor Unit 2, TEPCO does not even have a clear idea of the timeline.
Currently, we are analyzing the limited data provided by TEPCO to understand what happened at Reactor Units 1 through 3. The primary purpose of our analysis is to determine whether this current disaster was really triggered by the massive, “unexpected” tsunami. As discussed below, we believe that the seismic vibrations of this extremely large earthquake may have been the true cause of the fatal damage to the plant.
If the Fukushima Daiichi NPP was seriously damaged by the earthquake prior to the arrival of the tsunami, then earthquake safety measures at the other nuclear power plants on the Japanese Archipelago need to be questioned. In the following sections, I will present our views based on the preliminary results of our analysis.
1.1 Possibility of a Loss-of-Coolant Accident due to Pipe Fractures
From an early stage in our analysis, we have paid close attention to the situation in Reactor Unit 1. Soon after the earthquake, this reactor experienced an abnormally rapid decrease in “reactor water level.” The reactor water level is the distance from the surface of the coolant (light water) to the top of the fuel rods. During normal operation, the water level is approximately five meters above the top of the fuel rods. If the reactor water level is below zero, then a part or the whole of the fuel rods, which are approximately four meters long, are exposed out of the water. In this state, the zirconium alloy that covers the outer surface of the fuel rods could reach a temperature high enough to react with the steam and produce hydrogen or melt. If the situation worsens, the fuel pellets inside the rods could begin to melt, resulting in an extremely dangerous situation.
In the case of Reactor Unit 1, the reactor water level reached a meager 45 cm above the fuel rods by 7:30 p.m. on March 11th, only 4 hours and 44 minutes after the earthquake. This means that the reactor water level decreased by approximately 4.5 meters within this relatively short period of time. We have two questions about this rapid loss of water from Reactor Unit 1: Firstly, what was the cause of this abnormal and sudden drop in the water level, and secondly, where did the water go? There are only two possible explanations for these questions. One possibility is that one of the pipes connected to the pressure vessel (such as the main steam pipe, water supply pipe, and re-circulating pipes) was damaged or broken by the earthquake vibration, and as a result, the coolant gushed out of the pressure vessel. Another possibility is that the “safety relief valve” of the main steam pipe opened automatically (or was manually opened by an operator), and from there, steam under high temperature and pressure in the pressure vessel gushed out into the suppression chamber (suppression pool). As a result, the water level in the reactor fell.
Neither of these explanations is consistent with a series of TEPCO press releases immediately after the accident. According to TEPCO, from the period immediately after the accident to midnight on March 12, high temperature and high pressure steam in the pressure vessel was actually channeled out and cooled by the “emergency condenser” (isolation condenser), an external cooling system. If this was the case, then it does not make sense that the safety relief valve was automatically activated (or manually operated). There is no mention of the operation of the ‘safety relief valve’ in TEPCO’s press releases.
Upon close examination of the data made available by TEPCO, we found that the pressure in the containment vessel reached a dangerously high level by the late evening of March 11. However, by the morning of the following day, March 12, the pressure began to slowly decline. At the same time, the pressure and water level within the reactor began to decline as well. This cannot be explained by the use of the safety relief valve. We suspect that there was some sort of damage to one or more of the pipes.
Based on these observations, we believe that what happened at Unit 1 was the worst possible scenario, a loss-of-coolant accident. One or more pipes must have been damaged by the earthquake, which allowed the rapid outflow of coolant. Furthermore, we speculate that a loss-of-coolant accident also occurred in Unit 2, though further examination of data is necessary.
1.2 Was the Suppression Chamber Damaged by the Earthquake?
As we all know, in both Units 1 and 3, hydrogen explosions took place on the top floor of the building shells (the operation floor). In contrast, according to a TEPCO report, a hydrogen explosion in Unit 2 occurred “near” the suppression chamber (suppression pool). When a reactor is in operation, the suppression chamber is filled with nitrogen, and thus it is highly unlikely that hydrogen will explode inside the chamber. Therefore, if, as TEPCO claims, an explosion took place near the suppression chamber, then it is most likely that hydrogen accumulated in the suppression chamber leaked out of the chamber, reacted with air, and exploded. The question then is: how did the hydrogen leak in the first place?
The suppression chamber, which is shaped like a doughnut, is connected to the flask-shaped drywell of the containment vessel through multiple thick vent pipes. The joint section between the vent pipes and the chamber is a “soft” structure called the “bellows,” and which is designed to absorb the pressure differences occurring with thermal expansion and contraction. We speculate that it was the bellows structure that was damaged by the earthquake, and that it was from there that the leakage of hydrogen gas occurred.
