Appendix 1 - Summary of key events

An Investigation into the Falsification of Pellet Diameter Data in the MOX Demonstration Facility at the BNFL Sellafield Site and the Effect of this on the Safety of MOX Fuel in Use

20 August 1999: A member of the Quality Control Team in B33 MOX Demonstration Facility (MDF) identified a similarity between mean pellet fuel diameter measurements reported on the QC release certificates for the secondary sample checks of two successive Lots. These were discussed by the QC Team in MDF on 23 August. Plant management was informed of these similarities on
25 August: The Shift Team Leaders were asked to pay particular attention to inspection of pellets pending completion of QC release.
31 August: BNFL's analysis of data for several Lots showed many of the mean pellet diameter values in successive Lots to be the same, and the MDF QC management initiated a computerised analysis of the data. Discussion with individuals concerned began on 1 September 1999. On 6 September the MOX Senior Team was informed that some falsification of data may have occurred.
3 September: A process worker in MDF admitted deliberate falsification, and a second process worker said that he was aware falsification was taking place.
9 September: The QC management updated the MDF Operations management on the results of the preliminary investigation. Over 9/10 September Trade Union officials met plant management with individuals concerned to try to understand the extent of the problem.
10 September: The Independent Newspaper indicated to BNFL its intention to publish an article in the newspaper concerning the fact that BNFL inspectors had falsified QC data on MOX pellet diameter. The article was eventually published on 14 September.
10 September: Mitsubishi Heavy Industries (the fuel vendor to Kansai) and NII were informed of the situation. NII maintained contact with BNFL thereafter throughout the weekend until the beginning of its on-site investigation. BNFL reported to NII that on 12 September 1999 it had found 11 Lots with falsified data and 9 "unusual" Lots.
12 September: NII obtained BNFL's agreement not to restart production until NII had been notified.
14 September: NII was told that the BNFL QC Team reported a further five sets of falsified data, and one further set of falsified data a day later. On 14 September NII began its on-site investigation into the incident.
14-16 September: Visit to the MDF plant by NII Site Inspector and NII Management to begin on-site investigation into the event. This included some interviews.
16 September: BNFL reported four further sets of falsified data and one additional unusual dataset giving a total of 22 falsified datasets and 10 unusual datasets. On 16 September MDF Operations Manager reported that BNFL believed that falsification of data had been undertaken principally by one of the five shift teams.
20-21 September: Visit to plant by NII Site Inspector and NII Senior Management. This included a plant inspection and meeting with officials from the Ministry of International Trade and Industry (MITI), Japan. NII told MITI that it would be carrying out a thorough independent analysis of the pellet diameter data for Kansai.
21 September: NII wrote to the Japanese Embassy in London in response to a letter the previous day from the Economic Counsellor. The letter explained that it would "take some time, possibly several weeks, to check all of the data relating to the fuel which [was] currently en route to Japan". The letter also said that NII understood that BNFL had "already told the Japanese team visiting Sellafield that one Lot of MOX fuel pellets whose secondary sample checks on diameter show "unusual" results has been used in the manufacture of two fuel assemblies [then] currently en route to Fukui".
22 September: At a meeting at NII's offices in Bootle, BNFL reported that its continuing investigation had concluded that there were 22 falsified data Lots and one unusual data Lot. The other nine 'unusual Lots' were eliminated by BNFL. All pellet Lots for which falsified datasets had been reported had been used to produce fuel rods and assemblies for Takahama 3, and were still at Sellafield. The pellets for an unusual Lot had been used to produce fuel rods in two of the eight fuel assemblies for Takahama 4, which at that time were in the process of being transported to Japan.
22 September: HSE's independent statistical analysis of the pellet diameter data for Kansai was initiated.
28-29 September: Visit to plant by NII Site Inspector to conduct interviews with the Shift Team Leaders (STLs), Shift Team Managers (STMs) and the Head of MDF Operations.
8 October: Visit to plant by NII Quality Assurance (QA) Specialist to investigate QA aspects of the event.
12-13 October: Visit to plant by NII Site Inspector and Human Factors Specialist to discuss ergonomic aspects of the event.
25-26 October: Visit to plant by NII Site Inspector to witness three separate sets of dual 5% secondary diameter checks.
29 October: The statistical analysis by HSE's EMSU of the data was completed.
3 November: An update provided by BNFL reported 22 falsified data Lots, one Lot having some similarities with a previous Lot, one Lot having greater than normal number of pellets with three identical diameters (ie cylindrical), and one Lot having a greater than normal number of identical pellets.
8 November: BNFL was informed that it would have to produce a safety case and seek NII's agreement before it could restart MDF. NII wrote again to the Japanese Embassy confirming that "two of the assemblies containing pellets with suspect data are in Japan." A copy of this letter was placed in the House of Commons Library.
10 November: Visit to plant by NII Site Inspector and an Inspector from the Radioactive Materials Transport Division of the Department of Environment, Transport and Regions (DETR) to discuss BNFL countermeasures to prevent recurrence of the event.
11 November: A meeting took place between HSE and BNFL to discuss work necessary before MDF is permitted to restart.
17 November: A meeting took place between HSE (NII and EMSU) and BNFL to discuss the findings of HSE's statistical analysis of the secondary pellet diameter data. On the same day NII and BNFL met to discuss BNFL's proposals for a safety case for the restart of operation in MDF.
23 November: Visit to plant by NII Site Inspector to investigate ergonomics aspects of the event.
8-10 December: Visit to plant by NII Site Inspector and Human Factors specialist to undertake a restart readiness inspection.
13 and 14 December: Meeting between NII and MITI officials to explain the results of HSE's statistical analysis. NII confirmed the facts set out in earlier letters to the Japanese Embassy i.e. that two of the assemblies (MKP 005 and 006) in Japan contain pellets believed to have suspect data. HSE staff went to some lengths to explain that although the 8 November letter had used the word "suspect" in relation to these assemblies, HSE considered that there was a vanishingly small probability of these results [for Lots P783 and P824] having occurred by chance.
15 December: That evening BNFL reported to NII that following further investigation, data for a further Lot, P814, had been found to be copied from a previous lot.
16 December: Following the discovery by BNFL of the additional falsified Lot, P814, NII asked for a further meeting with MITI which was held the same day. NII confirmed to MITI that P814 had been falsified, and that this now meant that two further assemblies in Japan were considered to be affected. Taken together with those assemblies identified previously, this now meant that a total of four assemblies (MKP 005, 006, 007, and 008) out of the eight assemblies currently in Japan contained pellets whose secondary diameter data was considered to have been falsified.
19 December: Visit to MDF by the Chief Inspector for a plant inspection.
20 December: BNFL Senior Management met with NII Senior Management at Bootle to discuss the improvements which NII require to be implemented before permission to restart would be granted.
21 December: NII wrote to BNFL listing a number of areas for BNFL to address to NII's satisfaction before agreement to restart would be granted.
22 December: NII wrote to BNFL specifying under the nuclear site licence, that BNFL should demonstrate to its Nuclear Safety Committee how it has satisfied itself that the lessons learned from the MDF event will be disseminated to the rest of the site.
11 January 2000: NII met with BNFL to discuss the process which had been used to identify Lot P814 as containing falsified fuel pellet diameter data.