International law obligations for the disposal of Fukushima nuclear-contaminated water under the principles of nuclear safety

The disposal of contaminated water from Japan’s Fukushima nuclear power plant is a significant international nuclear safety issue with considerable cross-border implications.This matter requires compliance not only with the law of the sea but also with the principles of nuclear safety under international law.These principles serve as the overarching tenet of international and China’s domestic nuclear laws,applicable to nuclear facilities and activities.The principle of safety in nuclear activities is fully recognized in international and domestic laws,carrying broad legal binding force.Japan’s discharge of nuclear-contaminated water into the sea violates its obligations under the principle of safety in nuclear activities,including commitments to optimum protection,as low as reasonably practicable,and prevention.The Japanese government and the International Atomic Energy Agency(IAEA)have breached the obligation of optimum protection by restricting the scope of assessments,substituting core concepts,and shielding dissenting views.In the absence of clear radiation standards,they have acted unilaterally without fulfilling the obligation as low as reasonably practicable principle.The discharge of Fukushima nuclear-contaminated water poses an imminent and unpredictable risk to all countries worldwide,including Japanese residents.Japan and the IAEA should fulfill their obligations under international law regarding disposal,adhering to the principles of nuclear safety,including optimum protection,the obligation as low as reasonably practicable,and prevention through multilateral cooperation.Specifically,the obligation to provide optimum protection should be implemented by re-evaluating the most reliable disposal technologies and methods currently available and comprehensively assessing various options.The standard of the obligation as low as reasonably practicable requires that the minimization of negative impacts on human health,livelihoods,and the environment should not be subordinated to considerations of cutting costs and expenses.Multilateral cooperation should be promoted through the establishment of sound multilateral long-term monitoring mechanisms for the discharge of nuclear-contaminated water,notification and consultation obligations,and periodic assessments.These obligations under international law were fulfilled after the accidents at the Three Mile Island and Chernobyl nuclear power plants.The implications of the principles of nuclear safety align with the concept of building a community of shared future for nuclear safety advocated by China.In cases of violations of international law regarding the disposal of nuclear-contaminated water that jeopardize the concept of a community of a shared future for nuclear safety,China can also rely on its own strength to promote the implementation of due obligations through self-help.

Establishing a mechanism for international cooperation for Fukushima nuclear-contaminated water monitoring

The Japanese government’s unilateral decision to discharge the nuclear-contaminated water from the Fukushima nuclear power plant into the ocean has caused immense nuclear safety risks.Monitoring the unclear contaminated water is a starting point to combat these risks and seek remedies for the rights and interests of all concerned parties.The establishment of a mechanism for international cooperation in this respect is necessary to handle the risks of the Fukushima nuclear-contaminated water and to lay the foundation of a framework for tackling any future disposal of nuclear-contaminated water following Japan’s example.At present,the international legal systems in the spheres of nuclear safety and security,marine environmental protection,and other areas,as well as the questioning of the monitoring reports of the International Atomic Energy Agency(IAEA)by the relevant parties,the monitoring practices of historical nuclear accidents,and numerous radioactivity monitoring mechanisms have provided the institutional and practical basis for constructing such a mechanism.The mechanism can be promoted by the IAEA through its existing mechanisms or be jointly initiated by China,the Russian Federation,the Republic of Korea,the Democratic People’s Republic of Korea,and the Pacific Island countries,among other stakeholders.Specifically,this mechanism should consist of three levels:first,the framework of the basic legal system,including the cooperative principles of national sovereignty,interest-relatedness,and procedural fairness,and the signing of the Framework Convention on the Monitoring of Fukushima’s nuclear-contaminated water and its Optional Protocol;second,the organizational structure and its responsibilities,which may include the Conference of Parties as the decision-making body,the Secretariat as the central coordinating body,and the monitoring committees in various fields as specific implementing agencies;and third,specific administrative arrangements,which involve the standardization of monitoring,the management system of monitoring networks and stations,the rules for monitoring procedures,and the rules for the utilization of the monitoring data,etc.With the urgent need for the scientific and fair monitoring of Fukushima’s nuclear-contaminated water,China,as a stakeholder country,can promote the establishment of such a mechanism for monitoring nuclear-contaminated water through the following paths:①It is necessary to clarify the factors affecting the construction of an international cooperation mechanism for monitoring nuclear-contaminated water so as to ascertain the standpoints of the stakeholders,claims of their interests,contents of their cooperation,and the relevant international relations.②On the basis of existing practices,China should consider improving the monitoring mechanism to cope with the risks of the discharge of Fukushima’s nuclear-contaminated water by formulating targeted policies and systems,setting up specialized monitoring institutions,and establishing a systematic monitoring network system.③This is an effective way for China to actively promote the participation of stakeholders in the construction of an international cooperation mechanism for monitoring nuclear-contaminated water in Fukushima by further innovating the dissemination mechanism to address the risk of Fukushima’s nuclear-contaminated water discharging into the sea and facilitating the identification of issues for international cooperation in monitoring Fukushima’s nuclear-contaminated water based on the concept of a community with a shared future for mankind.

