XXXVII, No. 4, Pp. 259-339
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Authors: Yue Zhao, Guo P. Qu, and Jian L. Zhou
To assess the characteristics of 13N decay, a monitoring method of the primary loop leakage rate based on the γ-γ coincidence method was proposed. In this work, sampling and measurement devices were designed, in which NaI (Tl) crystals were used as coincidence detectors. The Geant4 simulation method was used to study the relationship between the efficiency ɛ and capacity V change of different devices, and the ɛV value under the corresponding capacity was obtained. According to the value of ɛV, the optimal sampling and measurement device was determined, and then the detection efficiency of the device was calibrated experimentally. Taking the 600.000 kW reactor of Qinshan Phase II as the research object, the lower limit of detection was discussed.When the sampling point was located in the fume hood of the control rod drive mechanism, the theoretical lower limit of the coincidence method was 0.756 Lh-1.
Key words: 13N, coincidence method, sampling and measurement device, detection efficiency, lower limit of detection
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