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Planned Systems Based Inspections at Magnox Ltd’s Wylfa licensed site, undertaken as part of a series of planned interventions outlined in the ONR Integrated Strategy Plan Wylfa Power Station 2015/16

Executive summary

Purpose of intervention

The purpose of this intervention was to complete a systems based inspection (SBI) on the Wylfa nuclear reactor gas circulators.

This was undertaken as part of the planned Decommissioning and Fuel Waste (DFW) intervention programme strategy for the Wylfa site for 2015/16.

Interventions Carried Out by ONR

A planned System Based Inspection (SBI) on the reactor gas circulators was undertaken with an ONR Mechanical Engineering specialist inspector.  The objectives of the SBIs are to confirm that the relevant safety systems and structures important to safety meet the safety functional requirements defined in the safety case and to test implementation of the Licence Condition (LC) arrangements for: LCs 10 (training), 23 (operating rules), 24 (operating instructions), 27 (safety mechanisms, devices and circuits), 28 (examination, inspection, maintenance and testing), and 34 (leakage and escape of radioactive material and radioactive waste). We also undertook a plant walk down as part of this inspection.

A reactive inspection into Magnox Ltd’s response to a reported incident associated with the Reactor 2 Reactor Ancillary Cooilng Water (RACW) Vent System was undertaken.

Routine liaison meetings were held to review progress against a number of site projects, regulatory issues and ONR permissioning activities.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

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

In relation to the LC 10 element of the SBI, we concluded that individuals were clearly identified as being SQEP through the use of a SQEP matrix which identified for each individual the training they had received together with their experience undertaking the work and similar tasks.  The training material was examined was of a high standard and clearly demonstrated a commitment to quality focused training.  There was evidence these were reviewed regularly to ensure the training needs of individuals were met.  Taking all these factors into account, we assigned an Integrate Intervention Strategy (IIS) rating of 2 (good standard) to LC10.

In relation to the LC 23 element of the SBI, although a link was ultimately established between the safety case and operating rules, this was not transparent.  A number of inconsistencies in documentation were noted during our examination which was pointed out to the licensee. Taking these factors into account, we assigned an IIS rating of 3 (adequate) for compliance with LC23.

In relation to the LC 24 element of the SBI, we found a clear link exists between operating rules and operating instructions.  Check sheets were being utilised to ensure compliance with operating instructions and these were being completed on a regular (daily) basis.  During our examination of a number of maintenance instructions we identified that test pass/fail criteria was not always clear.  In response to this a level 4 issue has been raised requesting the license to provide justification for the calculations performed in the Instruction.  Taking these factors into account, we assigned an IIS rating of 3 (adequate) for compliance with LC24.to provide justification.

In relation to the LC 27 element of the SBI a clear set of allowable combinations of plant item unavailability and plant configuration when a reactor is operating or shutdown is clearly identified, together with a high level transparency demonstrated through maintenance of restart to service, prestart logs and handover statements.  In response, we have assigned an IIS rating of 2 (good practice) for compliance with LC27.

In relation to the LC 28 element of the SBI examination of a sample of maintenance instructions exposed a number of inconsistencies in the completion of documentation.  The pass/fail criteria of a number of examined maintenance procedures examined was not always transparent.  The maintenance procedures are currently undergoing review in light of the immanent shutting down second of the two Wylfa reactors and new maintenance procedures will reflect this new operating regime.  An IIS rating of 3 (adequate) was allocated for LC 28.

In relation to the LC 34 element of the SBI, we were able to verify that leakage of potentially contaminated oil can be captured in a sump provided under the whole of each oil supply system for ach reactor.  It was also demonstrated that CO2 leakage can be detected through CO2 detectors placed around the gas circulator shielding plug.  From the discussion with the systems engineer we were provided with sufficient evidence that demonstrate appropriate management of leakage and escape of radioactive material and radioactive waste. An IIS rating of 3 (adequate) therefore was allocated for LC34.

The inspection into Magnox Ltd’s response to a reported incident associated with the Reactor 2 Reactor Ancillary Cooilng Water (RACW) Vent System was undertaken in conjunction with the Environment agency and an ONR Human Factors specialist inspector. Constructive discussions were held with Magnox Ltd site representatives regarding the potential causes of the event, the potential consequences of similar events and work currently underway to prevent recurrence / ensure future risks are ALARP.  Overall, the actions proposed by the Licensee to minimise the risk of recurrence of this incident were acceptable, however more general improvements in the quality and adherence to instructions is required to prevent similar incidents elsewhere on the station. Magnox Ltd has agreed to undertake additional reviews of operation tasks with view to validating the adequacy of the documented instructions and also review current arrangements for control of instructions against accepted good practice.

