|NEWS AND INFORMATION
|Year : 2017 | Volume
| Issue : 2 | Page : 103-105
Summary of IAEA safety standards series no. SSG-42: Specific Safety guide on 'safety of nuclear fuel reprocessing facilities' (May 2017)
Head, Radiation Safety Systems Division, Radiation Hazards Control Section, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, India
|Date of Web Publication||13-Jul-2017|
R K Gopalakrishnan
Head, Radiation Safety Systems Division, Radiation Hazards Control Section, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gopalakrishnan R K. Summary of IAEA safety standards series no. SSG-42: Specific Safety guide on 'safety of nuclear fuel reprocessing facilities' (May 2017). Radiat Prot Environ 2017;40:103-5
|How to cite this URL:|
Gopalakrishnan R K. Summary of IAEA safety standards series no. SSG-42: Specific Safety guide on 'safety of nuclear fuel reprocessing facilities' (May 2017). Radiat Prot Environ [serial online] 2017 [cited 2019 Jun 25];40:103-5. Available from: http://www.rpe.org.in/text.asp?2017/40/2/103/210578
The Safety Guide on the Safety of Nuclear Fuel Reprocessing Facilities gives recommendations on how to meet the requirements established in the Safety Requirements publication on the Safety of Nuclear Fuel Cycle Facilities, IAEA Safety Standards Series No. NS-R-5 (Rev. 1). It covers the safety of reprocessing facilities, the protection of workers, the public and the environment and does not include Thorex process and waste storage and conditioning.
This guide comprises eight sections and two annexes and provides general safety recommendations for a reprocessing facility. Guidance is also provided for safety considerations at the design stage, including safety analysis for operational states and accident conditions, the safety aspects of radioactive waste management in a reprocessing facility and other design considerations. The guide also addresses safety considerations in the construction stage, commissioning, operation including maintenance, criticality control, radiation protection, industrial safety, management of waste and effluents, and emergency planning and preparedness. The safety aspects during preparation for the decommissioning of a reprocessing facility is also addressed. Two important annexures are included in this guide. Annex-I shows the typical main process routes for a reprocessing facility and Annex II provides examples of structures, systems, and components important to safety in reprocessing facilities, grouped in accordance with the processes identified in Annex I.
The following sections give summary of the siting, design, construction, commissioning, operation and decommissing aspects mentioned in this report.
| Siting|| |
Specific requirements for site evaluation, site selection criteria, and the site selection process for nuclear facilities are given in various safety documents and guides of IAEA, namely, IAEA Safety Standards Series No. NS-R-3 (Rev. 1), SSG-9, SSG-18, SSG-21, SSG-35, NS-G-3.2, and NS-R-5 (Rev. 1). In the siting of new reprocessing facilities, particular consideration should be given to the following: (a) The site's ability to accommodate normal discharges of radioactive material to the environment during operation, including the physical factors affecting the dispersion and accumulation of released radioactive material and the radiation risk to workers, the public, and the environment. (b) The suitability of the site to accommodate the engineering and infrastructure requirements of the facility, and (c) Feasibility of implementing the requirements of GSR Part 7 in an emergency, external hazards such as flooding and earthquake and nuclear security.
| Design|| |
The main safety functions in the design stage of a reprocessing facility are: (1) Prevention of criticality; (2) Confinement of radioactive material (including protection against internal exposure, removal of decay heat and dilution of gases from radiolysis); (3) Protection against external exposure. Criticality hazards are required to be controlled by design as far as practicable. Where a credible hazard cannot be eliminated, the double contingency principle is the preferred approach for the prevention of criticality using design. In accordance with the criticality safety analysis, instruments specifically intended to detect accumulations and inventories of fissile material should be installed where required. Such instruments should also be used to verify the fissile inventory during decommissioning. For confinement of radioactive materials, in a reprocessing facility (for most areas), three barriers (or more, as required by the safety analysis) should be provided, in accordance with a graded approach. For the protection of workers, static barriers (at least one is required between radioactive material and working areas) should be provided to protect workers from internal and external exposure. The design should specify details to ensure their integrity and effectiveness and where appropriate, to facilitate maintenance. Where easily dispersible radioactive material is processed and a loss of containment with the potential for contamination (or ingestion/inhalation) is a major risk, glove boxes are often the preferred design solution. To avoid the inadvertent spread of contamination by personnel, control points with personnel contamination monitoring equipment for workers (for exposed skin surfaces, clothing, and working suits) should be located at the exit airlocks and barriers from areas that could be contaminated. These should be located close to workplaces with contamination hazards, to the extent practicable. The design feature with respect to the protection of public and environment should ensure that all engineered discharge points from the ventilation system should be provided with equipment for the reduction of airborne activity. Such equipment should be designed to provide protection in normal operation, anticipated operational occurrences, and accident conditions.
| Construction|| |
A construction phase for a fuel reprocessing facility will involve a large number of designers and contractors, over a considerable span of time, with the likelihood that design, construction and early commissioning will be taking place simultaneously in different sections of the facility (SSG-38). Reprocessing facilities are large and complex chemical and mechanical facilities, and as such, modularized, standardized components should be used in their construction as far as practicable.
