Office for Nuclear Regulation

This website uses non-intrusive cookies to improve your user experience. You can visit our cookie privacy page for more information.

Trawsfynydd system based inspection (SBI)

Executive summary

Purpose of intervention

This report covers a system based inspection (SBI) carried out at Magnox Ltd’s Trawsfynydd licensed site undertaken as part of a series of routine interventions set out in the Integrated Intervention Strategy document.

As part of this planned SBI, I examined Magnox Ltd’s Trawsfynydd compliance with the following licence conditions (LC’s):

The inspection focused on the ILW store and in particular the nuclear lifting and handling systems which were inspected against ONR guidance and the specialist inspector’s knowledge of relevant good practice (RGP).

Interventions Carried Out by ONR

The SBI team inspection, was undertaken by the ONR Site Inspector and a Specialist Mechanical Engineering Inspector, and examined the key hazards and related control / mitigation claims made within the safety case.   A number of nuclear lifting and handling safety systems and safety mechanisms were sampled that were associated with providing protection against the key safety case fault sequences.

Explanation of Judgement if Safety System Not Judged to be Adequate

I judged that there was adequate implementation of the safety case requirements applicable to the nuclear lifting system.  Evidence was found of compliance shortfalls in some individual licence conditions.  

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

Site Licence Condition 23 – Operating Rules

Through examination of the pre-construction safety case I judged that operating rules were adequately specified and I considered that an IIS rating of 3 (Adequate) was appropriate.  The structure of the safety case however resulted in some loss of clarity and two recommendations were made to improve implementation of the operating rules.

Site Licence Condition 24 – Operating Instructions – IIS Rating 3 (Adequate)

I identified a number of inconsistencies and shortfalls in the licensee’s operating instructions, particularly relating to pre-start checks and procedures.  The licensee responded positively and appropriate actions were proposed.  In view of this I consider an IIS rating of 3 (Adequate) to be appropriate.  One recommendation was made:

Site Licence Condition 27 – Safety Mechanisms, Devices and Circuits

I identified that the licensee had potentially been operating the ILW store crane without an adequately tested overload protection system.  The licensee is aware of this test anomaly and is seeking its resolution with the crane manufacturer.  I am content that this is being progressed and therefore consider an IIS rating of 3 (Adequate) to be appropriate.

Site Licence Condition 28 – Examination, Inspection, Maintenance and testing

Maintenance of the ILW store cranes is undertaken by the crane manufacturer on a 6 monthly cycle.  The statutory thorough in service examination is undertaken by a third party competent authority.  I consider an IIS rating of 3 (Adequate) to be appropriate.

I noted that the competent authority had not noted the absence of two tests and so I made the recommendation that:

Site Licence Condition 10 – Training – IIS Rating 3 (Adequate)

Training records of individuals are available and these specify what tasks they are SQEP to undertake.

Individuals are allocated to tasks in line with authorisation instructions specifying what tasks they are SQEP to undertake, however a record of who is allocated to any particular task was not available, leading to potentially the loss of task experience data , in view of this I consider that an IIS rating of 3 (Adequate) to be appropriate.

Site Licence Condition 34 – Leak and Escape of Radioactive Material and Radioactive Waste – IIS Rating 3 (Adequate)

The escape of radioactive material is managed through the integrity of the ILW packages.  Environmental condition monitoring and package inspection arrangements are additionally in place to facilitate early identification of package degradation and judge these systems to be adequate.  In view of these arrangements an IIS rating of 3 (Adequate) is considered appropriate.

Plant Walkdown – IIS Rating – Not Applicable

A number of housekeeping issues were identified.  The licensee took immediate action in all occasions to instigate remedial action.  All the ILW package transport equipment was in good condition and was appropriately stored and maintained.  One recommendation was made.

Conclusion of Intervention

From the information examined and evidence gathered during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety on the Magnox Ltd’s Trawsfynydd licensed site at this time.

Crynodeb gweithredol

Diben yr Ymyrraeth

Mae'r adroddiad hwn yn trafod archwiliad seiliedig ar system (SBI) a gyflawnwyd yn safle trwyddedig Magnox Ltd Trawsfynydd , a gyflawnwyd yn rhan o gyfres o ymyraethau cyffredinol a sefydlir yn y ddogfen Strategaeth Ymyrraeth Integredig.

Yn rhan o'r SBI arfaethedig hwn, fe archwiliais gydymffurfiad Trawsfynydd Magnox Ltd gyda'r amodau trwyddedu (LCs) canlynol:

Canolbwyntiodd yr archwiliad ar y storfa ILW ac yn benodol ar systemau codi a chario niwclear a archwiliwyd yn erbyn canllaw'r ONR a gwybodaeth yr arolygydd arbenigol o arfer da perthnasol (RGP).

Ymyraethau a Gyflawnwyd gan yr ONR

Cyflawnwyd yr archwiliad tîm SBI gan yr Arolygydd Safle ONR ac Arolygydd Peirianneg Fecanyddol Arbenigol, gan archwilio'r peryglon allweddol a hawliadau rheoli / lliniaru perthnasol a wnaethpwyd yn yr achos diogelwch.   Samplwyd nifer o systemau diogelwch codi a chario niwclear a mecanweithiau diogelwch sy'n gysylltiedig â darparu amddiffyniad yn erbyn y dilyniannau diffyg achos diogelwch allweddol.

