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Planned Internal Hazards SBI at Magnox Ltd's Wylfa licensed site, undertaken as part of a series of planned interventions outlined in the ONR Integrated intervention Strategy Plan Wylfa 2015/16

Executive summary

Purpose of intervention

Planned intervention at Magnox Ltd’s Wylfa licensed site. This report covers the nuclear safety related inspection of Wylfa power station undertaken as part of a series of system based inspections (SBIs) deemed necessary to cover safety related systems as outlined in the Wylfa safety case.

Interventions Carried Out by ONR

In line with ONR’s guidance, this systems inspection covered the following Licence Conditions (LCs):

The above LCs were covered as part of the internal hazards inspection of the Wylfa power station arrangements for the emergency cooling water system.

A reactive inspection also was undertaken in response to an opportunity to witness a maintenance activity on an item of Minimum Safety Related Plant (MSRP), in conjunction with the Magnox Ltd site inspector for Wylfa.

In addition to the inspections identified above a number of liaison meetings were attended to monitor progress with current activities and maintain awareness of any matters of regulatory interest. These included the following topics:

Explanation of Judgement if Safety System Not Judged to be Adequate

On the basis of the inspection, I judge that overall, the emergency water cooling systems, meet the requirements of the internal hazards safety case and are, on the basis of this inspection, considered adequate.

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

An internal hazards safety system inspection of the emergency cooling water systems was undertaken as part of the programme of SBIs included on the Wylfa site intervention plan for 2015/16. The purpose of the inspection was to assess the adequacy of the station’s implementation of its arrangements currently in place to ensure that the system safety function is delivered.

A sample of primary implementation (Operating Rules) and supporting documents (SOIs, PIOIs) was examined during the inspection.  There was clear evidence of limits and conditions derived from the safety case being implemented through a variety of operating instructions.  Consequently an IIS rating of 3 is assigned to LC23 & LC24.

The overall condition of plant inspected was adequate. There was evidence of good use and completion of compliance check sheets, work requests and proactive recording of defects not directly associated with the system EMIT being undertaken, which is considered good practice.  An IIS rating of 2 is assigned to LC28 and IIS rating of 3 to LC27. 

The inspection confirmed that the safety case implementation was supported by a specific awareness training package for the Emergency Feed and Back-Up Feed System and evidence provided of training and SQEP assessment in relation to the safety case.   An IIS rating of 3 is assigned to LC10.

The reactive inspection of the maintenance activity provided an opportunity to inspect the implementation of arrangements for the control and supervision of contractors. The inspection found evidence of good communications between the license and the contractor resulting in a demonstrable understanding of the maintenance task and safety significance, supported by examples of training/SQEP records. Given the sample inspected, ONR concluded that adequate arrangements for control and supervision of contractors were implemented.

The liaison meetings undertaken provided useful updates on matters of regulatory interest and confirmed adequate progress is being made by Magnox Ltd in delivering against the topics discussed.

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

From the information obtained and evidence gathered during this intervention, I do not believe there are any matters identified that have a significant negative effect on the system integrity and there were no issues identified that were considered to adversely affect nuclear safety.


Diben yr Ymyrraeth

Ymyrraeth arfaethedig ar safle trwyddedig Wylfa Magnox Ltd. Mae'r adroddiad hwn yn cwmpasu'r archwiliad yn ymwneud â diogelwch niwclear gorsaf bŵer Wylfa a gyflawnir yn rhan o gyfres o ymyraethau seiliedig ar system (SBIs) a bennir i fod yn angenrheidiol i gwmpasu systemau yn ymwneud â diogelwch fel yr amlinellir yn achos diogelwch Wylfa.

Ymyraethau a Gyflawnwyd gan yr ONR

Yn unol â chanllaw'r ONR, roedd yr archwiliad systemau hwn yn cwmpasu'r Amodau Trwyddedu (LCs) canlynol:

Trafodwyd yr LCs uchod yn rhan o'r archwiliad peryglon cychwynnol o drefniadau gorsaf bŵer Wylfa ar gyfer y system dŵr oeri argyfwng.

Cynhaliwyd archwiliad adweithiol hefyd mewn ymateb i gyfle i weld gweithgaredd cynnal a chadw ar eitem o Offer Yn Ymwneud ag Isafswm Diogelwch (MSRP), ar y cyd LC28 â'r arolygydd safle Magnox Ltd at gyfer wylfa.

