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General Articles
Vol.2, No.1, GA11

Activities on Public Awareness of a Prototype Fast Breeder Reactor, Monju, and Casebook of Potential Troubles

Tsutomu Yanagisawa1, Hiroaki Tabata2, and Masaomi Mori3
1 Senior Adviser, Japan Atomic Energy Agency (JAEA).
2 Deputy Director General, Fast Breeder Reactor Research and Development Center, JAEA.
3 General Manager, Public Relations Section, Administration Department, Tsuruga Head Office, JAEA.

* We'd like to notify that this article was written on April 12th, 2010, and Monju has started normal operation on May 6th.

1. Introduction

A prototype fast breeder reactor (FBR), named Monju, is located in Tsuruga city, Fukui prefecture of Japan, which plan was made as national project to secure future energy for Japan. The construction of Monju started  in October 1985 and it accomplished the first criticality in April 1994 and subsequently the first power transmission in August 1995 of  the following year. However, due to the accident of sodium leakage, the operation has been stopped since the incident in December 1994. For the time being, all kinds of preparatory works are presently on the way towards resuming the operation in 2009.
In 2006, the FBR cycle technology was considered as one of five national key technologies which should keep Japanese technological presence in the world. Monju is positioned as core facility for the research and development, for which should begin with paying attention to secure safety and to earn public trust. For this reason, it is important for us not only to take all possibly preventive measures against accidents and troubles in design and operation management, but also to keep in mind a remark, “man makes mistakes and machine fails” as quoted in “the Framework for Nuclear Energy Policy”. In addition, Monju is the new type of a nuclear plant, which has new and different machine and equipment from that of an established reactor type. It is necessary to overcome incidents and troubles caused by the newly different part and to improve the operation on building up the technology. That is also an important aspect of Monju.
The operational record in the number of commercial reactors shows about 13,000 reactor/year including light water reactors. On the other hand, that of FBRs is about 300 to 400.  Although Monju has lost a public confidence to a great extent due to the incident of sodium leakage, it has continued to make organizational efforts intensely toward regaining the public confident. In the efforts, we always had topics on the approach to potential accidents and troubles  in the future operation for this time on.
To promote  a effective dialogue with the local community and the people concerned as risk communication, and also to lead public confidence, we published a booklet to brief potential accidents and troubles, and the corrective and preventive measures (referred as casebook in this article), which is made based on questions and answers, and comments received through our activities. We then introduced the publication at meetings and on our homepage* (the English version is planned). The publication explains contents in the following steps, renovation construction, plant verification test, performance test, and rated power operation, for which we pay close attention to characteristics in each step. We also use the casebook for managing accidents and troubles which is caused by an employee. For collecting cases, we referred to  a casebook entitled “Potential Troubles in the Reprocessing Plant during a Plant Performance Test using Uranium”, which was published by Rokkasho Reprocessing Plant (reference book 1).

2. Outline and Distinctive Characteristics of Monju

Monju is a sodium cooled FBR using uranium-plutonium mixed oxide.  The reactor produces more fuel than fuel spent by utilizing fast neutron generated by fission.  The reactor will  make effective use of  uranium resources by reusing reprocessed spent uranium. Uranium resources is thought to be exhausted  in about 100 years, yet it will make the resources usable for the period of more than a few centuries in this way.  We can continue to use nuclear power for a long   period in the environment that produces no carbon dioxide as cause of global warming.
Additionally FBR will bring decrease in environmental load because it can burn  long-lived radioactive waste as fuel and can covert high level radioactive waste generated in reprocessing spent fuel into short-lived radioactive materials.
To make use of advantages of the reactor, it is important to use sodium as coolant. That is the distinctive characteristics of the reactor. Because sodium is a solid in the normal temperature, melts in 90c degree and boils in 880c degree, it is not necessary to pressurize sodium to control the coolant boiling. For this reason, the structure of the plant is for high temperature and low pressure.  Since sodium is chemically active and reacts on air or water, we have taken all necessary measures for  prevention of  sodium leaking by providing the sealed structure by welding and so forth. We also have diverse safety measures in cases of sodium leaking. Our ultimate goal is to advance technology development for a high performance reactor. For Monju, we resume the operation and to prove its reliability as power plant as well as establishing the sodium handling technology.

