14.7 - Fault and Protection Schedule - EDF Hinkley Point

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PRE-CONSTRUCTION SAFETY REPORT CHAPTER 14: DESIGN BASIS ANALYSIS SUB-CHAPTER : 14.7 PAGE : 45 / 48 Document ID.No. UKEPR-0002-149 Issue 02 SUB-CHAPTER 14.7 - FIGURE 2 SG level scale SG level MAX2 VIV [MSIV] closure VDA [MSRT] setpoint increase in SGi PROTECTION MAX2 PC → PROTECTION MAX1 ASG [EFWS] isolation in SGi → PROTECTION MAX1 RT ARE/AAD [MFWS/SSS] isolation in SGi PROTECTION LCO Alarm Nominal Control LCO Alarm MIN1 RT → PROTECTION MIN2 ASG [EFWS] actuation in SGi → PROTECTION MIN2 ASG [EFWS] actuation in SGi → RRC MIN3 RT → RRC MIN4 Reactor coolant pumps OFF → RRC
PRE-CONSTRUCTION SAFETY REPORT CHAPTER 14: DESIGN BASIS ANALYSIS SUB-CHAPTER : 14.7 PAGE : 46 / 48 Document ID.No. UKEPR-0002-149 Issue 02 SUB-CHAPTER 14.7 - APPENDIX 1 Diversity in Emergency Operating Procedure Introduction The Emergency Operating Procedures (EOP), based on the State Oriented approach, are out of the GDA scope. However, in order to demonstrate the diversity within the path from the controlled state to the safe shutdown state, an analysis is presented here. This analysis explains how, in principle, the safe shutdown state can be reached by at least two diverse means. This analysis strays from the actual emergency operating procedures, which will be defined at the site-specific stage. The actual EOPs aim at transferring the plant from the controlled state to the safe shutdown state depending on the availability of the systems. The documents used in the safety analyses are similar to those used during plant operations. Consequently, as a first means of operating the plant, the operational systems will be used by the operator if they are available. In the safety analysis, the safe path corresponds to the EOP path in which operational systems are not available. This safe path corresponds to the ultimate line that can be reasonably considered in PCC analyses. Further means can be considered for defence in depth purposes but not within the main line of defence. It must be noted that the first means is not claimed in the safety demonstration and thus, no requirements for classification or qualification such as those required for the diverse line of protection apply to it; it is only for illustrative purposes. Prerequisite A prerequisite for the transition from the controlled state to the safe shutdown state is that the controlled state was reached, i.e. that the plant level safety functions did not fail due to the postulated failure of a lower level safety function. This demonstration has been made in Subchapter 16.5. For example, the feed and bleed back-up operating procedure is consequently not claimed in the current analysis but could be claimed as the ultimate means to ensure heat removal from the core. Analysis For the transition from controlled state to the safe shutdown state, the following system actions have to be performed. Only the actions which are listed below are absolutely necessary in principle, which means that actions which are normally performed, and which are not absolutely necessary (e.g. switch off reactor coolant pumps), are not listed. • Depressurisation of the reactor coolant system • Boration of the reactor coolant system • Cooldown to residual heat removal system connecting conditions • Connection to residual heat removal system or containment heat removal system. These actions are performed by different systems and have a second line of defence. They are presented in the table below.
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14.7 - Fault and Protection Schedule - EDF Hinkley Point

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