燃耗信任制技术在压水堆乏燃料贮存水池中应用的研究
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摘要
传统上，在分析乏燃料贮存、运输中的临界安全问题时，以燃料的最高富集度，即以新燃料的富集度为依据。采用新燃料假设，可以简化计算，而且对相关的管理措施要求较少，但这是一种过于保守的方法，大大限制了乏燃料在贮存和运输中的效率。燃耗信任制则是在分析临界安全时考虑辐照后燃料的反应性降低。它可以有效的提高乏燃料在贮存和运输中的经济性。
本文分析PWR乏燃料贮存水池在采用燃耗信任制技术时所需注意的问题。采用燃耗信任制技术进行乏燃料水池临界计算，要分两步进行。首先要计算乏燃料组件中同位素的积存量。然后再利用上一步计算得到的乏燃料成分，对特定结构的水池进行临界安全分析。这里需要解决几个问题：对计算乏燃料同位素组成程序的选取和验证；对进行临界分析程序的选取和验证；选取燃料组件在反应堆内和堆外各参数条件的包络情况以确保最后的临界安全分析是保守的。最终要清晰地表示出一个特定的水池对可装入(符合临界安全标准)乏燃料组件的要求。本文针对这些问题进行了一系列分析。推荐SCALE4加MCNP4的程序组合作为燃耗信任制分析的工具；分析了要考虑的包络因素，特别是对乏燃料轴向燃耗的不均匀分布对临界安全分析的影响；利用推荐的程序和包络分析结论对大亚湾乏燃料贮存水池进行了初步的临界安全分析，给出了一个清楚的燃耗信任制计算流程。
尽管燃耗信任制技术能够带来很大的经济效益，但要在实际中应用，必须在技术上和管理上达到相当高的水平，如核电站提供可靠的燃耗数据，对每个燃料组件在堆内的辐照历史都要有详尽的记录，必须有组件燃耗测量装置，所有的理论分析都需有适当的实验数据支持等。
In general, when doing analyses of criticality safety of spent fuel transport or storage, one assumption is that the compositions of the spent fuel are same as the fresh fuel. Using the "fresh fuel" assumption can simplify the analysis of criticality safety and associated administrative controls. But this assumption is very conservative, which limits the efficiency of the transport and storage of the spent fuel. The concept of taking credit for the reduction in nuclear fuel reactivity due to burnup of the fuel is referred to as "burnup credit". It can greatly improve economic efficiency of the transport and storage of the spent fuel.
This paper describes the analytical methods for applying burnup credit in the spent fuel pools for pressurized water reactor (PWR). The analyses of criticality safety of the spent fuel pool on burnup credit concept consists of two steps: at first, to calculate isotopic concentrations, and then to do the safety analyses of criticality about the spent fuel pools basing the isotopes concentrations obtained at the first step. There are some problems must be considered: to select and validate a computer code system to calculate isotopes concentrations in spent fuel by irradiation in the reactor core and subsequent decay; to select and validate a computer code system to predict the sub-critical multiplication factor of a spent fuel pool (safety analyses of criticality of a spent fuel pool); to establish bounding conditions for the isotopes concentration and criticality calculations to ensure the results of the safety analyses of criticality to be conservative; to generate a clear spent fuel assemblies loading crit
eria (to meet the criticality criteria of the safety analyses) for a special spent fuel pool. This paper has done a series of analyses on those problems. Specially, detail analyses on the effect of axial burnup heterogeneity have carried out in this paper. Finally, the methodology for applying burnup credit in the calculation work is presented, which uses the computer code system of scale4 and the computer code of MCNP4.
In the last chapter of the thesis, a preliminary safety analyses of criticality is done on the spent fuel pool of Daya bay nuclear power plant using the selected computer code system and the method which is gotten before. The objective of this part is to show a clear calculation process of the burnup credit technology.
Although the burnup credit technology is of great economic benefit, if it is used into practice, high level technology and administrative controls are needed. For example, the nuclear power plants are required to provide the reliable burnup values; the records of the irradiation history of each fuel assembly must be kept; there must be a device for burnup measurement of assemblies; all the analysis must be supported by the appropriate experiment data, and so on.
