Office for Nuclear Regulation

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Wylfa Power Station – Planned Intervention

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 Civil Nuclear Reactor Programme (CNRP) 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).

Interventions Carried Out by ONR

I (the nominated site inspector for Wylfa) with an Electrical Technical Specialist from AMEC Foster Wheeler carried out a System Based Inspection (SBI) on the Pile Cap Control and Instrumentation (C&I) Systems.  I also held a number of information exchange meetings with station staff and observed elements of an emergency exercise supported by an ONR fire safety inspector.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable – the Pile Cap (C&I) Systems were judged to be adequate.

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

From the system based inspection on the Pile Cap C&I Systems we concluded that:

LC 10 (Training) – We sampled work orders for Fuelling Machine Instrumentation calibration and Fuel Handling area maintenance activities. We examined the SQEP records for the personnel executing the work and found that all essential training was in date. We also sampled the training requirements for a Flask Filling operator and found the training module to be comprehensive, and the SQEP records of the person doing the work were up to date. We therefore assigned an IIS rating of 3 (adequate) to this inspection.

LC 23 (Operating Rules) – We reviewed the Fuelling Machine and Dry Store Cell Operating Rules, and found that the Operating Rule for Dry Store Cells 1, 2 and 3 are in the process of being changed to accommodate the defuelling process. We sampled the Fault Schedule for the Flask Filling Area Power Tongs and the Flask Handling Area to explore the nature of the risks and consequences. We found a good understanding of the issues on the part of Magnox staff. We therefore assigned an IIS rating of 3 (adequate) to this inspection.

LC 24 (Operating Instructions) – We observed the Flask Filling Area control room operations and noted how smoothly the flask filling process was progressing. The human machine interface (HMI) and CCTV systems are effective, and the level of automation is impressive considering the age of the installation. We sampled the Flask Filling operating procedure and several Maintenance procedures associated with the Flask Filling. These are of good quality, to a standardised format. We assigned an IIS rating of 3 (adequate) to this inspection.

LC 27 (Safety Mechanisms, Devices and Circuits) – We undertook a plant walkdown of selected Pile Cap and Flask Filling Area equipment. We found the equipment to be in good condition, with obsolescence being managed. The latest System Health Report shows no causes for concern. Clearly there has been investment in the plant to be ready for final defuelling. We therefore assigned an IIS rating of 2 (good) to this inspection.

LC 28 (Examination, Inspection, Maintenance and Testing) – We sampled the Maintenance Schedule and work order cards for the Fuelling Machine Instrument calibration, and for selected Flask Handling Area maintenance actions. The System Health report does not flag up any backlogs for Maintenance Schedule work, nor any event trends in the Pile Cap C&I systems. The Post Office Relays in the Auto Sequence Programme panels are identified as a potential reliability concern; however, we are satisfied that the station have taken suitable mitigating actions. We assigned an IIS rating of 3 (adequate) to this inspection.

LC 34 (Leakage and Escape of Radioactive Material and Radioactive Waste) – We found that a recent incident where radioactive material was discovered under a Reactor Servicing Machine on the Pile Cap showed how the radioactivity was detected and contained in a timely manner, and was disposed of without any material impact on staff or the environment. We therefore assigned an IIS rating of 2 (good) to this inspection.

Overall, we concluded that the arrangements and their implementation on the Pile Cap C&I Systems met the requirements of the safety case and were deemed to be adequate.

I discussed the following matters whilst on site:

I was satisfied with the content and conduct of these meetings, which are essential to understanding the future site plans and aspirations.

In response to Magnox Ltd’s proposals to reduce its emergency response capability during defueling operations I observed some elements of a shift exercise intended to train staff in the new arrangements and test suitability of proposals. The exercise was well delivered and represented the first time that North Wales Fire & Rescue Service had participated in an exercise at Wylfa for some years. The Welsh Ambulance Service also participated. A number of learning points were identified during the exercise some generic and some specific to the proposed arrangements. These matters were also captured by Magnox Ltd observations and ONR expects that they will be addressed during the process of refining the implementation of the revised arrangements.

The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.

Conclusion of Intervention

There were no findings from this inspection that could significantly undermine nuclear safety.  At present, no additional regulatory action is needed over and above the planned interventions of Wylfa power station as set out in the Integrated Intervention Strategy, which will continue as planned.


