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PROJECT ASSESSMENT REPORT

Unique Document ID and Revision No:

ONR-CNRP-PAR-14-025 Revision 0

TRIM Ref: 2015/1490

Project: Hartlepool and Heysham 1 Boiler Spines Return to Service

Site: Heysham 1

Title: EC354024 Version 03 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine

Licence Instrument No’s:

Heysham 587

Nuclear Site Licence No’s: Heysham 60

Licence Condition: 22(1)

Document Acceptance and Approval for Issue / Publication

Role Name Position Signature Date

Author Inspector 09/01/2015

Reviewer Principal Inspector

Accepted by1 Superintending

Inspector

Approval for publication

2

Superintending Inspector

Revision History

Revision Date Author(s) Reviewed By Accepted By Description of

Change

A 09/01/2015 1st draft for AUH

review

0 09/01/2015 First accepted issue

1 Acceptance of the PAR to allow release of LI

2 Approval is for publication on ONR web-site, after redaction where relevant

Report ONR-CNRP-PAR-14-025 TRIM Ref: 2015/1490

Office for Nuclear Regulation Page 2 of 27

Circulation (latest issue)

Organisation Name Date

Office for Nuclear Regulation - Head of CNRP (DCI)

– Delivery Lead of Operating Reactors

– Graphite Core Integrity Inspector

– Structural Integrity Inspector

– Fault Studies Inspector

- Fault Studies Inspector

- Structural Integrity Inspector

– PSA Specialist Inspector

- PSA specialist Inspector

- Heysham 1 Site Inspector

– Hartlepool Site Inspector

Environment Agency Heysham Site Regulator

Licensee TSSM, Heysham 1



Heysham 1 Reactor 1 Boiler Spines Return to Service

EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine

Project Assessment Report ONR-CNRP-PAR-14-025

Revision 0 09th January 2015



© Office for Nuclear Regulation, 2015 If you wish to reuse this information visit www.onr.org.uk/copyright for details. Published 01/2015

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EXECUTIVE SUMMARY

Title

EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine

Permission Requested

EDF Energy Nuclear Generation Ltd (NGL), the licensee of Heysham 1 power station, has requested ONR’s Agreement under arrangements made under Licence Condition 22(1) to the implementation at Heysham Reactor 1 “EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine”. The safety justification of this safety case is time limited to 31st August 2015 or 240 days at reduced power, whichever is sooner.

Background

Heysham 1 is a nuclear licensed site operating two Advanced Gas-cooled Reactors, known as Reactor 1 and Reactor 2. Within each reactor there are four boilers designated from A to D. Within each boiler there are two pod boiler units numbered 1 and 2. During the periodic shutdown (also known as a statutory outage) of Heysham 1 Reactor 1, which commenced on 27th August 2013, an unexpected test result was found on boiler spine 1D1. The boiler spine is a welded hollow cylinder approximately 21.5m long that provides the main structural support of the boiler.

During a subsequent inspection of Heysham 1 Reactor 1 boiler spine 1D1 in July 2014 with that reactor shut down, a through wall crack was identified within the region of Weld 12.3 about half way down the boiler spine. Since all four reactors at Hartlepool and Heysham 1 have similar boiler spines the identification of this crack resulted in NGL making the decision to shut down reactors Heysham 1 Reactor 2, Hartlepool Reactor 1 and Hartlepool Reactor 2 in August 2014 to allow investigations on all of the boiler spines on all four reactors to be completed.

NGL has now undertaken detailed visual inspections in the region around Weld 12.3 (where access has been possible) and inspections using a guided wave ultrasonic technique on all 32 boiler spines. NGL has also undertaken radiography inspections on a limited number of boiler spines where access has been possible. These inspections have confirmed that widespread structurally significant defects are not present across the population of boiler spines.

NGL’s analyses and investigations have identified that the nuclear safety risk for an operational reactor is dominated by boiler spine failure resulting in a drop of the boiler, potentially resulting in failure of the boiler tubes. NGL’s analyses and investigations have also determined that high temperature is a significant contributing factor to the crack identified on Heysham 1 Reactor 1 boiler spine 1D1, which is attributed to creep damage during operational service.

Because of this, NGL produced a safety case for operation of Hartlepool Reactor 1 and Reactor 2 and Heysham 1 Reactor 2 at a reduced operating temperature to reduce the likelihood of new cracks initiating and to reduce the rate of growth of postulated cracks. ONR issued Agreement to implement this safety case for return to service of Heysham 1 Reactor 1 and Hartlepool Reactor 1 and Reactor 2 on the 21st November 2014.

NGL has now produced safety case modifications to justify a return to service of Heysham 1 Reactor 1 at reduced temperature and with D quadrant boiler isolated until 31st August 2015 or 240 days at reduced power, whichever is sooner. This case contains the claims and arguments used to support the return to service of Heysham 1 Reactor 2 and Hartlepool Reactor 1 and Reactor 2. Furthermore, it contains claims and arguments relevant to the defective boiler 1D1.

Following the period of time limited operation identified in the safety case, NGL must shut the reactor down for a refuelling outage and will produce a consolidated boiler spine safety case for Heysham 1 and Hartlepool to enable continued operations.



Assessment and inspection work carried out by ONR in consideration of this request

The ONR site inspector, the ONR project inspector and ONR specialist inspectors have sampled NGL’s safety case and arrangements for implementation at Heysham 1 Reactor 1.

The specialist inspectors have undertaken assessments and produced reports for each specialism. The site inspector has reviewed the site readiness for implementation of the safety case and produced a statement of his findings. I have made use of these reports and records in the production of this Project Assessment Report.

Matters arising from ONR’s work

No matters preventing issue of Heysham 1 Licence Instrument 587 for Reactor 1 remain from the work undertaken by ONR, since any matters arising from ONR’s assessment have been adequately addressed by NGL.

Conclusions

Following ONR assessment and inspection I am satisfied that NGL’s safety case for return to service of the Heysham 1 Reactor 1 is adequate and that the Heysham 1 site is ready to implement the safety case; consequently, Agreement to implement the safety case at Heysham 1 Reactor 1 can be granted.

Recommendation

I recommend that the Superintending Inspector:

Signs this Project Assessment Report to confirm support for the ONR technical and regulatory arguments that justify issuing Heysham Licence Instrument 587 for Reactor 1.

Signs this Project Assessment Report approving its release for publication, after redaction where appropriate.

Signs Heysham Licence Instrument 587.