本文分析PWR乏燃料贮存水池在采用燃耗信任制技术时所需注意的问题。采用燃耗信任制技术进行乏燃料水池临界计算，要分两步进行。首先要计算乏燃料组件中同位素的积存量。然后再利用上一步计算得到的乏燃料成分，对特定结构的水池进行临界安全分析。这里需要解决几个问题：对计算乏燃料同位素组成程序的选取和验证；对进行临界分析程序的选取和验证；选取燃料组件在反应堆内和堆外各参数条件的包络情况以确保最后的临界安全分析是保守的。最终要清晰地表示出一个特定的水池对可装入(符合临界安全标准)乏燃料组件的要求。本文针对这些问题进行了一系列分析。推荐SCALE4加MCNP4的程序组合作为燃耗信任制分析的工具；分析了要考虑的包络因素，特别是对乏燃料轴向燃耗的不均匀分布对临界安全分析的影响；利用推荐的程序和包络分析结论对大亚湾乏燃料贮存水池进行了初步的临界安全分析，给出了一个清楚的燃耗信任制计算流程。
尽管燃耗信任制技术能够带来很大的经济效益，但要在实际中应用，必须在技术上和管理上达到相当高的水平，如核电站提供可靠的燃耗数据，对每个燃料组件在堆内的辐照历史都要有详尽的记录，必须有组件燃耗测量装置，所有的理论分析都需有适当的实验数据支持等。
In general, when doing analyses of criticality safety of spent fuel transport or storage, one assumption is that the compositions of the spent fuel are same as the fresh fuel. Using the "fresh fuel" assumption can simplify the analysis of criticality safety and associated administrative controls. But this assumption is very conservative, which limits the efficiency of the transport and storage of the spent fuel. The concept of taking credit for the reduction in nuclear fuel reactivity due to burnup of the fuel is referred to as "burnup credit". It can greatly improve economic efficiency of the transport and storage of the spent fuel.
This paper describes the analytical methods for applying burnup credit in the spent fuel pools for pressurized water reactor (PWR). The analyses of criticality safety of the spent fuel pool on burnup credit concept consists of two steps: at first, to calculate isotopic concentrations, and then to do the safety analyses of criticality about the spent fuel pools basing the isotopes concentrations obtained at the first step. There are some problems must be considered: to select and validate a computer code system to calculate isotopes concentrations in spent fuel by irradiation in the reactor core and subsequent decay; to select and validate a computer code system to predict the sub-critical multiplication factor of a spent fuel pool (safety analyses of criticality of a spent fuel pool); to establish bounding conditions for the isotopes concentration and criticality calculations to ensure the results of the safety analyses of criticality to be conservative; to generate a clear spent fuel assemblies loading crit
eria (to meet the criticality criteria of the safety analyses) for a special spent fuel pool. This paper has done a series of analyses on those problems. Specially, detail analyses on the effect of axial burnup heterogeneity have carried out in this paper. Finally, the methodology for applying burnup credit in the calculation work is presented, which uses the computer code system of scale4 and the computer code of MCNP4.
In the last chapter of the thesis, a preliminary safety analyses of criticality is done on the spent fuel pool of Daya bay nuclear power plant using the selected computer code system and the method which is gotten before. The objective of this part is to show a clear calculation process of the burnup credit technology.
Although the burnup credit technology is of great economic benefit, if it is used into practice, high level technology and administrative controls are needed. For example, the nuclear power plants are required to provide the reliable burnup values; the records of the irradiation history of each fuel assembly must be kept; there must be a device for burnup measurement of assemblies; all the analysis must be supported by the appropriate experiment data, and so on.
引文
1．阮可强等，《核科学技术丛书—核临界安全》，原子能出版社，2001年6月
2．薛小刚，沈雷生，阮可强，核电厂乏燃料贮存中燃耗效应的反应性余量研究《核科学与工程》，第16卷第4期，1996
3．薛小刚、刘振华等，广东大亚湾核电站乏燃料贮存水池密集贮存可行性研究，中国原子能科学研究院(内部资料，1999年)
4．燃耗信用制在LNPS乏燃料密集贮存临界计算中的应用以及k_(eff)不确定性分析(2000年9月6日在NNSA现场评审对话会上的发言，内部资料)
5. Training Course on Implementation of Burnup Credit in Spent Fuel Management Systems. J. C. Neuber, Framatome-ANP GmbH Germany; J. M. Conde Lopez, Consejo de Seguridad Nuclear Spain
6. M. Brady, M. Takano, M. D. DeHart, H. Okuno, A. Nouri and E. Sartori, "Finding of an International Study on Burnup Credit," Proc. of Intl. Conf. on the Physics of Reactors, PHYSOR 96, September 16-20, 1996, Volume 4, L-41 - L-52 (1996).
7. M. Brady, H. Okuno, M.D.DeHart, A. Nouri and E. Sartori, "International Studies on Burnup Credit Criticality Safety by an OECD/NEA Working Group," Proc. of Intl. Conf. on the Physics of Nuclear Science and Technology, October 5-8, 1998, Volume 1,624-630 (1998).
