In Part 1, we reviewed the welding-related issues identified by the UK Office for Nuclear Regulation (ONR) during its February 2025 inspection of ADF tanks and vessels associated with Hinkley Point C (HPC). The inspection was triggered by previous operating experience where quality issues had been identified in welding and radiography. ONR rated both LC12, relating to suitably qualified and experienced persons, and LC19, relating to construction or installation control, as Amber.

The key welding-related findings included uncertainty over nozzle weld failure consequences, lack of demonstrated WPS/PQR review by suitably qualified and experienced persons, unspecified welding inspector qualification requirements, unspecified surveillance checks for welding inspection, lack of welding consumable control, radiography shortfalls for weld repairs, unspecified radiograph delivery timeframes, and weaknesses in licensee oversight.

The solution to these issues is not simply to increase final inspection. The correct approach is to strengthen the complete welding quality chain. That is,

1. Design consequence assessment,
2. WPS/PQR approval,
3. Welding inspection competence,
4. ITP control,
5. Consumable traceability,
6. NDT repair control,
7. Radiograph review, and
8. Licensee surveillance.

1. Establish the Welding Quality Control Strategy

The first step is to classify the welds according to their safety significance. For tanks and vessels, nozzle welds, pressure boundary welds, shell seams, attachment welds and repaired welds should not all be treated the same. The consequence of failure should determine the level of control.

A safety-significant nozzle weld, for example, should have a documented link between:

• its design and safety function;
• the consequence of weld failure;
• the applicable WPS/PQR;
• the required inspection and NDT scope;
• repair acceptance requirements;
• final release documentation.

This creates the “golden thread” from design intent to weld acceptance.

2. Update the ITP with Clear Hold and Witness Points

The Inspection and Test Plan should be revised so that welding activities cannot proceed without the correct checks, approvals and records. A practical approach is to divide the ITP into the control stages as shown in Table 1.

Table 1: ITP Control Stages

Stage	Welding / Fabrication Activity	Control Type	Required Evidence
1	Material receipt and traceability	Witness	MTC, heat number, material identification – i.e. obtain 3.1 Material certificate
2	Joint preparation and fit-up	Hold	Fit-up inspection sheet signed before welding
3	WPS/PQR and welder qualification verification	Hold	Approved WPS/PQR and welder qualification record
4	Consumable issue and control	Witness	Consumable batch/heat number linked to weld ID
5	Production welding	Surveillance	Weld log, parameters, preheat/interpass records
6	Visual inspection after welding	Hold	VT report and dimensional acceptance
7	NDT completion	Hold	RT/UT/PT/MT report accepted
8	Weld repair, if required	Hold	Repair approval, repair WPS, re-examination record
9	Final dossier review	Hold	Complete weld records accepted before release

Hold Point means work must not proceed until the required inspection or approval is completed. Witness Point means the activity must be available for observation, but work may continue if the notified party does not attend within the agreed time.

3. Use a Fit-Up and Welding Check Sheet

The ITP should be supported by simple check sheets. These help convert project requirements into evidence that can be reviewed later by QA, the licensee, or the regulator as shown in Table 2.

Table 2: Updated ITP Check Sheet for Fit-Up and Welding

Check Item	Acceptance Requirement	Record Required	Status
Material identification verified	Correct grade, heat number and traceability	Material traceability record	OK / Not OK
Joint preparation checked	Bevel angle, root face and root gap as drawing/WPS	Fit-up report	OK / Not OK
Joint cleanliness confirmed	Free from oil, grease, moisture, scale and contamination	Inspector sign-off	OK / Not OK
WPS confirmed	Correct approved WPS available at workface	WPS reference recorded	OK / Not OK
Welder qualification checked	Welder qualified for process, material, thickness and position	Welder qualification record	OK / Not OK
Consumable batch recorded	Correct filler material, batch/heat number traceable	Consumable issue log	OK / Not OK
Preheat/interpass controlled	As required by WPS	Temperature record	OK / Not OK
Tack welds inspected	Acceptable size, location and quality	Fit-up inspection record	OK / Not OK
Welding released	Hold point signed before welding starts	Inspector/client release	Released / Not released

This type of check sheet prevents welding from becoming an uncontrolled production activity. It also gives objective evidence that the weld was made under the conditions required by the approved procedure.