| Commissioning|| |
This Safety Guide addresses only the commissioning of safety related aspects of reprocessing facilities. Commissioning should be conducted, as far as practicable, as if the facility were fully operational. In particular, the requirements for good operational practices, housekeeping and access to supervised and controlled areas should be increasingly applied through commissioning. For a reprocessing facility, the commissioning is required to be divided into a number of distinct stages, according to the objectives to be achieved. In general, this may involve four stages, construction, inactive, or cold commissioning, Trace active or U commissioning, Active or “hot processing” commissioning.
| Operation|| |
Given the large scale and complexity of fuel reprocessing facilities, there is a particular need for rigorous control, planning and coordination of the work to be undertaken in the facility, whether for operation, routine maintenance, and non-routine maintenance. Suitable arrangements should be made to gather, assess, and propagate any lessons learned during the commissioning stage of the facility and on an on-going basis, during the operations stage. Comprehensive training should cover both automatic operations and manual operations. Dedicated training facilities should be established as necessary, with the training emphasis on activities according to their potential safety consequences. To ensure that, under normal circumstances, the reprocessing facility operates well within its operational limits and conditions, a set of operational sub-limits should be defined at lower levels by the operating organization. The margins should be derived from the design considerations and from experience of operating the facility (both during commissioning and subsequently). As reprocessing facilities are large and complex facilities, maintenance should be coordinated and managed to ensure that unanticipated interactions, either with the operation or between two maintenance activities, will not result in negative safety consequences. The accurate and timely calibration of equipment is important for the safe operation of a reprocessing facility. Calibration procedures and standards should cover equipment used by facilities and by organizations that support the reprocessing facility. The management system for a reprocessing facility should include a standard process for all modifications. The requirements for criticality safety and radiation protection in operation in a reprocessing facility are established in NS-R-5 (Rev. 1) and general recommendations are provided in SSG-27.
The operational radiation protection programme should take into account the large inventories, the variety of sources, the complexity and the size of the reprocessing facility. It also should include provisions for detecting changes in the radiation status (e.g., hot spots, slow incremental increases or reductions in radiation or contamination levels) of equipment (e.g., pipes, vessels, drip trays, and filters) or rooms (e.g., contaminated deposits and increase of airborne activity), including monitoring of effluents or environmental monitoring. There should be appropriate provisions for the measurement of radiation and contamination to ensure compliance with regulatory and operational limits controlling doses to individuals. Instrumentation should be provided, where appropriate, to give prompt, reliable, and accurate indications of airborne radiation and direct radiation in normal operation and accident conditions. Doses to personnel should be estimated in advance and should be monitored during work activities, using suitably located devices and/or personal dosimeters (preferably alarm type) where appropriate. The methodology for assessing doses due to internal exposure should be based on in vivo and in vitro monitoring, supplemented by the timely collection of data from air sampling in the workplace, in combination with worker occupancy data. Where necessary, the relationship between fixed detectors and individual doses should be verified by the use of personal air samplers in sampling campaigns.
The potential for fire or exposure to chemical and other industrial hazards is significant for reprocessing facilities due to their size and complexity, the nature of the materials processed and stored and the processes used. The procedures and training for responses to fires in areas containing fissile material should pay particular attention to the prevention of a criticality and preventing any unacceptable reduction of criticality safety margins and from the hazards associated with the use of strong acids and hazardous chemicals. Particular attention should be given to all processes at elevated temperatures and to the hazards associated with the use of organic solvents in the extraction stages. A strategy for the management of radioactive waste should be established by the operating organization. The strategy should be implemented on the site of the reprocessing facility in accordance with the types of waste to be processed and the national waste management policy and strategy. The operating organization should establish an appropriate management structure to operate and control discharge points from the facility as well as the overall discharge. Radioactive gaseous discharges should be treated, as appropriate, by dedicated off-gas treatment systems and by means of HEPA filters. All liquids collected from the site of the reprocessing facility (e.g., surface and underground water near buildings and process effluents) that have to be discharged into the environment should be assessed and managed in accordance with authorizations. The scale, complexity, and the level of potential hazards of reprocessing facilities mean that arrangements for emergency preparedness (for protecting workers, the public and the environment in the event of an accidental release) and maintaining and updating the emergency plan are particularly important.
| Decommissioning|| |
The reprocessing facility should be sited, designed, constructed and operated (maintained and modified) to facilitate eventual decommissioning, as far as practicable. Recommendations for the decommissioning of nuclear fuel cycle facilities are provided in WS-G-2.4 based on the requirements established in GSR Part 6. The developed decommissioning plan and the safety assessment should be periodically reviewed and updated throughout the reprocessing facility's commissioning and operation stages. For any period between a planned or unplanned shutdown and before decommissioning starting, safety measures should be implemented to maintain the reprocessing facility in a safe and stable state, including measures to prevent criticality, the spread of contamination and fire.
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