Module 6 Quiz

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Excelsior University *

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271

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Mechanical Engineering

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Apr 3, 2024

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Question 1: The functional restoration procedures are going to end up being utilized by the reactor operators of the plant under direction of the senior reactor operators based on observations from the plant. These observations will fall under the critical safety functions, which are indicated by special instrumentation that has inputs into a computer with a dedicated logic tree known as the CSF Status Trees. The FRP network is primarily there to protect the three fission product barriers. “The Function Restoration Procedures provide instructions for maintaining the plant in a safe state without regard to initiating event or continuations of subsequent failures.” (NRC) Question 2: Procedure E-0 – Commonly titled reactor trip or safety injection, Procedure E-1 – Loss of Reactor or Secondary Coolant, Procedure E-2 – Faulted Steam Generator and Procedure E-3 – Steam Generator Tube Rupture. The ECAs are a set of sub-guidelines that fall under the Optimum Recovery Guidelines. There are situations where the ORGs are not fully applicable, like when the plant conditions do not support an ORG. In this case the ECAs typically are applicable in these situations. Question 3: In a Westinghouse PWR reactor design, the steam generator tubes are a pressure boundary between the reactor coolant system and the steam plant. In the even that one of these tubes ruptures, the reactor coolant system, which operates at a much higher pressure, will leak into the steam generator and then flow through the steam plant and contaminate equipment and components. Because the pressure is so high, the reactor plant will register as a loss of coolant casualty. To mitigate the spread of contamination the affected steam generator should be isolated by shutting off the feed system isolation valve and the steam side isolation valve. By isolating one steam generator the other steam generator (in a 2 loop system) can be used to cool down the reactor coolant system. Question 4: Symptom based procedures came about from industry experiences from the Three Mile Island accident. Prior to this accident procedures were event based, which means the operators had to determine which casualty they were in then used the appropriate procedure for that casualty. Event based procedures required the event be diagnosed prior to taking operator action. Whereas in a symptom-based procedures the operators can diagnose the casualty on observation from the plant conditions which are identified in the procedure. This is considered superior event based procedure as it allows operator actions based on symptoms. Question 5:

High Containment Building Pressure, Low Reactor Coolant System Pressurizer Pressure and Low Steam Line Pressure. When the SI signal is sent two actions will occur. The first action will initiate the actuation of the emergency core cooling system. The emergency core cooling system will help mitigate and loss of coolant casualty. The first action is important as it maintains core cooling which would help the core cooldown or in the worst case prevent or mitigate core meltdown. The second action will be sent to the containment isolation system. This signal will isolate any of the openings that are going through the containment boundary. By doing so this will secure the 3 rd barrier of fission product protection. By shutting all of the exits to the containment boundary it keeps all the potential fission products in. This works directly with the defense in depth of barriers. References: Excelsior University. (n.d.). Module 6 Notes . https://excelsior.instructure.com/courses/40226/files/18691288?wrap=1 NRC. (n.d.). Emergency operating procedure writers guide https://www.nrc.gov/docs/ML1417/ML14174A956.pdf NRC. (n.d.). Steam generator tube rupture. https://www.nrc.gov/docs/ML1121/ML11216A211.pdf

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