It should also be kept in mind that the suppression chamber, measuring almost five meters in diameter, is a large, welded structure with a number of weld seams. Thus, it is also possible that one or more of these weld seams may have been damaged by the earthquake.
In any event, the fact that there was an explosion outside of the suppression chamber strongly points to the possibility that the earthquake itself caused damage to the containment vessel suppression chamber.
1.3 Why Did the Pressure within the Containment Vessel Rise Abnormally?
Another phenomenon that deserves close examination is the abnormal rise of the pressure within the containment vessels in Units 1 through 3. Under normal circumstances, the pressure within the containment vessel in operation is close to atmospheric pressure (to be precise, it is slightly lower than atmospheric pressure). It is important to note, however, that containment vessels are designed to withstand up to approximately 4 atmospheres. The reasons are as follows.
Assume that the thickest pipe of the recirculation system pipe (i.e., the recirculation outlet pipe) is completely damaged (this scenario is called a “guillotine break”). If this happens, all the coolant inside the pressure vessel will gush out through the broken sections in a very short time, and high temperature steam will be released into the drywell of the containment vessel. The steam will ultimately travel toward the suppression chamber, where it will be channeled into the water inside the chamber and condense to water. As it does so, the volume is reduced and thus the pressure within the containment vessel will decrease. In theory, therefore, the pressure within the Mark I type containment vessel (the type used in Units 1 to 5 of Fukushima Daiichi) should never exceed 4 atmospheres.
In reality, however, the pressure in the containment vessels of Units 1 through 3 did exceed 4 atmospheres. In particular, the pressure of Unit 1 reached as high as approximately 7.4 atmospheres only nine hours after the earthquake. This fact indicates that the suppression chamber did not function in the way it was designed. While our analysis is still in progress, the pressure was extremely high and the change occurred in a short period of time. We suspect that the system intended to channel the vast amount of steam in the drywell into the water of the suppression chamber was damaged by the earthquake.
1.4 Reliability of Data Provided by TEPCO and the Oyamada Statement
Our current view presented above is based on the limited amount of data provided by TEPCO, and thus our results are still provisional. As of May 16, 2011, TEPCO has not released the most critical data for understanding exactly what occurred at Fukushima Daiichi NPP: the operation record for the first 12 hours immediately after the earthquake. Not only that but TEPCO also repeatedly modified or deleted data that had already been publicized on their website. This suggests to us that TEPCO’s past tendency to conceal, falsify and fabricate data has not changed. We need to make sure that TEPCO will not fabricate data in order to ascribe the accidents at Fukushima Daiichi NPP solely to the tsunami.
Related to this issue is a statement by Mr. Osamu Oyamada, a member of Japan’s Nuclear Safety Commission. It is said that when he visited the Fukushma Daiichi NPP on April 20, he indicated that the earthquake itself did not damage the nuclear plant. Was this statement based on objective data? If so, the Nuclear Safety Commission must immediately make the data available to the public. If there are no such data, then the statement is utterly irresponsible and misleading.
1.5 TEPCO’s Analysis of the Meltdown at Reactor Unit 1
On May 16, TEPCO held a press conference in which they admitted that a fuel meltdown had begun at Reactor Unit 1 five hours after the earthquake (which occurred at 14:46 on March 11). By 06:50 on March 12, about 16 hours after the initial meltdown, the majority of the fuel had melted and fallen to the bottom of the pressure vessel. This shocking announcement is not only radically different from the contents of previous TEPCO announcements, but also requires closer examination. The announcement was based on TEPCO’s computer simulation results of the meltdown process with a severe accident simulation program. Needless to say, the result of the simulation is strongly influenced by the conditions of the accident input to the program. For example, the result would be radically different depending on whether the conditions of the simulation included possible damage in piping by the earthquake or not. However, TEPCO has not published the conditions for this simulation. Furthermore, the changes in reactor water level estimated by this simulation are very different from the water level data that TEPCO had previously published. TEPCO admits that the result of this simulation is one of many possible scenarios. At this stage, we should also regard this result as such.
2. How Should We Face the Problem of Radiation Contamination?
By Hiromitsu INO
2.1 Critical Situations in Fukushima
Recent news has revealed that the annual radiation level will exceed 20 millisieverts per year (mSv/yr) in some areas outside the Fukushima Daiichi NPP 30 km zone. On April 22, the Japanese government finally declared Iidate Village, Kawamata Town and Katsurao Village to be part of the “Planned Evacuation Zone,” and evacuation was underway by the end of May. Because of the delay in issuing this evacuation order, residents in these areas were unnecessarily exposed to high levels of radiation. In particular, pregnant women, infants and elementary and junior high school children were exposed to a high level of risk. Even though the simulation results of SPEEDI (the System for Prediction of Environmental Emergency Dose Information) were available shortly after the earthquake, these results were not publicized. The justification for this was that they were only simulation results and thus might create a false sense of crisis. The Nuclear Safety Commission neglected their first priority to protect the safety of the residents. We strongly protest the attitude of the Commission Chair, Dr. Madarame and the other members of the Safety Commission.
