Impact Analysis of Single Fuel Rod Damage during Fuel Assembly Repair
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摘要: 以核电厂燃料组件修复过程中单根燃料棒损坏释放的放射性物质为分析对象，就放射性物质释放对组件修复的工作人员产生的累积有效剂量进行评估，对向环境释放的气态流出物的放射性总活度进行计算，并对气态流出物排放监测的影响开展分析。分析结果表明单根燃料棒损坏后，执行燃料组件修复的每位工作人员接受的累积有效剂量为12.2 mSv，低于GB 18871—2002规定的工作人员职业照射年平均有效剂量限值20 mSv；向环境释放的气态流出物中惰性气体与碘的放射性总活度分别为3.51×1011 Bq和2.17×108 Bq，远小于GB 6249—2011规定的年排放控制值6.0×1014 Bq和2.0×1010 Bq。燃料棒损坏后40 min烟囱排气惰性气体测量仪的读数小于1.0×1011 Bq/h，核电厂无需进入应急待命状态。Abstract: The cumulative effective dose to fuel assembly repair workers, the total radioactive activity of gaseous effluent released to the environment and the impact on gaseous effluent discharge monitoring are calculated and evaluated by taking the radioactive substances released from single fuel rod damage during the fuel assembly repair in nuclear power plant as the analysis object. The analysis results show that in case of single fuel rod damage, the cumulative effective dose received by each worker involved in the fuel assembly repair is 12.2 mSv, which is lower than 20 mSv—the annual average effective dose limit for workers’ occupational exposure stipulated in GB 18871-2002; the total radioactive activities of noble gases and iodine in the gaseous effluent released to the environment are 3.51 × 1011 Bq and 2.17 × 108 Bq respectively, which are far lower than the annual emission control values (6.0 × 1014 Bq and 2.0 × 1010 Bq) specified in GB 6249-2011. The reading of noble gas exhaust measuring instrument is lower than 1.0 × 1011 Bq/h 40 minutes after the fuel rod damage, so the nuclear power plant does not need to be put on emergency standby.
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表 1 单根燃料棒源项积存量
Table 1. Source Term Inventory in Single Fuel Rod
核素 积存量/Bq 核素 积存量/Bq 129I 6.11×106 137Cs 2.56×1013 131I 5.48×1012 85Kr 2.53×1012 132I 1.38×1010 131Xem 6.54×1011 134Cs 3.53×1013 133Xe 1.33×1012 136Cs 1.10×1012 133Xem 5.42×106 
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表 2 各核素释放份额及辐射源项
Table 2. Release Fraction and Source Term of Each Nuclide
核素 释放份额/% 辐射源项/（Bq·m−3） ξi ηi Ci(0) Bi(0) 129I 0.25 5 2.51 2.07×102 131I 0.4 8 3.60×106 2.97×108 132I 0.25 5 5.67×103 4.68×105 134Cs 0 12 0 2.87×109 136Cs 0 12 0 8.95×107 137Cs 0 12 0 2.08×109 85Kr 10 0 4.16×107 0 131Xem 5 0 5.37×106 0 133Xe 5 0 1.09×107 0 133Xem 5 0 4.45×101 0
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表 3 不同时刻燃料操作大厅气载源项
Table 3. Airborne Source Term in Fuel Handling Hall at Different Times
核素 燃料操作大厅气载放射性浓度/（Bq·m−3） 10 min 20 min 1 h 24 h 129I 2.36 2.22 1.75 4.29×10−4 131I 3.39×106 3.19×106 2.50×106 5.66×102 132I 5.08×103 4.54×103 2.92×103 6.91×10−4 85Kr 3.92×107 3.69×107 2.90×107 7.13×103 131Xem 5.05×106 4.76×106 3.73×106 8.68×102 133Xe 1.03×107 9.64×106 7.55×106 1.64×103 133Xem 4.18×101 3.93×101 3.06×101 5.56×10−3
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表 4 不同时刻乏燃料水池辐射源项
Table 4. Radiation Source Term of Spent Fuel Pool at Different Times
核素 乏燃料水池的放射性浓度/（Bq·m−3） 10 min 20 min 24 h 36 h 129I 2.05×102 2.03×102 4.79×101 2.30×101 131I 2.94×108 2.91×108 6.30×107 2.90×107 132I 4.41×105 4.15×105 7.70×101 9.87×10−1 134Cs 2.84×109 2.81×109 6.63×108 3.19×108 136Cs 8.86×107 8.76×107 1.96×107 9.19×106 137Cs 2.06×109 2.04×109 4.81×108 2.31×108
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表 5 各核素照射系数
Table 5. Irradiation Coefficient of Each Nuclide
核素 照射系数/[(mSv·h−1)/Bq] 129I 1.24×10−15 131I 1.76×10−14 132I 7.69×10−14 134Cs 7.08×10−14 136Cs 1.03×10−13 137Cs 2.73×10−14
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表 6 单根燃料棒损坏后单个工作人员的累积有效剂量
Table 6. Cumulative Effective Dose to a Single Worker after Single Fuel Rod Damage
停留时间/min 累积有效剂量/mSv 浸没照射 吸入照射 直接照射 总计 10 3.27×10−3 6.21 6.71×10−2 6.28 20 6.35×10−3 1.20×101 1.34×10−1 1.22×101 30 9.25×10−3 1.75×101 1.99×10−1 1.77×101
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