4. Define Welding Inspector Competence and Authorisation

One ONR finding was that welding inspector qualification requirements had not been specified. To correct this, the project should create an LC12-style competence register for all personnel who perform safety-affecting welding duties.

The register should define:

• role title;
• required qualification;
• required experience;
• authorised inspection scope;
• limitations of authority;
• expiry date or review date;
• approving authority.

For example, a welding inspector may be authorised only for visual inspection and ITP sign-off on specific vessel welds. An NDT interpreter may be authorised only for radiographic interpretation within a defined product sector. A welding engineer may be authorised to review WPS/PQR packages on behalf of the licensee.

The key point is that competence should be defined and approved before inspection or acceptance work is performed.

5. Control WPS and PQR Approval

For safety-significant fabrication, it is not enough to hold a WPS and PQR in the manufacturing file. The WPS/PQR package should be reviewed and accepted by a suitably qualified and experienced welding engineer or welding coordinator acting on behalf of the licensee.

The approval record should confirm:

• WPS number and revision;
• supporting PQR number;
• welding process;
• base material and thickness range;
• filler material;
• heat input or arc energy range, where applicable;
• preheat/interpass requirements;
• PWHT requirements, where applicable;
• NDT and mechanical test evidence;
• approval signature and date.

This provides evidence that production welding was not only procedurally qualified, but also technically accepted for the project application.

6. Strengthen Welding Consumable Control

The lack of welding consumable control is a direct welding quality risk. Consumables should be controlled from receipt to final use.

A practical consumable control system should include:

• receipt inspection and certificate verification;
• batch and heat number recording;
• segregated storage by type and classification;
• oven and holding cabinet temperature records, where applicable;
• issue logs linked to welder ID and weld number;
• return rules for unused consumables;
• quarantine of damaged, expired or uncontrolled consumables.

The consumable issue log should make it possible to trace the filler material used on each weld. This is essential for weld quality, repair investigation and final dossier acceptance.

7. Control Radiography and Weld Repairs

Weld repairs require particular control because the repair process can create new weld quality risks. A repair should not be treated as ordinary welding.

For each weld repair, the quality system should define:

• defect location and original NDT reference;
• method of excavation and defect removal;
• repair WPS;
• approval authority before repair;
• welder qualification;
• re-welding record;
• NDT method and extent after repair;
• radiographic review and acceptance;
• repair history in the weld dossier.

Radiographs should also be delivered to the licensee within a defined timeframe. This should be controlled through an agreed radiograph delivery log or service-level requirement so that the licensee can review NDT evidence before later manufacturing or installation stages continue.

8. One-Page ITP and Surveillance Matrix for ADF Tanks and Vessels

The table below shows a concise ITP and surveillance matrix suitable for safety-significant tanks and vessels.

Stage	Activity	Inspection / Surveillance	Acceptance Basis	Point	Record
1	Material receipt	Certificate and visual verification	Drawing, material specification, EN 10204 certificate	W	MTC and receipt log
2	Cutting and edge preparation	Dimensional and visual check	Drawing, WPS, fabrication procedure	W	Cutting/edge prep report
3	Fit-up and tack welding	Gap, alignment, cleanliness, tack quality	Drawing and WPS	H	Fit-up check sheet
4	WPS/PQR verification	Confirm correct approved procedure	Accepted WPS/PQR package	H	WPS/PQR approval sheet
5	Welder qualification	Confirm qualification range	Welder qualification record	H	Welder qualification check
6	Consumable control	Batch, heat number, storage and issue check	Consumable control procedure	W	Consumable issue log
7	Production welding	In-process surveillance	WPS parameters and weld plan	W	Weld log
8	Visual inspection	Weld profile, surface condition, dimensions	Project acceptance criteria	H	VT report
9	NDT	RT/UT/PT/MT as specified	Project NDT procedure and acceptance criteria	H	NDT report
10	Weld repair	Repair approval and re-examination	Repair WPS and NDT procedure	H	Repair dossier
11	Care and maintenance	Wrapping, storage and corrosion check	Care and maintenance procedure	W	Storage inspection log
12	Final release	Dossier review	Complete inspection and test records	H	Final release pack

This matrix should be included in the project quality plan and used during fabrication surveillance, document review and final release.

9. Licensee Oversight and Surveillance

The licensee should not rely only on supplier self-certification for safety-significant welding. Oversight should be active, risk-based and documented.