Radiation contamination in Fukushima City (63 km from Fukushima Daiichi NPP) is also serious. It is predicted that the annual radiation level will exceed 20 mSv/yr. Several other large cities within Fukushima Prefecture, including Koriyama City and Iwaki City, are also in danger. Since the level of radiation contamination depends not only on the distance from Fukushima Daiichi NPP but also the direction of the wind and the local topography, it is important that we closely monitor the changes in the contamination level in each area.
The Ministry of Education, Culture, Sports, Science and Technology (MEXT) states that elementary and junior high schools, kindergartens and daycare centers should open for a new semester as long as the estimated annual radiation level is below 20 mSv/yr. According to the Ministry, the annual level of radiation exposure will remain below this limit as long as children are instructed to stay indoors when the radiation level is higher than 3.8 microsieverts per hour (μSv/hr). The fundamental problem behind this statement is that the Ministry increased the normal legal limit from 1 mSv/yr to 20 mSv/yr, which is the upper limit of radiation exposure for residents suggested by the International Commission on Radiological Protection (ICRP). According to ICRP, 20 mSv/yr implies a 0.2% increase (20 per 10,000 people) in the cancer rate. In other words, the change from 1 mSv to 20 mSv per year implies that the Japanese government has forced its citizens to endure a higher risk of cancer. Given that children are 3 to 10 times more sensitive to radiation than adults, this means that the health of future generations is being sacrificed.
On April 30, Toshiso Kosako, Professor of the University of Tokyo, resigned his position as a Cabinet Secretariat Counselor to protest the national government’s decision to raise the legal upper limit from 1 to 20 mSv/yr. His protest is justifiable, and we support his decision.
The Japanese government has not issued an evacuation order to any of the major cities within Fukushima Prefecture. Some residents, who felt that their safety was in danger, began to evacuate voluntarily from these cities and move in with relatives and friends in distant locations. However, not everybody has relatives and friends who would welcome evacuees, and anyway fleeing is not an option for most residents of these cities because their jobs are tied to this region. The situation of residents of highly contaminated areas near the Fukushima Daiichi NPP is even more serious. Although the media has reported that many of these residents do not wish to leave their hometowns, it is likely that this is partially because these people are not accurately informed of the reality of the high level of radiation contamination.
We, people who live in the Tokyo metropolitan area, need to be aware of the difficulties that the residents of the heavily contaminated areas are facing and provide them with active support. Actions we can take include 1) asking the national and local governments to facilitate and systematize evacuation procedures, and 2) establishing support networks at the grass roots level. Residents of the contaminated area should be guaranteed the right to evacuate if they wish to. In particular, the possibility of group evacuations of school children should be discussed by each municipal government. When a group evacuation is not feasible, a variety of alternative strategies, including the decontamination of school yards and buildings, needs to be taken.
2.2 Playing Down the Effects of Radiation Exposure
The Japanese government rated the accident at the Fukushima Daiichi NPP as a Level 7 crisis on the International Nuclear Event Scale (INES), the highest INES rating, assuming a release of more than several tens of thousands of terabecquerels of radioactive material (1 terabecquerel [Tbq] = 1012 bq). Despite this, the tendency to underestimate the level of radiation contamination is becoming even stronger, and it is often said that the amount of the released radioactive materials is one order of magnitude smaller than (i.e one-tenth of) that of Chernobyl.
Results of aircraft monitoring by MEXT and the United States Department of Energy, published on May 6, were shocking. They revealed a highly contaminated zone to the northeast of Fukushima Daiichi NPP. In particular, the radiation level of most of Iidate Village, which is located outside the Fukushima Daiichi NPP 30 km zone, exceeds 3.8 μSv/hr. In the southern part of Iidate Village, as well as in Namidate Village, the radiation level reached as high as 19 μSv/hr. The accumulation of cesium-137 on the ground surface of these areas measures over 1,000,000 bq/m2. The distribution range of these heavily contaminated areas is only slightly smaller than that of the Chernobyl incident. Data also indicate that portions of Fukushima City, a major city with a large population, are also highly contaminated. It is also important to note that, in some locations within Fukushima City, the air dose rate is as high as 1.9 to 3.8 μSv/hr, and the accumulation of cesium-137 is as high as 300,000 to 600,000 bq/m2.