LIST OF ABBREVIATIONS

ALARP As Low As Reasonably Practicable

CNRP Civil Nuclear Reactor Programme

EA Environment Agency

EC Engineering Change

fpd Failure per demand

GWT Guided Wave Testing

HAZ Heat Affected Zone

HYA Heysham 1

HRA Hartlepool

HOW2 (Office for Nuclear Regulation) Business Management System

INA Independent Nuclear Assurance

INSA Independent Nuclear Safety Assessment

IR Intervention Report

LC Licence Condition

LI Licence Instrument

LRUT Long Range Ultrasonic Testing

NGL EDF Energy Nuclear Generation Ltd

NSC Nuclear Safety Committee

ONR Office for Nuclear Regulation

PAR Project Assessment Report

pry Per Reactor Year

PSA Probabilistic Safety Analysis

R1 Reactor 1

R2 Reactor 2

SAPs ONR Safety Assessment Principles for Nuclear Facilities



TABLE OF CONTENTS 1 PERMISSION REQUESTED.............................................................................................. 9 2 BACKGROUND ................................................................................................................. 9 3 SUMMARY OF LICENSEE’s SAFETY CASE .................................................................. 10 4 ONR’s ASSESSMENT AND INSPECTION SCOPE ......................................................... 13 5 ONR’s ASSESSMENT IN CONSIDERATION OF THIS REQUEST ................................. 14 6 OVERALL CONCLUSIONS OF SPECIALIST INSPECTORS .......................................... 18 7 SITE INSPECTION READINESS REVIEW ...................................................................... 18 8 ONR PROJECT INSPECTOR’S REVIEW OF LICENSEE’S PROCESS .......................... 18 9 ONR PROJECT INSPECTOR’S REVIEW OF LICENSEE’S SAFETY CASE ................... 19 10 CONCLUSIONS ............................................................................................................... 21 11 RECOMMENDATIONS .................................................................................................... 22 12 REFERENCES ................................................................................................................ 23



1 PERMISSION REQUESTED

1 EDF Energy Nuclear Generation Ltd (NGL), the licensee of Heysham 1 (HYA) power station, has requested the Office for Nuclear Regulation’s (ONR) Agreement to the implementation of EC354024 Proposal Version 03 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine [1], in accordance with its licence condition 22 arrangements. The request [2] has been made in accordance with HYA’s arrangements to comply with Clause 1 of Licence Condition (LC) 22 “Modifications or experiment on existing plant”. This Project Assessment Report (PAR) considers ONR’s assessment of NGL’s safety case and the readiness of the site to implement it and makes recommendations on whether an Agreement should be granted3.

2 BACKGROUND

2 During the periodic shutdown of HYA Reactor 1 (R1), which commenced on 27th August

2013, an unknown test result was found on quadrant 1D1 boiler spine4. This unexpected

result was found from inspection using an ultrasonic technique, known as guided wave testing (GWT) or long range ultrasonic testing (LRUT). The purpose of this inspection technique is to verify that the integrity of the boiler spine is intact by receiving a return echo from the bottom of the boiler spine. In light of this anomaly, NGL presented a safety case [3] to justify a limited period of reactor operation of HYA1 R1 (6 months) with the D boiler quadrant isolated such that both boiler pods stored dry and in a nitrogen atmosphere. This mode of operation is known as three quadrant operation.

3 The ONR assessment of work undertaken during the periodic shutdown for HYA R1 in 2013 was considered by ONR [4,5]. Based on the recommendations within the assessment work, ONR granted Consent to restart HYA R1. ONR qualified the basis for this Consent by ensuring that the licensee fulfilled three commitments provided in the station’s letter requesting Consent. These commitments in effect required HYA R1 to be shut down after 6 months of three quadrant operation to allow a suitable and sufficient inspection of boiler 1D and production of a suitable and sufficient safety case for subsequent restart.

4 At the end of this six month period of three quadrant operation, HYA R1 was shut down in order for NGL to undertake an extensive period of work including the development of non-destructive and sampling tests, including construction of mock-ups and training to allow the inspections to take place on boiler 1D1. On 28th July 2014 a crack (approximately 475mm long which is approximately 25% of the circumference) was identified within the region of Weld 12.3 about half way down the boiler spine. This weld supports the weight of the main boiler and reheater.

5 In light of this confirmation of a crack NGL took the decision on 11th August 2014 to shut down the operating reactors at HYA R2 and Hartlepool (HRA) R1 and R2 to allow

3 According to NGL’s LC22 arrangements, changes to safety cases are treated as modifications. NGL has created an

Engineering Change (EC) to change the safety case at HYA R1 (EC354024). Permission for NGL to implement these modifications and hence operate under the revised safety case is in the form of an ONR Agreement issued under arrangements made by NGL to comply with LC22. 4 There are eight boiler unit pod’s per reactor, each reactor being divided into four quadrants (A, B, C and D), each

quadrant containing two boiler unit pods (see diagram 1 in Appendix 1). The purpose of each boiler pod is to remove heat from the reactor coolant gas and generate high pressure steam for power generation.

The boiler spine is approximately 21.5 metres long and runs down the centre of the boiler unit pod which is suspended within the boiler unit and supports sections of the boiler internals. The boiler spine consists of a number of butt-welded pipe sections of differing materials, each selected to suit the local design conditions.



further investigations on all of the boiler spines in each of the 4 reactors. This decision was supported by ONR.

6 NGL’s analyses and investigations have identified that the nuclear safety risk for an operational reactor is dominated by boiler spine failure which could result in a drop of the boiler, potentially resulting in failure to the boiler tubes. NGL’s analysis and investigations further determined that high temperature is a significant contributing factor to the crack identified on HYA R1 boiler spine 1D1, which has been attributed to creep crack growth5 damage during operational service.

7 On the basis of its inspection and analysis, NGL produced a nuclear safety case, which in recognition of its safety significance was classified as Category 1 which required ONR’s formal Agreement. On 21st November 2014 ONR issued its Agreement [6,7,8] to the implementation of a safety case for return to service of HYA R2 and HRA R1 and R2 at reduced temperature operation [9].

8 NGL has now produced a Category 2 safety case, EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine [1], for return to service of HYA R1 at reduced temperature operation and with boiler quadrant 1D isolated (i.e. three quadrant operation).

9 NGL’s arrangements [10] to satisfy condition 22(1). Modification or experiment on existing plant includes the provision for ONR, if it so wishes, to specify a Category 2 safety case for Acknowledgement, Agreement or identification of Hold-points.

10 On the 16th December 2014 ONR wrote to NGL [11] to specify that the safety case ‘EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine’, shall be submitted to and not implemented without the Agreement of the ONR.

11 On the 17th December 2014 the Station Director for HYA wrote to ONR [2] under HYA’s LC22 (1) arrangements requesting ONR’s Agreement for implementation of EC354024 Heysham Reactor 1: Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine [1].

3 SUMMARY OF LICENSEE’s SAFETY CASE

12 This safety case details the operation of HYA R1 at reduced temperature with D quadrant boiler pods stored dry and in a nitrogen atmosphere for a period of 240 days at reduced power, or up to the 31st August 2015, whichever is sooner. Following the period of time limited operation identified in the safety case, NGL must shut the reactor down for a refuelling outage and will produce a consolidated boiler spine safety case for Heysham 1 and Hartlepool to enable continued operations [12].

