Acta Scientiarum Naturalium Universitatis Pekinensis

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Determination of Trace 14C in Nuclear Reactor Cooling Water

XIE Jinglin, LIU Xinqi, WANG Shuxuan, QU Chuanxing, ZHU Aijun, LIU Yuanfang   

  1. Department of Technical Physics, Peking University, Beijing, 100871
  • Received:1993-06-22 Online:1995-03-20 Published:1995-03-20

核反应堆循环冷却水中14C含量的测定

谢景林,刘新起,王树轩,屈传星,朱爱军,刘元方   

  1. 北京大学技术物理系,北京,100871

Abstract: For determining the trace 14C in nuclear reactor coolingwater, two methods based on sorption of 14CO2 in a solution and subsequent liquit scintillation (LS) counting of the 14C were developed. Initially, a water sample was acidified by H2SO4 and distilled in a distillator to produce 14CO2 gas which was converted from CO2-3 anion in the water. In the first method of Ca14CO3 formation, 14CO2 gas was collected as Ca14CO3 precipitate by NaOH and CaCl2 solution, and then Ca14CO3 was dispersed in a colloidal liquid scintillator (toluene : TritonX-100 : water = 2 : 1 : 1.5) for LS counting. The sorption yield was >90%. The detection limit of this sorption in Ca14CO3-LS method was 3.3×10-10g/L. In the method of sorption by organic alkali, 14CO2 gas was absorbed by an ethanolamine cocktail(PPO 6g, POPOP 0.2g, ethanolamine 120mL, ethylene glycol monomethyl ether 400mL, toluene 480mL) which can be directly counted in a LS counter. The sorption yield was also >90%, and the detection range of 14C concentration was wider, and the detection limit was improvedto 3.3×10-11g/L, lower than the previous one order of magnitude. By taking the second method, cooling water samples from two nuclear reactors were assayed. 14C content of the samples taken from a reactor of the Chinese Institute of Nuclear. Energy was determined as 5.0×10-11g/L. In the same samples 6 other trace radionuclides (58Co, 46Sc, 54Mn, 110mAg, 60Co and 51Cr),ranging from 0.40 to 30.0 Bq/L in specific activity, were also detected by γ-ray spectrum measurement. Whereas, no radioactivity was detected in another reactor water sample.

Key words: 14C, nuclear reactor cooling water, liquid scintillation counting, etha-nolamine, Triton X-100

摘要: 本文探索了“Ca14CO3法”和“有机碱法”两种测定水中痕量14C的方法,并进行了核反应堆循环冷却水的实际测量。“Ca14CO3法”是先把水样(约300ml)用5mol/LH2SO4酸化并加热蒸馏出14CO2气体,再用NaOH和CaCL2浓集吸收14CO2并生成Ca14CO3沉淀;最后把此沉淀悬浮于胶状闪烁液(Toluene:Triton×100:Water=2:1:1.5)中,在FJ-353液体闪烁计数仪上检测14C的量,此法的14C检测限为3.3×10-10g/L.“有机碱法”是用含有乙醇胺的闪烁液浓集吸收蒸流产生的痕量14CO2 气体,该吸收液可直接用于FJ-353液体闪烁计数仪测量14C 。此方法不仅有较高的14CO2气体吸收效率(>90%),而且有较低的14C 检测限(3.3×10-11g/L)。用“有机碱法”对两种核反应堆的循环冷冻水进行14C测量,其中测量一个样品的14C含量为 5.0×10-11g/L,并用γ能谱测出另外6种痕量放射性核素(58Co, 46Sc, 54Mn, 110mAg, 60Co and 51Cr);而在另一样品中未检测出包括14C在内的放射性核素。

关键词: 14C, 核反应堆冷却水, 液闪测量, 乙醇胺, TritonX-100

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