Chernobyl: Assessment of Radiological and Health Impact
2002 Update of Chernobyl: Ten Years On

Chapter VIII
Shutdown of the Chernobyl plant*

The agreement to build the Chernobyl power plants dates from 1966, when the former Soviet Union decided to develop nuclear production of electricity. The RBMK reactor design also dates from this period. Six 1 000 MWe reactors were planned at that time.

Unit 1, which begin production in 1977, stopped in November 1996. In December 1997, it was decided to decommission.

Unit 2, which was first connected to the grid in December 1978, was stopped in 1991 after damage due to fire. The Ukrainian national authorities decided to definitely close this plant in March 1999.

Unit 3, which started in 1981 has had many shut downs for maintenance, inspections and repairs since 1997. In June 2000, the Ukrainian authorities decided to close it definitely on 15 December 2000.

Units 5 and 6 were under constructions at the site at the time of accident, but were never finished.

After the accident in reactor 4 and the fire in reactor 2, western countries attempted to persuade the Ukrainian authorities to definitively close reactor number 3. This was a priority for many countries in the bilateral exchanges and agreements with Ukraine. This western pressure crystallised when the Ukrainian parliament decided, in October 1993, to cancel a 1990s decision which recommended to immediate stop of all RBMK reactor construction, and the closure of the Chernobyl site. Later the European Union and the Ukraine concluded, on 20 December 1995, a memorandum of understanding for the closure of Chernobyl plant. In exchange for the definitive closure of all Chernobyl plants, the European Union (in the framework of TACIS programme) and western countries agreed to provide financial assistance to the Ukraine for the provision of electricity, and to solve social problems resulting from the closure of the site. Financial projects were estimated, in 1995, to be 2.3 billion dollars. A part of these funds has been committed to modifications of reactor number 3, creation of building for used fuel, and workshops for liquid and solid waste treatments.

Later, many other projects relating to the modernisation of VVER reactors have been discussed with the European Bank for Reconstruction and Development (EBRD).

Concerning the stabilisation of reactor 4, the safety analyses for all installations described in the next paragraphs will be jointly performed. From the European side, the Riskaudit consortium, a common subsidiary of the French IPSN (now the IRSN) and the German GRS in collaboration with ANPA (Italy) and AVN (Belgium) under contract of the European Union will perform this work. From the Ukrainian side, the Ukrainian State Scientific Technical Center for nuclear and radiation safety (SSTC) will perform the work. The two groups will combine their analyses for the benefit of the Ukrainian Safety Authority (Nuclear Regulatory Department, NRD).

Preparation of the definitive dismantling of the Chernobyl power plant

It is planned to build different installations on the Chernobyl site to accomplish the dismantling of the reactors. These facilities will be for the:

Storage of used fuel

Used fuel coming from the three reactors is today stored inside reactor cores, in pools close to the reactors, and in a former storage building. A new dry storage installation is under construction, using the Nuhoms process, certified by the US Nuclear Regulatory Commission. Two other building are under construction. The first new building will be used for the cutting of fuel rods, and the storage of control rods. The second building will consist to modular cells in which containers including fuel will be inserted. Each cell will receive one container. Cooling will be passive. It is planed to build 256 cells in 10 years. Funding for this operation is provided through the EBRD, Westinghouse (USA), Bouygues and Campenon Bernard (France), the operating western companies for the Chernobyl Nuclear Power Plant operator.

This project began in June 1999, and buildings are under construction and forecast receiving operating licenses in the beginning of 2003. Transfer of all fuel assemblies is planned for the following ten years.

Treatment of liquids effluents

Liquid effluents, containing mainly 60Co, 137Cs, 134Cs, are stored on the site in two groups of tanks. The first group contains 5 outside tanks of 5 000 m3 each, the second contains 9 tanks of 1 000 m3 in individual cells. Today 26 000 m3 are stored, the total capacity of the installation being 34 000 m3.

The treatment of these liquid wastes is a delicate operation, requiring the construction of ventilated boxes for pumping operations. For the 5 000 m3 tanks, it will be necessary to construct coverage.

Another building has been under construction since 2000, and will be used for the transformation of these liquid wastes into solid wastes. Licensing of this facility is planned for completion by the end of 2002. Transformation operations will consist of mixing liquid wastes with concrete. The resulting solid packages will be stored in a surface storage center close to Chernobyl. All effluents produced by dismantling operations would be treated in these installations. Liquid effluent processing operations are planned to last for ten years.

These buildings are funded by the EBRD, Westinghouse (USA), Belgatom (Belgium), SGN (France) and Ansaldo (Italy).