Effective oversight should include:

• planned surveillance visits;
• review of WPS/PQR approval status;
• sampling of welding inspection records;
• witnessing of fit-up, welding and NDT activities;
• review of consumable control records;
• review of weld repairs and radiographs;
• tracking of non-conformances and corrective actions;
• verification that actions are effective.

The purpose is to confirm that the supplier’s welding quality system is not only documented, but being implemented.

Conclusion

The welding quality issues identified in the ONR inspection show the importance of controlling the full welding quality chain. The solution is not limited to more final inspection. It requires stronger arrangements for weld classification, WPS/PQR acceptance, welding inspector competence, ITP hold and witness points, consumable control, repair welding, radiography review and licensee oversight.

For nuclear and other high-integrity fabrication, weld quality must be demonstrated by evidence. A completed weld is only acceptable when the project can prove that it was made using the correct material, approved procedure, qualified personnel, controlled consumables, defined inspection stages, accepted NDT and complete final documentation.

This article provides a practical framework for converting regulatory findings into welding quality controls that can be applied to safety-significant tanks, vessels and similar pressure-boundary fabrications.

Publication note: This article uses the February 2025 ONR inspection as a welding quality assurance case study. ONR subsequently published a later ADF-related inspection record in 2026 which judged the sampled LC12 and LC19 arrangements to be adequate from a structural integrity and installation assurance perspective, while noting one SQEP sample that did not fully meet expectations.

Read Part 1…

Welding Quality Issues Identified in the Hinkley Point C ADF Tanks and Vessels Inspection – Part 1

Common Questions on Practical Welding Quality Solutions: Welding Quality Issues Identified in the Hinkley Point C ADF Tanks and Vessels Inspection – Part 2: Practical Welding Quality Solutions

1. What is the purpose of Part 2 of this article?

Part 2 explains practical welding quality solutions that can be used to address the welding-related shortfalls identified in the ONR inspection of ADF tanks and vessels for Hinkley Point C. It focuses on how to improve control of WPS/PQR approval, welding inspection, consumables, weld repairs, radiography, ITPs and licensee oversight.

2. What was the main welding quality problem that needed to be solved?

The main problem was not simply the presence of weld defects. The deeper issue was whether the complete welding quality chain was under effective control. This included procedure qualification, technical review, production welding, inspection competence, consumable control, NDT, weld repair verification, documentation and oversight.

3. What is the first step in solving this type of welding quality problem?

The first step is to classify the welds according to safety significance. Welds such as nozzle welds, pressure boundary welds, shell seams, attachment welds and repaired welds should be assessed based on their function and consequence of failure. The higher the consequence, the stronger the welding control, inspection and documentation requirements should be.

4. Why is nozzle weld consequence assessment important?

Nozzle welds can be critical locations in tanks and vessels because they may introduce stress concentration, geometric discontinuity and potential leakage paths. If the consequence of nozzle weld failure is not understood, it becomes difficult to justify the inspection level, NDT coverage, repair requirements and final acceptance criteria.

5. How should WPS and PQR control be improved?

WPS and PQR documents should be reviewed and accepted by suitably qualified and experienced welding personnel before production welding starts. The approval should confirm that the procedure is suitable for the material, thickness, welding process, filler metal, heat input, preheat, interpass temperature, position, NDT requirements and project acceptance criteria.

6. Is it enough for a supplier to have a WPS and PQR?

No. For safety-significant fabrication, it is not enough for the supplier to simply hold WPS and PQR documents. The licensee or client must be able to demonstrate that the procedures were technically reviewed, accepted and authorised by competent personnel acting on its behalf.

7. What should be included in an updated welding ITP?

An updated welding Inspection and Test Plan should include material receipt, fit-up, WPS/PQR verification, welder qualification, consumable issue, production welding, visual inspection, NDT, weld repair, care and maintenance, final dossier review and release. It should also identify hold points, witness points, acceptance criteria, responsible parties and required records.

8. What is the difference between a hold point and a witness point?

A hold point means work must stop until the required inspection or approval has been completed and formally released. A witness point means the activity must be made available for inspection or observation, but work may continue if the notified party does not attend within the agreed notification period.

9. Why should fit-up checks be a hold point?

Fit-up should be a hold point because many welding quality problems begin before welding starts. Root gap, bevel angle, alignment, cleanliness, tack weld quality, material traceability and WPS availability all affect weld quality. Once welding has started, some of these conditions may no longer be visible or easy to verify.

