The system of management of spent sealed radiation sources (SRS) in Russian Federation is based on centralised approach. This system involves 16 regional facilities (with the name “Radon”) which provide safe management of SRS. The scientific and methodical guidance on activities of regional facilities “Radon” carries out the Scientific and Industrial Association “Radon”, Moscow.
Recently the Moscow SIA “Radon” examined activities at regional facilities “Radon” accordingly with the program approved by the State Supervision Authority of Russia (GAN). It was revealed that spent sources are the main type of radioactive waste at these facilities. This is the case both on summarised quantity of accumulated radioactivity (more than 99%) and on general quantity of the containers with waste (more than 80%). The average radionuclide composition of the SRS accumulated at regional facilities “Radon” is as follows: Cs-137 (40%), Co-60 (25%), Sr-90 (22%), Ir-192 (8%) and Tm-170 (4%). The content of other radionuclides in SRS is not more than 1%.
SRS as a rule are disposed of in bore hole type repositories at regional facilities “Radon”. Nevertheless SRS are also stored in containers being placed into repositories for solid radioactive waste. SRS which contain long lived radionuclides are stored until the decision on their final disposal into a deep geological formation.
Not conditioned storage of SRS can not provide safe conditions for environment for a long time. It is necessary to immobilise sources additionally into a suitable matrix material. Supplemental sources inclusion in a lead (or lead based alloy) matrix using Moscow SIA “Radon” mobile plant was carried out at five regional “Radon” facilities as follows: Zagorsk branch of Moscow SIA “Radon”, Volgograd, Ekaterinburg, Nizhny Novgorod, and Ufa. More than 1 million Ci of SRS are stored at present time in conditioned form in bore hole repositories.
In 1998–1999 the Moscow SIA “Radon”, State Scientific Centre VNIINM and Institute of Biophysics of Russian Academy of Science completed a detailed analysis of spent and disused sealed radioactive sources safe storage in bore hole repositories. The analysis has showed that reliable radionuclide isolation from environment during the whole storage time of 500–1000 years is provided through source’s immobilisation in a metal matrix material (lead matrix). Even in the hypothetical case of total flooding with simultaneous damaging of all engineering barriers, radionuclides release will cause a summary dose load not exceeding (5.5–7.5)×10−5 Sv.
Due to very low corrosion rate of lead and low solubility of lead salts there is practically no impact to environment due to application of lead material. This impact was assessed to be very low earlier and confirmed recently by detailed calculations for near surface repositories containing large amounts of lead waste.
Module type mobile plants for source immobilisation can be applied both for standard bore hole repositories and for source immobilising in containers. A new mobile plant to be used at regional facilities “Radon” in Russia is currently under construction at Moscow SIA “Radon”.
The analysis of the work on SRS management shows that the operating system is able to solve basic problems, providing safe conditions for the environment.