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Feasibility Study of Beta Detector for Small Leak Detection inside the Reactor Containment

  • 투고 : 2018.10.30
  • 심사 : 2018.12.04
  • 발행 : 2018.12.31

초록

Background: To prevent small leakage accidents, a real-time and direct detection system for small leaks with a detection limit below that of existing systems, e.g. $0.5gpm{\cdot}hr^{-1}$, is required. In this study, a small-size beta detector, which can be installed inside the reactor containment (CT) building and detect small leaks directly, was suggested and its feasibility was evaluated using MCNPX simulation. Materials and Methods: A target nuclide was selected through analysis of radiation from radionuclides in the reactor coolant system (RCS) and the spectrum was obtained via a silicon detector simulated in MCNPX. A window was designed to reduce the background signal caused by other nuclides. The sensitivity of the detector was also estimated, and its shielding designed for installation inside the reactor CT. Results and Discussion: The beta and gamma spectrum of the silicon detector showed a negligible gamma signal but it also contained an undesired peak at 0.22 MeV due to other nuclides, not the $^{16}N$ target nuclide. Window to remove the peak was derived as 0.4 mm for beryllium. The sensitivity of silicon beta detector with a beryllium window of 1.7 mm thickness was derived as $5.172{\times}10^{-6}{\mu}Ci{\cdot}cc^{-1}$. In addition, the specification of the shielding was evaluated through simulations, and the results showed that the integrity of the silicon detector can be maintained with lead shielding of 3 cm (<15 kg). This is a very small amount compared to the specifications of the lead shielding (600 kg) required for installation of $^{16}N$ gamma detector in inside reactor CT, it was determined that beta detector would have a distinct advantage in terms of miniaturization. Conclusion: The feasibility of the beta detector was evaluated for installation inside the reactor CT to detect small leaks below $0.5gpm{\cdot}hr^{-1}$. In future, the design will be optimized on specific data.

키워드

참고문헌

  1. U.S. Nuclear Regulatory Commission. Guidance on monitoring and responding to reactor coolant system leakage. Regulatory Guide 1.45, Rev. 1. 2008;5-6.
  2. Korea Hydro & Nuclear power Co., Ltd. APR1400 design control document TIER2. Chapter 11 Radioactive Waste Management. APR1400-K-X-FS-14002-NP, 2014;11.1.27-11.1.28.
  3. Knoll GF. Radiation detection and measurement. 4th Ed. New York, NY. John Wiley & Sons Inc. 2010;398-399.

피인용 문헌

  1. Radiation Hardness Test of a Silicon Detector under Radiation Dose Rate of Nuclear Power Plant for In-Containment Coolant Leakage Detection System vol.253, pp.None, 2018, https://doi.org/10.1051/epjconf/202125305004