Crynodeb gweithredol

Diben yr Ymyrraeth

Roedd hwn yn archwiliad a gynlluniwyd o orsaf bŵer Wylfa Magnox Ltd, a gyflawnwyd yn rhan o'r strategaeth ymyrraeth a gynllunnir ar gyfer Rhaglen Adweithyddion niwclear Sifil (CNRP) y Swyddfa dros Reoli Niwclear (ONR).

Cyflawnwyd y gwaith yn unol a'r rhaglen archwilio a gynlluniwyd yn Strategaeth Ymyrraeth Integredig (IIS) Wylfa.

Ymyraethau a Gyflawnwyd gan yr ONR

Cyflawnais i (yr arolygydd safle enwebedig ar gyfer Wylfa) ynghyd ag Arbenigwr Technegol Trydanol o AMEC Foster Wheeler Archwiliad Seiliedig ar System (SBI) ar y Systemau Rheoli Cap Stanc ac Offeryniaeth (C&I).  Cynheliais hefyd nifer o gyfarfodydd cyfnewid gwybodaeth gyda staff yr orsaf ac arsylwi elfennau o ymarfer argyfwng a gefnogir gan arolygydd diogelwch tân o'r ONR.

Esboniad o’r Dyfarniad os Nad oedd y System Ddiogelwch wedi cael ei Barnu yn Ddigonol.

Amherthnasol – barnwyd bod y Systemau Cap Stanc (C&I) yn ddigonol.

Casgliadau Allweddol, Barnau’r Arolygydd a Rhesymau dros Wneud Dyfarniadau

O'r archwiliad seiliedig ar system ar y Systemau Cap Stanc (C&I), fe ddaethom i'r casgliadau canlynol:

LC 10 (Hyfforddiant) – Fe samplom archebion gwaith ar gyfer calibradu Offeryniaeth Peiriant Tanwydd a gweithgareddau cynnal a chadw'r ardal Trin Tanwydd. Fe archwiliom y cofnodion SQEP ar gyfer y personél sy'n cyflawni'r gwaith a gweld bod yr holl hyfforddiant hanfodol yn gyfredol. Samplom hefyd y gofynion hyfforddiant ar gyfer gweithredwr Llenwi Fflasg a chanfod fod y modiwl hyfforddi yn gynhwysfawr y sawl sy'n gwneud y gwaith yn gyfredol. Felly fe ddynodwyd graddiad IIS o 3 (digonol) i'r archwiliad hwn.

LC 23 (Rheolau Gweithredu) – Fe adolygom y Rheolau Gweithredu Peiriant Tanwydd a Chell Storfa Sych, a chanfod fod y Rheol Weithredu ar gyfer Celloedd Storfa Sych 1, 2 a 3 yn y broses o gael ei newid i ddarparu ar gyfer y broses gwagio tanwydd. Fe samplom yr Amserlen Gwallau ar gyfer Gefeiliau Pŵer yr Ardal Llenwi Fflasg a'r Ardal Trin Fflasg i archwilio natur y risgiau a goblygiadau. Fe welsom ddealltwriaeth dda o'r materion hyn ar ran staff Magnox. Felly fe ddynodwyd graddiad IIS o 3 (digonol) i'r archwiliad hwn.

LC 24 (Cyfarwyddiadau Gweithredu) – Fe arsylwom ar weithrediadau ystafell reoli'r Ardal Llenwi Fflasg a nodi pa mor esmwyth oedd y broses llenwi fflasg. Mae'r systemau rhyngwyneb peiriant dynol (HMI) a CCTV yn effeithiol, a'r lefel o awtomeiddio yn drawiadol o ystyried oed y gosodiad. Fe samplom y weithdrefn weithredu Llenwi Fflasg a nifer o weithdrefnau Cynnal a Chadw yn gysylltiedig â Llenwi'r Fflasg. Roedd y rhain o safon dda, i fformat safonol. Fe ddynodwyd graddiad IIS o 3 (digonol) i'r archwiliad hwn.

