July-August 2018 NPJ

Nuclear Plant Journal, July-August 2018 NuclearPlantJournal.com 27 (Continued on page 28) Brian Arnholt Brian Arnholt is the Supervisor for Instrumentation and Controls with NuScale Power, LLC and is responsible for leading the design and licensing of the instrumentation and control systems for the NuScale Small Modular Reactor development project. In his career that spans more than 20 years, Mr. Arnholt has extensive experience in leading the design and licensing of digital instrumentation and control systems for the next generation of advanced nuclear power plants. His expertise is in the areas of safety instrumentation and control system design, control automation and simulation. Brian began his career with Exelon Corporation at the Byron Nuclear Power Station and served in multiple positions in reactor engineering, real time process systems and plant operations. Brian earned his Bachelors of Science in Nuclear Engineering from the University of Michigan in Ann Arbor, Michigan. “Periodic surveillance testing capability is incorporated to ensure that functional tests and checks, calibration verification, and time response measurements are validated. Periodic surveillance testing of sensors that are part of the Module Protection System (MPS) is performed in accordance with the plant technical specifications.” To satisfy the surveillance requirements of the MPS and associated sensors, laboratory testing must be performed on the selected sensors that will be installed in the NPM at representative ambient and process conditions to: establish baseline sensor performance characteristics, develop empirical correlations to reduce uncertainties associated with extrapolation of laboratory baseline data to actual in- service conditions, and develop analytical hardware and software tools to measure static and dynamic sensor performance after installation in the plant. This effort is already underway with work conducted by AMS over a three-year period with funding from DOE. The project covers all process sensors although this paper is focused only on NuScale’s temperature sensors. NPM RCS Temperature Measurement The sensors selected by NuScale Power for all safety-related temperature measurements will be existing nuclear qualified resistance temperature detectors (RTDs). Existing nuclear qualified RTDs have a long and successful history of satisfactory performance in large scale PWRs. However, in conventional PWRs, the average containment temperature is about 120°F while the containment temperature profile of the NPM can range from 295°F at the containment inner wall to 551°F at the reactor pressure vessel outer wall during normal operation. It must be determined through laboratory testing and measurements if these RTDs as they exist today can perform adequately when subjected to these high containment temperatures long-term. In addition, periodic testing of these sensors to verify calibration, response time, and cable and connector integrity via remote in-situ or OLM technologies will help plant personnel efficiently manage degrading or aging sensors. Maintenance Plan For NuScale Temperature Sensors Based on technical discussions with NuScale engineers, AMS has proposed the periodic surveillance testing of the NPM RTDs as outlined in the following steps to verify RTD functionality and performance and to satisfy plant technical specifications: 1. Mode 5 – “Cold” Tests (Prior to Initial Startup/During a Refueling Outage) While the NPM is located in the maintenance dry dock and readily accessible to plant personnel, RTDs shall be tested to identify any functional issues and to determine gross performance problems. These tests will be performed at ambient or “cold” conditions and will consist of: cable and connector testing (i.e. Inductance - L, Capacitance - C, and Resistance – R (LCR) measurements, time domain and/or frequency domain reflectometry, and insulation resistance (IR) measurements), calibration checks, and thermal response testing to verify proper installation in a thermowell. This set of testing will help plant personnel identify and resolve RTD problems before installing the NPM back into its operating bay within the reactor pool. These tests may be hands-on or manual. 2. Mode 2 – “Hot Shutdown” Tests (During Startup) Figure 1. Simple Diagram of the NuScale Power Module.