Reflections on nuclear safety culture from the perspective of traditional Chinese culture

Nuclear safety is a major concern given the rapid development of nuclear power in the modern era.Fostering a nuclear safety culture is an important means of ensuring nuclear safety.In China,a country with a rich historical and cultural heritage,traditional culture will influence the development of a nuclear safety culture.This study explored the origin and levels of nuclear safety culture and reflected on nuclear safety culture from the perspective of traditional Chinese culture.The purpose of this study is to integrate the essence of traditional culture into the nuclear safety culture and foster a nuclear safety culture with Chinese characteristics.

Ensuring Nuclear Safety

The Fukushima accident precipitates overall safety inspection by China Guangdong Nuclear Power Holding Corp The Fukushima nuclear accident in Japan had barely made headlines around the world when China Guangdong Nuclear Power Holding Corp.(CGNPC),a nuclear power magnate in China。

Status of Severe Accident Management Guidelines at Kozloduy Nuclear Power Plant

The objective of this paper is to present the current organization of the Emergency Procedures including Emergency Operating Procedures (EOP) and Severe Accident Management Guidelines (SAMG) in Kozloduy Nuclear Power Plant (KNPP) as a function of the severity of the accident conditions. Special attention is paid to SAMG. It is described when the SAMG are used and at which conditions in a transition between the EOPs and the SAMG should be made. The Critical Safety Function Restoration Guidelines and their connections with SAMGs and EOPs are also discussed. The arrangement of SAMG is described in detail, since in the KNPP exist 2 types of SAMGs for Main Control Room (MCR) and for the Accident Management Centre (AMC) and they contain the same strategies, but they are different in format. Both types are symptom oriented procedures, but those for MCR are in 2-column-format with interconnections, whereas those for the AMC are developed in a logical manner and simplified for people, who take decisions. In the paper, they are also discussed the adopted strategies in existing SAMG that should be followed to recover from a damaged core condition and to prevent or mitigate the release of fission products. In the paper, they are also described a number of technical measures for management and mitigation of severe accidents, which are implemented in KNPP before and after the Fukushima accident. Many of them are common for WWER-1000 type of reactors, but some of them are unique and plant specific. This information can be useful for operators of other WWER type reactors or even PWR reactors.

Assessment of Axial Power Peaking Factors in GHARR-1 LEU Core: A Decadal Simulation Analysis

This study aims to thoroughly investigate the axial power peaking factors (PPF) within the low-enriched uranium (LEU) core of the Ghana Research Reactor-1 (GHARR-1). This study uses advanced simulation tools, like the MCNPX code for analysing neutron behavior and the PARET/ANL code for understanding power variations, to get a clearer picture of the reactor’s performance. The analysis covers the initial six years of GHARR-1’s operation and includes projections for its whole 60-year lifespan. We closely observed the patterns of both the highest and average PPFs at 21 axial nodes, with measurements taken every ten years. The findings of this study reveal important patterns in power distribution within the core, which are essential for improving the safety regulations and fuel management techniques of the reactor. We provide a meticulous approach, extensive data, and an analysis of the findings, highlighting the significance of continuous monitoring and analysis for proactive management of nuclear reactors. The findings of this study not only enhance our comprehension of nuclear reactor safety but also carry significant ramifications for sustainable energy progress in Ghana and the wider global context. Nuclear engineering is essential in tackling global concerns, such as the demand for clean and dependable energy sources. Research on optimising nuclear reactors, particularly in terms of safety and efficiency, is crucial for the ongoing advancement and acceptance of nuclear energy.

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.

