Improvement and Application of Water Chemistry Control Process during Shutdown of One 3rd Generation PWR Unit
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摘要: 有效降低压水堆机组反应堆冷却剂系统（RCP）材料腐蚀速率的同时有效去除活化腐蚀产物，可降低堆芯外辐射场、减少工作人员受照剂量，从而确保核电机组大修工作的顺利展开。某三代PWR机组采用富集硼酸（EBA）进行反应性控制的同时，利用其在功率运行期间对RCP系统冷却剂实施水化学控制的显著优势，同时在机组首次大修期间对停堆水化学控制工艺采取的改进措施（包括碱性环境向酸性环境转换、还原环境向氧化环境转换、强制氧化期间多次向一回路添加双氧水维持氧化性、化学和容积系统混床最大流量净化等），在机组停堆下行阶段实现了降低机组辐射剂量并减少工作人员受照剂量的目的。
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关键词:
- 三代压水堆 /
- 富集硼酸（EBA) /
- 停堆水化学控制 /
- 酸碱和氧化还原环境转换 /
- 辐射剂量率
Abstract: In order to effectively reduce the corrosion rate of reactor coolant system (RCP) materials of pressurized water reactor (PWR) units and effectively remove activated corrosion products, so as to reduce the exposure dose of workers to ensure the smooth progress of unit overhaul, a 3rd Generation PWR unit uses enriched boric acid (EBA) for reactivity control, while taking advantage of its significant advantage of water chemistry control of RCP system coolant during power operation. At the same time, during the first overhaul of the unit, improvement measures are taken for the shutdown water chemistry control process (including the conversion from alkaline environment to acid environment, the conversion from reducing environment to oxidizing environment, the repeated addition of hydrogen peroxide to the primary loop during forced oxidation to maintain oxidizability, the maximum flow purification of the mixed bed of chemical and volumetric system, etc.), and the purpose of reducing the radiation dose of the unit and the radiation dose of workers is realized in the downward stage of unit shutdown. -
图 1 首堆机组与某 CPR1000 机组功率运行期内 pH300℃、CB变化趋势对比
Figure 1. Comparison of Variation Trend of pH300℃ and CB between the First Reactor Unit and a CPR1000 Unit during Power Operation
图 2 首堆机组首循环功率运行末期到首次大修中冷却剂水化学环境变化
注：横坐标刻度8:10及以后为次日；pHT(n)—温度 T 时水的中性 pH 值；B/R 工况—碱性还原工况；A/R 工况—酸性还原工况；A/O 工况—酸性氧化工况
Figure 2. Changes of Coolant Water Chemistry Environment from the End of the First Cycle Power Operation to the First Overhaul of the First Reactor Unit
图 3 首堆机组与 CPR1000 机组首次大修强制氧化阶段氧含量变化对比图
Figure 3. Comparison Diagram of Oxygen Content Change in Forced Oxidation Stage of First Reactor Unit and CPR1000 Unit during the First Overhaul
图 4 首堆机组首循环功率运行末期到首次大修中冷却剂水化学环境变化
注：横坐标刻度0:00及以后为次日
Figure 4. Changes of Coolant Water Chemistry Environment from the End of the First Cycle Power Operation to the First Overhaul of the First Reactor Unit
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[1] WANG Z, GE Z W, LIU Z T. Water chemistry management for the primary circuit of the first EPR unit during hot functional testing[J]. The Journal of All Power & Plant Chemistry Areas, 2020, 22(1): 20-29. [2] JEFFREY A, GORMAN. PWR Primary water chemistry guidelines, Volume 2: TR-105714-R5[R]. U.S.: EPRI, 2014: 503. -
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