Technical Support on Sampling Systems for GDA of UK ABWR

Descriptions

1BACKGROUND TO THE PROJECT 1.1ONR is undertaking a phased Generic Design Assessment (GDA) of the Hitachi General Electric (Hitachi-GE) UK Advanced Boiling Water Reactor (UK ABWR). Hitachi-GE’s submissions to ONR are similarly phased, providing increasing detail and evidence as the design is finalised and the UK regulatory requirements are better understood. 1.3 Step 4 of GDA of the UK ABWR design commenced in November 2015. A key part of Step 4 is for ONR inspectors responsible for assessing the UK ABWR design to identify areas where timely input from Technical Support Contactors (TSCs) is required to enable GDA to progress to programme, and to ultimately inform ONR’s regulatory decision on the acceptability of the UK ABWR design, or otherwise, for construction in the UK. ONR have identified that one such area relates to the sampling system(s) design for UK ABWR. 1.4Importantly, during Step 3 of GDA, Hitachi-GE provided a fit-for-purpose demonstration of the safety benefits and detriments associated with, and decision on the primary cooling system operating chemistry regime for UK ABWR. The operating chemistry selected is Hydrogen Water Chemistry (HWC), Noble Metal Chemical Addition (NMCA) and Depleted Zinc Oxide (DZO) injection. Hitachi-GE also intend to implement oxygen injection into the feedwater system of UK ABWR. As such, submissions including details on the design of H2, platinum, DZO and O2 injection systems will be made to ONR during Step 4 of GDA. The sampling system of a nuclear power station is vital in ensuring that the operator understands, and hence can control, the numerous chemical systems and functions that are required for safe operation of the plant. For example, sampling of the reactor coolant and feedwater is undertaken in relation to a number of safety related functions including; •Monitoring fuel, circuit integrity and radiation levels (fission products and corrosion products etc.) •Controlling chemistry parameters (H2, NMCA, DZO, O2, Fe/Ni ratio) and impurities (F-, Cl-, SO42-, silica etc.) •Monitoring operational system performance (ion exchange and filters etc.)