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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
Hajime Kabashima, Fumio Kasahara
Nuclear Technology | Volume 205 | Number 5 | May 2019 | Pages 694-707
Technical Paper | doi.org/10.1080/00295450.2018.1518556
Articles are hosted by Taylor and Francis Online.
Large-scale electric discharges events called high energy arcing faults (HEAF) have been reported in a nonnegligible number at nuclear power stations (NPSs) worldwide. If a HEAF occurs, the pressure and temperature in the electrical equipment rise rapidly, causing an explosive phenomenon with destructive force that results in serious damage to the equipment. In addition, a HEAF may cause a fire, which would have a serious impact on cables and other components in and around the equipment with the potential to disrupt power, instruments, and control in the plant.
In order to investigate the HEAF progression and to understand well the phenomena involved, the Regulatory Standard and Research Department in the Secretariat of the Nuclear Regulation Authority conducted a series of experiments (HEAF tests). High-energy electric arcs were generated at the facility simulating the design and operating conditions of the medium-voltage metalclad switchgears (M/Cs) at Unit 1 of the Onagawa NPS where the fire subsequently spread to multiple M/Cs via cable duct due to HEAF.
The test data have been obtained for the M/Cs on the threshold values of the arc energy that results in ensuing fires and on the characteristics of high-energy arcs.
On the basis of the knowledge obtained by the test results, measures for prevention of ensuing fire and mitigation of explosion are proposed as a new requirement for fire protection regulation of Japanese NPSs. Amendments to the regulatory requirements were issued on August 8, 2017 and enforced on the same day.
This paper summarizes the information on the high-energy arc characteristics and arc energies resulting in ensuing fires that was used as the basis of the new requirements and discusses the trend of arc power.
