Complex of Works to Support BN-350 Fast Reactor Decommissioning

30 Projects to the 30th Anniversary of NNC RK!

Project No.9. 1999–2010. Complex of Works to Support BN-350 Fast Reactor Decommissioning

The direct decommissioning of BN-350 reactor was preceded by a large volume of research, organizational, project, design work in which the managers and specialists of scientific, project and production units of RSE NNC RK took an active part.

In 1997, the US Department of Energy and the Ministry of Science-Academy of Sciences of the Republic of Kazakhstan concluded the Executive Agreement “Concerning Long-Term Storage of BN-350 Nuclear Materials”.

The basis for starting of the work was the Resolution of the Government of the Republic of Kazakhstan as of April 22, 1999, No.456 “On the Decommissioning of BN-350 Reactor in Aktau, Mangystau Region”. Since at the time of the Resolution was issued, the decommissioning project had not been developed and it was decided to proceed based on a specially designed and approved Priority Measures Plan (PMP), and the “Main Provisions of BN-350 RF Decommissioning Project”.

The main provisions provide for the following areas of work:

• The first stage. Measures for BN-350 reactor spent nuclear fuel long-term storage;
• The second stage. Measures for handling with BN-350 RF liquid-metal coolant;
• The third stage. Measures for handling with BN-350 RF liquid radioactive wastes;
• The fourth stage. Measures for handling BN-350 RF solid radioactive wastes;
• The fifth stage. Measures for BN-350 RF buildings, facilities and engineering systems preparation for reliable long-term storage.

The first and most important stage of plan included the work on handling with BN-350 spent nuclear fuel (SNF). During its implementation within the period of 1999 to 2010, RSE NNC RK took an active part in conducting feasibility studies on possible use of dual-use containers for transportation and storage of BN-350 SNF, development  of special technical regulations  for BN-350 decommissioning project, development of  BN-350 SNF handling technology.

After positive decision about utilization of dual-use containers and siting of the long-term storage, specialists of RSE NNC RK in 2008 developed the project “Long-Term Storage at RRC “Baikal-1” and the Refueling Point of BN-350 RF Spent Fuel Transport Packaging Containers”, as well as the safety justification report of BN-350 SNF handling.

At the end of 2009, after completion of the construction and installation work, certification and registration of the installed equipment, the storage area at RRC “Baikal-1” and the reloading point of transport packaging containers in Kurchatov were put into operation by the state acceptance commission.

In 2010, 60 transport packaging containers were transported by rail and road transport from Aktay and then were placed at RRC “Baikal-1” for long-term storage.

The implementation of the first stage of the plan made it possible to convert BN-350 reactor into nuclear-safe condition, thus the Republic of Kazakhstan fulfilled all obligations for the most important part of PMP for BN-350 reactor decommissioning.

The second state of PMP included the work on handling with liquid metal coolant of BN-350 reactor.

In 2002, RSE NNC RK developed a “Cesium trap” project, the aim of which was to reduce the amount of radioactive cesium (Cs-137) in the BN-350 primary sodium. The implementation of the project allowed to reduce specific activity of radioactive cesium (Cs-137) in sodium almost 2000 times, from 7.25×10⁸ Bq/kg to 3.7×10⁵ Bq/kg.

In 2003, RSE NNC RK developed the project “BN-350 Pressure Manifold Drilling Device” to perform drilling at a depth of more than 13 m in a sodium medium at a temperature of 280-300 °C, as well as to implement “Drainage Device” project. Implementation of the projects allowed to remove more than 1 ton of sodium from the non-draining space of BN-350 reactor vessel.

In 2005, RSE NNC RK developed working draft “Sodium Coolant Processing Facility” according to which the equipment was manufactured and installed, as well as start-up and adjustment operations were carried out in the building of BN-350 sodium processing facility. In 2015, the project was amended, taking into account the requirements of the Environmental Code of the Republic of Kazakhstan.  The facility is designed for processing 610 m³ of the primary sodium in 70% alkali, with the possibility of subsequent processing into geo-cement stone at a promising processing area.

The implementation of these measures made it possible to ensure nuclear safety, as well as to reduce radiation factors in preparing BN-350 plant for long-term storage.