13 As stated in section 2, Boiler pod 1D1 within D quadrant contains a defect in the Heat Affected Zone (HAZ) of Weld 12.3 of the boiler spine structural support approximately 475mm long which is approximately 25% of the circumference of the support.

14 The four reactors across HYA and HRA power stations have previously operated for significant periods with one quadrant isolated for a number of operational reasons such as boiler tube leaks or boiler feed issues.

5 Creep is a phenomenon which begins to affect structural materials at a temperature approaching half their melting

point measured in degrees Kelvin (temperature in degrees Kelvin = temperature in degrees Celsius + 273). At these temperatures when exposed to significantly high stress a material will slowly deform and its internal structure degrade forming micro-cracks. The degradation rate is temperature dependent and therefore can vary from a few hours to several centuries. Structures are designed such that the accumulated damage from creep (and other damage mechanisms) will not compromise their operation by the introduction of safety margins based on test data produced on the material of interest.



HYA R1 = 515 days and HYA R2 = 211 days

HRA R1 = 468 days and HRA R2 = 276 days

15 The last period of three quadrant operation was for 120 days at HYA R1 and was justified in [3]. Therefore, the proposed three quadrant operation sets no precedent in terms of operational experience. The operational experience gained from the previous periods of three quadrant operation has been used in this safety case [1] to demonstrate that the majority of reactor components experience no significant change from four to three quadrant operation. Where small differences have been identified it is NGL’s judgement that these are acceptable for short periods of reduced power with three quadrant operation as proposed by this safety case [1].

16 To support this safety case [1] NGL has claimed that three quadrant operation of HYA R1 at reduced temperature is justified in part by the Category 1 safety case which supported the return to service of HYA R2, HRA R1 and R2 [9]. In that safety case NGL established that creep damage in the region around Weld 12.3 of the defective boiler 1D1 has occurred during service and that this has led to the development of the crack in the HAZ of Weld 12.3 in boiler spine 1D1. This form of damage is sensitive to temperature and it increases as temperature increases. Therefore, to ensure that the rate of creep damage is at an acceptably low level in the three operating quadrants of HYA R1, NGL has proposed to operate HYA R1 at a reduced operating load, with an aim of achieving a target of 40°C temperature reduction in the region of Weld 12.3 of all non-isolated boilers in quadrants 1A, 1B and 1C of HYA R1.

17 With this temperature reduction, NGL considers that a factor of ten-fold reduction in damage rates is achievable [9]. Furthermore, NGL state that there is no associated cliff-edge effect regarding creep damage at Weld 12.3, however, it is fully recognized that effect of creep damage is cumulative during operations. NGL has developed a set of limits and conditions to ensure the revised safety case intent is achieved; therefore ensuring that during operations accumulation of creep damage is monitored.

18 The additional claims and arguments made in this case [1] deal specifically with the additional hazard posed by operation of the reactor with an isolated quadrant which contains a defective boiler spine. Broadly, these hazards are twofold. Firstly, the presence of a defect in spine 1D1 presents a structural hazard and increased failure potential of the defective boiler. Secondly, three quadrant operation reduces the available reactor cooling during normal operation and faults.

19 NGL’s safety case [1] presents arguments to demonstrate that the likelihood of failure of boiler 1D1 and 1D2 remains acceptably low despite the presence of a defect in boiler spine 1D1 because the operating temperature of the isolated boilers is much lower (~300°C) than that of the non-isolated boilers. Therefore, NGL’s safety case present arguments that material properties and crack growth rates are such at these temperatures that sufficient margin is maintained even with the presence of a 475mm long defect. Furthermore, the charging of the isolated boiler pods with nitrogen gas to maintain inert conditions and the physical addition of an engineered restraint system to boiler pod 1D1 mitigate the consequences of spine failure by negating water ingress from boiler tube failure and preventing gas circulator penetration impact damage in the event of spine failure.

20 NGL’s safety case [1] presents arguments to demonstrate that adequate protection is available on three quadrants and that adequate post-trip cooling can be maintained during postulated faults. These arguments are supported by a review of the probabilistic safety assessment risk associated with the reduction in post trip cooling availability on three quadrant operation.

21 Overall, NGL seek to demonstrate that the hazards posed are acceptable and the nuclear safety risk is As Low As Reasonably Practicable (ALARP).



22 NGL’s safety case is based on 4 claims with supporting arguments:

CLAIM 1: INTEGRITY OF KEY BUTT WELDS ON OPERATING BOILERS IS ADEQUATE TO JUSTIFY AN INFREQUENT BOILER SPINE FAILURE AT A FREQUENCY OF 10-3 PRY6

23 The arguments that support this claim are presented as follows:-

Argument 1.1: The structural integrity safety case provided in safety case NP/SC 7717 [9] remains applicable to the three operating boilers on HYA R1.

Argument 1.2: Weld 12.3 temperature compliance algorithm remains valid for reduced power operation on the operating quadrants.

CLAIM 2: THE RISK OF SPINE FAILURE IN 1D QUADRANT WITH THE REACTOR OPERATING ON THREE QUADRANTS IS NOT SIGNIFICANTLY CHANGED FROM THE SHUTDOWN STATE


Argument 2.1: Operating conditions with 1D boiler quadrant shutdown are understood and can be adequately monitored. 1D2 boiler is not considered to be at risk of failure whilst remaining isolated.

Argument 2.2: In-service degradation of the defect at weld 12.3 at T1 temperature is shown to be sufficiently slow to ensure no change in 1D1 spine integrity in this operating state.

Argument 2.3: In the event of 1D1 spine failure, consequences to nuclear safety have been significantly reduced as there is no water ingress risk to reactor and a spine restraint system is fitted under 1D1 to minimise any potential threat to the reactor pressure boundary and primary circuit components.

Argument 2.4: If 1D1 or 1D2 spine failure was not detected, consequences would remain acceptable during a future trip and shutdown cooling transients.

CLAIM 3: ADEQUATE PROTECTION REMAINS AVAILABLE TO ENSURE CONSEQUENCES FROM FAULTS ON THREE QUADRANTS REMAINS TOLERABLE


Argument 3.1: The performance of reactor trip and shutdown protection at reduced power and on three quadrants is understood and acceptable.

Argument 3.2: Adequate post-trip cooling remains available following plant faults and hazards.

Argument 3.3 Extended three quadrant operation with 1D1 isolated does not introduce any new faults.

Argument 3.4: There is no significant challenge to reactor internals from the proposed operating configuration.

Argument 3.5: Operator procedures for start-up on three quadrants and response to faults is adequately covered in Station operating Instructions.

6 A frequency of 10

-4 per reactor year (pry) is considered infrequent. A frequency of 10

-3 pry is regarded as the border

between frequent and infrequent.



