Development of Safety Assessment Code for Decommissioning of Nuclear Facilities (DecDose)
Development of Safety Assessment Code for Decommissioning of Nuclear Facilities (DecDose)
复制标题
制定核设施退役安全评估规范（DecDose）
DOI：
10.1115/icone17-75123
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
T. Sukegawa
中科院分区：
文献类型：
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作者：
T. Shimada;S. Ohshima;T. Sukegawa
根据日本原子能研究所（现为日本原子能机构）日本动力示范反应堆（JPDR）退役项目的经验，制定了核设施退役安全评价规范DecDose。DecDose根据核电站退役的进度评估公众和工作人员的年暴露剂量，并评估火灾和爆炸等意外情况下的公众剂量。退役期间正常情况下的公众剂量是根据从工厂排放到大气和海洋的放射性核素量来评估的。放射性核素的排放量取决于哪些活化和（或）受污染的部件和结构被拆除以及如何拆除。这个量是根据核电站给出的放射性清单来预测的。还考虑了通风系统的过滤效率和工厂废液处理系统的去污因素。对所有可能的途径都计算了吸入和摄入农作物和海产品引起的内剂量，以及空气传播的放射性气溶胶和土壤表面放射性沉积引起的外剂量。外部剂量还包括直接辐射和来自临时存放在现场建筑物内的废物容器的天光辐射。对于工作人员的外部剂量，使用先前由点核屏蔽代码评估的剂量率库来计算拆除受污染部件和结构的辐射剂量率。在这种情况下，辐射源被认为由两部分组成；一个是拆解感兴趣的物体，另一个是周围物体的总和。考虑工作类型或职位的差异；切割工人位于离拆卸部件较近的位置，其他工人在一定距离处帮助他们，主管从远处观察他们的活动。对于工人的内部剂量，空气中单个放射性核素的放射性核素浓度是根据拆卸条件计算的，例如切割速度、拆卸部件的切割长度和排气速度。采用更分段的工作分解结构（WBS）建立了拆解工作时间的计算模型。通过与JPDR退役项目中工作人员的外照射量进行比较，对DecDose进行了部分验证。预计DecDose将有助于公用事业公司制定合理的拆除计划，并有助于安全当局估计许可证申请或基于风险的监管标准的安全评估的保守性。ASME版权所有©2009
A safety assessment code, DecDose, for decommissioning of nuclear facilities has been developed, based on the experiences of the decommissioning project of Japan Power Demonstration Reactor (JPDR) at Japan Atomic Energy Research Institute (now Japan Atomic Energy Agency). DecDose evaluates the annual exposure dose of the public and workers according to the progress of decommissioning of the plant, and also evaluates the public dose at accidental situations including fire and explosion. The public dose at normal situations during decommissioning is evaluated from the amount of radionuclides discharged from the plant to the atmosphere and the ocean. The amounts of radionuclides discharged depend on which and how activated and/or contaminated components and structures are dismantled. The amount is predicted by using the radioactive inventory given by the plant. The filtration efficiency of the ventilation system and decontamination factors of the liquid waste treatment system of the plant are also considered. Both of the internal dose caused by inhalation and ingestion of agricultural crops and seafood, and the external dose by radioactive aerosols airborne and radioactive deposition at soil surfaces are calculated for all of possible pathways. Also included in the external dose are direct radiation and skyshine radiation from waste containers which are packed and temporarily stored in the in-site building. For external dose of workers, the radiation dose rate from dismantling contaminated components and structures is calculated using the dose rate library which was previously evaluated by a point kernel shielding code. In this condition, radiation sources are regarded to be consisted of two parts; one is a dismantling object of interest, and the other is the sum of surrounding objects. Difference in job type or position is taken into account; workers for cutting are situated closer to a dismantling component, other workers help them at some distance, and the supervisor watches their activities from away. For worker’s internal dose, the radionuclide concentrations in air for individual radionuclides are calculated from a dismantling condition, e.g. cutting speed, cutting length of the dismantling component and exhaust velocity. A calculation model for working time on dismantling was developed using more segmented WBS (work breakdown structure). DecDose was partially verified by comparison with measured the external dose of workers during JPDR Decommissioning Project. The DecDose is expected to contribute to utilities in formulating rational dismantling plans and to the safety authority in estimating conservativeness in safety assessment of licensing application or risk-based regulatory criteria.Copyright © 2009 by ASME