Date(s) of inspection:
- May 2023
Aim of inspection
The inspection assessed the investigations and further testing being undertaken by Framatome and NNB Generation Company (HPC) Ltd (NNB GenCo) in response to potential implications of inappropriate conduct at Japan Steel Works (JSW) with regards to the Hinkley Point C (HPC) primary circuit forgings.
The inspection reviewed:
- the activities undertaken by Framatome in its further investigation of inappropriate conduct at JSW in relation to HPC primary circuit components;
- how Framatome is ensuring the veracity of the information provided by JSW in its further investigation;
- the work undertaken to assess the reliability of test coupons and archive material;
- the additional testing activities being considered to restore confidence in the integrity of the forgings.
The inspection evidence will be used to inform ONR’s permissioning decisions for the HPC reactor pressure vessel (RPV), steam generators and pressurisers.
Subject(s) of inspection
- LC19 – Construction or installation of new plant – Rating: Amber
Key findings, inspector’s opinions and reasons for judgement made
The inspection concluded that Framatome’s activities with regard to the phase 2 investigation and its analysis of the information emerging from this investigation, although ongoing, was comprehensive. Framatome’s own surveillance arrangements through its independent inspection body, EIRA, was judged to be effective in demonstrating the reliability of the information being provided by JSW.
NNB GenCo had demonstrated why it was confident that the identifications on the archive test coupons are correct, and while surveillance for the marking and removal of the test coupons had not been performed for all the forgings, there was evidence to demonstrate that the risk of misrepresentation of the test coupons was low.
NNB GenCo recognised that because of the JSW irregularities, additional testing was required to restore confidence in the high integrity claims for the primary circuit vessels. As NNB GenCo had undertaken a programme of independent repeat ultrasonic inspections of the forgings, it concluded that no additional testing was required in this area. Regarding mechanical testing, NNB GenCo concluded that the reliability of the JSW results had been largely confirmed through its investigations and results obtained from the fracture toughness testing programme. It had, however, identified a residual risk relating to the independency of the testing laboratory and to this end had proposed a relatively small number of tests to be performed by a French accredited test laboratory.
ONR considered that, based on the information available at the point in time of this inspection and without a systematic review of the evidence for each forging and an overarching work plan, it was not possible to conclude whether the proposed additional testing will be sufficient.
Based on the current information and without a systematic review of each forging and overarching work plan, it was not possible to conclude whether the proposed additional testing will be sufficient. On this basis the inspection was rated as amber and a regulatory issue will be raised to address these findings.