制订公众的放射性核素年摄入量限值时考虑的几个问题

本文讨论了制订公众成员的放射性核素年摄入量限值时所涉及的一些问题,包括:公众成员的剂量当量限值及其相应的危险水平、年龄依赖的代谢资料、年龄依赖的剂量学模型和年龄依赖的危险度及权重因子。     

国际辐射防护委员会(ICRP)1985年巴黎会议声明

国际辐射防护委员会(ICRP)于1985年3月在巴黎举行会议。委员会审查了其下属各专门委员会和工作小组的工作,并批准公布一份用于制定统一的危害指数的数值依据的报告。委员会认定有四个论题需加以说明公众成员的剂量限值在委员会1977年建议书(ICRP26号出版物)中,关于公众成员的有效剂量当量限值的建议,曾提到过两个数值。使用每年5n Sv 的限值,虽仍被承可,但仅适用于 ICRP26号出版物之第120段到第128段中所描述的情况。对于其它的情况,委员会建议,根据一生的年平均剂量为1mSv 来限制照射量,应是慎重的。     

肿瘤放射性粒子植入术后病区工作人员辐射防护的再认识

通过对不同距离与屏蔽条件下肿瘤放射性粒子植入后患者的放射性检测,实现辐射防护个体化与最优化。随机选择35例北京大学深圳医院微创介入病区并接受¹²⁵I放射性粒子植入的患者,植入术后2 h内使用x-γ射线检测仪在不同距离处检测未屏蔽、0.25 mmPb屏蔽、0.5 mmPb屏蔽条件下患者的剂量当量率,采用统计软件包SPSS19.0对结果进行t检验分析,并按照病区工作人员平均每人每日接触患者2 h计算相应的年剂量当量。未屏蔽时,0.5 m处工作人员所受的年剂量当量小于放射工作人员限值20 mSv,2 m处接近公众限值1 mSv,4 m处相当于病室内本底;在0.25 mmPb屏蔽下,尽管零距离处35位患者的平均年剂量当量小于公众限值,但其中有6位患者的年剂量当量大于公众限值;在0.5 mmPb屏蔽下,零距离处所有患者的年剂量当量已接近本底。结果表明,¹²⁵I粒子植入后病区工作人员的工作时间、距离、屏蔽防护中,重点要做好个体化的屏蔽防护。0.25 mmPb的铅胶布是最常使用的屏蔽物,对于粒子植入数量较多或植入部位表浅的患者必要时也应使用0.5 mmPb的铅胶布屏蔽,以实现辐射防护个体化和最优化。     

关于核动力站放射性流出物排放限值的讨论

核动力站向环境排放的放射性物质在核工业排放量中占相当大的部分。本文收集了国内外关于核动力站对公众的剂量当量限值、压水堆电站排放量限值及实际排放量等方面的数据,试图推荐符合我国实际的、合理可行的排放量限值,为制订我国核动力站辐射防护标准提供依据。     

辐射安全——有关论点

辐射安全——有关论点１公众和职业照射１．１公众照射核电厂运行对大多数受照公众的个体成员造成的剂量为每年１—２０μＳｖ范围——通常视为微不足道或可忽略的水平。甚至由大型加工厂对公众成员所造成的最高剂量大约为每年２００μＳｖ，这是ＩＡＥＡ剂量限值每年１０...     

一起工业探伤作业引起的辐射事件的处理及经验反馈

介绍了2017年浙江省宁波地区一起工业探伤作业中(⁷⁵Se放射源)射线误照射事件和该事件处理情况。根据调查及保守剂量估算结果,本次事件中现场非探伤作业人员所受误照射剂量估计值约为29.54 μSv,该估算剂量小于1 mSv的公众年有效剂量当量限值,也小于0.25 mSv每年的管理限值,管理部门根据调查和计算结果将本次误照射定性为辐射事件并通过该事件经验反馈提出监管建议。     

放射性废水的排放标准

评述了1977年以前一些国家和组织的放射性废水浓度和排放标准,讨论了ICRP第2号出版物计算MPC_W的方法。为了控制低放废水向环境排放,提供液体流出物处理的基础,应该考虑导出水浓度(DWC)。DWC的计算是基于公众的年摄入量限值(ALI)和年有效剂量当量限值。给出了计算的导出水浓度。     

外照射辐射监测中的运用量——ICRU第39号报告简介

辐射防护的基本限值量是人体器官剂量当量 H_T 和有效剂量当量 H_E。但是,H_T 和 H_E 都无法直接测量。为便于辐射防护评价,国际放射防护委员会(ICRГ)曾建议,在外照射情况下,采用剂量当量指数 H_I 作为辐射防护的次级限值量,即当身体内剂量当量的实际分布不明时,可以估算由软组织等效材料组成,直径为30cm 的 ICRU 球中,深度大于10mm 范     

光子和电子辐射外照射剂量当量的测定

光子和电子辐射外照射剂量当量的测定１引言多年以来，剂量当量就是辐射防护中的基本量。然而，在什么条件下来测定剂量当量却一直意见不一。１９７７年国际放射防护委员会（ＩＣＲＰ，１９７７）建议，对随机性效应的剂量限值应基于有效剂量当量ＨＥ来制定。国际辐射单位...     

