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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:28 |
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Conference: Bucharest University Faculty of Physics 2016 Meeting
Section: Atomic and Molecular Physics. Astrophysics. Applied Nuclear Physics
Title:
Evaluation of Gamma Emitters Activity in Spent PHT Mechanical Filters at CANDU Stations
Authors:
Alexandru Emilian NEDELCU, Alexandru CHIROSCA, Octavian SIMA
Affiliation:
1) Facultatea de Fizica Bucuresti
2) CNE Cernavoda
E-mail
anedelcu@cne.ro
Keywords:
CANDU, reactor, gamma, spectroscopy, purification, corrosion, fission, efficiency, calibration, dose
Abstract:
Currently, in all CANDU nuclear stations, one of the most challenging areas of interest consists in evaluation of radioactivity inventory retained by purification system of PHT (Primary Heat Transport System).
The In-Situ Gamma spectroscopy measurement techniques combined with dose rate measurements along mechanical filters profiles proved to be the most adequate way to achieve the following objectives:
- evaluation of PHT mechanical filters efficiency (by comparing the activity retained on filters and overall radionuclide production on a specific period of time);
- optimization in operation of purification systems (time of operation, seize of filtration);
- understanding of correlations between PHT chemistry changes and radionuclides activity transport in PHT system;
- data required to establish appropriate methodologies for treatment and conditioning of radioactive waste;
The measurement methodology presented in this paper was tested at Cernavoda NPP in December 2015 and it includes:
- segmented ã dose rate measurements (by using FH 40 GL-10 and FHZ 632 L-10 proportional counters used for highly sensitive dose rate measurement of X-ray and gamma radiation developed by Thermo ScientificTM) along the profile of mechanical PHT filter to determine the spatial distribution of ã dose rate;
- segmented in-situ ã spectroscopy measurements (by using INSPECTOR 2000, a HPGe detector based system developed by Canberra) to determine spatial distribution of radionuclides and overall ã emitters activity retained on the filter; system efficiency calibration had been performed by ISOCS simulation software;
The measurement results indicate a non-uniform distribution of both ã dose rate and ã emitters activity along the profile of PHT mechanical filter. A dominant contribution of insoluble activated corrosion products (eg Co-60) and a very low one for fission products (eg Cs-137) had been observed. However, further development of measurement method is required for discrete “hot-spot” identification and evaluation.
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