Office for Nuclear Regulation

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Site Inspection - Wylfa

Executive summary

Purpose of Intervention

This was a planned inspection of Magnox Ltd’s Wylfa power station, undertaken as part of a series of planned inspections at Site contained in the Integrated Intervention Strategy (IIS) for 2017/18.

Interventions Carried Out by ONR

Planned inspection of Licence Condition (LC) 11 was undertaken

Additional meeting held on progress with reactor defuelling

Explanation of Judgement if Safety System Not Judged to be Adequate

No safety system based inspections were undertaken during this intervention.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

Licence Condition 11 requires the licensee to undertake regular rehearsals of the site emergency arrangements. “Exercise Charlie 17” was a safety exercise designed to demonstrate the effectiveness of the post-generation emergency arrangements at Wylfa. The elements of the exercise witnessed demonstrated a high level of Control & Command both within the Central Control Room (CCR), Access Control Point (ACP) and Emergency Control Centre (ECC). During the site de-brief it was confirmed that only minor areas for improvement were identified and that these had been identified either by the site staff or Magnox Ltd internal regulators. Consequently, given the successful demonstration exercise, the improvements established from the previous exercise and identifying further areas for improvement from this exercise the arrangements were judged to be adequate.

A meeting to review current defuelling progress focussed on a number of rope related issues that have caused some concern and present a potential risk to successful defuelling. A review of predicted defuelling completion dates was also provided taking into account fuel route performance up to the end of May 2017. This indicated some potential slippage in projected completion dates but with expectation of completion before end of 2019.

Conclusion of Intervention

From the information obtained and evidence gathered during this intervention, I believe there were no issues identified that were considered to adversely affect nuclear safety.


Pwrpas yr Ymyrraeth

Roedd yr archwiliad hwn o orsaf bŵer Wylfa Magnox Cyf wedi ei gynllunio, ac wedi ei ymgymryd fel rhan o gyfres o archwiliadau a drefnwyd ar Safle a gynhwysir yn y Strategaeth Ymyriad  Integredig (IIS) ar gyfer  2017/18.

Ymyriadau a Gynhaliwyd gan y Swyddfa dros Reoli Niwclear (ONR)

Cynhaliwyd archwiliad, wedi ei gynllunio, o Amodau Trwydded 11 (LC)

Cynhaliwyd cyfarfod ychwanegol ar gynnydd parthed cael gwared ar danwydd oddi ar safle’r adweithydd

Eglurhad o’r Dyfarniad os Nad oedd y System Diogelwch wedi ei Ystyried yn Ddigonol

Ni chynhaliwyd archwiliadau diogelwch ar sail system yn ystod yr ymyriad hwn.

Canfyddiadau Allweddol, Barn yr Arolygydd a’r Rhesymau dros y Dyfarniadau a Wnaed

Mae Amod Trwydded 11 yn disgwyl i’r daliwr trwydded ymgymryd ag ymarferion rheolaidd o drefniadau argyfwng y safle. Ymarfer diogelwch oedd “Ymarfer Charlie 17” i ddangos effeithlonrwydd trefniadau ôl-genedlaethau argyfwng  Wylfa. Roedd yr elfennau hynny o’r ymarfer a welwyd yn dangos lefel uchel o Reoli a Gorchymyn oddi mewn i’r Ystafell Reoli Ganolog (CCR), Pwynt Rheoli Mynediad (ACP) a’r Ganolfan Reoli Argyfwng (ECC). Yn ystod yr ôl-drafodaeth ar y safle cafwyd cadarnhad mai mewn mân feysydd yn unig oedd angen gwelliannau ac roedd y rhai hyn wedi eu nodi naill ai gan staff y safle neu gan reolyddwyr mewnol Magnox Cyf. O ganlyniad, o ystyried yr arddangosiad ymarfer llwyddiannus, y gwelliannau a sefydlwyd o’r ymarfer cynharach ac o nodi meysydd eraill ar gyfer gwelliannau, daethpwyd i’r casgliad bod y trefniadau yn ddigonol.

Roedd cyfarfod i adolygu’r cynnydd ar gael gwared ar danwydd oddi ar y safle wedi canolbwyntio ar nifer o faterion perthnasol i raff sydd wedi peri ychydig o bryder ac yn cyflwyno risg posibl i gael gwared ar danwydd oddi ar y safle yn llwyddiannus. Yn ogystal â hyn darparwyd adolygiad o’r dyddiadau cwblhau arfaethedig ar gyfer cael gwared ar danwydd oddi ar y safle, gan gadw mewn cof perfformiad taith y tanwydd hyd at ddiwedd mis Mai 2017. Roedd hyn yn awgrymu ychydig o lithro yn y dyddiadau cwblhau arfaethedig ond gan ddisgwyl cwblhau cyn diwedd 2019.

Casgliadau’r Ymyriad

O’r wybodaeth a’r dystiolaeth a gasglwyd yn ystod yr ymyriad hwn, yn fy marn i nid oedd unrhyw faterion wedi dod i’r amlwg a ystyrid fel rhai i effeithio yn anffafriol ar ddiogelwch niwclear.