氨水溶液在γ场中的稳态辐射分解行为研究

Study on the Steadyγ-Radiolysis of Ammonia Solution

含氨冷却剂被应用于压水堆中,可以清除冷却剂辐射分解产生的O_(2)、H_(2)O_(2)等氧化性产物,从而减轻结构材料腐蚀。本文研究了氨水在γ辐射场中的辐射分解行为,考察氨浓度、辐射吸收剂量和吸收剂量率、气液体积比和不同饱和气体对氨水辐射分解行为的影响,重点关注辐射分解产物H_(2)O_(2)和NO_(2)^(-)的浓度变化。结果表明,随着体系中氨浓度的增加,H_(2)O_(2)的浓度受到明显抑制,NO_(2)^(-)的浓度则呈现出上升趋势;吸收剂量的增加使得H_(2)O_(2)浓度明显升高,NO_(2)^(-)的浓度则在吸收剂量为8 kGy时达到最大(>100μmol/L),而后降低;吸收剂量率的差异(2.78~25 Gy/min)并未导致H_(2)O_(2)和NO_(2)^(-)浓度产生明显变化;氨水中的O_(2)是NO_(2)^(-)生成的关键,但O_(2)过多会促进NO_(2)^(-)氧化为NO_(3)^(-)从而降低NO_(2)^(-)浓度,此外O_(2)的存在促进了H_(2)O_(2)的生成。本文研究结果可为后续含氨冷却剂体系的优化提供参考。

Ammonia is applied in the coolant to eliminate the O_(2)and H_(2)O_(2)in the PWR,thus mitigating the corrosion of structural materials.The present work studied theγ-radiolysis of ammonia solution under different conditions including ammonia concentration,absorbed dose,absorbed dose rate,gas-liquid volume ratio,and different saturated gases.The results show that ammonia significantly inhibits H_(2)O_(2)because of the consumption of H_(2)O_(2)and suppression of its precursors.The concentration of NO_(2)^(-)rises with the ammonia concentration.Ammonia is continuously consumed as irradiation progresses,while the concentration of H_(2)O_(2)increases significantly with the absorbed dose.The NO_(2)^(-)reaches a peak maximum(>100μmol/L)when the absorbed dose is 8 kGy.However,NO_(2)^(-)has a drop when the absorbed dose grows further,due to the fact O_(2)oxidizes NO_(2)^(-)into NO_(3)^(-).The concentrations of H_(2)O_(2)and NO_(2)^(-)are not obviously affected within the absorbed dose rate range(2.78~25 Gy/min).The presence of O_(2)is critical to the formation of NO_(2)^(-),though excessive O_(2)in the system could lead to the oxidization of NO_(2)^(-)by increasing the oxidizing species.Besides,the oxygen dissolved in aqueous ammonia promotes the production of H_(2)O_(2).This work is expected to provide a helpful reference for the optimization of the ammonia-containing coolant system.