8. M. Takano, "OECD/NEA Burnup Credit Criticality Benchmark - Result of Phase-1A-," NEA/NSC/DOC(93)22, JAERI-M 94-003 (1994).
9. M. D. DeHart, M. C. Brady and C. V. Parks, "OECD/NEA Bumup Credit Criticality Benchmark Phase I-B," NEA/NSC/DOC(96)06, ORNL-6901 (1996).
10. M. Takano and H. Okuno, "OECD/NEA Burnup Credit Criticality Benchmark - Result of Phase IIA-," NEA/NSC/DOC(96)01, JAERI-Research 96-003 (1996).
11. M. D. DeHart, "Parametric Analysis of PWR Spent Fuel Depletion Parameters for Long-Term-Disposal Criticality Safety" ORNL/TM-1999/99 (1999)
12. J. C. Wagner, M. D. DeHart, "Review of Axial Burnup Distribution Considerations for Burnup Credit Calculations" ORNL/TM-1999/246 (2000)
13. CASMO-A Multigroup Two-dimensional Transport Theory Code User's Manual
14．黄学清、高应为、许立涛、蒲公旭 《ORIGEN2程序使用说明》内部资料 1987年10月
15．金文绵、李素梅 《MCNP3B使用手册》(1998年修订版) 中国原子能科学研究院计算机应用研究所 内部资料 1998年8月18日
16. O. W. Hermann, C. V. Parks, "SAS2H: a coupled one-dimensional depletion and shielding analysis module" NUREG/CR-0200 Revision 6 Volume 1, Section S2, ORNL/NUREG/CSD-2/V2/R6, March 2000
2．薛小刚，沈雷生，阮可强，核电厂乏燃料贮存中燃耗效应的反应性余量研究《核科学与工程》，第16卷第4期，1996
3．薛小刚、刘振华等，广东大亚湾核电站乏燃料贮存水池密集贮存可行性研究，中国原子能科学研究院(内部资料，1999年)
4．燃耗信用制在LNPS乏燃料密集贮存临界计算中的应用以及k_(eff)不确定性分析(2000年9月6日在NNSA现场评审对话会上的发言，内部资料)
5. Training Course on Implementation of Burnup Credit in Spent Fuel Management Systems. J. C. Neuber, Framatome-ANP GmbH Germany; J. M. Conde Lopez, Consejo de Seguridad Nuclear Spain
6. M. Brady, M. Takano, M. D. DeHart, H. Okuno, A. Nouri and E. Sartori, "Finding of an International Study on Burnup Credit," Proc. of Intl. Conf. on the Physics of Reactors, PHYSOR 96, September 16-20, 1996, Volume 4, L-41 - L-52 (1996).
7. M. Brady, H. Okuno, M.D.DeHart, A. Nouri and E. Sartori, "International Studies on Burnup Credit Criticality Safety by an OECD/NEA Working Group," Proc. of Intl. Conf. on the Physics of Nuclear Science and Technology, October 5-8, 1998, Volume 1,624-630 (1998).
8. M. Takano, "OECD/NEA Burnup Credit Criticality Benchmark - Result of Phase-1A-," NEA/NSC/DOC(93)22, JAERI-M 94-003 (1994).
9. M. D. DeHart, M. C. Brady and C. V. Parks, "OECD/NEA Bumup Credit Criticality Benchmark Phase I-B," NEA/NSC/DOC(96)06, ORNL-6901 (1996).
10. M. Takano and H. Okuno, "OECD/NEA Burnup Credit Criticality Benchmark - Result of Phase IIA-," NEA/NSC/DOC(96)01, JAERI-Research 96-003 (1996).
11. M. D. DeHart, "Parametric Analysis of PWR Spent Fuel Depletion Parameters for Long-Term-Disposal Criticality Safety" ORNL/TM-1999/99 (1999)
12. J. C. Wagner, M. D. DeHart, "Review of Axial Burnup Distribution Considerations for Burnup Credit Calculations" ORNL/TM-1999/246 (2000)
13. CASMO-A Multigroup Two-dimensional Transport Theory Code User's Manual
14．黄学清、高应为、许立涛、蒲公旭 《ORIGEN2程序使用说明》内部资料 1987年10月
15．金文绵、李素梅 《MCNP3B使用手册》(1998年修订版) 中国原子能科学研究院计算机应用研究所 内部资料 1998年8月18日
16. O. W. Hermann, C. V. Parks, "SAS2H: a coupled one-dimensional depletion and shielding analysis module" NUREG/CR-0200 Revision 6 Volume 1, Section S2, ORNL/NUREG/CSD-2/V2/R6, March 2000