Description
BACKGROUND TO THE PROJECT
The four remaining graphite moderated Advanced Gas Cooled Reactor (AGR) power stations represent a technology unique to the UK. Together they account for the large majority of the electricity generated by nuclear power within the UK. The AGRs commenced operation between 1978 and 1988 and are now experiencing ageing and obsolescence issues. The licensee, EDF Energy Nuclear Generation Limited (EDF), wishes to operate the reactors for as long as they are safe and economic to run. As well as dealing with the physical ageing, there is a need for continuity of knowledge and experience that is faced both by ONR and the licensee.
The use of graphite as a moderator and carbon dioxide as a coolant has led to two significant technical issues that potentially challenge the essential safety functions of the core. These issues are graphite dimensional change and graphite oxidation. The former leads to cracking of the graphite moderator bricks, which could ultimately challenge the maintenance of adequate core geometry, and the latter leads to graphite weight loss. Both these phenomena lead to diverse and complex challenges including the implications of graphite brick cracking on safety functions and core moderation. Limits on these phenomena are defined and set in safety cases produced by the licensee and assessed by ONR.
There is a limited pool of expertise in these graphite ageing mechanisms and given the uniqueness of the problem to the UK AGRs, EDF dominate research activities on this subject. For ONR to sustain an informed and independent view on these matters, ONR has for the last 20 years maintained a pool of experts independent to EDF, who's views can be consulted on significant technical matters regarding graphite ageing phenomena.
o Over the course of the existing contracts the work performed has included the provision of specific advice, generally by the carrying out of specific analysis, according to a programme of work agreed with ONR inspectors.
o The support provided by these contracts has proved invaluable to ONR in its regulatory work. In particular, derivation of bespoke material property models and the analysis of the evolution of stress and graphite brick cracking morphologies.
o The current contract is due to end in January 2027 and ONR is seeking to put in place a new two year contract, for the provision of support services in this area. This contract will contain provision to extend the contract in 1 year increments (up to a maximum of 4 years total) depending on ONR needs.
SCOPE OF THE SERVICES REQUIRED
The scope of services outlined in this specification covers the initial two-year contract period, work is expected to commence in January 2027. Any required ongoing support and associated costs for further years will be agreed in advance, prior to commencement of any extension.
Provision of Independent Research:
For the research component and recognising that senior personnel may have other business or professional commitments, while some staff may be dedicated exclusively to ONR work, the main contract does not require or expect all the team members to work full time on ONR projects. Therefore, it should be assumed that the resources needed to deliver the required work under this contract will be approximately:
• Three full-time staff dedicated to ONR projects,
• Both a senior technical specialist and a project lead spending a quarter of their time specifically on ONR work.
• Additional effort at any level may be added as an option.
Work programmes would include:
• development of fracture models of nuclear graphite.
• contribution to the development and maintenance of independent materials property models.
• sensitivity studies of stress analysis of graphite bricks using finite element analysis both static and dynamic; and
• modelling of brick-to-brick interactions as the core ages.
General work areas would include:
(i) detailed modelling and analysis.
(ii) preparing reports and presenting work, either to ONR or groups including licensee representatives.
(iii) providing ONR with an expert view on particular technical topics, which may include attendance at regulatory meetings.
(iv) attendance of one member of staff at an internationally recognised conference to disseminate their work.
(v) Attendance at and support to relevant GTAC meetings and sub-group activities.
Provision of Independent Advice
For the advice element of the contract ONR expects that the provider arranges the continued operation of GTAC, such that:
• For the provision of expert advice element of the contract, ONR requires the supplier to establish and maintain a Graphite Technical Advisory Committee (GTAC).
The supplier should ensure that:
• The GTAC panel should be comprised of around 12 suitably qualified and experienced independent experts, with demonstrable knowledge in graphite behaviour, ageing, assessment methodologies, and nuclear safety.
• The composition of the panel must reflect a balanced range of technical disciplines relevant to graphite core performance, inspection, modelling, and structural integrity.
• Members should be selected on the basis of competence, credibility, and absence of conflicts of interest.
• The GTAC should be capable of providing impartial, authoritative, and timely advice to support ONR's regulatory decision-making.
• The membership should be resilient and sustainable; where any member holds unique specialist knowledge and may potentially leave or retire during the contract period, the supplier shall identify and maintain suitable potential replacements to ensure continuity.
• Appropriate facilities should be provided to support the operation of the GTAC, including suitable meeting venues, refreshments, and associated logistics.
• Suitable contractual arrangements must be in place to enable additional experts to be engaged as required, either through co-option to the GTAC or via specific sub-contracts for discrete tasks.
• Adequate administrative support to be provided to manage the GTAC effectively, including:
• administration of all sub-contracts with members and additional experts
• recording of time and travel & subsistence (T&S) claims
• processing of timely payments and invoicing
• preparation and distribution of reports, and
• preparation and maintenance of accurate meeting minutes.
• All sub-contracting arrangements with GTAC members and other experts must fully comply with the Income Tax (Earnings and Pensions) Act 2003 (ITEPA) and all other applicable legislation and regulations relating to income tax, including due consideration of IR35 requirements.
It is expected that the functions of GTAC will be as follows:
(i) Four full GTAC meetings per year attended by all members, who may charge one full day for preparation and one day for attendance. Occasional additional meetings may be called by ONR.
(ii) Preparation of reports, expected to average about six per year, upon request of ONR. These reports are likely to require the formation of sub-groups of some members and associated meetings, drafting, revisions etc. ONR will normally present the questions at GTAC meetings. The sub-group leader will then provide ONR with an estimate of the number of day's effort required to address the question.
(iii) Attendance of individual GTAC members to provide advice at specific events, such as meetings between the licensee and ONR.
(iv) attendance of up to 2 members of at an internationally recognised nuclear graphite seminars / conference with ONR approval.
(v) Provision of all necessary administrative support to facilitate objectives (i) to (iii)
It is recognised that the work required of GTAC evolves as particular information becomes available e.g. on graphite ageing. It is anticipated that the total cost will be approximately within limits described below, but that in exceptional circumstances significant departures from the planned annual spend may occur with ONR approval.
OBJECTIVES
This specification should be seen in terms of ONR's overall strategy of maintaining a pool of expertise on nuclear graphite technology that is independent of the major nuclear licensees. This new contract will assist with that overall objective and will enable ONR to mount a constructive challenge of the licensee's safety cases by performing independent analyses in the work programmes and general work areas described below.