改建后的研究性重水反应堆周围中子、γ混合辐射场的测量与评价

本工作对中国原子能科学研究院研究性重水反应堆周围的中子谱进行了测量。对于不同测点处的中子谱,中子平均能量在11—201keV 之间,最大能量低于5MeV;有效品质因数在2.5—5之间;在中子剂量当量总额中,以快中子剂量当量为主。还在反应堆正常运行条件下,测量了人员活动区的中子、γ剂量当量率。在大厅和地下室,中子、γ剂时当量之比的平均值分别为15%和31%,工作人员的年剂量当量有可能大于剂量当量限值。     

对计划照射中个人剂量约束的理解

基于对计划照射中个人剂量约束概念的理解,讨论了个人剂量约束在公众照射和职业照射中的应用。在计划照射情况下,公众照射的剂量约束值通常由国家监管机构建立或批准;对于职业照射,鼓励在核能行业组织和核能集团内建立职业照射个人剂量约束值,比审管部门规定具体的约束值可能更合适。     

Release of patients after therapy with unsealed radionuclides

After some therapeutic nuclear medicine procedures with unsealed radionuclides, precautions may be needed to limit doses to other people, but this is rarely the case after diagnostic procedures. Iodine-131 results in the largest dose to medical staff, the public caregivers, and relatives. Other radionuclides used in therapy are usually simple beta emitters (e.g. phosphorus-32, strontium-89, and yttrium-90) that pose much less risk. Dose limits apply to exposure of the public and medical staff from patients. Previously, the ICRP has recommended that a source-related dose constraint for optimisation of a few mSv/episode applies to relatives, visitors, and caregivers at home, rather than a dose limit. The present report recommends that young children and infants, as well as visitors not engaged in direct care or comforting, should be treated a s members of the public (i.e. be subject to the public dose limit.) The modes of exposure to other people are: external exposure; internal exposure due to contamination; and environmental pathways. Dose to adults from patients is mainly due to external exposure. Contamination of infants and children with saliva from a patient could result in significant doses to the child's thyroid. It is important to avoid contamination of children and pregnant women. After radioiodine therapy, mothers must cease breastfeeding immediately. Many types of therapy with unsealed radionuclides are contraindicated in pregnant females. Women should not become pregnant for some time after radioisotope therapy. Technetium-99m dominates discharges to the environment from excreta of nuclear medicine patients, but its short half-life limits its importance. The second largest discharges, iodine-131, can be detected in the environment after medical uses but with no measurable environmental impact. Storing patient's urine after therapy appears to have minimal benefit. Radionuclides released into modern sewage systems are likely to result in doses to sewer workers and the public that are well below public dose limits. The decision to hospitalise or release a patient should be determined on an individual basis. In addition to residual activity in the patient, the decision should take many other factors into account. Hospitalisation often involves a significant psychological burden as well as monetary and other costs that should be analysed and justified. Patients travelling after radioiodine therapy rarely present a hazard to other passengers if travel times are limited to a few hours. Environmental or other radiation-detection devices are able to detect patients who have had radioiodine therapy for several weeks after treatment. Personnel operating such detectors should be specifically trained to identify and deal with nuclear medicine patients. Records of the specifics of therapy with unsealed radionuclides should be maintained at the hospital and given to the patient along with written precautionary instructions. In the case of death of a patient who has had radiotherapy with unsealed radionuclides in the last few months, special precautions may be required.     

Dose Assessment for the Public due to Packages Shipping Radioactive Materials Hypothetically Sunk on a Continental Shelf

Abstract

Radioactive materials such as spent fuel (SF), PuO₂ powder, high level wastes (HLW) and fresh mixed oxide (MOX) fuel have been transported by sea between Europe and Japan for many years. Dose assessments for the public have been performed in the past for situations assuming packages shipping radioactive materials are hypothetically sunk on a continental shelf. These studies employed various conditions and methods in their assessments and the results were not always the same. In this study, the dose assessment for all types of package was performed under the same conditions and by the same methods. The effective dose to the members of the public for all materials is lower than previous evaluations due to more realistic assumptions used in this study. These evaluated effective doses are far less than the ICRP recommended limit (1 mSv.year^?1 averaged over 5 years).     