中法关于核能与环境的联合研究

本文聚焦核能的环境影响问题,将解决如下核能发电相关的主要环境问题:(1)控制正常运行条件下核设施的放射性排放,评估其非放射性环境影响(取水与非放射性水的排放);(2)乏燃料与放射性废物的长期管理,主要是通过地质处置库处理的乏燃料或放射性废物;(3)防止和缓解严重核事故以及核事故的放射性释放;(4)改善核安全水平,以限制核能的环境影响,提升公众的核能接受度。核能的温室气体排放水平非常低,可以根据需求供应大规模、可调度电力,在此方面核能具有独特的优势。在正常运行工况下,核电站每年释放到周围公众的有效辐射剂量可以忽略不计。国际社会已经开展了大量的努力,以确定可持续管理地质处置条件下高放长寿命放射性废物的方法。过去几次严重核事故中获得的经验为核能生产相关的安全问题提供了经验,也促成了重要的安全改进,其中包括反应堆的设计和运行管理方面的改善以及事故管理指导方针的制定等。事实证明,这些经验是非常宝贵的。严重事故的环境风险已经被大幅降低,相关的规约也已经建立起来,以最大限度地减少严重核事故条件下放射性物质的释放,并避免大规模的人员疏散。还需要继续采取措施,改善反应堆的安全性,提升核工业与核监管机构的透明度,以进一步降低核能的环境影响。

Fast nuclide identification based on a sequential Bayesian method

The rapid identification of radioactive substances in public areas is crucial.However,traditional nuclide identification methods only consider information regarding the full energy peaks of the gamma-ray spectrum and require long recording times,which lead to long response times.In this paper,a novel identification method using the event mode sequence(EMS)information of target radionuclides is proposed.The EMS of a target radionuclide and natural background radiation were established as two different probabilistic models and a decision function based on Bayesian inference and sequential testing was constructed.The proposed detection scheme individually processes each photon.When a photon is detected and accepted,the corresponding posterior probability distribution parameters are estimated using Bayesian inference and the decision function is updated.Then,value of the decision function is compared to preset detection thresholds to obtain a detection result.Experiments on different target radionuclides(137Cs and 60Co)were performed.The count rates of the regions of interest(ROI)in the backgrounds between[651,671],[1154,1186],and[1310,1350]keV were 2.35,5.14,and 0.57 CPS,respectively.The experimental results demonstrate that the average detection time was 6.0 s for 60Co(with an activity of 80400 Bq)at a distance of 60 cm from the detector.The average detection time was 7 s for 137Cs(with an activity of 131000 Bq)at a distance of 90 cm from the detector.The results demonstrate that the proposed method can detect radioactive substances with low activity.

Secondary and activated X(γ)radiation of SPHIC particle therapy facility

We report the secondary X(γ)radiation from the accelerator in a normal operating state and activated X(γ)radiation from the accelerator devices when the accelerator stops operating in the cancer treatment facility of the Shanghai Proton and Heavy Ion Center(SPHIC).These radiation measurements show us the structural radiation distribution along the beam lines and devices inside the accelerator room when the beam is on and off and can support the radiation protection design of the accelerator facility used for cancer treatment and help evaluate the accumulated radiation dose in the case of an emergency,such as a personal safety system failure or a radiation accident.The radiation dose rate measured in this facility shows that the facility is safe from the radiation protection point.After shooting the quality assurance(QA)beam,the radiation dose rate in the treatment room was also measured to investigate the radiation dose space distribution and decay time dependence.In addition,the time period before safely entering the treatment room after determining the shooting of the QA beam is recommended to be approximately 5 min.

An old issue and a new challenge for nuclear reactor safety

Nuclear reactor safety(NRS)and the branch accident analysis(AA)constitute proven technologies:these are based on,among the other things,long lasting research and operational experience in the area of water cooled nuclear reactors(WCNR).Large break loss of coolant accident(LBLOCA)has been,so far,the orienting scenario within AA and a basis for the design of reactors.An incomplete vision for those technologies during the last few years is as follows:Progress in fundamentals was stagnant,namely in those countries where the WCNR were designed.Weaknesses became evident,noticeably in relation to nuclear fuel under high burn-up.Best estimate plus uncertainty(BEPU)techniques were perfected and available for application.Electronic and informatics systems were in extensive use and their impact in case of accident becomes more and more un-checked(however,quite irrelevant in case of LBLOCA).The time delay between technological discoveries and applications was becoming longer.The present paper deals with the LBLOCA that is inserted into the above context.Key conclusion is that regulations need suitable modification,rather than lowering the importance and the role of LBLOCA.Moreover,strengths of emergency core cooling system(ECCS)and containment need a tight link.