Yn ogystal â'r archwiliadau a nodwyd uchod, mynychwyd nifer o gyfarfodydd cyswllt i fonitro cynnydd gyda gweithgareddau cyfredol a chynnal ymwybyddiaeth o unrhyw faterion o ddiddordeb rheoleiddiol. Roedd y rhain yn cynnwys y pynciau canlynol:

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

Ar sail yr archwiliad, rwy'n barnu ar y cyfan bod y systemau dŵr oeri argyfwng yn bodloni gofynion yr achos diogelwch peryglon mewnol a'u bod, ar sail yr archwiliad hwn, wedi eu hystyried i fod yn ddigonol.

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

Cyflawnwyd archwiliad system diogelwch peryglon mewnol o'r systemau dŵr oeri argyfwng yn rhan o'r rhaglen o SBIs a gynhwyswyd ar gynllun ymyrraeth safle Wylfa ar gyfer 2015/16. Diben yr arolygiad oedd asesu digonolrwydd gweithrediad yr orsaf o'i drefniadau presennol i sicrhau bod y swyddogaeth diogelwch system wedi ei chyflawni.

Archwiliwyd sampl o weithrediad sylfaenol (Rheolau Gweithredu) a dogfennau ategol (SOIs, PIOIs) yn ystod yr archwiliad.  Roedd tystiolaeth glir o derfynau ac amodau yn deillio o'r achos diogelwch yn cael eu gweithredu trwy amrywiaeth o gyfarwyddiadau gweithredu.  O ganlyniad, rhoddir sgôr IIS o 3 i LC23 ac LC24.

Roedd cyflwr cyffredinol y gwaith a archwiliwyd yn ddigonol. Roedd tystiolaeth o ddefnydd da a chwblhad o ddalenni gwirio cydymffurfiad, cyflawni ceisiadau gwaith a chofnodi rhagweithiol o ddiffygion nad ydynt yn uniongyrchol gysylltiedig â'r EMIT system, a ystyrir i fod yn arfer da.  Rhoddir sgôr IIS o 2 i LC28 a sgôr IIS o 3 i LC27. 

Cadarnhaodd yr archwiliad bod gweithrediad yr achos diogelwch wedi ei gefnogi gan becyn hyfforddiant ymwybyddiaeth penodol ar gyfer System Porthiant Argyfwng a Phorthiant Wrth Gefn a darparwyd tystiolaeth o hyfforddiant ac asesiad SQEP parthed yr achos diogelwch.   Rhoddir sgôr IIS o 3 i LC10.

Roedd yr archwiliad adweithiol o'r gweithgaredd cynnal a chadw yn gyfle i archwilio gweithrediad trefniadau ar gyfer rheoli a goruchwylio contractwyr. Canfu'r archwiliad dystiolaeth o gyfathrebu da rhwng y trwyddedai a'r contractwr yn arwain at ddealltwriaeth profadwy o'r dasg cynnal a chadw ac arwyddocâd diogelwch, wedi ei gefnogi gan enghreifftiau o hyfforddiant/cofnodion SQEP. O ystyried y sampl a archwiliwyd, casglodd yr ONR bod trefniadau digonol ar gyfer rheoli a goruchwylio contractwyr wedi eu gweithredu.

Roedd y cyfarfodydd cyswllt a gynhaliwyd yn gyfle i gael diweddariad defnyddiol ar faterion o ddiddordeb rheoleiddio gan gadarnhau bod Magnox Ltd yn sicrhau cynnydd digonol yn erbyn y pynciau a drafodwyd.

Cyflawnwyd yr ymyrraeth yn unol â gofynion canllaw'r ONR (fel y disgrifir yn ein canllawiau archwiliadau technegol) sydd ar gael ar www.onr.org.uk/operational/tech_insp_guides/index.htm.

Casgliad yr Ymyrraeth

O'r wybodaeth a gafwyd a'r dystiolaeth a gasglwyd yn ystod yr ymyrraeth hon, nid wyf yn credu bod yna unrhyw faterion a nodwyd sy'n cael effaith negyddol arwyddocaol ar gywirdeb y system ac nid oedd unrhyw faterion a nodwyd a ystyriwyd i fod yn effeithio'n andwyol ar ddiogelwch niwclear.