Analysis of the criteria used by the International Commission on Radiological Protection to justify the setting of numerical protection level values

This report compiles the various numerical protection level values published by the International Commission on Radiological Protection (ICRP) since its 1990 Recommendations (Publication 60). Several terms are used to denominate the protection levels: individual dose limit, 'maximum' individual dose, dose constraint, exemption level, exclusion level, action level, or intervention level. The reasons provided by the Commission for selecting the associated numerical values is quoted as far as available. In some cases the rationale is not totally explicit in the original ICRP report concerned; in such cases the Task Group that prepared the present report have proposed their own interpretation. Originally, this report was prepared by a Task Group at CEPN, a French research and development center, in behalf of IRSN, a French public expert body engaged in radiological protection and nuclear safety. It is published here with kind permission by CEPN and IRSN.     

Radiological impact of transport of radioactive material in UK by road and rail

Abstract

A survey has been carried out on the transport of radioactive materials by road and rail in the UK by the Health Protection Agency's Radiation Protection Division. This survey, carried out in 2004, is the latest in a series of periodic studies on the transport of radioactive materials by all modes of transport. Questionnaires were sent to hospital departments, radionuclide manufacturers, suppliers, and carriers, and to the nuclear and other industries, in order to obtain data on shipments of radioactive materials. Visits were made to hospitals, suppliers, carriers and some railway premises in order to observe working practices and radiological surveys were made while packages were handled. Assessments of individual doses to workers and members of the public were made, and occupational dosimetry data were also obtained. It was found that ～500 000 package movements take place by road annually in the UK, with ～4000 package movements annually by rail. Radiation doses to most transport workers are low, with an average dose of 0·6 mSv to general workers transporting medical and industrial sources. Doses to individual members of the public are very low, with average annual doses of less than 0·02 mSv.     

低放固体废物核素活度浓度上限值的推导

介绍了近地表处置设施在300 a监护期前及其以后的任何时间,公众个人及闯入者通过各种途径的受照剂量分别小于剂量限值时所要求的低放固体废物核素活度浓度上限值的推导方法及过程。以我国放射性废物近地表处置的基本安全要求为前提,并以遥田处置场和北龙处置场为对象,分析处置设施关闭后各景象的核素迁移过程和照射途径,建立各景象核素迁移的概念模型、数学模型,并计算各景象对人类产生的照射剂量。假设核素活度浓度与剂量之间呈线性关系,推导满足剂量准则下各景象各放射性核素的活度浓度上限值,选择最小的上限值,从而确定出低放固体废物各核素活度浓度上限值的量级。     

关于公众成员某些放射性核素的剂量转换因子的探讨

摄入放射性核素后,个体所受的剂量随年龄、代谢及身材大小的不同而变化。为了反映单位摄入量所产生的剂量随年龄的变化,本文把公众成员分为婴儿(1岁)、儿童(10岁)及成人三个年龄组,分别给出了某些放射性核素的剂量转换因子。但由于目前还缺乏可供应用的数据,不得不把国际放射防护委员会(ICRP)第30号出版物的剂量学模型和代谢数据用于公众成员(包括儿童和婴儿)的剂量估算,在计算儿童的剂量时,只考虑了体重的影响。本文还给出了公众成员吸入短寿命氡,(气土)子体的剂量转换因子。     

A dose constraint proposal for members of the public taking into account multi-unit nuclear power plants in Korea

In the 2007 recommendations, the International Commission on Radiological Protection (ICRP) changed from a process-based system of practices and intervention to a system based on the characteristics of the radiation exposure situation. In addition, the ICRP now recommends the application of source-related dose constraints under a planned exposure situation as a tool for the optimization of measures to protect the workers and members of the public. In this study, an analysis of radioactive effluents from Korean nuclear power plants and a public dose assessment were conducted using these source-related dose constraints. As a result, this analysis suggests appropriate dose constraints for members of the public taking into account the operation of multi-unit nuclear reactors at a single site in Korea.     

2001年绵阳科学城地区辐射环境监测与质量评价

2001年绵阳科学城地区主要环境介质(大气、河水、土壤和沉降等)中放射性水平与科学城开工前天然本底辐射没有显著性差别。通过对每个核设施烟囱流出物的测量与估算,获得了烟囱排放源项数据。利用该地区的大气扩散模式和多烟囱排放的剂量叠加原理,在评价坐标系中计算了叠加剂量分布。辐射环境质量评价表明80km范围内最大个人有效剂量是公众剂量限值的十万分之四,健康危害是危害约束值的千万分之二。表明环境影响是微弱的,是人们可以接受的。