3. Progress after Incident of Monju

We carried out the intensive inspection of Monju for cause determination and the safety inspection of the whole plant in collaboration with external experts after the incident of sodium leak. Based on lessons learned from the incident, we  have also carried out the inspection which covers both aspects of  physical and non physical means, all the way from other facilities to quality assurance activities, and instructions and manuals. We also have laid down the solutions to troubles and the preventive measures for recurrence of the trouble, which has been implemented.
On the other hand, due to a succession of the following incidents, the first accident in sodium leaking, improper actions of hiding the video tape which recoded the accident scene, and delay in informing the accident to the outside,  the responsible organization lost their credibility, which organization was then Power Reactor and Nuclear Fuel Development Corporation and the name changed to “Japan Nuclear Cycle Development” later, and is now under Japan Atomic Energy Agency referred as the organization in this article). These incidents draw a social problem, which eventually made the organization to be resolved and reformed.   
For the local community, we initiated a meeting to explain the significance of development of Monju, the result of  the whole inspection, and  cause determination of the accident. We also opened the accident site to the public. Since 1997, we have held town meetings at a city hall and the like in every single municipality. After these town meetings, we started a cycle meeting, in which we ourselves show up and hold a small meeting  to explain about Monju and to exchange participant’s opinions. We had such meetings as often as 1,013 times by July, 2009.
In the following year of the accident,  those who takes on public relations  at our Tsuruga head office thought that they should be able to do something for the accident and then formed a voluntary woman group named “Apple”, which has played a central role in these activities and are still working actively (pic-1).  In April 2009, the group received a prize for Science and Technology in category of promotion for public understanding from Minister of Education, Culture, Sports, Science and Technology. It appreciates their continuously positive activities in the community on promoting people’s interests in science and technology, and awareness of nuclear power, the prize appreciated their manner to speak on what they learnt within their ability, in their own language, and in the citizen’s view. We understand that it was awarded in expectation of their activities which make contribution to awareness of fast breeder reactor and nuclear fuel cycle.
Picture 1 Cycle meeting by Apple
In the meantime, we started visiting local companies within Fukui Prefecture as the organization came to open their own patents to private companies from October, 1998, and besides we visited their working sites for the cycle meeting as well. These approaches have brought an opportunity for the local business community to have a technology exchange. Now we see some companies taking the patents and doing their business with them.  The exchange in this way was spreading out in the local business community where used to be in less chance to do so.  We are sure that the activities led a way to Fukui Energy Research & Development Centralization Plan made in 2005, which will be a heart of industry and academia collaboration.
Regarding further progress of Monju, the regulatory body conducted the safety review of the renovation construction plan to implement remedies for sodium leak submitted by the organization, which review was made based on the results of the cause determination and the whole safety inspection. In  December 2002, the government subsequently gave a permit for the renovation contsruction. On the Fukui Prefecture side, as unrest was mounted to people in the community,  a special committee on nuclear safety of Monju (chairman, Shinpei Kojima,  then president of Fukui University) was set up to study the safety of Monju in technical and professional view points. The committee reported to the Governor of Fukui prefecture in November 2003 with the conclusion of the committee that the renovation construction makes safety of Monju advanced to a greater extent,  and that Monju is a sufficiently safe and a technologically proved facility. As we received these deliberations and the approval of the local community for the renovation construction to implement corrective measures to sodium leakage, we started the construction February, 2002, for which the completion test was completely achieved later. In August, 2009 we successfully completed the plant performance test and refueling to make sure integrity of both facilities and systems of which operations had been in a shutdown for a long period of time. We are now in preparation to resume the operation.

4. Casebook for Approaches to Accidents and Troubles

Regarding approaches to awareness activity such as holding an explanatory meeting, Special Committee on Nuclear Safety of Monju gave us a comment that the organization should try to open information more actively than usual.  The organization responded to the comment by having a plan to promote public relations and dialogue with the community, that is Risk Communication and is to promote awareness and confidence in the local community, in which includes such activity on provide the local community with information of potential accidents and troubles, and safety assurance program for Monju.
In the fall of 2004, we started producing a casebook targeting for the renovation construction. The publication was completed and has been disseminated widely before starting the key field work to cut sodium piping sets.  Moreover, in August, 2006, before the beginning of the completion test, we also made and distributed a trial version of the casebook covering potential accidents and troubles in operations, and then we received diverse comments on the structure, its purpose and other from the local community as well as the people concerned. After this endeavor, we revised the casebook reflecting analysis of the Niigata-ken Chuetsu-oki Earthquake case in February, 2008.

