IAEA Develops New Benchmarks for Computational Methods for Utilization, Operation and Safety Analysis of Research Reactors

Under a recently completed IAEA project, experts have developed a benchmark database for computational methods and tools used for the utilization, operation and safety analysis of research reactors.
A benchmark in this context is an experiment conducted in a research reactor, including the measured data and sufficient details about the research reactor and the experimental facility.
“The benchmark allows modelling the experiment using a computer code,” said Frances Marshall, the lead officer of the four-year IAEA coordinated research project (CRP). “The results of the calculations are compared with the data to assess whether the code and the modelling done are adequate for the case under study.”
Benchmarking computational codes and methods against experimental data is key to assessing the validity of the codes’ application to the design, operation, utilization and safety analysis of research reactors.
The benchmarks can be used to:
- train new professionals in research reactors by allowing them to develop their modelling skills using well-documented cases (benchmarks);
- improve modelling requiring advanced code functions and user knowledge;
- conduct formal validation of codes, models or user qualifications.
The CRP benchmarked many of the most common research reactor codes used at international level, and demonstrated that the codes, methods and the nuclear data available yield results that, in the majority of cases, meet the operational requirements of research reactor facilities.
The collected data will be used to update the IAEA’s Research Reactor Benchmarking Database: Facility Specification and Experimental Data, which is a valuable resource for assisting the optimization of research reactor core management and experimental programmes, while maintaining safety.
The project was carried out by several research reactor operating organizations with ongoing irradiation and measurement activities in fuel burnup and material and target activation. The participants provided experimental data and research reactor facility specifications covering a broad range of research reactor types and power levels. The quality of the data was assessed by an independent review to confirm its use as benchmarks, leading to the establishment of 14 benchmark specifications using data from nine different research reactors. Calculations were then made by at least two participants for each of the benchmarks, using a wealth of codes, leading to a total of 53 analysis contributions.
The overall objective of the CRP was to encourage cooperation, foster the exchange of information and increase the knowledge and expertise in numerical analysis to improve the design, operation, utilization, safety and decommissioning of research reactors, in particular in fuel multicycle depletion analysis, and material and target activation calculations.

Climate Change Is Expected to Have Far-reaching Effects and DOE and FERC Should Take Actions

Climate change is expected to affect every aspect of the electricity grid—from generation, transmission, and distribution, to demand for electricity. For example, more frequent droughts and changing rainfall patterns may diminish hydroelectricity in some areas, and increasing wildfires may damage transmission lines.
We testified about how the Department of Energy and the Federal Energy Regulatory Commission could enhance grid resilience. We recommended that DOE develop a strategy for doing so and coordinate efforts within the department, and that FERC assess grid risks and plan how to promote resilience.
Climate change is expected to have far-reaching effects on the electricity grid that could cost billions and could affect every aspect of the grid from generation, transmission, and distribution to demand for electricity, according to several reports GAO reviewed. The type and extent of these effects on the grid will vary by geographic location and other factors. For example, reports GAO reviewed stated that more frequent droughts and changing rainfall patterns may adversely affect hydroelectricity generation in Alaska and the Northwest and Southwest regions of the United States. Further, transmission capacity may be reduced or distribution lines damaged during increasing wildfire activity in some regions due to warmer temperatures and drier conditions. Moreover, climate change effects on the grid could cost utilities and customers billions, including the costs of power outages and infrastructure damage.
Since 2014, the Department of Energy (DOE) and the Federal Energy Regulatory Commission (FERC) have taken actions to enhance the resilience of the grid. For example, in 2015, DOE established a partnership with 18 utilities to plan for climate change. In 2018, FERC collected information from grid operators on grid resilience and their risks to hazards such as extreme weather. Nevertheless, opportunities exist for DOE and FERC to take additional actions to enhance grid resilience to climate change. For example, DOE identified climate change as a risk to energy infrastructure, including the grid, but it does not have an overall strategy to guide its efforts. GAO's Disaster Resilience Framework states that federal efforts can focus on risk reduction by creating resilience goals and linking those goals to an overarching strategy. Developing and implementing a department-wide strategy that defines goals and measures progress could help prioritize DOE's climate resilience efforts to ensure that resources are targeted effectively. Regarding FERC, it has not taken steps to identify or assess climate change risks to the grid and, therefore, is not well positioned to determine the actions needed to enhance resilience. Risk management involves identifying and assessing risks to understand the likelihood of impacts and their associated consequences. By doing so, FERC could then plan and implement appropriate actions to respond to the risks and achieve its objective of promoting resilience.
According to the U.S. Global Change Research Program, changes in the earth's climate are under way and expected to increase, posing risks to the electricity grid that may affect the nation's economic and national security. Annual costs of weather-related power outages total billions of dollars and may increase with climate change, although resilience investments could help address potential effects, according to the research program. Private companies own most of the electricity grid, but the federal government plays a significant role in promoting grid resilience—the ability to adapt to changing conditions; withstand potentially disruptive events; and, if disrupted, to rapidly recover. DOE, the lead agency for grid resilience efforts, conducts research and provides information and technical assistance to industry. FERC reviews mandatory grid reliability standards.
This testimony summarizes GAO's report on grid resilience to climate change. Specifically, the testimony discusses (1) potential climate change effects on the electricity grid; and (2) actions DOE and FERC have taken since 2014 to enhance electricity grid resilience to climate change effects, and additional actions these agencies could take. GAO reviewed reports and interviewed agency officials and 55 relevant stakeholders.

