TOKAIMURA NUCLEAR ACCIDENT FROM AN OCCUPATIONAL SAFETY AND HEALTH VIEWPOINT

Kansai

A nuclear flash at the JCO company’s Tokaimura nuclear plant on 30 September 1999 resulted in the deaths of two inexperienced workers [see ALU 32 for details]

The JCO Tokai plant employed 120 people. In this facility, uranium was re-processed, and supplied to fuel makers. Apart from being a rare specialist in nuclear material, the facility is one of many medium- or small- sized chemical plants.

The workers at JCO are ordinary people engaged in daily tasks with a focus on safety and productivity. We will re-examine the criticality (uncontrolled nuclear reaction) accident stressing working practices and behaviour from an occupational safety and health (OSH) viewpoint.

On the day of the accident, the work being undertaken at the conversion building was to enrich nuclear material for use with JOYO, an experimental reactor used to obtain various data for the development of fast reactor technologies.

The three major roles of JOYO are conducting irradiation tests on fuel and materials, advancing technology through operation, and experimenting with innovative technology for development of future fast reactors.

Lack of effective OSH procedure at JCO

The Accident Investigation Committee of the Nuclear Safety Committee published an interim report with urgent recommendations, which described the course of the accident. When the accident occurred, three workers, designated as a special crew, had put about 2.4 kg of uranium powder into a 10-litre stainless steel bucket with a specialised acid and water.

The procedure of homogenisation to a uniform consistency was supposed to be controlled using a specially shaped narrow storage column tank on a one-batch basis.

Instead a large precipitation tank with a stirrer was used. The chemical in the bucket was moved to a five-litre beaker through a filter and tipped into the precipitation tank with a funnel. As a result, about 16.6 kg of uranium (equivalent to six or seven normal batches) was poured into the precipitation tank which was originally designed for 2.4 kg of uranium per batch. This probably caused the criticality.

The procedures used were completely different from official specifications for the equipment and methods used, and were not approved by the regulatory authorities.

The worker involved described the reasons for his methods which were directly responsible for the accident:

1. The accumulation tower was only 10cm above the floor, making it inconvenient to put the liquid into the container. Therefore, the remaining liquid in the tower was removed using a dipper. The worker thought it was improper to handle the material in this way, but the equipment had not been improved.
2. It was common practice to put 16kg of uranium into the tower, and he thought that it would be acceptable to put an equivalent quantity of uranium into the precipitation tank, because the tower and the tank had a similar capacity.
3. He was obliged to work in a remote and strange workplace.
4. Although his supervisor gave him no instructions to accelerate the operation including sampling after homogenisation, he wanted to complete these operations earlier to allow new staff, who were scheduled to join the crew in October 1999, to handle the liquid waste process from the outset.
5. The workers were involved not only in the highly enriched uranium handling operation, but also in the low level radioactive waste handling operations, which was a confusing situation for them.

These reasons suggest that there had been no effective or substantial occupational safety and health activities at JCO.

Facility improvement neglected

It is evident that a lack of knowledge by the workers about criticality was directly responsible for the accident, but equal blame should be given to the lack of effective OSH procedures, including facility improvement.

In fact, the workers were aware of the necessity to implement all recommended equipment improvements, but nothing was done. The workers decided to homogenise the uranium in the precipitation tank, which seemed to them the next best method to save time.

The fact that the worker thought that it was acceptable to put 16kg of uranium into the precipitation tank because an identical quantity of uranium was put into the accumulation tower suggests that as a part of routine OSH measures, official operational procedures were not followed.

The operation responsible for the accident was not during the manufacturing process of uranium fuel for light water reactors (which accounts for almost all the nuclear processing plants in Japan and most operations for the JCO company) but was during the manufacturing process of uranium fuels for JOYO. This means that the accident occurred during a process in which special products are manufactured in small quantities.

This operation, which is assigned to five workers - including the three workers exposed to heavy doses of radiation in this incident - is not a routine job. Special attention was therefore required to implement effective safety measures. The operational processes were reportedly examined by JCO officials who approved the use of buckets, although the approval was not documented in any minutes.