CLAIM 4: THE NUCLEAR SAFETY RISK ASSOCIATED WITH RESTART OF HYA R1 ON THREE QUADRANTS IS ALARP


Argument 4.1: Effect of reduced power operation on reactor internals, fuel, graphite and boiler conditions does not challenge underlying safety limits..

Argument 4.2: Risk .of uncontrolled radiological release from inadequate protection against faults is understood.

Argument 4.3 Overall station risk remains ALARP to allow further extended period of three quadrant operation to 31st August 2015 (240 days at reduced power), and to ensure a double reactor outage is avoided.

27 Supplementary to the arguments and evidence to substantiate the four Claims of its safety case, NGL has identified 6 commitments, which are additional to the 19 raised in [9]. These commitments are part of NGL’s justification that risks will remain ALARP and NGL state they are to be completed by September 2016.

4 ONR’s ASSESSMENT AND INSPECTION SCOPE

28 ONR has assessed NGL’s safety case and considered the on-site inspections conducted by NGL’s Independent Nuclear Assurance (INA) department to determine NGL’s readiness to implement the safety case. The scope of these two aspects of ONR’s work is considered below.

4.1 Assessment Scope

29 Reference 13 is the ONR Task Sheet for this work. The task sheet outlines the scope of ONR’s assessment and identifies the following specialists assigned to assess NGL’s safety case:

Structural integrity.

Fault studies.

Probabilistic Safety Analysis (PSA).

30 These specialists have sampled NGL’s safety case [1] focusing their attention on the following Claims:

4.2 Structural Integrity

31 The scope of the assessment covered the structural integrity aspects associated with the case, in particular those aspects which differ from the consolidated safety case for the boiler spines [14] and the recent update [9], both of which were previously assessed by ONR in [15] and [16].

32 Assessment of Claim 1 focused on whether ONR assessment of [9] is challenged by operation on three quadrants. Assessment of Claim 2 focused on the arguments justifying operation of the reactor with a circumferential defect in a structural component of one of the boiler pods. Assessment of Claim 3 focused on Argument 3.4 that there is no significant challenge to reactor internals from the proposed operating configuration. Assessment of Claim 4 took an overall view on the ALARP position with regard to Structural Integrity.

4.3 Fault studies



33 The main focus of the assessment of the fault studies arguments has been Claim 3. This claim aims to demonstrate that adequate protection remains available to ensure the consequences from faults on three quadrants remains tolerable. In particular the assessment has focussed on NGL’s review of fault studies during three quadrant operation and an associated fault schedule review.

34 A further focus of the fault studies assessment has been the claim that the algorithm used to assess the temperature of Weld 12.3 in the operating boilers is conservative (Claim 1, Argument 1.2). This argument supports the structural integrity safety case presented in Claim 1 in terms of the effect of operating the reactor at reduced temperature to significantly reduce the rate of creep crack growth.

35 Also considered in the fault study assessment is the evidence presented in relation to the temperature of Weld 12.3 in the isolated boilers (noting that the algorithm discussed above is not applicable) in quadrant 1D (Claim 2, Evidence 2.1.1), which is important in terms of ensuring that there is no further degradation of the defect in boiler spine 1D1.

36 Finally, the fault studies assessment of Claim 4 has reviewed Argument 4.1 which aims to demonstrate that the effect of reduced power operation on reactor internals, fuel, graphite and boiler conditions does not challenge underlying safety limits.

4.4 PSA

37 The PSA assessment has considered the evidence supporting Claim 3 (Argument 3.2, Evidence 3.2.5 to 3.27) and Claim 4.

38 The scope of the assessment has focused on the adequacy of the PSA used to support the safety case, acceptability of any increase in assessed level of risk and the change in risk from operating on three quadrants compared to four. In terms of judging the acceptability of the level of risk it has focused on whether the level of risk has been reduced to ALARP, and whether there are any reasonably practicable improvements that should be implemented prior to return to service.

4.5 Site Inspection Scope

39 The nominated site inspector has considered the scope and findings of the INA concurrence on operational readiness of HYA R1. The nominated site inspector has formally questioned the site about changes to operational documents covering three quadrant operation, three quadrant operational training and the operational readiness of protection systems particularly those relevant to water ingress and depressurisation faults. These questions and responses are in reference [17].

5 ONR’s ASSESSMENT IN CONSIDERATION OF THIS REQUEST

5.1 CLAIM 1 - Integrity of key butt welds is adequate to justify an infrequent boiler spine failure at a frequency of 10-3 pry

40 I provide a summary of the structural integrity [18] assessment first, since this technical area is most significant to ONR’s assessment of this claim. This is followed by a summary of the faults studies assessment [19] of claim 1 argument 1.2, which is an important supporting argument to the structural integrity claims and allows ONR to make an overall conclusion on this claim.

5.1.4 Structural Integrity Assessment of Claim 1

41 The structural integrity assessment report of NGL’s safety case [1] concluded that the evidence supports a random failure frequency for boiler spine at reduced power of the order of 10-3 pry, which provides support to Claim 1. This is made on a judgement basis due to the difficulty in quantifying the failure frequency for a number of reasons explained within the assessment of Claim 1. This is consistent with ONR’s assessment [15] of the previous return to service safety case for HYA R2 and HRA R1 and R2 [9].



42 The structural integrity assessment report of NGL’s safety case [1] concluded that the view of Claim 1 that the failure frequency will be on the infrequent side of the 10-3 pry boundary was not acceptable due to the difficulties in quantifying this number. The structural integrity specialist inspector considered that a cautious approach should be taken and the failure frequency should be considered to be on the frequent side of the boundary. This is also consistent with ONR’s assessment [15] of the previous return to service safety case for HYA R2 and HRA R1 and R2 [9].

5.1.5 Fault Studies Assessment of Claim 1 Argument 1.2 - Weld 12.3 temperature compliance algorithm remains valid for reduced power operation on the operating quadrants

43 The fault studies specialist inspector noted that a key element of Claim 1 is that Weld 12.3 of the operational boilers will operate with a target reduction in temperature of 40ºC using an algorithm to calculate Weld 12.3 temperature (as per the return to service for Heysham Reactor 1 and Hartlepool reactors [9]).

Overall, based on the evidence and arguments provided by NGL, the faults studies specialist inspector judged that the claim that the Weld 12.3 algorithm is conservative (claim 1 argument 1.2) to be reasonable for the operating conditions justified in the case [1].

5.2 CLAIM 2 - The risk of spine failure in 1D quadrant with the reactor operating on three quadrants is not significantly changed from the shutdown state.

44 I provide a summary of the structural integrity assessment [18] first, since this technical area is most significant to ONR’s assessment of this claim.

45 This is followed by a summary of the fault studies assessment [19] of claim 2, argument 2.1, evidence 2.1.1 and relates to the operating temperature in the isolated pods. This temperature is important in terms of ensuring that there is no further significant degradation of the defect in boiler spine 1D1 and supports the structural integrity claims.


