Implications of safety requirements for the treatment of THMC processes in geological disposal systems for radioactive waste

The mission of nuclear safety authorities in national radioactive waste disposal programmes is to ensure that people and the environment are protected against the hazards of ionising radiations emitted by the waste.It implies the establishment of safety requirements and the oversight of the activities of the waste management organisation in charge of implementing the programme.In Belgium,the safety requirements for geological disposal rest on the following principles:defence-in-depth,demonstrability and the radiation protection principles elaborated by the International Commission on Radiological Protection(ICRP).Applying these principles requires notably an appropriate identification and characterisation of the processes upon which the safety functions fulfilled by the disposal system rely and of the processes that may affect the system performance.Therefore,research and development(R&D)on safety-relevant thermo-hydro-mechanical-chemical(THMC)issues is important to build confidence in the safety assessment.This paper points out the key THMC processes that might influence radionuclide transport in a disposal system and its surrounding environment,considering the dynamic nature of these processes.Their nature and significance are expected to change according to prevailing internal and external conditions,which evolve from the repository construction phase to the whole heatingecooling cycle of decaying waste after closure.As these processes have a potential impact on safety,it is essential to identify and to understand them properly when developing a disposal concept to ensure compliance with relevant safety requirements.In particular,the investigation of THMC processes is needed to manage uncertainties.This includes the identification and characterisation of uncertainties as well as for the understanding of their safety-relevance.R&D may also be necessary to reduce uncertainties of which the magnitude does not allow demonstrating the safety of the disposal system.

Towards Safer and More Sustainable Ways for Exploiting Nuclear Power

Future electricity systems are challenged by deep decarbonization and concurrently increasing demand and there are growing concerns that renewables cannot shoulder this alone. Starting from the proven principle of diversity, we argue for keeping the nuclear option open or even for expanding its use. However, the perspectives are dim for the current technology as safety concerns and social aversion remain as fundamental problems. While looking for future revolutionary safe and more sustainable nuclear concepts we first review the main characteristics of civil nuclear energy, as well as its safety records and technical progress. We then list the key requirements for innovative nuclear systems designs which are less dependent on active safety systems and human performance as well as social stability. This allows us to provide a concept by concept comparison and assessment of existing and novel technologies and designs including different coolants and neutron spectra. The results indicate a high potential for far-reaching improvements compared to most advanced LWRs, although none of the candidate concepts meets all requirements convincingly, yet, helium cooled, small modular reactors (HTR-PM) come closest. We end by stressing the need for future research and development, and keeping human capital and know-how in nuclear energy;we call for an urgent increase in government and international RD&D funding by the order of a few hundreds of billions of USD per year, which will likely lead to breakthroughs that will restart productivity growth in severely affected stagnating modern economies.

燃料电池电动车安全要求国家标准解析

In order to meet new challenges brought by the development of fuel cell electric vehicle(FCEV)industry,we are in urgent need to update and refine the safety requirements for FCEVs.To this end,GB/T 24549-2020,Fuel cell electric vehicles-Safety requirements,was issued on September 29,2020.This paper analyzes the main technical content of the standard as well as its similarities and differences with the 2009 Version.

Safety Guide-Line and Requirements for Distributed Raman Amplification and its Applications to WDM Transmission Systems

This paper discusses optical safety issues in distributed Raman amplification systems. Given the extremely high pump powers, network service operators have critical issues for safety. This paper focuses on both " eye-hazard" and " fire-hazards" .

Experience gained in analyzing severe accidents for WWER RP using CC SOCRAT

The current Russian regulatory documents on the safety of nuclear power plant(NPP)specify the requirements regarding design basis accidents(DBAs)and beyond design basis accidents(BDBAs),including severe accidents(SAs)with core meltdown,in NPP design(NP-001-15,NP-082-07,and others).For a rigorous calculational justification of BDBAs and SAs,it is necessary to develop an integral CC that will be in line with the requirements of regulatory documents on verification and certification(RD-03-33-2008,RD-03-34-2000)and will allow for determining the amount of data required to provide information within the scope stipulated by the requirements for the structure of the safety analysis report(SAR)(NP-006-16).The system of codes for realistic analysis of severe accidents(SOCRAT)(formerly,thermohydraulics(RATEG)/coupled physical and chemical processes(SVECHA)/behavior of core materials relocated into the reactor lower plenum(HEFEST))was developed in Russia to analyze a wide range of SAs at NPP with water-cooled water-moderated power-generating reactor(WWER)at all stages of the accident.Enhancements to the code and broadening of its applicability are continually being pursued by the code developers(Nuclear Safety Institute of the Russian Academy of Sciences(IBRAE RAN))with OKB Gidropress JSC and other organizations.Currently,the SOCRAT/В1 code can be used as a base tool to obtain realistic estimates for all parameters important for computational justification of the reactor plant(RP)safety at the in-vessel stage of SAs with fuel melting.To perform analyses using CC SOCRAT/В1,the experience gained during execution of thermohydraulic codes is applied,which allows for minimizing the uncertainties in the results at the early stage of an accident scenario.This study presents the results of the work performed in 2010–2020 in OKB Gidropress JSC using the CC SOCRAT/В1.Approaches have been considered to develop calculational models and analyze SAs using CC SOCRAT.This process,which is clearly structured in OKB Gidropress JSC,provides a noticeable reduction in human involvement,and reduces the probability of erroneous results.This study represents the principal results of the work performed in 2010–2020 in OKB Gidropress JSC using the CC SOCRAT,as well as a list of the tasks planned for 2021–2023.CC SOCRAT/B1 is used as the base thermohydraulic SAs code.