Dose Rate Calculation and Shields Estimation for the Reactor Vessel Model Simulation Concept using MicroShield Code at the VVR-S Nuclear Research Reactor, Bucharest Magurele

I. Iorgaa, b aHoria Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), P.O. Box MG-6, RO-077125, Magurele, Romania bFaculty of Physics, University of Bucharest, P.O. Box MG-11, 077125, Bucharest-Magurele, Romania

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The VVR-S Nuclear Research Reactor owned by Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), was built in Romania between 1955 and 1957. The research reactor operated until 1997 and was permanently shut-down in 2002. During his life-time, it was functional for 113467 h, including 2000 h at 3.0 MW power. It had a utilization factor of 65% with an average of 1 MW thermal power. VVR-S means that is a thermal neutrons reactor model S moderated cooled and reflected with distilled water, fueled with enriched uranium 10% in the beginning and 36% subsequently. Maximum values of dose rate at external aluminum vessel wall were between 3.5 mSv/h. and 9 mSv/h. Maximum values of the inner aluminum vessel near the active core were between 7.85 mSv/h. and 16.62 mSv/h in accordance with the location the experimental channels. Problematic dose rate appeared on the vessels parts that included reactor core with maximum value that was 140 mSv/h at 10 cm, near thermal column inside the aluminum vessel. Other internal values vary between 400 Sv/h and 35 µSv/h at 10 cm from the wall. The principal radionuclides implicated were: 60Co, 137Cs, 152Eu and 154Eu with theirs correlation factors respectively for (90Sr-90Y) for beta active radionuclide evaluation. We needed to respect the radiation protection program dose limit of 20 mSv/year for the personnel professionally exposed. For this reason the simulation of the potential dose rate exposure and the shield calculation was necessary.

DOI:10.12693/APhysPolA.135.1087 topics: modelling, methodology simulation, dose rate assessment, exposure rate