Several scholars have also actively played down the effect of the radiation contamination at the time of the Chernobyl accident. For example, Professor Shun’ichi Yamashita of Nagasaki University, who was appointed radiation health risk management advisor of Fukushima Prefecture after the Fukushima accident, and Professor Kenji Kamiya of Hiroshima University state that the only correlation that we know between nuclear accidents and an increased cancer rate is that of thyroid cancer in children. They also state that the correlation between low dose radiation exposure and cancer rate is not clear. Given the high incidence of thyroid cancer among children in Chernobyl, it is a truly bogus story that no other types of cancer occurred. Numerous reports from Chernobyl convey the struggle of people who are suffering not only from cancer but also from various other diseases. It is well known that the radiation exposure limit set by ICRP is based on the assumption that even low dose radiation will result in a proportionate increase in cancer incidence. On the basis of the amount of released radioactive materials from Chernobyl and the total amount of radiation exposure, it is estimated that tens of thousands of people will eventually suffer from cancer.
Unless we take action, it is likely that a similar situation will occur in Fukushima. Because we Japanese people tend to eat more seaweed, our bodies might absorb less radioactive iodine (I-131) and as a result the thyroid cancer rate might be lower. It is likely, however, that other types of cancer and disease will increase. Appropriate actions for the residents need to be taken immediately, and detailed long-term follow-up surveys are required.
2.3 How Should We Deal with the Issue of Food and Water Contamination?
As we know, the legal food contamination limit does not imply that contaminated food below the limit is safe. In particular, after the Fukushima accident, the Japanese government raised the original legal limit of 1 mSv/yr to the current legal limit of 5 mSv/yr and justified this by stating that this is an emergency situation. The legal limit for iodine-131 in the tap water (300 bq/kg) that was set on the basis of this new regulation and is 300 times higher than that of WHO, 600 times higher than that of Germany, and 2700 times higher than that of the United Sates. Needless to say, the risk of cancer incidence does not decrease just because it is an emergency situation.
Radiation contamination of agricultural produce and sea food has caused devastating damage to farmers and fishers in Fukushima Prefecture as well as in several other Prefectures in the northern Kanto Region. Farmers in these prefectures have demanded that TEPCO not only stabilize the situation at the Fukushima NPP but also compensate for financial loss caused by the accident, including the so-called “rumor damage” or fuhyo higai (damage caused by “groundless” rumors). We strongly support their justified demands. Even though the Nuclear Power Compensation Examination Board, which was established on April 15, has announced that the targets of the compensation will include damage caused by “groundless” rumors, we need to make sure that all the damage caused by the Fukushima accident will be properly compensated by TEPCO.
Compensation for financial loss itself will not help remove the radiation contamination of land and the ocean. Radiation damage not only affects humans: all the lives of the animals and plants in this region will be damaged by the invisible poison. We have no choice but to accept this serious situation as reality. Residents of these prefectures are facing the question of whether they can continue to work there and whether the food produced there is suitable for consumption. We suggest that all future discussion needs to start from the recognition of this reality. How should the consumers in the rest of Japan, including those in the Tokyo metropolitan area, face this reality? How can we collaborate with residents of the areas damaged by the “nuclear earthquake disaster”?
Food distribution routes in contemporary society are not limited to the mainstream routes, which start from the Agricultural and Fisheries Cooperatives and end at large grocery supermarkets via the major distributors. Other distribution operations include networks of consumer cooperatives and organic agricultural food producers as well as grass-roots networks that work through personal connections. Even when the scale of distribution is smaller, the importance of these networks is invaluable. We need to find a way to protect Japanese food and agriculture while valuing these networks and protecting ourselves from radiation contamination (see note).
Note: This statement was written after a series of discussions. Opinions about how to deal with contaminated food varied among group members. Three examples of opinions from our members are as follows:
Opinion 1. Given that there is no safe dose for internal radiation exposure, people should make individual decisions about whether they should or should not eat slightly contaminated food. It is known that the effect of internal radiation varies significantly between individuals on the basis of various factors, including age, sex (especially whether women are pregnant or not), and immunological capacity. Some elderly people may be less concerned about the effects of radiation contamination than younger people. In any case, it is not appropriate for the Group of Concerned Scientists and Engineers to encourage people to eat agricultural and animal products below a certain radiation level (such as the legal limit set by the Japanese government).
