2016-01 enforcement recommendation for wylfa supply fan issue (redacted)

Wylfa supply fan extracting - November 2015 of 11

File Note: Wylfa miscellaneous events Date: January 2016 Subject: Potential for particulate discharges via an unauthorised route, due

to reversed flow of a supply fan 1. Introduction In November 2015 a large supply fan (S3F2S) in the Shielded Facilities Ventilation system at Wylfa Power Station was found to be rotating the wrong way. The fan is designed to provide clean air to areas within the Reactor Equipment Building, but was effectively extracting air from these areas (albeit at a much lower rate). 2. Relevant permissions The relevant permission is the radioactive substances permit for Wylfa Power Station, EPR/GB3235DL/V002, which was issued to Magnox Ltd on 11 November 2015. 3. Circumstances of the event The event was identified by Magnox Ltd staff during project work on heating modifications in preparation for the transition to defueling. Staff who had repaired a P2 defect on the heater bank between the dust filters on the intake & supply fan S3F2S noticed, during leak checking when the plant was being returned to service (the fan had been taken out of service to enable the repair) that warm air was coming out of the inlet ducting. Subsequent investigations revealed that fan S3F2S was turning the wrong way. This is considered most likely to have been happening since June 2014, when the fan was last returned to service following work on the motor (ie for a period of ~17 months). The fan is located on the 108’ level, in a room with one other (smaller) supply fan, supply & extract ductwork, & the discharge monitoring equipment – all part of the Shielded Facilities Ventilation (SFV) system. Fan S3F2S is part of the supply side of the SFV system. It is approx 5’ in diameter & is rated at 28,000 cubic feet/minute. The fan is fully enclosed within steel ducting, with no access for visual inspection.


Fan S3F2S is on the right; a smaller fan (S3F1S) is on the left

Fan S3F2S is designed to supply clean, dry air to around 12 areas in the Reactor Equipment Building (REB), including areas classified as C2 (ie contamination controlled areas, which are likely to have ‘fixed’ radioactive contamination present). The general arrangement is shown below:

Initial monitoring of the inlet filters (which were ‘downstream’ of the fan while it was operating in reverse) using contamination probes did not indicate any detectable contamination. Further monitoring was carried out within the ventilation system to provide reassurance that there was no detectable activity, including monitoring of the grilles. The dust filters were removed for further monitoring. They were assayed in


the Rados bag monitor normally used to demonstrate that waste arising within the Reactor Equipment Building is ‘out of scope’ of the radioactive substances regulations, & samples subjected to gamma spectrometry. The dust filters failed bag monitoring, with 600-900 Bq of Co-60 present on each of the 12 filters. Bag monitoring of the dust filters from the intake of the smaller adjacent fan (S3F1S, which is located in the same room) also indicated the presence of low levels of Co-60 activity. Levels on the S3F1S filters were around 25% of those found on the S3F2S filters. This clearly indicates that some particulate radioactive material has been discharged via the inlet supply for fan S3F2S. 4. Adequacy of operator’s response Notification & initial discussions Mark Elsworth (Head of Health Physics & Chemistry, Magnox Ltd) notified me about the event by phone on 12 November 2015. Email updates with monitoring data were provided on 13 & 16 November, & we discussed the event during a meeting at NRW’s offices at Buckley on 18 November 2015. Site visit I arranged a site visit on 17 December 2015 (jointly with the ONR site inspector) to carry out a plant walkdown & discuss Magnox’s draft investigation findings. Based on the information provided through initial discussions, I considered there were non-compliances with one or more conditions of the radioactive substances environmental permit (EPR/GB3235DL). I therefore issued a Code B notice (number 07977) at the start of the visit. We carried out a plant walkdown & held discussions with the lead investigator, two System Engineers, the Principal Health Physicist, & the Head of Health Physics & Chemistry. Magnox Ltd staff were fully co-operative, & were open & honest about the draft findings from their internal investigation into the root cause of the event. Investigation of event and identification of causes I received a copy of Magnox Ltd’s approved investigation report (WYA/REP/10073) on 14 January 2016. Magnox classified the event as:

REC01(C) – an inadequacy in arrangements, or failure to comply with arrangements, for compliance with the environmental permit

REC23 – discovery outside of a Controlled Area of radiation or contamination, including contamination on equipment, clothing or skin, significantly above that permitted by the local arrangements

NPE99 – a nuclear plant event or near miss which merits recording but does not fit any of the above (NPE) categories, but which is useful for trending purposes and/or action.

Magnox Ltd have carried out a thorough root cause investigation (WYA-01154). This reconstructs a timeline of the event, & clearly sets out what happened & considers the safety/environmental impact.