4.1 Structure of Casebook

The casebook mentions as part of the purpose that it is crucial to have all parties concerned, which are people in the local community, the local government, the emergency and fire fighting stations and the news media, to understand what will be the consequence, what are the prevention measures, how we should response to the accident and trouble if happened.
For the casebook design, we take in the fact that Monju is still a nuclear reactor amid research and development and also is different from a light water reactor in the working mechanism, for which the casebook is designed in an easy-to-understand style by providing sections of development significance, basic plant structures and mechanism to secure safety.
Typical cases in potential accidents and troubles are selectively put in the casebook, in which lays down the following items, the outline of a case, the impact, the immediate actions to be taken, the recovery time, the category for public release, preventive measures, the international nuclear event scale, and the brief drawing of the location involved the incident. The individual items are as follows:
  • The outlines includes the description of where and what happened in Monju and of what was an operational condition of the plant at that time as well as possible causes 
  • an item, “the impact” describes for impacts to the surrounding areas where people in the community are most concerned about,
  • an item, “the impact to the safety” describes in view of the crucial safety measure to bring a reactor into shutdown, cooling-off, and  sealing-off as immediate action,
  • an item, “the impact to the field workers” describes for operators and workers in the plant,
  • an item, “the impact to the plant” describes for how the plant should be operated  amid the trouble,
  • an item, “the actions and the period of the recovery time” describes actions to be taken for the operations when the accident occurs, and recovery steps to be taken and time necessary for recovery,
  • an item, “category of public release”, describes the category and the code for which is depending on a kind of the trouble and is used for releasing information to the public, the one as “A” is for the case that needs to release immediately as ruled by the law or on an agreement, and the one as “B” is for the case that is less serious in trouble and information is released on the regular weekly report,
  • an item, “the preventive measures” describes how the preventive measures are taken against occurrence of the potential incident on Monju.
Besides, the casebook shows, as self-assessment, a level of seriousness of the accident and trouble that is classified by International Nuclear Event Scale. The casebook also shows the location of the accident and trouble for which is pointed on the system chart of Monju, and also attaches the illustration of the case (fig-1).
Fig.1 Outline of the potential troubles in Monju

4.2 Cases Selected for the Casebook

We have fully been bringing together information of troubles on FBR as well as a light water reactor at home and abroad, and have made use of the cases for improvement of the Monju operations.  Cases selected in the book include 413 incidents on FBRs abroad, 15 incidents on FBR, named Jyoyo, 54 incidents on Monju , and 390 incidents on other nuclear plants in Japan. These are mostly incidents to be reported in accordance with the law and the administrative order, however incidents on Monju so far are in mostly minor troubles which are handled as not necessary to inform. Troubles on a fast breeder reactor are mainly ones in foreign countries, of which more than half are related to sodium such as sodium leakage and, sodium fouling and clogging(fig-2).
Fig. 2 Potential troubles expected from the operating experience in overseas FBR
The casebook includes together with the cases that had gone through a safety review by the regulatory body when processing the application for nuclear reactor construction permit for Monju.  12 cases are selected to be presented as severe cases in the casebook from similar ones where handle abnormal transient in the operation and accident analysis, which is as analysis of safety review by the regulatory body.
To narrow down roughly 900 cases into possible cases for Monju,  we reviewed the difference in design between Monju and the others that caused an accident, in which eliminated the ones that Monju already has taken special measures in the design stage. We sorted out the similar accidents and troubles in groups and put 122 cases  (Table-1) together in a casebook. Regarding potential troubles at the renovation construction, we have had no precedent of the similar case at home and abroad. For this reason, we made risk analysis by a risk prediction method referring to the specifications and instructions of the renovation construction for measures against sodium leakage, which is performed at each step of about 250 works of the construction. We included 27 potential trouble cases in the casebook including ones caused by human error at the construction.
Table 1 Number of potential trouble events
Category # of Cases
Na leakage (primary/secondary Na, fuel storage Na) 16
Na fouling/clogging, mixture of foreign materials in Na 14
failure of instrument/control systems 14
failure or malfunction of equipment 14
leakage of vapor, seawater, water, chemicals or oil 9
structural deformation (vessels, piping, fuel assembly, heat exchanger) 8
radiation leakage (gas, liquid, solid) 8
during completion tests, plant performance tests, or performance tests 4
fire (electricity, turbine oil, controlled area, welding) 4
failure of electrical system (diesel, power-generating facility, electric motor) 4
Sodium-water reaction (small scale, medium/large scale) 2
fuel damage  2
others (physical injury, events governed by outside factors, human error) 23

4.3 Continual Efforts

In making and publishing the casebook, we have been advised to a great extent by an external advisory body on safety activities, primarily our own activities on maintenance and quality control to secure and enhance safety of the facility. The external advisory body is committee on nuclear safety of Monju opened to public and chaired by Professor Emeritus of Kyoto University, Hideki Nishihara.

