Tomsk-7 Graphite Contamination
Determination of Radioactive Contamination of Weapons-grade Pu Production Reactors Graphite of Siberian Groups of Chemical Enterprises, SGCE, (Tomsk-7).
Tech Area / Field
- FIR-DEC/Decommissioning/Fission Reactors
8 Project completed
Senior Project Manager
Tocheny L V
MIFI, Russia, Moscow
- Siberian Chemical Combine, Russia, Tomsk reg., Seversk
- CEA / DCC / CEN Cadarache, France, Cadarache\nFRAMATOME, France, Paris La Défense\nPacific Northwest National Laboratory, USA, WA, Richland
Project summaryAt present time more than 10 reactors-producers of the weapons-grade plutonium have been put out of operation. The main source of radioactivity during dismantling these reactors after unloading of fuel is graphite, its amount can reach thousand tons. High radioactivity of graphite is result of neutrons interactions with carbon and its impurities, and also result of presence of fission products and products of construction material corrosion which can get into graphite stack.
Similar problem will arise in the not very distant future for uranium-graphite reactors RBMK which will be put out of operation.
It is difficult to estimate by calculation the radioactivity of reactor graphite due to lack of information on initial composition of impurities, irradiation history, incidents (trickling of water into a stack, seal failure of fuel elements and others) which could take place during long time of operation of these reactors (30-40 years). So, reliable prediction of radionuclides contents isn't possible without detailed experimental investigations results of which will be used for validation of calculation methods. The available information from abroad cannot be used directly because of differences in technology of graphite production, design and conditions of such reactors operation. The main difference is graphite of the shut down Russian reactors was used in contact with nitrogen that caused high 14C of graphite that gives the most contribution into its radioactivity
At present time the first preparatory stage of investigation of graphite samples from the Russian reactors was fulfilled at МЕPhI and SGCE. Preliminary analyses of contamination of graphite with tritium, carbon–14, fission and corrosion products, actinides using beta-, alpha-, gamma- and X-rays spectrometry and the original methods have been carried out at MEPhI in cooperation with specialists from SGCE. Analyses of samples from the reactors AV-2, EI-2, AV-3, AD, ADE-1 were made using these methods, obtained results were published, reported and discussed partly with foreign specialists.
Finance support of ISTC will make it possible to continue and complete this work, to provide with necessary experimental information and to develop a semi-empirical method for estimation of radioactive contamination of separate parts of Russian reactors graphite stacks and graphite bushings. Analysis of data that will be obtained will make it possible to improve interpretation of processes of production and migration of radionuclides in graphite, that will lead to prediction of situation at operating RBMK reactors with more accuracy, including in connection with actuality of problems of putting out of operation these ones.
Specialists from SGCE (sampling, data on irradiation conditions) and specialists from МЕPhI and IPhCh (measurements, treatment of results) will take part in works under this project. In the third year of the project fulfillment measurements will be transferred to SGCE, where corresponding equipment methodical basis will be created by this time. Analysis of obtained results,