Possibility for Incineration of Spent Graphite Sleeves From Plutonium-Production Reactors of the SGCE (Tomsk-7)

For the lengthy process of different reactor types operation, huge amounts of spent graphite were accumulated in several countries. Spent reactor-grade graphite constitutes the largest fraction of the solid radioactive wastes accumulated all over the world. So, search for ways of spent graphite utilization is an urgent problem of international character. The purpose of the present work is to evaluate radioactive contamination of spent graphite sleeves from decommissioned reactors I-1, EI-2, ADE-3 of the Siberian Group of Chemical Enterprises and to consider a possibility for spent graphite sleeves utilization by incineration. Planning of actions on spent graphite management requires to take into account the reactor type, properties of spent graphite, peculiarities of spent graphite usage and storing. Beginning from 1996, authors have conducted the detailed studies on radioactive contamination of spent graphite from the SGCE reactors. In these studies, contents of some radionuclides in spent reactor-grade graphite were measured, including content of isotopes generated by neutron-induced activation of impurities (⁶⁰Co, ³H, ¹⁴C, etc.) and the isotopes generated in result of uranium penetration into the graphite reactor components (¹³⁷Cs, ⁹⁰Sr, ^241,243Am, ²⁴⁴Cm, Pu isotopes, etc.). It was revealed the largest contribution to the graphite radioactivity was given by ¹⁴C. Using data on inhalation and ingestion rate for different age groups, the evaluations were carried out for ¹⁴C intake into human organism with air and food. Analysis of the results obtained in the performed investigation enabled us to make the following conclusions: 1. the most part of the SGCE storage vaults where spent graphite sleeves are disposed of do not meet contemporary requirements; 2. the radioactive contamination level of spent graphite sleeves from the SGCE reactors allows their utilization by incineration at the SGCE territory; ¹⁴C exhaust into the atmosphere will not cause any significant risk of negative consequences for human health of cities Seversk and Tomsk population; 3. spent sleeves incineration and subsequent storing of incineration products can not lead to appearance of nuclear dangerous situation; 4. there is an available technology and associated equipment for conduction of experiment on spent graphite incineration. Thus, it can be concluded that nowadays there are all the conditions for planning, preparation and conduction of fullscale experiment on incineration of some spent graphite sleeves taken from the SGCE storage vaults. The results obtained in the test graphite incineration will allow to evaluate and, if necessary, improve the utilization technology and the applied equipment.