10. What should a fit-up and welding check sheet include?

A fit-up and welding check sheet should include material identification, joint preparation, root gap, alignment, cleanliness, tack weld inspection, WPS reference, welder qualification, consumable batch, preheat and interpass requirements, inspector sign-off and release to weld.

11. Why is welding inspector competence important?

Welding inspection records are only reliable when the inspector is competent and authorised for the work being inspected. Competence should be defined by qualification, experience, product knowledge, material familiarity, inspection scope and project authorisation. It should not be assumed simply because someone holds a general inspection certificate.

12. What is an LC12-style competence register?

An LC12-style competence register is a controlled record showing who is authorised to perform safety-affecting duties. For welding work, it should identify welding engineers, welding coordinators, welding inspectors, NDT personnel and other personnel involved in acceptance or surveillance. It should list qualifications, experience, authorised scope, limitations, expiry dates and approving authority.

13. How should welding consumables be controlled?

Welding consumables should be controlled from receipt to use. This includes certificate verification, batch and heat number traceability, correct storage, baking and holding oven records where required, issue logs linked to welder and weld number, return rules and segregation of damaged, expired or uncontrolled consumables.

14. Why does consumable traceability matter?

Consumable traceability proves that the correct filler material was used for the correct weld under the required conditions. Without traceability, it becomes difficult to confirm compliance with the WPS, investigate defects, validate mechanical properties or accept the final weld dossier.

15. Why do weld repairs need special control?

Weld repairs need special control because repair welding can introduce new defects or fail to remove the original defect completely. Each repair should have a clear defect reference, excavation record, repair approval, repair WPS, welder qualification, re-welding record, post-repair NDT and final acceptance evidence.

16. How should radiography of weld repairs be controlled?

Radiography of repaired welds should be clearly specified in the NDT procedure or repair plan. The record should identify the repaired weld area, the extent of examination, radiographic technique, acceptance criteria, interpreter qualification, review result and link to the original defect and repair record.

17. Why is radiograph delivery time important?

Radiographs are part of the weld acceptance evidence. If they are not delivered to the licensee or client within a defined timeframe, technical review and oversight may be delayed. This can weaken the ability to challenge results, identify defect trends or stop later manufacturing stages before unresolved issues continue.

18. What is a one-page ITP and surveillance matrix?

A one-page ITP and surveillance matrix is a simplified control table that shows the key welding and fabrication stages, inspection type, acceptance basis, hold or witness point and required record. It helps engineers, inspectors and auditors quickly see how welding quality is being controlled.

19. What should licensee oversight include?

Licensee oversight should include planned surveillance visits, WPS/PQR review, sampling of welding inspection records, witnessing of fit-up and welding activities, review of consumable logs, review of weld repairs and radiographs, non-conformance tracking and verification that corrective actions are effective.

20. Is final inspection enough to prove weld quality?

No. Final inspection is only one part of weld quality assurance. In safety-significant fabrication, weld quality must be demonstrated by a complete evidence chain covering material control, approved procedures, qualified personnel, controlled welding conditions, inspection, NDT, repair control and final documentation.

21. What evidence would demonstrate improved welding quality control?

Useful evidence would include approved WPS/PQR records, welding inspector competence records, updated ITPs, fit-up check sheets, consumable issue logs, weld maps, weld logs, NDT reports, repair dossiers, radiograph delivery logs, surveillance reports, NCR closure records and final release packs.

22. What did ONR’s later follow-up inspection show?

ONR later published follow-up Inspection ID 54194. In that inspection, ONR judged the sampled LC12 and LC19 arrangements relating to ADF to be adequate from a structural integrity and installation assurance perspective and gave Green ratings. ONR also noted that seven actions linked to the Level 3 Regulatory Issue had been closed, with two remaining open but with credible closure plans.

23. What is the main lesson from the practical solution stage?

The main lesson is that welding quality problems should be solved by strengthening the complete quality system, not by relying only on final inspection. A robust system should connect weld criticality, WPS/PQR approval, competent personnel, controlled consumables, defined ITP stages, NDT, repair control, documentation and active oversight.

24. Can these lessons apply outside nuclear fabrication?

Yes. Although the case relates to Hinkley Point C, the principles apply to pressure vessels, tanks, pipelines, offshore structures, power plant equipment and any safety-significant welded fabrication where weld integrity, traceability, inspection competence and documentation are critical.