Ensuring the Safety of Nuclear Installations: Lessons Learned from Fukushima

The Fukushima Daiichi nuclear accident reinforced the importance of having adequate national and international safety standards and  guidelines in place so that nuclear power and technology remain safe and continue to provide reliable low carbon energy globally.
By recognizing the lessons learned from the 2011 accident, the IAEA has been revising its global safety standards to ensure that Member States continue to receive up-to-date guidance of high quality.
“The Fukushima Daiichi accident has left a very large footprint on nuclear safety thinking, which manifested itself in a distinct shift from the prevention of design basis accidents to the prevention of severe accidents and, should an accident occur, the practical elimination of its consequences,” said Greg Rzentkowski, Director of the IAEA’s Division of Nuclear Installation Safety.
Following the accident, through a review of relevant standards, including the IAEA safety standard on design safety, experts found that a higher level of safety could be incorporated into existing nuclear power plants by adhering to more demanding requirements for protection against external natural hazards and by enhancing the independence of safety levels so that, even if one layer fails, another layer is unimpacted and stops an accident from happening.
While requirements for protection against natural hazards have always been included in the design of nuclear reactors, these have been strengthened since the accident. In general, the design requirements now take into account natural hazards of an estimated frequency above 1 in 10 000 years, as opposed to 1 in 1000 years used previously.
Incorporating these new safety standards into the design of existing reactors was subsequently tested through comprehensive safety assessments and inspections. The assessments took into account the design features of installations, safety upgrades and provisions for the use of non-permanent equipment to demonstrate that the probability of conditions that may lead to early or large releases is practically eliminated.
“New power plants are designed to account for the possibility of severe accidents,” said Javier Yllera, a senior Nuclear Safety Officer at the IAEA. “Different safety improvements have been implemented at existing power plants, together with accident management measures.”
Safety assessments or ‘stress tests’ implemented in the European Union following the Fukushima Daiichi nuclear accident focused on the assessment of natural hazards such as earthquakes and flooding, and on the behaviour of power plants in cases of extreme natural events and severe accidents. The overall objective was to analyse the robustness of reactors to such events and, if necessary, increase it. The margins of the safety of reactors were analysed and possible improvements were identified. The implementation of those stress tests remained the responsibility of Member States, and resulted in many design and operation enhancements in Europe.
[Source: IAEA]
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