Fan S3F2S was taken out of service in November 2013 because the motor was tripping out. The fan was removed & sent off-site for a rewind. It was returned to site in January 2014, but not refitted until April 2014 following a request from Operations (who wanted the supply ventilation available for when Reactor 1 was ‘gassed up’ following an outage). The plant was handed over from Maintenance to Operations in April for re-commissioning. The need for a rotational check is normally specified in the safety document & handover certificate. However, return to service was only attempted in late May 2014 & was not completed then because a separate defect (damaged fuse holder) was then identified on the electrical system. This was repaired in early June 2014. Fan S3F2S was out of service for an extended period of time (almost 6 months). The fact that the rotational check on the fan had not been completed when Operations attempted to return to fan to service in late May 2014 was ‘lost’, & the rotational check was not completed when the fan was returned to service in early June 2014. Magnox Ltd concluded that the root cause of the event was an inadequacy in the handover procedures for plant. They also identified five contributory causes:

Poor communication between teams/inadequate planning of parallel tasks – because of the ‘disconnect’ between the fan & fuse repairs, which resulted in the need for the rotational check not being carried forward

Lack of attention to detail – because the fuse holder damage could have been identified when the fan was removed from service, rather than when it was being returned to service

Indications on plant not adequate – because there was no sign/label on the plant to indicate the need for a rotational check (this might have been missed anyway as it was originally removed for inspection, not rewinding), & there is no method of checking the direction of air flow other than the rotational check on return to service

Lack of questioning attitude – because the need to ensure the rotational check on the fan was completed was not considered

Corrective actions proposed (& timescales) Magnox Ltd have proposed the following actions to prevent a recurrence of the event:

Review MCP/012/000 to formalise/enhance the plant handover process

Introduce a process to signpost need for rotational check of fan during return to service directly on plant (note the ONR inspector is not keen on “operator aids”)

Fit ‘tell-tales’ to ducting to indicate direction of air flow

Brief operations staff on the event, in respect of inattention to detail (during isolation of plant, resulting in further delays) & lack of questioning attitude (during return to service, in considering how the need for a rotational check was carried forward)

Review the tracking process for out of service plant These are all due to be completed within 2 months (ie by mid-March 2016).


5. Potential compliance issues Relevant permit conditions potentially include:

1.1.1(a) – operate the activities in accordance with a written management system sufficient to achieve compliance with the permit

1.1.1(b) – operate the activities using sufficient competent staff & resources

2.3.2(c) – use BAT to dispose of radioactive waste at times, in a form, and in a manner so as to minimise the radiological effects on the environment and members of the public.

2.3.4(a) – maintain in good repair the systems & equipment provided to meet the requirements of the BAT conditions

2.3.5 – requirement to check effectiveness of systems, equipment & procedures provided to meet the BAT conditions at an appropriate frequency; and/or

2.3.6 – have & comply with appropriate criteria for accepting equipment into service

3.1.1 – radioactive waste shall only be disposed of by the disposal routes specified in schedule 3 (ie specified disposal outlets for gaseous waste).

Consideration of whether the discharge was via a permitted route Discussion with the System Engineers confirmed that the supply & exhaust sides of the SFV system are separate. Air is drawn into the REB by the supply fans, distributed via ducting to various areas & released via grilles into areas throughout the REB (from pile cap to 18’ basement). The exhaust side fans are rated slightly higher than the supply side fans, to ensure there is a negative pressure (to ensure containment of any potential airborne contamination) & force ventilation. The system is not balanced, & the exhaust side will force ventilation even if the supply fans are not working. Approved discharge outlet A7 is described in Magnox Ltd’s techniques document (WYA/REP/7813):


This clearly covers the exhaust side of the SFV only. The HEPA filters on the exhaust are part of the station’s BAT arrangements for ensuring that discharges of gaseous radioactive waste (particulate) to the environment are minimised. Required availability of the SFV HEPA filters & discharge sampling equipment is specified in SOI A11. While the dust filters on the inlet to S3F2S provided some abatement of particulate discharges (as evidenced by the fact that Co-60, an activation product which is characteristic of the fuel route, was detected on the inlet filters), their efficiency is much lower than HEPA filters & (because Co-60 was also detected on the dust filters on the inlet to the adjacent fan) it is clear there has been some release via this route. I consider that a discharge via fan S3F2S, in the supply side of the SFV system, was a discharge via an unauthorised route. This therefore represents a non-compliance with condition 3.1.1 of the permit. Fan S3F2S supplies a number of areas with the REB, including fuel route (fuelling machine & loading/unloading facilities for the dry store cells 2 & 3), active waste facilities & the Active Effluent Treatment Plant. Given the above, I do not consider that conditions 2.3.4(a) & 2.3.5 are relevant, because the supply side of the SFV system is not identified as equipment provided to meet the BAT conditions. In addition, condition 2.3.6 is not relevant because it specifically relates to acceptance into service checks on (discharge) measuring equipment. Environmental impact Monitoring of the dust filters indicates that very low levels of particulate activity were present, typically 600-930 Bq Co-60 per filter accumulated over an 18 month period