Liaison meetings covered the following topics

For each of the topics covered suitable responses by either Magnox Ltd or ONR were identified to progress matters towards adequate conclusions.

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 evidence obtained during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety on the station at this time.  Therefore, no additional regulatory action arising from this visit is considered necessary at this time.


Crynodeb gweithredol

Diben yr Ymyrraeth

Diben yr ymyrraeth hon oedd cwblhau archwiliad seiliedig ar systemau (SBI) ar gylchedau nwy adweithydd niwclear Wylfa.

Cyflawnwyd hyn yn rhan o'r strategaeth rhaglen ymyrraeth Datgomisiynu a Thanwydd Gwastraff (DFW) ar gyfer safle Wylfa yn 2015/16.

Ymyraethau a Gyflawnwyd gan yr ONR

Cyflawnwyd Archwiliad Seiliedig ar System (SBI) arfaethedig ar gylchredwyr nwy'r adweithydd gydag archwilydd arbenigol Peirianneg Fecanyddol yr ONR.  Amcanion yr SBIs yw cadarnhau'r systemau a strwythurau diogelwch perthnasol sy'n bwysig i fodloni'r gofynion swyddogaeth diogelwch a ddiffinnir yn yr achos diogelwch ac i brofi gweithrediad y trefniadau Amod Trwyddedu (LC) ar gyfer: LC 10 (hyfforddiant), 23 (rheolau gweithredu), 24 (cyfarwyddiadau gweithredu), 27 (mecanweithiau diogelwch, dyfeisiau a chylchedau), 28 (archwilio, adolygu, cynnal a chadw a phrofion), a 34 (deunydd ymbelydrol a gwastraff ymbelydrol sy'n gollwng neu ddianc). Cyflawnom daith drwy'r gwaith hefyd yn rhan o'r archwiliad hwn.

Cyflawnwyd archwiliad adweithiol i ymateb Magnox Cyf i ddigwyddiad a adroddwyd yn gysylltiedig â System Awyru Dŵr Oeri Ategol Adweithydd 2 (RACW).

Cynhaliwyd cyfarfodydd cyswllt rheolaidd i adolygu cynnydd yn erbyn nifer o brosiectau safle, materion rheoleiddiol a gweithgareddau caniatâd ONR.

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

Ddim yn berthnasol.

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

Parthed elfen LC 10 yr SBI, fe gasglom fod yr unigolion a nodwyd yn glir i fod yn SQEP trwy ddefnyddio matrics SQEP a nododd ar gyfer pob unigolyn yr hyfforddiant yr oeddynt wedi ei dderbyn ynghyd â'u hyfforddiant yn cyflawni'r gwaith a thasgau tebyg.  Roedd y deunydd hyfforddi a archwiliwyd o safon uchel ac yn dangos ymroddiad clir i hyfforddiant gyda ffocws ar ansawdd.  Roedd tystiolaeth bod y rhain yn cael eu hadolygu'n rheolaidd i sicrhau y bodlonwyd anghenion hyfforddiant unigolion.  Gan ystyried yr holl ffactorau hyn, fe neilltuom raddiad Strategaeth Ymyrraeth Cyfunedig (IIS) o 2 (safon dda) i LC10.

Parthed elfen LC 23 yr SBI, er y sefydlwyd cyswllt yn y pen draw rhwng yr achos diogelwch a rheolau gweithredu, nid oedd hyn yn dryloyw.  Nodwyd nifer o anghysondebau mewn dogfennaeth yn ystod ein harchwiliad, a nodwyd i'r trwyddedai. Gan ystyried y ffactorau hyn, fe neilltuom raddiad IIS o 3 (digonol) ar gyfer cydymffurfiad gyda LC23.

Parthed elfen LC 24 yr SBI, gwelsom fod yna cyswllt clir rhwng rheolau gweithredu a chyfarwyddiadau gweithredu.  Roedd dalenni gwirio yn cael eu defnyddio i sicrhau cydymffurfiad gyda chyfarwyddiadau gweithredu ac roeddynt yn cael eu cwblhau yn rheolaidd (dyddiol).  Yn ystod ein harchwiliad o nifer o gyfarwyddiadau cynnal a chadw, fe nodom nad oedd meini prawf pasio/methu yn glir pob tro.  Mewn ymateb i hyn, codwyd mater lefel 4 yn gofyn i'r drwydded ddarparu cyfiawnhad o'r cyfrifiadau a gyflawnwyd yn y Cyfarwyddyd.  Gan ystyried y ffactorau hyn, fe neilltuom raddiad IIS o 3 (digonol) ar gyfer cydymffurfiad gyda LC24.

