Research on Evaluation Method of Actinide Nuclide Activities in Primary Coolant System of Pressurized Water Reactor Nuclear Power Plant
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摘要: 为评估压水堆核电厂燃料包壳破损时的工作人员辐射风险和燃料包壳破损程度，基于特征物理量建立一回路冷却剂系统中锕系核素质量评估方法。本文基于锕系核素的生成和迁移机理，建立了一回路冷却剂系统中锕系核素的平衡方程组，并选取3种易监测的特征物理量用以评估锕系核素向一回路冷却剂系统的释放量及其分布，并建立了一回路冷却剂系统中锕系核素质量的评估方法。然后分别采用国内在役压水堆核电厂无燃料包壳破损和有燃料包壳破损的实测数据对建立的评估方法进行了验证，验证结果表明：建立的评估方法可在无燃料包壳破损和有燃料包壳破损的情况下对一回路冷却剂系统中锕系核素质量进行评估，评估结果和预期符合。本文研究成果可为压水堆核电厂运行期间一回路冷却剂系统中锕系核素质量及其分布评估提供指导，从而优化后端的工作人员防护措施，降低辐射风险。Abstract: In order to evaluate the radiation risk of workers and the damage degree of fuel cladding in PWR nuclear power plant, it is necessary to improve the evaluation approach of actinide nuclide activities in the primary coolant systems based on characteristic physical quantities. Based on the generation and migration mechanism of actinide nuclides, the balance equations of actinide nuclides in primary coolant system are established, and three easy-to-monitor characteristic physical quantities are selected to evaluate the release and distribution of actinide nuclides to the primary coolant system. Hence, the evaluation approach of actinide nuclide activities in primary coolant systems is established. The evaluation approach is validated by the measurement data without and with fuel cladding damage from in-service nuclear power plant in China, respectively. The validation results show that the established approach is applicable for the evaluation of actinide nuclide activities in the primary coolant system without and with fuel cladding damage, and the evaluation results are in line with expectations. The results of this paper can provide guidance for the assessment of actinide nuclides and their distribution in the primary coolant system during the operation of PWR nuclear power plants, so as to optimize the back-end staff protection measures and reduce the radiation risk.
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表 1 国内典型二代压水堆核电厂设计参数
Table 1. Design Parameters of a Typical Second Generation PWR Plant in China
物理量 参数值 物理量 参数值 堆芯铀装量/t 72.46 堆芯热功率/MW 2895 燃料棒数量/根 41448 循环长度/d 320 线功率密度/( W·cm−1) 186.0 堆内壁面锕系核素沉积速率/s−1 4.0×10−4 一回路冷却剂总质量/t 169.4 堆内壁面沉积的锕系核素腐蚀释放速率/s−1 3.0×10−9 下泄净化流量/(t·h−1) 13.6 堆外壁面锕系核素沉积速率/s−1 4.0×10−4 下泄净化效率 0.9 堆外壁面沉积的锕系核素腐蚀释放速率/s−1 5.0×10−9 受中子辐照的冷却剂质量占冷却剂总质量的比例 0.3573 
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表 2 国内典型二代压水堆不同燃料富集度时冷却剂中134I活度浓度
Table 2. Specific Activity of 134I in Primary Coolant for a Typical Second Generation PWR Plant in China with Different Fuel Enrichment
锕系核
素来源锕系核素
初始质量/g初始富
集度/%134I活度浓度/
(102 MBq·t−1)沾污铀 1 3.20 4.31 沾污铀 1 3.80 4.06 沾污铀 1 4.45 3.76 侵蚀铀 1 3.20 2.23 侵蚀铀 1 3.80 2.12 侵蚀铀 1 4.45 1.99
