A cabinet containing copper bus before the HEAF test (left) and after the test(right). Source: NRC
Massive electrical discharges, referred to as high energy arcing faults (HEAF), have occurred in nuclear power plant switching off components throughout the world. These incidents have been increasing because of ageing infrastructures and growing energy demand. Co-ordinated by the US Nuclear Regulatory Commission (NRC), the HEAF Project was initiated in 2012 to perform experiments on a variety of electrical cabinets in order to obtain scientific data on HEAF phenomena through carefully designed experiments. Phase 1 of the HEAF project was completed in 2016. The report concluded with recommendations for areas requiring further testing, in particular to better understand the importance of specific variables such as bus bar material, operating voltage, current and arc duration on the severity of the HEAF.
In February 2017, an International Phenomena Identification and Ranking Table (PIRT) exercise was held to identify phenomena of the highest importance with the least amount of knowledge available on HEAF events. This exercise tentatively identified aluminium oxidation, pressure effects, the characteristics of target structures and mitigating factors (e.g. HEAF shields) as being areas for further research. Discussions were completed with representatives from ten partners in nine countries to initiate a second phase of the project. The current, second phase of the project (2019-2024) comprises electrical enclosures and bus ducts tests. Electrical enclosure tests have been designed using the same enclosure configuration for repeatability and based on typical plant design for representativeness. Some of the enclosures were dismounted from nuclear power plants under decommissioning to be tested in the project. The bus bar tests were designed for a known and reliable arc location and plasma ejection direction. Due to the COVID-19 pandemic, first tests had been postponed to the middle of 2022. A first series of six tests was conducted at the end of August 2022 together with additional domestic tests. The focus of these tests was on bus bar and bus duct, comparing material effect between aluminium and copper. Originally scheduled to end in 2022, the HEAF project was extended by the project partners until June 2024 to cover completion of the second and final test series.
In parallel with the HEAF-2 project, the NRC is conducting a domestic test programme together with the Electric Power Research Institute (EPRI), focusing, among other things, on the influence of aluminium oxidation. Relevant test results are shared with HEAF-2 project members.
Belgium, Canada, France, Germany, Japan, Korea, Netherlands, Spain and United States.
February 2019-June 2024
EUR 2.38 million