Opinion 2. Given that internal radiation exposure from food will cause significant health damage, people will look for less contaminated food. Realistically speaking, however, it is impossible to completely avoid food contaminated with radiation. Each individual will make an informed decision on whether s/he should or should not eat a particular food item after acknowledging how much risk s/he is taking if s/he eats a certain amount of food of a certain radiation contamination level. In order to do so, consumers need to possess the basic knowledge for evaluating the risk involved in consuming a certain amount of radioactive material, as well as to have access to information concerning food contamination levels. Food producers in the agricultural, livestock and fishing industries should also provide products to consumers upon full knowledge of the contamination levels. If it is determined that the products are not suitable for consumption and therefore cannot be shipped, the producers should demand compensation from TEPCO. In sum, both consumers and producers need to be active agents in the decision-making process.
Opinion 3. Should we decide “to eat or not to eat” solely on the basis of the level of radiation contamination? I am a member of a food distribution network of an organic farm in Ibaraki Prefecture. Like many other prefectures in the Kanto region, the area is not free of radiation contamination. Nevertheless, my family and I have decided to eat the food which the farm has decided to distribute to the consumers. We do not intend to switch our food supply to less contaminated products from western Japan or from overseas. We strongly believe that it is important to maintain the existing ties with the farm people. Similar ties exist between Consumer Cooperatives and food producers. We need to remember that even the food in the commercial markets is distributed through human connections.
3. Halt Operation of the Kashiwazaki-Kariwa Nuclear Power Plant Immediately, and Initiate a Fundamental Reexamination of the Necessity of Nuclear Power Plants
By Yukio YAMAGUCHI
On April 21, TEPCO submitted a document titled “Emergency Safety Measures at the Kashiwazaki-Kariwa Nuclear Power Plant (Implementation Report)” to Niigata Prefecture. It was supposed to be an answer to a directive issued on March 31 from the Minister of Trade, Economy and Industry.
According to this document, the direct causes of the accident at Fukushima Daiichi NPP were the following incidents that resulted from the tsunami associated with the extraordinarily large earthquake:
(1) Inability to secure emergency electric power after the loss of external power supply;
(2) Loss of the reactor cooling system using sea water (or the loss of its function) to release heat from the reactor cores into the ocean after the reactors were shut down; and
(3) Failure to supply cooling water efficiently when the cooling system for the spent fuel pools failed and when water supplies within the power plant were cut off.
There is no mention of the effects of the shaking of the earthquake itself.
Was this really the case? It is important to note that, at Units 2, 3 and 5 of Fukushima Daiichi NPP, the peak accelerations in the east-west direction measured 15-16% in excess of the seismic design standard. Given this evidence, we suggest that the earthquake itself may have caused pipe breakages or fractures, which resulted in the loss-of-coolant accident. An accident analysis on the basis of currently available data is presented in Section 1 of this statement.
At the end of March 2008, two sub-committees within the Technical Committee of Niigata Prefecture closed discussions without resolving many critical issues. The operation of Units 1, 5, 6 and 7 of the Kashwazaki-Kariwa NPP was resumed under the name of an “engineering judgment.” The committee dismissed numerous critical issues as being unimportant. For example, the northern portion of the fault on the eastern edge of the Sado Basin was considered as nonexistent. Plastic distortions of devices were assumed to be no problem. The motor casing of the recirculating water pump is assumed to be earthquake resistant. The misalignment of the scale that indicates the location of the hanger was not caused by the earthquake. The tilt of the building shell is also not a problem. The earthquake safety of both the containment vessels and the control rods is secure. The safety of the NPP will be maintained for a tsunami wave of up to 3.3 m and backwash of 3.5 m.
At Fukushima Daiichi NPP, the Reactor Units 1 to 3 are still out of control two months after the earthquake, and the situation remains critical. If the Technical Committee of the Niigata Prefecture and others had thoroughly examined the degree of the damage on the Kashiwazaki-Kariwa NPP caused by the Niigata Chuetsu Earthquake, and if TEPCO had been willing to reflect the results of the discussion in security measures at the Fukushima Daiichi NPP, then this severe accident might have been avoided. This is in hindsight, but we can still stop Units 1, 5, 6 and 7 of the Kashiwazaki-Kariwa NPP that have resumed operation and examine all the potential problems without leaving any remaining ambiguities. Needless to say, there is simply no justification to use the shortage of electricity due to the Fukushima accident as an excuse to resume the operation of Unit 3 of Kashiwazaki-Kariwa NPP. Residents of the Tokyo Metropolitan Area do not want electric supplies which come associated with such a huge risk.
Statement by Scientists and Engineers Concerning Fukushima Daiichi Nuclear Power Plant (no.2) (April 7, 2011)
Statement by Scientists and Engineers Concerning Fukushima Daiichi Nuclear Power Plant (no.1) (March 23, 2011)
