Office for Nuclear Regulation

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Wylfa Site inspection

Executive summary

Purpose of intervention

This was a planned inspection of Magnox Ltd's Wylfa power station, undertaken as part of the planned intervention strategy for the Decommissioning, Fuel and Waste (DFW) Programme of the Office for Nuclear Regulation (ONR).

The work was carried out in line with the planned inspection programme contained in the Wylfa Integrated Intervention Strategy (IIS).and Magnox Ltd Corporate IIS.

Interventions Carried Out by ONR

Planned inspection of Licence Conditions (LCs) 17 and 35 were undertaken.

ONR Mechanical Engineering inspectors also undertook inspections to progress findings arising from a System Based Inspection of the heating and ventilation systems during July 2017.

Additional meetings were undertaking to review the following matters:

The ONR site inspector also attended the Wylfa Site Stakeholder Group Meeting.

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

The LC35 inspection confirmed that arrangements exist for compliance with the licence condition and that a decommissioning strategy and programmes exist for Wylfa that are commensurate with its current operational phase of defuelling. The site is now at the point where it is starting to develop its safety case and, consequently, strategy for post defueling activities. Magnox Ltd is in the process of implementing companywide site decommissioning arrangements MCP-099 "Unified Arrangements for Regulatory Compliance in Projects during Defuelling and/or Decommissioning" at Wylfa. The main document and a number of relevant supporting parts have been implemented and it includes a revised process for management and delivery of plant modifications. The inspection has confirmed that adequate arrangements are established and being implemented at Wylfa. This inspection identified no matters of significant concern.

The LC17 inspection confirmed that Magnox Ltd is a mature licensee with long established management systems. There are opportunities that could be explored to ensure that the managements systems and approach to delivering quality management are aligned to the operational phases. The site remains focused on ensuring adequate quality management and delivering this within the operational status of the site. No significant issues have been identified.

Under LC 34, an inspection was undertaken to review the progress from the previous inspection of the heating and ventilation systems. The previous inspection provided an adequate demonstration of contractor confidence, pre-inspection of filters, and adequate storage of HEPA filters. However, there were two areas of concern identified during the course of the inspection:

The random check on the adequacy and accuracy of process flow diagrams (PFDs) identified some issues that cast doubt on the implementation of arrangements. The ventilation drawings require validation of accuracy, and Magnox Ltd should confirm it is meeting the requirements of its arrangements on PFDs. Actions have been raised with Magnox Ltd to address this matter.

Performance testing of a sample of the site ventilation systems, by Magnox Ltd, has identified that the systems tested are not operating in line with design intent. Actions have been raised with Magnox Ltd to address this matter.

Although the above matters are considered to be a significant weakness in the implementation of the safety case, appropriate mitigation was provided during the inspection to indicate that risks remain low and Magnox Ltd is responding appropriately to the findings.

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.


Crynodeb gweithredol

Pwrpas yr Ymyrraeth

Roedd hwn yn arolygiad cynlluniedig o safle Wylfa Magnox Cyf., a wnaed fel rhan o'r rhaglen strategaeth ac arolygiad cynlluniedig y Rhaglen Datgomisiynu, Tanwydd a Gwastraff (DFW) ar gyfer (ONR).

Gwnaed y gwaith yn unol â'r rhaglen arolygiadau cynlluniedig a gynhwysir yn Strategaeth Ymyriadau Integredig Wylfa (IIS) ac IIS Corfforaethol Magnox Cyf.

Ymyriadau a Wnaed gan ONR

Gwnaed arolygiad cynlluniedig o Amodau Trwydded (LCs) 17 a 35.

Hefyd gwnaeth arolygwyr Peirianneg Fecanyddol ONR arolygiadau i gynyddu canfyddiadau oedd yn codi o Arolygiad Seiliedig ar System o'r systemau Gwresogi ac Awyru yn ystod Gorffennaf 2017.

Ymgymerwyd â chyfarfodydd ychwanegol i adolygu'r materion dilynol:

Hefyd fe wnaeth yr arolygydd safle ONR fynychu Cyfarfod Grŵp Rhanddeiliaid Safle Wylfa.