The major advice and recommendation we received from them are as follows:
  • it is good to explain potential incidents by assorting them into two groups, one that a magnitude of the incident is clear and the other one that the magnitude should be within an assumption,
  • it is good to present the casebook regarding renovation construction, which is separated from the one for  operations, to people in the local community first and then to take improvements into action,
  • each case needs to have something to illustrate time series of a trouble flow ,
  • it would be appropriate that the casebook presents information well balanced with both aspects of  the cause and a solution to the trouble. For example in a case of oil leaking, it is important to show such information that the leaking is caused by o-ring ageing degradation, and that the remedy is simply done by changing the o-ring,
  • it would be suggested to make the casebook in collaboration with people in the local community,
  • the casebook is based on past incidents, of which analysis and assessment  should be made  rightly, and the results be shared with engineers in the organization.
This casebook, “casebook for potential troubles during the operation” as a tentative version was made and then improved by taking in comments from experts in a fast breeder reactor and experts in the area of risk communication, of which presentation was made to the regulatory body before publishing. The casebook is also made for the field workers at the plant to check diverse measures against potential accidents and troubles in operation of Monju. In the same time, the casebook has also been used for safety awareness.  As another version of a casebook, we have fully been used a leaflet made by “Apple”, in which contents are made easy.
When briefing a general outline of the plant renovation construction and when opening the site  to mass media, we  have explained potential accidents using a casebook for the plant renovation construction.  Recently we are taking actions to promote more profound understanding for the public, for example, we had a briefing session on the refueling to mass media before the arrival of refueling for the first time in 15 years, in which we explained the potential troubles in handling the fuel as shown in the casebook.
The public has shown strong interest in handling of sodium as coolant which is part of the distinguishing feature of Monju. We will make a public announcement about the alert for a sodium leakage warning, for which we clearly define how to inform the incident and what are the action to be taken in case when we receive an alert for a sodium leakage warning. The alert information is  defined further in detail, which are as follows: we will inform the incident as “trouble information” in case that the leakage is confirmed to be true, as “maintenance quality information” in case that is declared as “deviation from limiting condition for operation”, or as “other information” even in a case of a false alert. However it is not considered as sodium leakage alert in a case of an alert made falsely by a previously planned work that presumably causes it.

5. Summary

Monju is a facility aiming at research and development. In the operation, safety first is the most crucial issue. We need to move on in dissolving a fear of the community people, but nevertheless various troubles could happen. We must play important roles to overcome these difficulties in dealing with a nuclear reactor and to promote the public understanding of which includes on how we cope with troubles at the time of the occurrence. There are 15 nuclear power plants in Fukui prefecture. Monju under the development is unfamiliar to the outside as opposed to a light weight reactor which has a long history of operation experience. For that reason, we still need more such activities as mentioned earlier.

We know the strong voice that there is no circumstances where the party involved themselves explains a trouble by way of citing such a phrase, “humans make a mistake and machine breaks down” as we used to say, and the voice that it is a plant operator’s duty to dissolve the problem.  

On the other hand, we know now the reality that our society has a good chance of facing risks in our daily life, for example such risk as we experienced  BSE (Bovine Spongiform Encephalopathy) and the similar incidents. As seen in the cases of food, we are now capable of sharing of information on the risk and that climate is establishing itself in our society. We have transformed ourselves into a way of life where we can share easily idea of risk. Another significant factor lies in the concept of a risk management looming out in society.  When we had a briefing of the casebook for persons concerned in the local government, they appreciated that we touched on the situation where it was unthinkable the casebook, during the time of the accident on Monju, for the operator to takes in making and distributing, and also appreciated the fact of change in the public attitude towards information disclosure.

For a revised version of the casebook, we are putting different cases together, which reflects the case of outdoor exhaust duct corrosion found in Monju  2008 as well as cases in other plants at home and abroad, and moreover it includes potential accidents and troubles during the core verification test as the first step towards resuming its operation.  We hope that the revised version will contribute to mutual understanding of Monju, and will help further development for diverse ways of risk communication as the time for resuming of the operation is approaching.

We will keep revising the casebook to reflect back new knowledge and information, and inputs from the parties concerned, and moreover we consider to make every endeavor to improve our works in collaborate with FBR plants overseas.


[1]  Japan Nuclear Fuel Limited; “potential troubles and solutions” (10, 2004)