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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Ho Nieh nominated to the NRC
Nieh
President Trump recently nominated Ho Nieh for the role of commissioner in the Nuclear Regulatory Commission through the remainder of a term that will expire June 30, 2029.
Nieh has been the vice president of regulatory affairs at Southern Nuclear since 2021, though he is currently working as a loaned executive at the Institute of Nuclear Power Operations, where he has been for more than a year.
Nieh’s experience: Nieh started his career at the Knolls Atomic Power Laboratory, where he worked primarily as a nuclear plant engineer and contributed as a civilian instructor in the U.S. Navy’s Nuclear Power Program.
From there, he joined the NRC in 1997 as a project engineer. In more than 19 years of service at the organization, he served in a variety of key leadership roles, including division director of Reactor Projects, division director of Inspection and Regional Support, and director of the Office of Nuclear Reactor Regulation.
Tawfik A. Al-Kusayer
Nuclear Technology | Volume 69 | Number 3 | June 1985 | Pages 293-307
Technical Paper | Nuclear Safety | doi.org/10.13182/NT85-A33612
Articles are hosted by Taylor and Francis Online.
The availability of the emergency core cooling system (ECCS) as a long-term safety backup system following a small loss-of-coolant accident (LOCA) has been analyzed for the Pickering NGS Unit A, a Canada deuterium uranium (CANDU) type of pressurized heavy-water reactor (PHWR). Fault tree analysis methodology was used to assess the unavailability of the ECCS. The PREP and KITT computer codes were used to estimate the failure probabilities. From these computations, the unavailability of the ECCS to supply sufficient coolant to the core is estimated as 3.63 × 10−3. This figure is higher than the failure probability target 3 × 10−3 that is specified by the Canadian Atomic Energy Control Board for the safety systems of CANDU PHWRs. It has been found that human error might make a very important contribution to ECCS unavailability, especially if the human error rates have been assigned the upper bound values in the fault tree calculations. That should be the case, therefore, for any fault analysis and reliability assessment of nuclear generating stations. Unlike the case for light water reactors, the ECCS in a CANDU PHWR is not the last defense against the LOCA, because of the availability of quite a large amount of D2O moderator in the calandria around the pressure tubes.
