快堆一回路钠的放射性监测技术研究

Study on the Monitoring Technology of Radioactivity in Primary Sodium of Fast Reactor

快堆一回路钠具有高放射性,无法使用γ谱仪直接测量其中的放射性核素,本文介绍了一种在线监测放射性核素的技术。设计了可组合和拆分的分段准直器,通过拆分准直器可以提高探测效率,而通过组合准直器可以降低死时间效应。采用点源模拟法对γ谱仪进行效率刻度,6种标准点源的能量区间包括了所有待测核素的能量范围。采用本技术对中国实验快堆一回路钠的监测结果表明,现阶段监测到的放射性核素为^(24)Na、^(22)Na以及^(124)Sb,由本研究中的效率刻度计算,^(124)Sb的放射性活度为104 Bq/g量级。

Primary sodium in fast reactor has a high radioactivity.The radioactive nuclide can＇t be detected by gamma spectrometer directly.An on-line radioactive monitoring technology was introduced in this paper.A series of collimators that could be disassembled and assembled were designed.Collimators were disassembled to increase detection efficiency while assembled to decrease dead time effects.Point source simulation method was used to calibrate the efficiency of gamma spectrometer.The energy range of the 6standard point sources had covered the energies of all the interest nuclides.The monitoring results of primary sodium in China Experimental Fast Reactor adopted by this technology showed that the first three radioactive nuclides at the present stage were ^24Na、^22Na and ^124Sb,respectively.By the efficiency calibration in this study,the radioactivity of ^124Sb was in the order of 104 Bq/g.