Even if this story were true, effective OSH procedures would have integrated improvements by front-line workers, so avoiding the disaster.

Ineffective corporate style OSH procedures

What OHS techniques did JCO follow in its Tokai plant?

The company had sufficient procedures to claim that it operated a safe and healthy working environment. For example it ran a series of educational courses annually to all employees in addition to legally required training for radiation-related workers. Also, it had set up an education programme for different departments every year.

The company encouraged employees to participate in educational seminars organised by external agencies. To check the workplace practices and environment, an internal occupational safety and health committee carried out safety and quality assurance inspections regularly. The company set technical specifications to meet legal requirements for plants where nuclear materials are handled, requiring patrol, inspection and recording at least once a day.

Actually the managers of the manufacturing department and the workplace patrolled the plant at least once every several days, and once per day, respectively. They had equipment and nuclear protection for any abnormalities, and recorded the inspection results. The records were then submitted to the plant and the manufacturing department managers for review, and approved by the safety manager. The inspection records format is very simple. Since a form should be completed every day after the routine patrol, it is desirable to give a brief description, but instead, the forms were simply rubber stamped ‘No Abnormality’.

The rubber stamp reflects extremely ritualised patrol activities, and the form seems designed for it.

Inadequate training

Though Japan has one of the most developed economies, companies like JCO save money by not training staff properly. This is the case in this disaster.

Almost unbelievably, all three workers who were directly contaminated by the accident were inexperienced in handling toxic chemicals, and so did not realise the danger when they mixed eight times the normal amount of this type of uranium.

Two of these men had never previously performed the dangerous task, while the third had done it only once.

Proper training would have educated them about the dangers of working with nuclear material. Instead, the company decided minimal instruction was sufficient, and showed them how to mix the material in much the same way as a bricklayer would make up a small amount of concrete in a bucket. The result of the penny-pinching policy for two of these unfortunates was death.

Effective OSH procedures would have prevented the accident

A key unanswered question is why did the workers engage in uranium processing without knowledge of criticality levels?

The injured workers lacked information about the materials they handled. This led to the accident. If the OHS committee had discussed their concerns about the materials involved and the processes used, or if there had been a system of complaints and recommendations from workers, OHS practices would have prevented the accident.

Another problem is that the equipment was not designed to prevent a criticality accident during any departure from standard procedures. If integrated mechanisms or fail-safe procedures had been incorporated into the equipment use, the criticality accident would not have occurred.

A third assumption is that strict and effective inspection by the Science and Technology Agency or the Nuclear Safety Committee would have identified andy unauthorised procedures.

The accident could have been prevented if effective OSH measures had been taken in the workplace. If fully trained workers had taken steps for a safer workplace, the accident would have been avoided.

The JCO accident demonstrates the need for more effective OSH procedures. The JCO plant which handles highly hazardous materials, including uranium, is subject to safety regulations under nuclear energy laws, local government safety agreements, and regulations under OSH laws.

Although JCO had apparently reported that they were committed to the Nuclear Safety Committee’s regulations or occupational safety, the company’s own OSH procedures had become highly ritualised. The accident revealed the ineffective nature of its OSH operations.

Apart from regulations for hazardous materials, the JCO plant is listed with conventional manufacturing or chemical plants. In this sense the accident casts new light on the quality of OSH procedures in specific workplaces which are seldom reviewed for effectiveness. When asked about OSH activities, plant safety representatives often describe their procedures by presenting records and documents. Records are one thing, but real improvement is another. The three special team members who put 16.6kg of uranium into the precipitation tank, were exposed to a large amount of radiation. Mr. Hisashi Ouchi died in December 1999 after he was exposed to a radiation level of 17Sv, which is several times greater than the lethal amount.

The workers did not intentionally omit standard procedures to speed up their work in defiance known dangers. On the contrary, they were trying to implement what they considered safe measures to reduce the workload.

In this sense, the three workers were the primary victims of the accident.

Source: ALU Issue No. 39, April - June 2001

By Kansai Occupational Safety and Health Centre;
from Japan Occupational Safety and Health Resource Centre
Newsletter No.21 [August 2000]