Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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A study on the uncertainty of setpoint for reactor trip system of NPPs considering rectangular distributions

  • Youngho Jin (Global Institute for Nuclear Initiative Strategy) ;
  • Jae-Yong Lee (Department of Quantum and Nuclear Engineering, Sejong University) ;
  • Oon-Pyo Zhu (Global Institute for Nuclear Initiative Strategy)
  • Received : 2023.04.19
  • Accepted : 2023.12.18
  • Published : 2024.05.25
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Abstract

The setpoint of the reactor trip system shall be set to consider the measurement uncertainty of the instrument channel and provide a reasonable and sufficient margin between the analytical limit and the trip setpoint. A comparative analysis was conducted to find out an appropriate uncertainty combination method through an example problem. The four methods were evaluated; 1) ISA-67.04.01 method, 2) the GUM95 method, 3) the modified GUM method developed by Fotowicz, and 4) the modified IEC61888 method proposed by authors for the pressure instrument channel presented in ISA-RP67.04.02 example. The appropriateness of each method was validated by comparing it with the result of Monte Carlo simulation. As a result of the evaluation, all methods are appropriate when all measurement uncertainty elements are normally distributed as expected. But ISA-67.04 method and GUM95 method overestimated the channel uncertainty if there is a dominant input element with rectangular distribution among the uncertainty input elements. Modified GUM95 methods developed by Fotowicz and modified IEC61888 method by authors are able to produce almost the same level of channel uncertainty as the Monte Carlo method, even when there is a dominant rectangular distribution among the uncertainty components, without computer-assisted simulations.

Keywords

Acknowledgement

This research was supported by Development of Core Technology to improve Nuclear Power Plant Safety Operation Program (Grant No 20224B10100090) funded by Ministry of Trade, Industry and Energy (MOTIE).).

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