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表 3 冷却剂系统各节点中锕系核素分布（1 g沾污铀）
Table 3. Distribution of Actinide Nuclides in Primary Coolant System (1 g Contaminated Uranium)
核素 堆内壁面沉积
质量/g堆外壁面沉积
质量/g冷却剂中
质量/g238U 8.91×10−1 3.62×10−2 3.47×10−6 235U 1.92×10−2 9.85×10−4 7.62×10−8 239Pu 1.90×10−2 4.62×10−4 7.22×10−8 241Pu 2.04×10−3 2.49×10−5 7.60×10−9 242Amm 2.30×10−7 1.96×10−9 8.50×10−13 238Pu 1.22×10−5 1.39×10−7 4.52×10−11 240Pu 3.27×10−3 5.50×10−5 1.22×10−8 241Am 2.10×10−5 4.39×10−7 7.95×10−11 242Cm 3.15×10−6 1.99×10−8 1.16×10−11 244Cm 1.13×10−6 6.75×10−9 4.17×10−12 234U 2.10×10−8 3.79×10−10 7.90×10−14 236U 2.08×10−3 4.46×10−5 7.87×10−9 237U 6.12×10−6 7.33×10−9 2.24×10−11 237Np 1.02×10−4 1.69×10−6 3.84×10−10 238Np 3.33×10−7 1.25×10−10 1.21×10−12 239Np 4.23×10−4 1.80×10−7 1.54×10−9 242Pu 2.09×10−4 1.91×10−6 7.76×10−10 243Am 1.26×10−5 9.14×10−8 4.65×10−11 243Cm 2.27×10−8 1.44×10−10 8.35×10−14 总α 9.35×10−1 3.78×10−2 3.64×10−6
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表 4 冷却剂系统各节点中锕系核素分布（1 g侵蚀铀）
Table 4. Distribution of Actinide Nuclides in Primary Coolant System (1 g Erosion Uranium)
核素 堆内壁面沉积质量/g 堆外壁面沉积质量/g 冷却剂中质量/g 238U 4.64×10−1 4.62×10−1 4.67×10−5 235U 9.94×10−3 1.23×10−2 1.01×10−6 239Pu 6.87×10−3 1.25×10−3 2.05×10−7 241Pu 4.83×10−4 6.36×10−5 1.84×10−8 242Amm 4.62×10−8 7.22×10−9 2.90×10−12 238Pu 6.21×10−6 2.02×10−6 6.32×10−10 240Pu 9.47×10−4 1.69×10−4 3.90×10−8 241Am 4.36×10−6 1.20×10−6 2.09×10−10 242Cm 6.14×10−7 6.70×10−8 3.62×10−11 244Cm 2.14×10−7 2.50×10−8 1.41×10−11 234U 1.44×10−7 1.45×10−7 2.60×10−11 236U 1.07×10−3 5.77×10−4 1.02×10−7 237U 3.14×10−6 8.28×10−8 2.51×10−10 237Np 5.16×10−5 2.09×10−5 4.63×10−9 238Np 1.67×10−7 1.62×10−9 1.54×10−11 239Np 2.18×10−4 5.05×10−7 4.32×10−9 242Pu 4.31×10−5 5.76×10−6 2.17×10−9 243Am 2.46×10−6 3.34×10−7 1.57×10−10 243Cm 4.34×10−9 6.10×10−10 3.23×10−13 总α 4.83×10−1 4.76×10−1 4.81×10−5
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表 5 国内某在役压水堆核电厂无燃料包壳破损时一回路冷却剂核素活度浓度
Table 5. Specific Activity of Nuclides in Primary Coolant for an In-service PWR Plant in China without Fuel Cladding Damage
核素 活度浓度/(MBq·t−1) 核素 活度浓度/(MBq·t−1) 131I 0.72 85Krm 2.40 132I 12.25 85Kr − 133I 8.10 87Kr 8.04 134I 25.11 88Kr 6.23 135I 13.69 133Xem − 134Cs − 133Xe 16.91 136Cs − 135Xe 22.20 137Cs − 138Xe 25.13 138Cs 41.51 239Np − 总α −
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表 6 国内某在役压水堆核电厂有燃料包壳破损时一回路冷却剂核素活度浓度
Table 6. Specific Activity of Nuclides in Primary Coolant for an In-service PWR Plant in China with Fuel Cladding Damage
核素 活度浓度/(MBq·t−1) 核素 活度浓度/(MBq·t−1) 131I 104 85Krm 628 132I 232 85Kr − 133I 270 87Kr 510 134I 323 88Kr 934 135I 257 133Xem 575 134Cs − 133Xe 27900 136Cs − 135Xe 3080 137Cs 119 138Xe 11500 138Cs 885 239Np − 总α −
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