Office for Nuclear Regulation

Planned Intervention at Dungeness B

Executive summary

Purpose of intervention

This was a planned inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Dungeness B (DNB) power station, undertaken as part of the planned Integrated Intervention Strategy (IIS) for the Civil Nuclear Reactor Programme (CNRP) of the Office for Nuclear Regulation (ONR).

The intervention included a system based inspection (SBI) of solid and gaseous radioactive waste systems to demonstrate compliance with the safety cases for these systems.  This inspection was performed by the ONR nominated site inspector, a radioactive waste specialist and the Environment Agency’s site inspector for Dungeness B.

Interventions Carried Out by ONR

The key inspections during the solid and gaseous radwaste SBI were for licence compliance covering the following Licence Conditions (LC):

During this intervention, the following key activities were also undertaken:

Explanation of Judgement if Safety System Not Judged to be Adequate

We judged that from the information sampled, interviews with licensee staff, and the plant inspected, the majority of the system adequately met the requirements of the associated safety cases.  This is reflected in the judgement of the adequacy of the compliance against the Licence Conditions 10, 23, 24, 27 and 34 and the condition of the plant described as noted below.  However, in relation to LC28, we did identify a shortfall in terms of inspection of waste package integrity, which we consider to be a weakness in demonstrating waste package integrity..  We agreed an action with the site to remedy the shortfall on a timescale that is consistent with its safety significance.  We do not consider that it is necessary to take any further regulatory action. 

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

Based on the evidence sampled, we concluded that the limits and conditions had been identified within the safety case documents.  A sample of limits and conditions were selected and identified within relevant operating and maintenance instructions, providing a demonstration that the relevant limits and conditions had been implemented in an adequate manner.  We judged that compliance with LC 23 was adequate and hence assigned an IIS rating of 3.

In relation to the LC 24 element of the system based inspection, two operating instructions were inspected by reviewing the instructions and witnessing a walkthrough of two operations.  The operational records from the previous time the two operations occurred were also reviewed.  From this, we considered that the operating instructions sampled had been completed competently and that all information required was recorded in a clear and effective manner. We judged that compliance with LC 24 was adequate and hence assigned an IIS rating of 3.

Following discussion with the Fuel Route System Engineer and Environmental Safety Group Head, and a review of the safety cases, we judged that there were no safety mechanisms, devices or circuits for this system. LC 27 was therefore not considered applicable for this inspection.

To demonstrate compliance with LC 28, records associated with tasks identified in the maintenance schedule were examined.  Generally the site provided evidence that the plant had been inspected, examined, maintained or tested within the time intervals in the maintenance schedule.  However, we identified that the licensee had not implemented six monthly inspections on the radwaste storage facility within the decontamination centre, which it had previously identified as being necessary.  We were not aware of any leakage of radwaste from the packages and therefore, whilst we considered this was a compliance shortfall, the safety significance was low and therefore does not need to be addressed immediately.  An action plan has been agreed and a regulatory issue has been raised to address the shortfall.  Based on the evidence sampled, we judged that compliance with LC28 was below standard and hence an IIS rating of 4.  

To demonstrate compliance with LC34, we reviewed the maintenance and inspection records for the main active waste vaults and the sumps within the Decontamination Centre.  These were implemented by the licensee to prevent and/or detect leakage and escape.  We concluded that the maintenance and inspection identified by the licensee to prevent and detect leakage and escape of radioactive material had been completed and no radioactive leaks had been identified.    We concluded that compliance with LC34 was adequate and hence assigned an IIS rating of 3.  

We inspected the training records for a range of staff involved in operations and maintenance associated with the system.  We considered that the records demonstrated that the operators and technicians undertaking the tasks selected were suitably qualified and experienced on the date the activity took place.  We judged that compliance with LC 10 was adequate and hence assigned an IIS rating of 3.

Finally, the system based inspection requires an assessment of the plant condition, which was based on discussions with the licensee on its own assessment and a walkdown of the plant.  For the main active waste vaults, the licensee had made improvements to the control panel and the system generally reflected the state of the plant described by the licensee.  For the decontamination centre, there appeared to be a lack of ownership of the plant and areas within the decontamination facility.  Areas of improvement were identified, including housekeeping and the volume of low level waste within the facility.  Overall the plant condition was judged to be acceptable.

The CNRP director inspected the site and the Station Director presented the station’s intentions for improving nuclear safety.  The CNRP director formed a positive view on the future proposals, although he was not able to explore any of the station commitments in any detail within the time available.

In relation to the other activities undertaken in this intervention, no key findings arose.

The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.

Conclusion of Intervention

From the evidence obtained during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety or protection of the public in the event of an emergency on the station at this time.  Therefore, no additional regulatory action arising from this visit is considered necessary at this time.