LC 27 (Mecanweithiau Diogelwch, Dyfeisiau a Chylchedau) – Cyflawnom daith trwy'r gwaith ar gyfer yr offer Cap Stanc ac Ardal Llenwi Fflasg. Gwelsom fod yr offer mewn cyflwr da, gyda darfodiad yn cael ei reoli. Nid yw Adroddiad diweddaraf Iechyd y System yn dangos unrhyw achos i boeni. Yn amlwg, cafwyd buddsoddiad yn y gwaith i fod yn barod ar gyfer gwagio'r tanwydd yn derfynol. Felly fe ddynodwyd graddiad IIS o 2 (da) i'r archwiliad hwn.

LC 28 (Archwilio, Arolygu, Cynnal a Chadw a Phrofi) – Fe samplom yr Amserlen Cynnal a Chadw a chardiau archebu gwaith ar gyfer calibradu yr Offeryn Peiriant Tanwydd, ac ar gyfer gweithredoedd cynnal a chadw Ardal Trin Fflasg dethol. Nid yw adroddiad Iechyd a System yn nodi unrhyw ôl-groniadau ar gyfer gwaith yr Amserlen Cynnal a Chadw, nac unrhyw dueddiadau digwyddiadau yn y systemau Cap Stanc C&I. Mae'r Releiau Swyddfa Post yn y paneli Rhaglen Dilyniant Awtomatig wedi eu nodi fel pryder dibynadwyedd posibl; fodd bynnag, rydym yn fodlon fod yr orsaf wedi cymryd camau lliniarol addas. Fe ddynodwyd graddiad IIS o 3 (digonol) i'r archwiliad hwn.

LC 34 (Gollwng a Dianc Deunydd Ymbelydrol a Gwastraff Ymbelydrol) – Fe welsom fod digwyddiad diweddar ble canfuwyd gwastraff ymbelydrol dan Beiriant Gwasanaethu Adweithydd ar y Cap Stanc yn dangos sut y canfuwyd yr ymbelydredd a'i ymatal mewn modd amserol, a chael gwared arno heb unrhyw effaith materol ar staff na'r amgylchedd. Felly fe ddynodwyd graddiad IIS o 2 (da) i'r archwiliad hwn.

Ar y cyfan, fe gasglom bod y trefniadau a'u gweithrediad ar Systemau Cap Stanc C&I yn bodloni gofynion yr achos diogelwch a'u pennu i fod yn ddigonol.

Trafodais y materion canlynol tra ar y safle:

Roeddwn yn fodlon gyda chynnwys a chyflawniad y cyfarfodydd hyn, sy'n allweddol i ddeall cynlluniau a dyheadau'r safle yn y dyfodol.

Mewn ymateb i gynigion Magnox Ltd i leihau ei allu i ymateb mewn argyfwng yn ystod gweithrediadau gwagio tanwydd, fe arsylwais rai elfennau o ymarfer shifft i hyfforddi staff ar y trefniadau newydd a phrofi addasrwydd y cynigion. Cyflawnwyd yr ymarfer yn dda gan gynrychioli'r tro cyntaf i Wasanaeth Tân ac Achub Gogledd Cymru gymryd rhan mewn ymarfer yn Wylfa am rai blynyddoedd. Roedd Gwasanaeth Ambiwlans Cymru yn cymryd rhan hefyd. Nodwyd nifer o bwyntiau dysgu yn ystod yr ymarfer, rhai'n gyffredinol a rhai'n benodol i'r trefniadau arfaethedig. Cafod dy materion hyn eu cipio gan arsylwadau Magnox Ltd hefyd ac mae'r ONR yn disgwyl y byddant yn cael sylw yn ystod y broses o fanylu ar weithrediad y trefniadau diwygiedig.

Cyflawnwyd yr ymyrraeth yn unol â gofynion canllaw yr ONR (a ddisgrifir yn ein canllawiau archwilio technegol, sydd ar gael o www.onr.org.uk/operational/tech_insp_guides/index.htm) yn y meysydd a archwiliwyd.

Casgliad yr Ymyrraeth

Nid oedd unrhyw gasgliadau o'r archwiliad hwn a allai danseilio diogelwch niwclear yn arwyddocaol.  Ar hyn o bryd, nid oes angen unrhyw weithredu rheoleiddiol atodol uwchlaw ymyraethau arfaethedig gorsaf bŵer Wylfa fel y sefydlwyd yn y Strategaeth Ymyrraeth Integredig, a fydd yn bwrw ymlaen yn ôl y bwriad.