(total for 12 filters ~10.8 kBq). Discharges of radioactivity associated with particulate matter via the permitted Shielded Facilities Vent outlet (outlet A7 in the RSR permit) are typically 0.08-0.2 MBq/month (from Apr-Sep 2015 returns). The levels of activity released are very low, & there is no indication from routine monitoring data of any detectable increase of activity in the environment. The environmental impact of the event is insignificant.

Adequacy of maintenance arrangements

The fan is subject to a 4 yearly overhaul of the motor, which was last completed in October 2013. Rewinding of the motor can result in a phase change, & the requirement for a rotational check to be completed when the fan is returned to service following a motor rewind is captured in the safety document. Ensuring the correct plant configuration is entirely dependent on this check being carried out when the fan is being returned to service. Due to the size of the fan & its enclosed nature, there are no routine surveillances in place to check the fan rotation or the direction/rate of air flow within the SFV system.

The inlet dust filters should be changed every 2 years (but this is not a Maintenance Schedule or Environmental Maintenance Schedule routine, so may not be rigorously done). The differential pressure across the filters is checked routinely by operators.

Although there are no (nuclear) safety case claims on supply fan S3F2S, the fan is designated as Plant Class 2. Magnox define four classes of plant (Plant Class 1-4) by reference to the consequence of the plant failing. The consequences can be in terms of radiological hazard, injury to persons, breach of licence condition or environmental permit requirements, cost penalty, etc. Plant Class 1 is the highest significance, & is anything related to maintaining the primary circuit gas pressure boundary (eg boron dust injection system, gas circulators). Plant Class 2 is plant with a major but less serious radiological risk (eg an isolatable section of the pressure circuit, acid/caustic bulk tanks). The supply fan is therefore recognised to be a reasonably significant plant item, & I find it somewhat surprising that it could be out of service for almost 6 months without any questions being raised.

Adequacy of plant handover arrangements

Handover certificates (WYA/ED/F004) record any actions that are required to be completed to return plant to service in the correct configuration when FIN, Maintenance, Projects or Engineering hand the plant item back over to Operations. The handover certificate requires a signature to confirm that the plant has been inspected & considered fit for use, & another signature to confirm that any outstanding work (including any pre-start or functional checks) has been completed. They are not permanent records, & only have a retention period of one year (despite maintenance intervals for some plant being longer than this, eg 4 years).

Magnox Ltd have not been able to establish whether a handover certificate was ever created for the return to service of the supply fan.

If it was, it shouldn’t have been signed off if the functional check(s) hadn’t been completed, so the plant (S3F2S) should not have been available for operational service.


If it wasn’t, then clearly the handover arrangements are not robust or are not always followed by Maintenance &/or Operations.

This raises a number of issues about the adequacy of the system in place for tracking plant availability, which I will follow up at a future inspection.

I consider that there was an inadequacy in the management arrangements which failed to ensure that the status of Plant Class 2 plant was adequately recorded during handover for re-commissioning. This represents a non-compliance with condition 1.1.1(a) of the RSR permit.

6. Classification of event CICS classification As this event is associated with a relatively long-term plant condition, resulting in an insignificant environmental impact, I have considered it as a non-compliance with the RSR permit rather than as a pollution incident, & have not classified it under CICS. Compliance Classification Scheme The reference documents for determining the CCS classification of this event was 156_10_SD02 (version 3, issued 09/12/2014): CCS scoring guide for radioactive substances facilities regulated under the Environmental Permitting Regulations 2010. Having reviewed the guidance, I consider that this event represents non-compliances with the following conditions of permit number EPR/GB3235DL:

Condition 3.1.1 – Category 3 (minor) breach under criteria a1 (permitted activities), because there was a discharge via an unauthorised route, but within site limits

Condition 1.1.1(a) – Category 3 (minor) breach under criteria c2 (management systems & operating procedures) because return to service procedures for the supply fan were not properly implemented, the plant handover procedures are not robust, & there are no routine checks in place between extended maintenance periods to check the effectiveness of systems