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

Barnais bod yna weithrediad digonol o ofynion yr achos diogelwch sy'n berthnasol i'r system godi niwclear.  Canfuwyd tystiolaeth o ddiffygion cydymffurfiad mewn rhai amodau trwyddedu unigol.  

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

Amod Trwyddedu Safle 23 – Rheolau Gweithredu

Trwy archwilio'r achos diogelwch cyn adeiladu, barnais bod rheolau gweithredu wedi eu pennu'n ddigonol ac fe ystyriais bod graddiad IIS o 3 (Digonol) yn briodol.  Fodd bynnag, arweiniodd strwythur yr achos diogelwch at rywfaint o golli eglurder a gwnaethpwyd dau argymhelliad i wella gweithrediad y rheolau gweithredu.

Amod Trwyddedu Safle 24 – Cyfarwyddiadau Gweithredu – Graddiad IIS 3 (Digonol)

Fe nodais nifer o anghysondebau a diffygion yng nghyfarwyddiadau gweithredu'r trwyddedai, yn arbennig parthed gwiriadau a gweithdrefnau cyn cychwyn.  Fe ymatebodd y trwyddedai yn bositif ac fe gynigiwyd camau priodol.  O ganlyniad i hyn, rwy'n ystyried graddiad IIS o 3 (Digonol) i fod yn briodol.  Gwnaethpwyd un argymhelliad:

Amod Trwyddedu Safle 27 – Mecanweithiau, Dyfeisiau a Chylchedau Diogelwch

Fe nodais y posibiliad bod y trwyddedai wedi bod yn gweithredu crawn y storfa ILW heb system amddiffyn gorlwytho wedi ei phrofi'n ddigonol.  Mae'r trwyddedai'n ymwybodol o'r anomaledd prawf hwn ac yn ceisio datrys y mater gyda gwneuthurwr y craen.  Rwy'n fodlon bod hyn yn cael ei ddatblygu ac felly'n rwy'n ystyried graddiad IIS o 3 (Digonol) i fod yn briodol.

Amod Trwyddedu Safle 28 – Arolygiad, Archwiliad, Cynnal a Chadw a Phrofi

Cyflawnir gwaith cynnal a chadw craeniau'r storfa ILW gan wneuthurwr y craen pob 6 mis.  Cyflawnir yr archwiliad mewn gwasanaeth trylwyr statudol gan awdurdod cymwys trydydd parti.  Rwy'n ystyried graddiad IIS o 3 (Digonol) i fod yn briodol.

Fe nodais nad oedd yr awdurdod cymwys wedi nodi absenoldeb dau brawf, ac felly fe argymhellais:

Amod Trwyddedu Safle 10 – Hyfforddiant – Graddiad IIS 3 (Digonol)

Mae cofnodion hyfforddiant unigolion ar gael ac mae'r rhain yn nodi pa dasgau maent yn Unigolyn gyda Chymhwyster a Phrofiad Addas (SQEP) i'w cyflawni.

Fe neilltuir unigolion i dasgau yn unol â chyfarwyddiadau awdurdodiad yn dynodi pa dasgau maent yn SQEP i'w cyflawni, fodd bynnag, nid oedd cofnod o pwy oedd wedi ei neilltuo i unrhyw dasg benodol ar gael, gan arwain at y posibiliad o golli data profiad tasg. O ganlyniad i hyn, rwy'n ystyried bod graddiad IIS o 3 (Digonol) yn briodol.

Amod Trwyddedu Safle 34 – Deunydd Ymbelydrol a Gwastraff Ymbelydrol yn Gollwng a Dianc – Graddiad IIS 3 (Digonol)

Fe reolir unrhyw ddianc o ddeunydd ymbelydrol trwy gyfanrwydd y pecynnau ILW.  Mae yna fonitro amodau amgylchedd a threfniadau archwilio pecynnau ar waith hefyd i hwyluso nodi diraddiad pecyn yn gynnar a bernir bod y systemau hyn yn ddigonol.  O ganlyniad i'r trefniadau hyn, rwy'n ystyried graddiad IIS o 3 (Digonol) i fod yn briodol.

Taith trwy'r Gwaith – Graddiad IIS – Amherthnasol

Nodwyd nifer o faterion cadw tŷ.  Fe weithredodd y trwyddedai ar unwaith ar bob achlysur i gychwyn gwaith i unioni.  Roedd yr holl offer cludo pecynnau ILW mewn cyflwr da ac wedi eu storio a chynnal yn briodol.  Gwnaethpwyd un argymhelliad.

Casgliad yr Ymyrraeth

O'r wybodaeth a archwiliwyd dystiolaeth a gasglwyd yn ystod yr ymyrraeth hon, ni nodwyd unrhyw faterion sy'n debygol o gael effaith arwyddocaol ar ddiogelwch niwclear ar safle trwyddedi Trawsfynydd Magnox Ltd ar hyn o bryd.