46 The structural integrity specialist inspector considered the potential for further degradation of 1D1 with the boiler isolated and judged that further degradation of the defect associated with Weld 12.3 in 1D1 will be insignificant as there are no active degradation mechanisms. This view is predicated on the operating limit of 350ºC not being exceeded and the gas temperature in the vicinity of Weld 12.3 being approximately 300°C (see section 5.2.5).

47 The structural integrity specialist inspector judged that operating 1D1 in the isolated condition with the structural restraint system fitted will not compromise the existing 10-

7pry claim on the gas circulator penetration and will minimise the nuclear safety consequences following the unlikely event of 1D1 failing.

48 The structural integrity assessment report [18] of NGL’s safety case [1] concluded from a structural integrity perspective that it can support Claim 2 and judge that risks posed following spine failure in D1 quadrant with the reactor operating on three quadrants is not significantly changed from the shutdown state.

5.2.5 Fault Studies Assessment of Claim 2, Argument 2.1, Evidence 2.1.2 – Operating conditions in the isolated boilers.

49 Temperature of Weld 12.3 cannot be predicted in the isolated quadrant using the Weld 12.3 temperature prediction algorithm. Instead NGL conducted a review of the thermal conditions in the vicinity of 12.3 [20] which confirms that the gas temperature in the vicinity of Weld 12.3 is approximately at T1 levels (~300ºC).

Based on the evidence presented the fault studies specialist inspector accepted that Weld 12.3 in quadrant 1D will operate at approximately T1 temperatures.



5.3 CLAIM 3 - Adequate protection remains available to ensure consequences from faults on three quadrants remains tolerable.

50 As identified in the scope section assessment of claim 3 was split between three disciplines; fault studies, PSA and structural integrity. The fault studies specialist inspector considered the majority of claim 3, arguments 3.1, 3.2 (evidence 3.2.1 to 3.2.4), 3.3, 3.4, 3.5 [19]. The PSA specialist inspector considered relevant parts of arguments 3.2 (evidence 3.2.5 to 3.2.7) and 3.3 Evidence 3.3.1 [23]. The Structural integrity specialist inspector considered the relevant aspects of argument 3.2.

51 I provide a summary of the fault studies assessments [19] of claim 3 first, since this technical area is most significant to ONR’s assessment of this claim. This is followed by a summary of the PSA assessment [23] and structural integrity assessment [18].

5.3.4 Fault studies Assessment of Claim 3

52 The fault studies specialist inspector noted that much of the evidence supporting Claim 3 is presented in a review of fault studies during three quadrant operation [21] and a review of the fault schedule for three quadrant operation [22]. These are important supporting documents and were taken into account by the fault studies specialist inspector.

53 In summary, the fault studies specialist inspector’s overall view from a deterministic fault studies perspective is that Claim 3 (that adequate protection remains available to ensure consequences from faults on three quadrants remains tolerable), is valid based on the arguments and evidence provided.

5.3.5 Probabilistic Safety Analysis (PSA) of Claim 3 Argument 3.2 - Adequate post-trip cooling remains available following plant faults and hazards and Argument 3.3 – Extended 3Q operation with 1D1 isolated does not introduce any new faults.

54 I provide a summary of the PSA assessment [23] which considered the PSA aspects of Claim 3, Argument 3.2 and 3.3 based on the adequacy of the supporting evidence.

55 The PSA specialist inspector concluded that operation on three quadrants equates to less than a 5% increase in assessed risk compared to operation on all four quadrants i.e. HYA R2. Furthermore, the changes resulting from the return to service safety case (compared to the existing safety case) do not challenge the ONR expectation that no single class of accidents should make a disproportionate contribution to the overall level of risk.

56 The PSA specialist inspector concluded that that the level of risk due to plant unavailability will not be significantly increased due to operating for a prolonged, continuous period on three quadrants, compared with 31 days previously allowed.

57 The PSA specialist inspector judged that due to the lack of specific PSA studies to support the return to service safety case there are a number of shortfalls against ONR PSA expectations (Safety Assessment Principles (SAP) FA.1 and FA.10 to FA.14). In response NGL provided a commitment to scope and undertake such a PSA study following return to service of HYA R1 [24]. This commitment has been captured in ONR issue 2714 and will be progressed as part of ONR’s routine interventions. Therefore, the specialist inspector has taken this commitment into account and alternative evidence provided by NGL and has judged that the adequacy of the supporting arguments and evidence was sufficient to support Claim 3.

5.3.6 Structural Integrity Assessment of Claim 3, Argument 3.4 – There is no significant challenge to reactor internals from the proposed operating configuration

58 The structural integrity specialist inspector noted that in general all the regions which normally operate under T1 conditions (up to 350oC) will continue to operate under similar conditions. The exceptions are the two boilers in Delta Quadrant; 1D1 and 1D2



which may be susceptible to oxidation if the temperature of the mild steel sections is not kept significantly below 400°C.

59 NGL have established an operating limit of 350ºC (Station Operating Instruction 01/05/07) to prevent such degradation although OPEX from three quadrant operation suggest that 300ºC is unlikely to be exceeded. On this basis the structural integrity specialist inspector judged that the spine integrity will not be challenged by oxidation damage during three quadrant operation.

60 The structural integrity specialist inspector judged that it was unlikely that other items of plant will be adversely affected during three quadrant operation. Therefore, the structural integrity specialist inspector accepted Claim 3 argument 3.4.

5.4 Claim 4 - The nuclear safety risk associated with the restart of Reactor 1 on three quadrants is ALARP.

61 I provide a summary of the PSA assessment first [23], since this technical area is most significant to ONR’s assessment of this claim. This is followed by a summary of the fault studies assessment [19] of claim 4, argument 4.1 and the structural integrity assessment [18] of overall view on the ALARP position.

5.4.4 Probabilistic Safety Analysis (PSA) of Claim 4 - The nuclear safety risk associated with the restart of Reactor 1 on three quadrants is ALARP.

62 The PSA specialist inspector concluded despite limitations in the evidence presented relating to Claim 4 compared to the ONR ALARP Technical assessment guide, the PSA specialist inspector supported NGL’s assertion that the nuclear safety risk associated with the return to service of Heysham 1 reactor 1 on three quadrants is ALARP. The PSA specialist inspector judged that the limitations are not significant and that it would be disproportionate, from the perspective of ALARP, not to agree to the implementation of the safety case [1] and therefore restart of Heysham 1 reactor 1.

5.4.5 Fault Studies Assessment of Claim 4, Argument 4.1 – Effect of reduced power operation on reactor internals, fuel, graphite and boiler conditions does not challenge underlying safety limits

63 The fault studies specialist inspector noted that the importance of Commitment 1 given in [1] which has been raised to confirm the condition of the 1D quadrant restrictor tubes either by fitting a thermocouple at an appropriate location or by measuring restrictor tube wall thickness.

