The purpose of this intervention was to conduct Licence Condition (LC) compliance inspections at EDF Energy Nuclear Generation Limited's (NGL's) Torness Power Station in line with the planned inspection programme contained in the Torness Integrated Intervention Strategy (IIS) for 2016/17.
As part of this intervention, two ONR chemistry specialist inspectors and the nominated site inspector performed compliance inspections against the following Licence Conditions (LCs):
The overall theme of this inspection was related to operational chemistry control on the site. The compliance inspections were therefore targeted at chemistry-related matters. In addition two other related interventions were addressed as part of this inspection:
Inspection of other matters relating to chemistry control were undertaken to fulfil the intent of the chemistry intervention strategy for the ONR Operating Facilities Programme; and
Follow up on the site specific arrangements for management of Carbon Deposition (CD), following an intervention conducted at the corporate centre.
No safety system inspection was undertaken, hence this is not applicable.
The LC 12 (Duly authorised and other suitably qualified and experienced persons) inspection focussed on the Nominated Oxygen Injection System Supervisor (NOISS) role, which is a defined role required during periods of oxygen injection to the boilers to remove carbon deposits. We reviewed the requirements for this role, how it is implemented into station arrangements and delivered during periods of operation. We discussed this with existing role holders and reviewed records for the latest oxygen injection campaign. Aside from a minor matter related to a lack of a specific NOISS role profile, which station have agreed to action using their own processes, we judge that the requirements for LC 12 have been satisfactorily met and on that basis have given this inspection an IIS rating of GREEN.
For the LC 26 (Control and supervision of operations) inspection, we sampled the operations associated with the boiler oxygen injection system. This included aspects of both the safety case and procedural controls in place. Based upon our further sampling of the NOISS role and review of associated sign-off and supervision, we are satisfied that the station is implementing adequate control and supervision of operations in respect of boiler oxygen injection. We also inspected the arrangements for control and supervision of chemistry and found that they generally met with our expectations. Overall, we judge therefore that LC26 warrants an IIS rating of GREEN.
While not the focus of our inspection, we did identify that the operation of the gas by-pass plant (GBPP) is no longer consistent with the original design intent for the plant due to consequences caused by boiler oxygen injection. This is recognised in a number of safety cases and does not appear to manifest in difficulties with operation chemistry control. However, the piecemeal nature of the changes raises questions which could not be resolved during the timescale of the inspection. We have raised an issue on ONR's issues database, to capture and monitor progress with resolving this matter.
The LC 28 (Examination, inspection, maintenance and testing - EIMT) inspection examined the EIMT arrangements for a number of items of plant associated with boiler oxygen injection, spent fuel pond and pressure vessel cooling system. Based on the sample inspection, we confirmed that the station has implemented its arrangements to meet the requirements of the safety case, and that overall the station is undertaking EIMT in a satisfactory manner. We judge the LC28 aspects of the inspection to be adequate, warranting an IIS rating of GREEN.
Regarding Carbon Deposition, we found that the station clearly understood the issues and potential consequences of CD and satisfactorily demonstrated an understanding for the management of CD. Further, the arrangements that the station currently has in place will allow the detection of adverse trends, with a good level of profile for CD with station management. Importantly, station arrangements and processes complemented those of the corporate centre.
For chemistry control more generally, we judged that station demonstrated adequate control of chemistry for the systems we sampled. Positively, the station was largely able to demonstrate compliance with the relevant requirements.
The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.
Independently of this licence condition inspection, we examined in further detail the circumstances surrounding a recently reported event at Torness concerning the maloperation of a pond bay level fascia alarm (INF1 event 2016/43). As a result of this further investigation, we have raised an issue at level 3 on ONR's issues database, which we will use to track progress and completion of three actions placed on the station. We have also entered an additional reactive IIS rating of 'amber' against LC28.
On the basis of our sample, we judge that the arrangements and their implementation at Torness for LC 12, LC 26 and LC 28 were adequate and merit a rating of GREEN. We were content that Torness could demonstrate adequate arrangements to monitor and control carbon deposition, as well as chemistry control more generally.
There were no findings from this inspection that could significantly undermine nuclear safety or which would result in changes to the planned interventions and inspections of Torness Power Station.