Provision of Support on Internal Hazards Safety Assessment of the AP1000 GDA Issues

BACKGROUND TO THE PROJECT 1) Westinghouse Electric Company is the Requesting Party (RP) for the AP1000 Generic Design Assessment (GDA). During Step 4 of the GDA programme for the AP1000 reactor, ONR completed a significant amount of work in its assessment of this design. 2) ONR concluded that it was largely satisfied with the design and safety cases presented by the RP for the AP1000, although some issues remained and required further work.

The additional work required to complete GDA was captured in the 51 GDA Issues reported at the end of Step 4 in 2011. Of these, six were Internal Hazards Issues and are summarised as: • GI‐AP1000‐IH‐01 GDA Issue, Revision 0 - Internal Fire Safety Case Substantiation; • GI‐AP1000‐IH‐02 GDA Issue, Revision 0 - Internal Flooding Safety Case; • GI‐AP1000‐IH‐03 GDA Issue, Revision 0 - Pressure Part Failure; • GI‐AP1000‐IH‐04 GDA Issue, Revision 0 - Internal Explosion Safety Case Substantiation; • GI‐AP1000‐IH‐05 GDA Issue, Revision 0 - Internal Missile Safety Case; and • GI‐AP1000‐IH‐06 GDA Issue, Revision 0 - Substantiation and Analysis of the Consequences of Dropped Loads and Impact from Lifting Equipment Included Within the AP1000 Design. 3) These GDA Issues should not be interpreted as a negative regulatory view of the AP1000 reactor design.

Rather, they should be seen as evidence of the operation of an independent and robust regulatory process and a demonstration of ONR’s mission to provide efficient and effective regulation of the nuclear industry, holding it to account on behalf of the public. 4) The GDA Issues close‐out stage will be an in‐depth ONR assessment of the additional design and safety or security case evidence submitted in response to the GDA Issues. Scope and timescales for this stage will depend on the programmes identified in the resolution plans provided by the RP. The final submissions will update the: • Generic PCSR; • GDA Design Reference. 5) ONR anticipate initiating engagement with the TSC at an early stage, with technical support being provided once submissions from the RP become available.