Treatment of solid wastes

A new installation for solid waste treatment is needed. Low and intermediate-level wastes were generated by reactor operations, and consist of metal, concrete, plastic, wood and paper. Today, these solid wastes are stored in a decrepit building consisting in three compartments, the two first of which (1 000 m3 each) are quite full. The third compartment (1 800 m3), containing the most highly contaminated wastes, is 20% filled, bring the total volume of waste in this facility to approximately 2 350 m3. Currently, these wastes are covered with concrete which must be removed and itself conditioned for disposal. This existing storage installation can be used for waste conditioning, but only at a rate of 3 m3 per day.

The solid wastes produced during dismantling of the reactors will also need to be treated. Wastes will be sorted, and low and intermediate-level wastes will be stored in the surface storage site, outside the exclusion area of Chernobyl site.

The most highly contaminated wastes will be inserted into waterproof containers for temporary storage before future treatment. The workshop to perform this waste conditioning will be built for a daily production of 20 m3.

These operations will be funded by European Union under the framework of the TACIS programme. A call for proposals is in progress. The choice of the western contractors will be decided for starting of operations at the end of 2003, beginning of 2004. These operations are planned to last for at least 5 years.

The Sarcophagus

In the aftermath of the accident several designs to encase the damaged reactor were examined. The Sarcophagus, build in only few weeks after the accident, is largely described in Chapter VII, along with the potential residual risks that the sarcophagus currently poses. Today, work is needed to reinforce the existing sarcophagus to prevent or to limit radioactive dust releases, and to reduce the risk of collapse either spontaneously of due to natural catastrophe. A list of about 15 tasks has been established on the basis of estimated risks. Today, only priority tasks have been performed, including the reinforcement of a common ventilation chimney for reactors 3 and 4, and the reinforcement of the roof concrete girders.

A new project, SIP (Shelter Implementation Plan) was launched in 1998, to last for 8 years, by a working group of nuclear safety experts coming from the G7 countries and the Ukraine. This project is funded by the EBRD, and its cost is estimated to be 760 million dollars, 50 million of which will be paid by the Ukrainian government.

The SIP project has two main objectives; reinforcement of the sarcophagus and enhancement of protection of workers and environment. Five subsidiary objectives have been defined:

This project is performed by a group independent from the Chernobyl plant operator, and is assisted by a project management team unit including Betchel and Battelle from USA, and EDF from France. This organization has to main tasks: to define the elementary tasks for reaching SIP objectives, and to request approval from competent Nuclear Regulatory Department of Ukraine. Once more, the Ukrainian NRD will be assisted by the SSTC and western companies (Scientech and Riskaudit).

Reinforcement of roof girders had involved about 300 workers. The collective dose estimated from Ukrainian information is 3.5 man Sv, 10% for preparation and 90% for the actual work. Preparative works had involved about 100 people, the highest doses were lower than 15 mSv, and approximately ten people have received doses ranging from 10 to 15 mSv. The reinforcement work has involved about 200 people, about 20 of whom have received doses ranging from 30 to 40 mSv.

Ukrainian authorities claim that no workers have exceeded fixed the limit for these operations, i.e. 40 mSv. The collective dose objective for the fifteen tasks planed in the SIP project is 25 man Sv. Particular attention is being paid to the monitoring of worker internal contamination.

Sarcophagus database

In the framework of "German-French initiative", the IRSN (France) and the GRS (Germany) have collaborated with the operator (CHNPP), the International Scientific and Technical Center (ISTC) of the Ukrainian Academy of Sciences, the Ukrainian National Engineering and Sciences Institute (NIISK), and the Kurchatov Institute (Moscow) to produce a database on the "health status" of the sarcophagus.

This database will facilitate and improve estimation of radiological risks inside and outside the damaged building, and validate the today's radiological protection guidelines. This database will be used by SIP projects operators. When finished this database will allow workers and planners to take a virtual visit of the sarcophagus and its immediate surroundings. This database is based on:

The first version of this database was transmitted to the Chernobyl Center in June 1999.

The social consequences

A large part of the 7 000 Chernobyl workers are living in Slavoutich city, 50 km east of Chernobyl. Ending the operation of the Chernobyl power plants will reduce manpower needs on the site by about 2 000 people.

The closure of the Chernobyl site will be an additional stress on this region, which has already suffered extensively as a result of the accident. The social, economic and personal effects that the loss of employment at the site will have on these individuals, these cities and this region should be studied and taken into account in any final resolution of this situation.

 

*This chapter was prepared with the assistance of E. Gailliez and J.B. Chérié (IPSN), (IP00, IP001).

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