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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-21 19:06 |
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Conference: Bucharest University Faculty of Physics 2008 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
VVR-S Spent Fuel Shielding Analysis
in a Storage Hypothetical Accident Scenario
Authors:
C.A.MARGEANU
Affiliation:
Institute for Nuclear Research Pitesti
E-mail
cristina.margeanu@nuclear.ro
Keywords:
VVR-S spent fuel, loss of cooling water accident, shielding analysis, spent fuel characteristics, radiation dose rates
Abstract:
Shielding analyses are an essential component of the nuclear safety analyses, the estimations of radiation doses in order to reduce them under specified limitation values being the main task here. The first stage in the spent fuel treatment is the so-called cooling phase. The spent fuel assemblies are transferred from the reactor to a tank in which the water is used to remove the radioactive decay heat and also to provide radiation shielding.
The spent fuel used in the VVR-S research reactor at the Magurele site consists of fuel element types EK-10 and C-36. The nominal power of this research reactor was 2 MW. Reactor operation was stopped at the end of 1997. The average burn up of the EK-10 fuel was 49%; average for the C-36 fuel was 54%. The spent fuel is stored in wet conditions at the site in storage ponds.
The purpose of this paper is to perform a Monte Carlo shielding analysis applied to the VVR-S research reactor spent fuel, in a storage pond hypothetical accident scenario.
In order to estimate the spent fuel characteristic parameters and obtain the source term, the burnup code ORIGEN-S has been used. ORIGEN-S code solves a set of coupled differential equations which describe the generation and transformation of all radioisotopes and provide the final composition of the spent fuel. For both types of fuel, calculations were performed considering the minimum, median and maximum wet storage time, as follows: EK-10: 14 years; 26 years; 40 years; C-36: 9 years; 12 years; 14 years.
For the shielding calculation purposes, the following storage pond hypothetical accident scenario has been considered: loss of cooling water layer (about 4.5 m in thickness) from a storage pond containing 60 spent fuel cassettes (full capacity loading) by the cassettes level.
The radiation dose rates to the storage pond wall and in air, at 1 m distance from the storage pond wall, for the two types of VVR-S fuels, have been estimated, by means of Monte Carlo MORSE-SGC shielding code. Both computer codes are integrated in the Oak Ridge National Laboratory’s SCALE 5 programs package.
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