Esboniad o'r Dyfarniad os Na Ddyfernir bod y System Ddiogelwch yn Ddigonol

Ni wnaed unrhyw arolygiadau seiliedig ar system ddiogelwch yn ystod yr ymyriad hwn.

Canfyddiadau allweddol, Barnau'r Arolygydd a Rhesymau am Ddyfarniadau a Wnaed

Fe wnaeth yr arolygiad LC35 gadarnhau bod trefniadau'n bodoli i gydymffurfio â'r amod trwydded a bod strategaeth a rhaglenni datgomisiynu'n bodoli ar gyfer Wylfa sy'n gymesur â'i gyfnod gweithredol cyfredol o ddatlenwi. Erbyn hyn mae'r safle ar y pwynt lle mae'n dechrau datblygu ei achos diogelwch ac, o ganlyniad, ei strategaeth ar gyfer gweithgareddau ôl-ddatlenwi. Ar hyn o bryd mae Magnox Cyf. wrthi'n gweithredu trefniadau datgomisiynu MCP-099 "Trefniadau Unol ar gyfer Cydymffurfiad Rheoleiddiol mewn Prosiectau yn ystod Datlenwi ac/neu Ddatgomisiynu" ar draws y cwmni yn Wylfa. Mae'r brif ddogfen a nifer o rannau cefnogol perthnasol wedi'u gweithredu ac mae'n cynnwys proses adolygedig i reoli a chyflenwi addasiadau i offer. Mae'r arolygiad wedi cadarnhau bod trefniadau digonol wedi'u sefydlu ac yn cael eu gweithredu yn Wylfa. Ni wnaeth yr arolygiad hwn nodi unrhyw faterion o bryder arwyddocaol.

Fe wnaeth yr arolygiad LC17 gadarnhau bod Magnox Cyf. yn drwyddedai aeddfed gyda systemau rheoli hirsefydlog. Mae cyfleoedd y gellid eu harchwilio i sicrhau bod y systemau rheoli a'r ymagwedd tuag at gyflenwi rheolaeth ar ansawdd wedi'u halinio i'r cyfnodau gweithredol. Mae'r safle'n dal i ganolbwyntio ar sicrhau rheolaeth ddigonol ar ansawdd a chyflawni hyn o fewn statws gweithredol y safle. Ni nodwyd unrhyw broblemau arwyddocaol.

O dan LC 34, ymgymerwyd ag arolygiad i adolygu'r cynnydd o'r arolygiad blaenorol o'r systemau gwresogi ac awyru. Darparodd yr arolygiad blaenorol arddangosiad digonol o hyder contractiwr, rhag-arolygiad o hidlwyr, a storio digonol o hidlwyr HEPA. Fodd bynnag, nodwyd dau faes oedd yn peri pryder yn ystod hynt yr arolygiad:

Fe wnaeth y gwiriad ar hap ar ddigonolrwydd a chywirdeb diagramau llif proses (PFDs) nodi rhai problemau sy'n peri amheuon ynghylch y trefniadau gweithredu. Mae angen dilysu cywirdeb y darluniau awyru, a dylai Magnox Cyf. gadarnhau ei fod yn diwallu gofynion ei drefniadau ar PFDs. Codwyd camau gweithredu gyda Magnox Cyf. i drafod y mater hwn.

Mae profi perfformiad ar sampl o systemau awyru'r safle, gan Magnox Cyf., wedi nodi nad yw'r systemau'n gweithredu yn unol â bwriad y cynllun. Codwyd camau gweithredu gyda Magnox Cyf. i drafod y mater hwn.

Er yr ystyrir bod y materion uchod yn wendid arwyddocaol yn y broses o weithredu'r achos diogelwch, darparwyd lliniaru priodol yn ystod yr arolygiad i awgrymu bod risgiau'n dal yn isel a bod Magnox Cyf, yn ymateb yn briodol i'r canfyddiadau.

Casgliad yr Ymyriad

O'r wybodaeth a gafwyd a'r dystiolaeth a gasglwyd yn ystod yr ymyriad hwn, credaf na nodwyd unrhyw broblemau yr ystyriwyd eu bod yn effeithio'n niweidiol ar ddiogelwch niwclear.