RETHINKING NUCLEAR POWER SAFETY

The Fukushima nuclear accident sounds alarm bells in China’s nuclear power industry In the wake of the Fukushima nucleara ccident caused by the earthquake andt sunami in Japan,the safety of nuclearp ower plants and the development of nuclear power have raised concerns,

Study of Accident Progression in Unsealed WWER-1000/V320 Reactor during Maintenance

This paper discusses the results obtained during an investigation of WWER-1000 Nuclear Power Plant (NPP) behavior at shutdown reactor during maintenance. For the purpose of the analysis is selected a plant operating state with unsealed primary circuit by removing the MCP head. The reference nuclear power plant is Unit 6 at Kozloduy NPP (KNPP) site. RELAP5/ MOD3.2 computer code has been used to simulate the transient for WWER-1000/V320 NPP model. A model of WWER-1000 based on Unit 6 of KNPP has been developed for the RELAP5/MOD3.2 code at the Institute for Nuclear Research and Nuclear Energy-Bulgarian Academy of Sciences (INRNE-BAS), Sofia. The plant modifications performed in frame of modernization program have been taken into account for the investigated conditions for the unsealed primary circuit. The most specific in this analysis compared to the analyses of NPP accidents at full power is the unavailability of some important safety systems. For the purpose of the present investigation two scenarios have been studied, involving a different number of safety systems with and without operator actions. The selected initiating event and scenarios are used in support of analytical validation of Emergency Operating Procedures (EOP) at low power and they are based on the suggestions of leading KNPP experts and are important in support of analytical validation of EOP at low power.

High-entropy(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))_(2)Hf_(2)O_(7) ceramic with superb resistance to radiation-induced amorphization

Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)high-entropy ceramic(HE-RE2 Hf_(2)O_(7))for control rod was prepared by solid-state reaction method.The ion irradiation of HE-RE_(2) Hf_(2)O_(7)with 400 keV Kr+at 400℃was investigated using a 400 kV ion implanter and compared with single-component pyrochlore Gd2 Hf_(2)O_(7)to evaluate the irradiation resistance.For HE-RE2 Hf_(2)O_(7),the phase transition from pyrochlore to defective fluorite is revealed after irradiation at 60 dpa.After irradiation at 120 dpa,it maintained crystalline,which is comparable to Gd2 Hf_(2)O_(7)but superior to the titanate pyrochlores previously studied.Moreover,the lattice expansion of HE-RE2 Hf_(2)O_(7)(_(0.2)2%)is much lower than that of Gd2 Hf_(2)O_(7)(0.62%),indicating excellent irradiation damage resistance.Nanoindentation tests displayed an irradiation-induced increase in hardness and a decrease in elastic modulus by about 2.6%.Irradiation-induced segregation of elements is observed on the surface of irradiated samples.In addition,HE-RE2 Hf_(2)O_(7)demonstrates a more sluggish grain growth rate than Gd2 Hf_(2)O_(7)at 1200℃,suggesting better high-temperature stability.The linear thermal expansion coefficient of HE-RE2 Hf_(2)O_(7)is 10.7×10-6 K-1 at 298–1273 K.In general,it provides a new strategy for the design of the next advanced nuclear engineering materials.

Influence of active and passive equipment for advanced pressurized water reactor on thermal hydraulic and source term behavior in severe accidents

Extensive studies have been carried out on the behavior of core degradation and fission products of common pressurized water reactors(PWRs).However,few of them have investigated the relationship between thermal hydraulic and fission product behavior in advanced passive PWRs.Due to the impact of thermal hydraulic be-haviors in different accident sequences on the release and transportation of fission products,an integrated severe accident analysis(ISAA)code with highly coupled thermal hydraulic and source term calculations is required to simultaneously analyze thermal hydraulic and source term behavior.For advanced passive PWRs,important safety systems that may affect the behavior of the core and fission products should be considered.It is therefore necessary to simulate the thermal hydraulic and fission product behavior of advanced passive PWRs.In this study,the ISAA code is adopted to simulate the occurrence of a hypothetical double ended cold leg LBLOCA of HPR1000 in three scenarios of equipment failure.The results show that the high-temperature fuel rods and cladding ma-terials exhibit delayed failure at the lower position of the active core,whereas earlier failure at higher position during the reflooding.Active and passive equipment affects fuel temperature,the oxidation conditions of the fuel,the interaction of fission products and structural materials,and the state of the fuel,thereby affecting the release of fission products in the fuel.HPR1000 only relies on passive equipment to relieve the core degradation in severe accidents,realize the in-vessel retention of melt,and eliminate the ex-vessel release possibility of fission product.It is hoped that the results can provide references for HPR1000 to formulate the severe accident management guidelines(SAMG).