64 The fault studies specialist inspector noted that the nuclear safety risk will be managed by NGL’s Project Safety Review Group supported by a Testing and Commissioning Panel, the Boiler Assessment Working Group and a Reduced Power Working Group. The specialist inspector found that this is consistent with the arrangements made for the return to service of HYA R2 and HRA Reactors [9].

65 Overall the fault studies specialist inspector accepted that the effect of reduced power operation on reactor internals, fuel, graphite and boiler conditions does not challenge underlying safety limits.


66 The structural integrity specialist inspector judged that the claim that it is ALARP to return the reactor to service was, from a structural integrity perspective, adequate. This was based on the inspections that have been undertaken during the shutdown period, the safety case presented [1], the reduction in operating temperature and the physical addition of an engineered structural restraint system.



6 OVERALL CONCLUSIONS OF SPECIALIST INSPECTORS

67 The structural integrity specialist inspector who undertook the assessment recommended that ONR should Agree to the request [2] made under LC22 arrangements for the return to service of Heysham 1 Reactor 1 for a time limited period to 31 August 2015 or 240 days at reduced power, whichever occurs first, on three quadrants and at reduced temperature as justified in the safety case presented in [1].

68 The structural integrity specialist inspector who undertook the assessment recommended that ONR undertake a full review of all structural integrity related commitments prior to the restart from the next planned shutdown period of HYA Reactor 1 in August 2015. This recommendation has been captured under ONR Issue 2714.

69 The fault studies specialist inspector who undertook the assessment recommended that ONR should Agree to the request [2] made under LC22 arrangements for the return to service of Heysham 1 Reactor 1 for a time limited period to 31 August 2015 or 240 days at reduced power, whichever occurs first on three quadrants and at reduced temperature as justified in the safety case presented in [1].

70 The PSA specialist inspector who undertook the assessment noted that NGL provided a commitment [24], additional to the 6 commitments in the safety case [1], to scope and undertake a PSA study following return to service of HYA R1. Monitoring of this additional commitment has been captured under ONR issue 2714.

The PSA specialist inspector who undertook the assessment recommended that ONR should agree to the request [2] made under NGL’s LC 22(1) arrangements for NGL to implement its safety case to enable the return to service of Heysham 1 reactor 1 on three quadrants and at reduced temperature as justified in the safety case presented in [1].

7 SITE INSPECTION READINESS REVIEW

71 The nominated site inspector has reviewed the work undertaken previously to support the return to service of HYA R2 at reduced power and the previous period of three quadrant operation of HYA R1 to support his conclusions on the operational readiness of the station to return HYA R1 to service. The nominated site inspector has raised a number of questions with the station relating to operational documentation, operator training and operational readiness of protection systems, particularly those relevant to water ingress and depressurisation faults. These have been satisfactorily addressed and a copy of the questions and subsequent responses can be found at Reference [17].

72 The nominated site inspector has worked closely with the internal regulator to ensure that the scope of their operational readiness inspections covered the areas of interest to ONR. He was satisfied that the operational readiness inspections undertaken by INA and reported in their concurrence reports at [25] and [33] adequately addressed the key areas and therefore he did not propose to undertake a separate operational readiness inspection. Overall, the nominated site inspector judged that there are no significant operational issues outstanding that would prevent ONR granting Agreement for the return to service of HYA R1.

8 ONR PROJECT INSPECTOR’S REVIEW OF LICENSEE’S PROCESS

73 ONR has established that HYA has made appropriate requests under their current LC22(1) arrangements [10]. For a Category 2 safety case, HYA LC22 arrangements require Verification. This is followed by Independent Nuclear Safety Assessment (INSA) clearance by NGL’s internal regulator, Independent Nuclear Assurance (INA). The arrangements also require retrospective consideration and advice by the relevant Nuclear Safety Committees (NSCs) using INSA’s approval certificate and proposal



summary. However, NGL took the decision to formally present this case to the NSC and the minutes from that meeting were provided to ONR to support NGL’s request for Agreement [26]. Following, Verification, INSA clearance and retrospective review by the NSC, Agreement from ONR is requested by NGL prior to implementation.

74 The Verification statement [27] indicates that a detailed and thorough verification process has taken place. The verifiers have challenged the impact of the safety case in several areas. They have concluded that the risks associated with return to service of HYA R1 with 1D quadrant isolated and a weld 12.3 temperature reduction are tolerable and ALARP.

75 INA has issued an INSA approval statement [28]. The overall INSA conclusions were that the risk from operation of HYA R1 on three quadrants and at reduced temperature is tolerable and ALARP, subject to satisfactory progress with the completion of the commitments in the case. INSA supported the RTS of HYA R1 until 31 August 2015 or 240 days at reduced power, whichever is the sooner.

76 A NSC meeting was held on the 17 December 2014 to consider and provide advice on the safety case and their responses recorded [26]. The NSC identified that all points had been addressed, but the clarity of the some of the arguments needed to be improved. This was considered a matter of presentation rather than outstanding nuclear safety concerns. NGL addressed the clarity of the arguments identified by the NSC in the final proposal version 003 of the safety case [1].

77 In addition to INSA, INA has also placed a hold point known as a Concurrence on return to service of HYA R1. Clearing this hold point requires INSA clearance of the modifications to the safety case but it also takes into account issues related to readiness of the station to implement the modifications to the safety case. INA clearance of each hold point is via issue of a Concurrence Part B [33].

78 I conclude that NGL’s due process for Category 2 safety cases has been completed and that the NGL internal regulator’s Concurrence process has reached a suitable stage.

9 ONR PROJECT INSPECTOR’S REVIEW OF LICENSEE’S SAFETY CASE

79 I have considered NGL’s request for ONR’s Agreement to the implementation of NGL’s Safety case submission [2], as part of my role as ONR project inspector assigned to this case. I have followed ONR procedures for delivering a permissioning project, as detailed in ONR’s Business Management System (HOW2) [29].

80 The ONR process for delivering a permissioning project requires preparation of a PAR to facilitate a permissioning decision by the Delegated Authority. The PAR is prepared in accordance with ONR guidance document AST/003 Guidance on the production of Reports Revision 7 and is informed by the Assessment Report (AR) findings of specialist inspectors assigned to the project. If the Delegated Authority decides to grant permission then a Licence Instrument (LI) is prepared and issued.

81 To enable ONR to undertake its assessment process it has maintained open dialogue via meetings and telephone conferences between ONR and NGL throughout the project. Reference 30 provides a full record of this dialogue.

82 To support my work I have:

Utilised the services of the ONR specialist inspectors assigned to this project by the ONR CNRP management team [13].

Considered the HYA site inspector’s readiness review record and its conclusions [31].

Considered NGL’s safety case Verification statement [27].



Considered the resolution of NGL INSA comments [32] and the issuing of the NGL INSA approval statement for HRA R1 [28].

Considered NSC comments and its overall support for the return to service of HYA R1 after the discovery of a defect in 1D1 boiler spine [26].

