- Site: Springfields
- IR number: 21-075
- Date: August 2021
- LC numbers: 8, 10, 12, 23, 24, 28, 36
Executive summary
Purpose of Intervention
This inspection was undertaken as one of a series of planned cross-site criticality inspections performed by ONR. The overall intervention (i.e., across a number of GB licensed nuclear sites) is focussed on the implementation of arrangements to manage criticality safety and has three main aims:
To identify any deficiencies in licensee’s management of criticality safety (and/or any legal non-compliances) and to work with licensees to ensure prompt and sustained rectification of any shortfalls;
- To identify areas of good practice across the licensees inspected and to share these across the UK nuclear industry; and
- To seek improvements in licensee’s management of criticality safety and to highlight and action areas where ONR’s own guidance may be improved.
To provide a consistent approach across each of the individual criticality inspections, it was deemed appropriate to conduct the inspection against a number of Licence Conditions (LCs) which were judged to have direct relevance to criticality safety i.e., LC 8 “Warning Notices”, LC 10 – “Training”, LC 12 - “Duly Authorised and Other Suitably Qualified and Experienced Persons (DAP/SQEP)”, LC 23 – “Operating Rules”, LC 24 –“Operating Instructions”, LC 28 – “Examination, Inspection, Maintenance and Testing” and LC 36 – “Organisational Capability”.
Interventions Carried Out by ONR
ONR criticality specialist inspectors conducted a planned criticality inspection of the Springfields Works nuclear site operated by Springfields Fuels Ltd (SFL). The inspection was conducted through a walk-down of the National Nuclear Laboratory (NNL) Plant (a tenant on the Springfields site), by discussions with key plant personnel and by examining the licensee’s criticality safety documentation, training records, maintenance schedules / records and on-site signage (e.g., criticality notices).
Explanation of Judgement if Safety System Not Judged to be Adequate
Not applicable.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
The key findings against each LC are recorded below.
LC 8 (Warning Notices)
We visited the NNL Preston Laboratory (Pellet Laboratory) which carries out simple operations on, and storage of, small quantities of fissile material.
SFL has procedures in place to prompt plant management to consider the need for signage when undertaking modifications to plant.
We observed fixed signage on the entrance showing the facility identification and the relevant Criticality Clearance Certificate (CCC). Within the facility, further signage showing additional CCCs (e.g. on a storage cabinet) was observed.
Signs showing the Criticality Evacuation routes in the building were permanently fixed to corridor walls and above head height, and readily visible to all.
All the signage that we observed was in good condition and free from defect, except for two criticality warning signs which were in disrepair, although visible and legible. We regard this a minor deficiency and have recorded it as an Observation.
Apart from the Observation above, we were satisfied with the licensee’s arrangements for warning notices.
LC 10 and LC 12 – Training and Duly Authorised and Other Suitably Qualified and Experienced Persons
Site arrangements for criticality safety training were reviewed and found to be comprehensive and of a good standard. All workers on site are required to have a basic awareness of criticality safety in order to be permitted to access the site. On plant Criticality SQEPs (e.g. operators) and Criticality DAPs (Supervisors) receive an enhanced level of criticality training.
SFL delivers criticality training that is tailored to individual plant and process areas. As well as classroom based, criticality training included an ‘on-plant’ training element and focus on why and how to comply with operating rules and requirements specific to that plant/process. It also included feedback from inspections/incident reports and used this operational experience to update training. Training included assessment, again tailored to plant/process with question sets varied (to avoid reptation of questions during refresher training).
There is a structured approach to training of criticality specialists and on plant criticality SQEPs. The criticality specialist skill plan aligned well with the Working Party on Criticality (WPC) Criticality Competence Framework.
We were satisfied with the licensee’s arrangements for criticality safety training.
LC 23 and LC 24 – Operating Rules and Operating Instructions
Criticality Clearance Certificate 218 and its supporting criticality safety assessment were examined in detail.
CCC 218 was clear to read and understand, with restrictions placed on measurable quantities (e.g. mass of fissile material), making it easy for operators to achieve compliance. No deficiencies were found in the underlying safety justification.
The criticality safety justifications are carried out by suitably qualified and experienced criticality assessors, following methodologies and procedures that are consistent with industry guidelines. All criticality assessment work is quality assured.
The safe working limits from CCC 218 are transferred verbatim by the plant management into plant Operating Instructions, resulting in a clear link between the operating instructions derived in the criticality assessments and operating instructions used on plant. Early engagement with plant ensures that the wording will be meaningful to operators.
We were satisfied with SFL’s arrangements for deriving and implementing operating rules and operating instructions.
LC 28 – Examination, Inspection, Maintenance and Testing (EIMT)
SFL uses a Maintenance Management System called Maximo for searching for maintenance information and provides prompts to the relevant group when action is required.
Maintenance schedules, engineering substantiation records and maintenance guidance notes were randomly sampled for plant of relevance to criticality safety (e.g., limited moderation storage lockers). The sampled documents were found to be well written, in date and appropriately authorised. There were clear links between the engineering substantiation records and maintenance guidance notes.
SFL described the approach adopted for verification of the continued presence of poisoned (PVC) slabs within Safe Geometry Bins (SGBs) which involved utilising a sacrificial strip of PVC within the SBG which could be used to destructively test the presence of poison without having to degrade the actual Safety Feature. We considered this to be a good practice.
It was noted that claims are made in the criticality safety cases regarding Safe Geometry Containers (SGCs) which are used widely across site to move fissile material within and between buildings and for storage. However, the SGCs are classed as “Operating Assumptions” rather than Safety Features. Therefore, the SGCs do not feature on the Maximo system and are therefore it is not clear how they are subject to systematic EIMT. This is important given the how widely the SGCs are used and also the nature of use i.e. movement and therefore more potential for damage.
The licensee received our observations positively and agreed to give consideration as to how it could ensure systematic EIMT for the SGCs.
We were satisfied with the licensee’s arrangements for EIMT.
LC 36 – Organisational Capability
In terms of human and financial resource, we consider that currently, and for the immediate future, SFL has an adequate system in place to ensure criticality safety.
We have a concern over the viability of SFL’s criticality safety management in the longer term.
Conclusion of Intervention
This criticality inspection focussed on criticality aspects of LCs 8, 10, 12, 23, 24, 28 and 36. Overall we judged SFL’s arrangements to be adequate, with no significant areas of concern.
Instances of Good Practice were also observed and recorded by the inspectors.
Some minor gaps to UK relevant good practice in respect of criticality were observed and these were drawn to the attention of the licensee who agreed to consider them.