I will ask to enter this event onto NRW’s CCS database with two Category 3 breaches as above. 7. Enforcement response The reference documents for determining the enforcement response to this event were:

Operational Instruction 1430_10 Offence Response Options (issued 01/06/2015)

Policy 1429_10 Enforcement & Sanctions Statement (issued 18/12/2014)

Operational instruction 1428_10 Enforcement & Sanctions Guidance (issued 08/10/2015)


Operational Instruction 156_10_SD02 CCS scoring guide for radioactive substances facilities regulated under the Environmental Permitting Regulations 2010 (version 3, issued 09/12/2014)

It is an offence under Regulation 38(2) of the Environmental Permitting Regulations 2010 to fail to comply with or to contravene a permit condition. The appropriate enforcement outcome is to bring the operator back into compliance. The relevant public interest factors are discussed below:

Intent – there is no reason to believe this was a deliberate act intended to lead to environmental harm, but it was caused by a neglect &/or absence of appropriate arrangements.

Foreseeability of the event and the circumstances leading to it – the risk of mis-connecting a fan is clearly understood, & this is normally managed by completing a rotational check on return to service. The operator’s investigation report includes examples of previous operating experience, including a fan rotating in reverse, failure to carry out a rotational check on return to service, & lack of robust plant handover procedures. Although these are isolated events (4 events in 10 years is not common given the scale of the site), a repeat event indicates that the root causes have not been adequately addressed in the past & that there is at least some element of ‘forseeability’.

Actual or potential environmental impact of the event – the actual impact of the discharge on people (in terms of dose) and the environment was insignificant. It is unlikely that the potential impact from this system would be more significant given the plant configuration & controls on operations within the areas served by the Shielded Facilities Ventilation system. It is difficult to predict what impact failure to complete return to service checks on other plant items could be.

Nature of the offence – this event represents a breach of two conditions of the radioactive substances environmental permit. The operator notified the event in line with the requirements of the permit, & provided regular updates following the event including photographs of the plant area & monitoring results. The operator was co-operative during our follow-up visit to site, & open & honest in their response to questions. The operator provided a copy of their internal root cause investigation report around 2 months after the event, & the scope of their investigation adequately reflected the seriousness of the event. The offences have not impacted our ability to effectively regulate the site.

Financial implication – the operator has not made any commercial gains or profit as a result of these non-compliances. The operator dedicated significant resource to investigate the cause of the event. The site regulator attended site to follow up the event, & provided briefings for NRW senior managers to brief Welsh Government.

Deterrent effect – while there was a deficiency in the management system, the actual environmental impact of this event was insignificant.

Previous history/past environmental performance – compliance with the RSR permit is generally good, with the last enforcement action (warning letter) taken in March 2012. NRW recorded CCS Category 4 scores for two separate events relating to leaks from the Reactor Ancillary Cooling Water (RACW) system in


2014 & 2015 which resulted in a discharge of, or potential to discharge, chromate-dosed water via the site’s drainage systems. There are some common factors between the two previous events & this one, in respect of lack of questioning attitude & inadequacies in management arrangements. However, it is worth noting that the initiating event occurred 17 months ago & that all Operations staff at Wylfa received refresher training on Conduct of Operations following the 2015 RACW event, which may reduce the likelihood of similar events.

Attitude of the organisation and whether there has been corrective action and measures to prevent recurrence – the operator recognises the seriousness of this event & has committed to a number of actions which should ensure a more robust plant handover process in future, as well as specific improvements to the indications on plant which should ensure more timely discovery of any similar issues with fan rotation in future.

The normal enforcement action for minor breaches with no environmental impact is to provide advice & guidance or, where this will not achieve the necessary outcome, to issue a warning. Although the environmental impact of this event was insignificant, it was entirely avoidable if the normal return to service procedures had been followed. I believe that on this occasion the deficiencies in the management arrangements are significant enough to justify a warning letter. I will recommend this action in a ROC form to be considered by the NRW Area Enforcement Panel. I consider that Magnox’s proposed corrective actions – in particular, review of the plant handover process – should be sufficient to address the root cause of this event, but I will follow up at a future site visit to ensure they can demonstrate that the new process is sufficiently robust. I will place an action, via a RASCAR, for Magnox to complete their corrective action programme as detailed in WYA/REP/10073. Nuclear Regulator Date: 22 January 2016 Signed:

TL review of proposed enforcement action Agree / disagree Comments:


Signed: Date: NRW account manager review of proposed enforcement action Agree / disagree Comments: Signed: Date:

2016-01 enforcement recommendation for wylfa supply fan issue (redacted)

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