Considered NGL’s internal regulator’s Concurrence Part B’s for HYA R1 [33].

I have consulted with the Environment Agency (EA), to establish if it had any specific objections that would prevent ONR from issuing its Agreement. EA [34] has confirmed it does not object to ONR issuing its Agreement to the implementation of the modification.

I have considered the overall safety case as presented [1].

I have drawn upon the ONR specialist inspector’s considerations and recommendations in the areas of structural integrity, fault studies and PSA. I have drawn together their findings and conclusions in this PAR to inform my overall judgement on NGL’s submitted safety case.

83 All of the specialist inspectors have provided an Integrated Intervention Strategy (IIS) rating [35] based on NGL’s safety case submission [1].

The structural integrity specialist inspector assigned an IIS rating of 4 – Below Standard. This was on the basis that several matters have been raised which will require regulatory follow-up as part of the proposed commitments programme. Notwithstanding this, it is judged that there are no significant issues that would prevent ONR giving Agreement for the return to service of Heysham 1 Reactor 1.

The fault studies specialist inspector assigned an IIS rating of 4 – Below Standard (Yellow). This was on the basis that it was necessary to raise a number of issues during the course of the assessment and the timescales for delivery and assessment of the safety case were extremely compressed.

The PSA assessment assigned an IIS rating of 4 – below standard (yellow). This is on the basis that a number of important issues had to be raised for clarification and further information, and the gap to ONR expectations (SAPs FA.1 and FA.10 to FA.14) regarding the adequacy and use of PSA to support the safety case.

84 However, notwithstanding this, all of the ONR specialist assessment reports [18,19,23] contain either a statement supporting issuing Agreement, or note that there is no reason to withhold Agreement to the implementation of the safety case in reference [1].

85 Each discipline has produced a report that presents the assessment findings, inspector’s opinions, judgments and recommendations. A number of queries arose from the inspectors’ work, these have adequately been closed out to the satisfaction of the specialist inspectors concerned [36].

86 All specialist inspectors assessments were undertaken in accordance with the requirements of the Office for Nuclear Regulation (ONR) How2 Business Management System (BMS) guide NS-PER-GD-014 [37].

87 All of the specialist inspectors assessment reports have undergone independent peer review in accordance with ONR How2 Business Management System (BMS) guide AST/005 Revision 03 [38] which supports the approach taken, conclusions raised and recommendations made by the specialist inspectors.

88 Recommendations raised by the specialist inspectors and the progress of NGL’s 6 commitments identified within its submitted safety case [1] have been captured under a



single issue, issue 2714, and will be progressed with NGL as part of ONR’s normal regulatory interventions.

89 I am content that the safety case has been adequately challenged by Verification, INSA and the NSCs.

90 I am satisfied that NGL’s submitted safety case [1] has been adequately challenged by the assessment undertaken by ONR’s specialist inspectors (within the identified bounds of their sampled assessment).

91 I am satisfied that the ONR HYA site inspector has established INA’s concurrence with respect to the site’s readiness to return to service on three-quadrant operation and is content with the arrangements in place for the implementation of the safety case.

92 In summary, to support this safety case [1] NGL has claimed that three quadrant operation of HYA R1 at reduced temperature is justified in part by the Category 1 safety case which supported the return to service of HYA R2, HRA R1 and R2 [9]. Furthermore, additional evidence that has been gained from the programme of 19 commitments identified in that safety case [9], and has been provided to further strengthen the claims of that safety case [9]. Therefore, based on the findings of the specialist inspectors and the outcome of the licensee’s own processes, I judge this aspect of the safety case to be adequate which is consistent with ONR’s previous assessment of the boiler spine return to service safety case for HYA R2 and HRA R1 and R2[9].

93 The additional claims and arguments made in this safety case [1], to those made in the return to service of HYA R2, HRA R1 and R2 [9], deal specifically with the additional hazard posed by operation of the reactor with an isolated quadrant containing a defective boiler spine. Based on the findings of the specialist inspectors and the outcome of the licensee’s own processes, I judge that although operation on three quadrants reduces the available post-trip cooling the licensee has demonstrated that adequate post-trip cooling margin remains to satisfy safe operation.

94 NGL has identified that there is an increased failure frequency associated with the isolated spine containing a defect (1D1). I judge, based on the findings of the specialist inspectors and the rigour of the licensee’s own processes that NGL has demonstrated that the nuclear safety consequences of failure of spine 1D1 have been adequately mitigated by the physical addition of a spine restraint system to 1D1. Furthermore, I judge the programme of commitments made by NGL [1,9,24] in relation to the boiler spines at HYA and HRA will be beneficial to increasing nuclear safety.

10 CONCLUSIONS

95 The submitted safety case [1] is dependent on a number of judgements and assumptions, in looking at ONR’s assessments of the safety case holistically, there is broad agreement that the case is adequate and that HYA R1 is in a position to operate the reactors in accordance with the bounds of the submitted safety case [1].

96 The licensee has followed its own arrangements culminating in the HYA Station Director writing to ONR requesting Agreement to start-up HYA R1 [2].

97 The licensee’s internal regulator, INA, have provided their Concurrence Part B documents. These support the start-up and subsequent operation of HYA R1 [33].

98 I have consulted with the EA who have confirmed that it does not object to ONR issuing its Agreement [34].

99 I have prepared Licence Instrument No. 587 in conjunction with this PAR for HYA R1. The Licence Instrument is consistent with the standard formats given within ONR procedures and do not require review by the Solicitors Office.



100 I judge that, based on the evidence presented within this report, ONR is in a position to issue its Agreement to restart HYA R1.

11 RECOMMENDATIONS

101 I recommend that the Superintending Inspector:

Signs this Project Assessment Report to confirm support for the ONR technical and regulatory arguments that justify issuing Heysham Licence Instrument 587 for Reactor 1.

Signs this Project Assessment Report approving its release for publication, after redaction where appropriate.

Signs Heysham Licence Instrument 587.



12 REFERENCES

1 EC No 354024 000 Proposal Version 03, Heysham Reactor 1, Interim Safety Case for

Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine December 2014 (TRIM 2014/470581).

2 EDF NGL - Heysham 1 - Unique No NSL/HYA/50747Y - Engineering Change 354024 (Version 3) Heysham Reactor 1 Interim Safety Case for Return to Service on Three Quadrants Following Discovery of a Defect in 1D1 Boiler Spine - 17 December 2014 (TRIM 2015/4463).

3 NGL Engineering Change Proposal EC No. 351365 000 Version1 - Justification For 3 Quadrant Start-Up and Operation of HYA R1 for a Short Period in Response to an Unexpected Inspection Finding On HYA 1D1 Boiler Spine (TRIM 2013/445172).

4 ONR Project Assessment Report ONR-HYA-13-035 - Heysham 1 – Reactor 1 – 2013 Statutory Outage. Assessment of the Heysham 1 Reactor 1 2013 Periodic Shutdown (TRIM 2013/399926).