Parthed elfen LC 27 yr SBI, fe nodir set glir o gyfuniadau a ganiateir o ddiffyg argaeledd eitem gwaith a ffurfweddiad gwaith pan mae'r adweithydd yn gweithredu neu os yw diffodd wedi ei nodi'n glir, ynghyd â lefel uchel o dryloywder a welir trwy gynnal a chadw ailgychwyn gwasanaeth, cofnodion cyn cychwyn a datganiadau trosiant.  Rydym wedi dynodi graddiad IIS o 2 (arfer da) ar gyfer cydymffurfiad gydag LC27.

Parthed lefel LC 28 yr archwiliad SBI, datgelodd sampl o gyfarwyddiadau cynnal a chadw nifer o anghysondebau o ran cwblhau'r ddogfennaeth.  Nid oedd meini prawf pasio/methu nifer o weithdrefnau cynnal a chadw a archwiliwyd yn dryloyw ar bob adeg.  Mae'r gweithdrefnau cynnal a chadw yn cael eu hadolygu ar hyn o bryd o ganlyniad i'r ffaith y bydd yr ail o ddau adweithydd Wylfa yn cael ei ddiffodd yn fuan a bydd y gweithdrefnau cynnal a chadw yn adlewyrchu'r weithdrefn weithredu newydd hon.  Dyrannwyd graddiad IIS o 3 (digonol) ar gyfer LC 28.

Parthed elfen LC 34 yr SBI, roeddem yn gallu gwirio y gellir cipio olew allai fod wedi ei halogi mewn swmp a ddarparwyd dan bob system cyflenwi olew cyfan ar gyfer pob adweithydd.  Dangoswyd hefyd y gellir canfod gollyngir CO2 trwy ganfodyddion CO2 a osodwyd o amgylch y plwg amddiffyn cylchredwr nwy.  O'r drafodaeth gyda'r peiriannydd system, cawsom ddigon o dystiolaeth sy'n arddangos rheolaeth briodol o ollwng a dihangfa deunydd ymbelydrol a gwastraff ymbelydrol. Felly dyrannwyd graddiad IIS o 3 (digonol) ar gyfer LC34.

Cyflawnwyd yr archwiliad adweithiol i ymateb Magnox Cyf i ddigwyddiad a adroddwyd yn gysylltiedig â System Awyru Dŵr Oeri Ategol Adweithydd 2 (RACW) ar y cyd ag Asiantaeth yr Amgylchedd ac arolygwr arbenigol Ffactorau Dynol yr ONR. Cafwyd trafodaethau adeiladol gyda chynrychiolwyr safle Magnox Cyf parthed achosion posibl y digwyddiad, goblygiadau posibl digwyddiadau tebyg a'r gwaith sy'n cael ei gyflawni ar hyn o bryd i atal ail achos / sicrhau bod risgiau yn y dyfodol yn ALARP.  Ar y cyfan, roedd y camau a gynigiwyd gan y Trwyddedai i leihau risg o ail achos o'r digwyddiad yn dderbyniol, ond mae angen gwelliannau mwy cyffredinol i ansawdd ac ymlyniad at y cyfarwyddiadau i ail achosion tebyg mewn rhannau eraill o'r orsaf. Mae Magnox Cyf wedi cytuno i gyflawni adolygiadau atodol o dasgai gweithredu gyda'r bwriad o ddilysu digonolrwydd y cyfarwyddiadau a ddogfennwyd a hefyd i adolygu trefniadau presennol ar gyfer rheoli cyfarwyddiadau yn erbyn arfer da a dderbyniwyd,

Trafododd cyfarfodydd cyswllt y pynciau canlynol

Ar gyfer pob un o'r pynciau a drafodwyd, nodwyd ymatebion addas gan naill ai Magnox Ltd neu'r ONR i symud materion ymlaen tuag at gasgliadau digonol.

Cyflawnwyd yr ymyrraeth yn unol â gofynion yr ONR (a ddisgrifiwyd yn ein canllawiau archwilio technegol, sydd ar gael ar: www.onr.org.uk/operation/tech_insp_guides/index.htm yn y meysydd a archwiliwyd.

Casgliad yr Ymyrraeth

O'r dystiolaeth a gasglwyd yn ystod yr ymyrraeth hon, ni nodwyd unrhyw faterion sy'n debygol o gael effaith arwyddocaol ar ddiogelwch niwclear yn yr orsaf ar hyn o bryd.  Felly, ni ystyrir bod unrhyw gamau rheoleiddiol yn angenrheidiol ar hyn o bryd yn deillio o'r ymweliad hwn.