安全壳通风系统放射性净化定量分析
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摘要
以先进压水堆核电厂为对象,开展了正常运行工况安全壳内气载放射性产生方式研究,并构建了分析模型,包括冷却剂泄漏及40Ar中子活化。在此基础上,定量的论证了安全壳空气过滤系统对放射性净化作用,结果表明:无排风净化情况下安全壳大气内放射性水平较高,可达DAC(导出空气浓度)限值15.5倍,应实行较严格的措施限制人员进入;通过敏感性分析,识别出85Kr及133Xe为主导核素,由于这些核素半衰期较长,仅依靠衰变较难去除,采用每周定期20 h净化方案可解决该问题。同时,进一步研究了降功率并发碘尖峰机理模型,论证了停堆工况通风策略的有效性,结果表明:实施大风量净化可在进入冷停堆状态时将安全壳内气载放射性降到DAC限值,为人员在安全壳内进行长期操作提供了条件。
Based on advanced pressurized water reactor nuclear plant,research on the producing way of airborne activity in containment at normal operation was carried out,and the analytical model was constructed,including primary coolant system leakage and neutron activation of 40 Ar. On this basis,the effect of containment air filtration system on the activity purge was quantitatively estimated. The results show that the overall containment atmosphere activity with no purge operation was at a pretty high level,reaching 15.5 times DAC(Derived Air Concentration)limit,which would significantly restrict personnel access. Sensitivity analysis identify that the predominant nuclides were 85 Kr and 133 Xe,which were hard to remove by decay due to long half-live. By 20 hours purge per week,this problem can beeffectively solved. Meanwhile,the mechanism model of iodine spike initiated by power reduction was further studied,and effectiveness of the purge strategy was demonstrated. The result shows that containment airborne activity would reduce to the DAC limit by large flow purge when cold shutdown was reached,which can provide condition for personnel spending significant periods of time in the containment.
Based on advanced pressurized water reactor nuclear plant,research on the producing way of airborne activity in containment at normal operation was carried out,and the analytical model was constructed,including primary coolant system leakage and neutron activation of 40 Ar. On this basis,the effect of containment air filtration system on the activity purge was quantitatively estimated. The results show that the overall containment atmosphere activity with no purge operation was at a pretty high level,reaching 15.5 times DAC(Derived Air Concentration)limit,which would significantly restrict personnel access. Sensitivity analysis identify that the predominant nuclides were 85 Kr and 133 Xe,which were hard to remove by decay due to long half-live. By 20 hours purge per week,this problem can beeffectively solved. Meanwhile,the mechanism model of iodine spike initiated by power reduction was further studied,and effectiveness of the purge strategy was demonstrated. The result shows that containment airborne activity would reduce to the DAC limit by large flow purge when cold shutdown was reached,which can provide condition for personnel spending significant periods of time in the containment.
引文
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[12]刘新华,方岚,祝兆文.压水堆核电厂正常运行裂变产物源项框架研究[J].辐射防护,2015,35(3):129-135.
[2]孙汉虹,程平东,缪鸿兴,等.第三代核电技术AP1000[M].北京:中国电力出版社,2010:263.
[3]GB 18871电离辐射防护与辐射源安全基本标准[S].北京:国家质量监督检验检疫总局,2002.
[4]10CFR 20 Standards for protection against radiation[S].Washington:U.S.Nuclear Regulatory Commission,2016.
[5]RG 1.52 Design,inspection,and testing criteria for air filtration and adsorption units of post accident engineered safety feature atmosphere cleanup systems in light water cooled nuclear power plants[S].Washington:U.S.Nuclear Regulatory Commission,2001.
[6]卢玉楷.简明放射性同位素应用手册[M].上海:上海科学普及出版社,2001:165.
[7]马崇智.放射性同位素手册[M].北京:科学出版社,1979:496.
[8]ANSI/ANS 6.1.2 Neutron and gamma-ray cross sections for nuclear radiation protection calculations for nuclear power plants[S].Illinois:American National Standards Institute,1999.
[9]郑明光,杜圣华.压水堆核电站工程设计[M].上海:上海科学技术出版社,2013:50.
[10]张姗姗,梅其良,付亚茹,等.SGTR事故并发碘尖峰研究[J].辐射防护,2013,33(6):349-354.
[11]LEWIS B J,LGLESIAS F C,POSTMA A K,et al.Iodine spiking model for pressurized water reactors[J].Journal of Nuclear Materials,1997,244(2):153-167.
[12]刘新华,方岚,祝兆文.压水堆核电厂正常运行裂变产物源项框架研究[J].辐射防护,2015,35(3):129-135.