5 ONR Project Assessment Report ONR-HYA-PAR-13-040, Revision 1, Reactor 1 Consent to start up (TRIM 2013/447225).

6 EDF NGL - Heysham 1 - Agreement to implement a safety case for return to service of Heysham 1 Reactor 2 at reduced temperature operation following the discovery of a defect on Heysham 1 reactor 1 boiler spine 1D1 - 21 November 2014 (TRIM 2014/431788)

7 EDF NGL - Agreement to implement a safety case for return to service of Hartlepool Reactor 1 at reduced temperature operation following the discovery of a defect on Heysham 1 reactor 1 boiler spine 1D1 - 21 November 2014 (TRIM 2014/431800).

8 EDF NGL - Hartlepool - Agreement to implement a safety case for return to service of Hartlepool Reactor 2 at reduced temperature operation following the discovery of a defect on Heysham 1 reactor 1 boiler spine 1D1 - 21 November 2014 (TRIM 2014/431793).

9 NPSC 7717 Ver 6 Final EC 354020 354021 354025 A Safety Case For Return To Service Of HYA R2 HAR R1 AND R2 At Reduced Temperature Operation Following The Discovery Of A Defect On HYA R1 Boiler Spine 1D1 (TRIM 2014/425760).

10 Email - NGL-181 HYA 1D1 Boiler Spine Recovery - HAR and HYA Licence Condition 22(1) Compliance Arrangements Current on 11 November 2014 (TRIM 2014/458814).

11 EDF NGL - Heysham 1 - Unique Nos HYA71062 R - SIGNED COPY - LI Nos 586 - Specification of EC 354024 000 Heysham Reactor 1 - Interim Safety Case for Return to Service on 3 Quadrants following Discovery of a Defect in1D1 Boiler Spine - 16 December 2014 (TRIM 2014/462607).

12 NGL - CNRP - Contact Record - 14-300 - HYA/HRA Boiler Spine Heysham Reactor 1 Return to Service Safety Case - Level 4 - 9 December 2014 (TRIM 2014/465877)

13 Task Sheet NGL – ONR – NGL – 181 (TRIM 2014/108622).

14 NP/SC 4226 Addendum 4 Hartlepool and Heysham 1 Power Stations. Consolidated Boiler Spine Safety Case. September 2010. (TRIM Ref. 2010/448252).

15 NGL - CNRP - Assessment Report - 14-079 - Structural Integrity Assessment of the Safety Case for Return to Service of Heysham 1 Reactor 2, Hartlepool Reactor 1 and Reactor 2 at Reduced Temperature Operation following the discovery of a - 21 November 2014 (TRIM Ref. 2014/411978).

16 Hartlepool and Heysham1 - AR 11001 - Assessment of Consolidated Boiler Spine Safety Case NP SC 4226 Addendum 4 - Structural Integrity (2011/83112).



17 CNRP NGL Heysham 1 Reactor 1 restart on 3 quadrants December 2014 Response to

Questions to station to Support the RTS of Reactor 1 (TRIM 2014/471744).

18 ONR-CNRP-AR-14-101 Structural Integrity Assessment of the Safety Case for Return to Service of Heysham 1 Reactor 1 at Reduced Temperature Operation on 3 Quadrants following the discovery of a defect on HYA R1 Boiler Spine 1D1 January 2015 (TRIM 2015/4575).

19 ONR-CNRP-AR-14-094 Fault Studies Assessment - Boiler Spine - Return to Service - HYA R1 (TRIM 2015/341).

20 EDF NGL Report: FNC 45631/78217V, HYA, Boiler Spine Recovery Programme Boiler Thermal Assessments, dated 15 May 2014. (TRIM 2014/474925).

21 Fraser Nash Report: FNC 45607/41227R, Review of Fault Studies during Three Quadrant Operation at HYA/HRA (TRIM 2014/442964).

22 EDF NGL Report: DAO/REP/JIFB/028/AGR/014, Hartlepool / Heysham 1 Review of Fault Schedule for Three Quadrant Operation, December 2014 (TRIM 2014/462549).

23 NGL - Heysham 1 - Assessment report - ONR-CNRP-AR-14-096 - PSA assessment of Heysham 1 reactor 1 RTS safety case on 3 quadrants and at reduced temperature - January 2015 (TRIM 2015/733)

24 NGL, post return to service PSA Commitment, email to ONR, 5 January 2015, TRIM 2015/2116.

25 SRD_REP_SUR_HYA_063 Heysham A R1 1D1 Boiler Spine Inspection Surveillance (TRIM 2015/4723)

26 EDF NGL Nuclear Safety Committee Minutes: Minutes of the Meeting Held at Heysham 1 on 17 December 2014, Meeting 12/14 (TRIM 2014/472156).

27 Final Verification Statement 18-12-14 EC354024 Heysham Reactor 1 Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine Proposal 03 (TRIM 2015/760).

28 INSA Approval Certificate EC354024 Heysham Reactor 1 Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine Proposal 03 (TRIM 2015/761).

29 ONR How2 Business Management System. Permissioning - Purpose and Scope of Permissioning. PI/FWD Issue 3. August 2011. http://www.onr.org.uk/operational/assessment/index.htm.

30 ONR TRIM File 4.4.2.15043., Contact Reports; ONR TRIM File 4.4.2.15039., Level 4 Meeting.

31 Heysham 1 Reactor 1 - Site Inspector Operational Readiness Review (TRIM 2015/6942).

32 INSA Comments and Responses for EC354024 Heysham Reactor 1 Interim Safety Case for Return to Service on 3 Quadrants Following Discovery of a Defect in 1D1 Boiler Spine Proposal 03 (TRIM 2015/762).

33 SRD_REP_CON_HYA_005B – Part 2 Rev 000 Heysham 1 1D1 Boiler Spine Inspections and Reactor 1 Return to Service Concurrence Part B – Part 2 (TRIM 2015/4717).

34 Heysham Reactor 1 - Environment Agency Email from HYA Regulator stating no objection to restart of HYA R1 on three quadrants and reduced temperature 7th January 2015 (TRIM 2015/6279).

35 ONR IIS Rating Guide Table (TRIM 2014/12522).

http://www.onr.org.uk/operational/assessment/index.htm



36 ONR TRIM File 4.4.2.15036., Actions and Queries

37 ONR HOW2 Guide NS-PER-GD-014 Revision 4 - Purpose and Scope of Permissioning. July 2014. http://www.onr.org.uk/operational/assessment/index.htm

38 ONR HOW2 Guide AST/005 Revision 3- Peer Review for Technical Assurance September 2013, http://www.onr.org.uk/operational/assessment/index.htm





APPENDIX 1



Documents

Title of document - ONR - Office for Nuclear Regulation ... · Title of document Template Ref: ONR-DOC-TEMP-005 Revision 8 Page 1 of 27 . ... LRUT Long Range Ultrasonic Testing NGL