Abstract
An influence evaluation by background radiation on a silicon detector, which will be used to detect a coolant leakage, and installed in a containment building of a nuclear power plant, was performed and the result was discussed. The detector that consists of a silicon sensor and preamplifier mounted in a shielding structure which composed of a 5 cm lead cylinder will be installed in an annulus zone that is influenced by background radiation (neutron and gamma ray) from an operation of a nuclear reactor. Absorbed dose rates on a silicon sensor and preamplifier were calculated as 2.15 mGy/hr and 1.05 mGy/hr, respectively, by Monte Carlo N-Particle (MCNP) simulation. Data of background radiation had referred to a Final Safety Analysis Report (FSAR) of a nuclear power plant in the Republic of Korea. A silicon sensor and preamplifier were irradiated by a Co60 gamma radiation source equipped in a facility of Korea Atomic Energy Research Institute Advanced Radiation Technology Institute (KAERI ARTI) of the Republic of Korea. A Po-210 alpha source was used as a check source to evaluate a state of a function of the detector during gamma irradiation. Absorbed dose rates were about 22.92 mGy/hr and 6.6 mGy/hr on silicon sensor and preamplifier, respectively. Before and during gamma irradiation, a count rates from the check source wasn`t changed (from 18.4 cps to 18.4±0.2 cps after irradiation), and any degradations of function also weren`t observed. Even more harsh condition than calculated dose rates referred by the condition of background radiation of in-containment, the silicon detector maintained the ability of function of charged particles detection. Based on the result, it has been demonstrated that a silicon detector is a suitable detector for detecting charged particles from a leaked coolant even during interfered by the background radiation of a primary system of a nuclear power plant.
Highlights
A silicon detector, which has a thin depletion layer, has a characteristic that has small reactivity with gamma ray, and has high reactivity with charged particles
There is no study to investigate the influence of a silicon detector under dose rate conditions of a nuclear power plant
To investigate the effects of background radiation on the detector during an operation of the reactor, absorbed dose rates to the silicon sensor and preamplifier were calculated through Monte Carlo N-Particle (MCNP) simulation
Summary
A silicon detector, which has a thin depletion layer, has a characteristic that has small reactivity with gamma ray, and has high reactivity with charged particles. The detector could be considered an option to use in a nuclear power plant that has a high dose of background gamma radiation during an operation. The annulus zone of a nuclear power plant, in which the detector would be installed, has high dose background radiation during a plants operation. Even though the absorbed doses on the silicon sensor and preamplifier were dramatically reduced because of the structure, background radiation could impact the detector such as interfering signal, etc. There is no study to investigate the influence of a silicon detector under dose rate conditions of a nuclear power plant. To investigate the effects of background radiation on the detector during an operation of the reactor, absorbed dose rates to the silicon sensor and preamplifier were calculated through MCNP simulation. Based on the results of the simulation, a gamma irradiation test was conducted at the KAERI ARTI facility using a Co-60 gamma source
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