The Nuclear Research Index (NRI) is produced by Office for Nuclear Regulation (ONR) to provide a focus for the UK reactor nuclear safety research programme. The NRI defines the current ONR thinking on the need for research into nuclear safety issues and explains how the research outcomes are expected to benefit these safety issues. The main driving force behind the programmes of nuclear safety research is the need to gain intelligence on issues that might undermine safe operation of UK nuclear facilities in the future if not properly managed. Research work is necessary to investigate the safety implications of such matters as through life ageing, as well as the maintenance of adequate safety cases for the facilities.
ONR is currently undertaking a review to identify the overall requirements for nuclear safety research with the intention of expanding the NRI to cover the full scope of ONR’s regulatory remit. Our intention is to publish a cross-industry research statement in 2013 but for 2012 the NRI remains an update of the 2011 issue.
The UK has three commercial reactor types currently operational: Magnox, Advanced Gas-cooled Reactors (AGR) and a Pressurised Water Reactor (PWR) system.
The only remaining operational Magnox station (Wylfa) is currently scheduled to cease generation in 2014 and thus the scope of the associated research programme reflects this situation. Significant research work is being undertaken with regard to storage of radioactive waste and the suitability of arrangements for long-term care and maintenance of the defuelled Magnox reactor structures and components.
The seven operational AGR stations are effectively unique to the UK. Their design is based on a high-temperature, gas-cooled graphite core matrix which creates a unique environment for the materials involved. Therefore the understanding of materials behaviour in this environment depends heavily on plant data gathered by the UK operators and the development and maintenance of mathematical predictive modelling techniques. These stations are now approaching the end of their nominal design lives and research plays an essential part in ensuring that these reactors can continue to operate safely.
The one PWR station (Sizewell B) is the most modern station and has a long expected remaining life. There is considerable international experience with PWR reactors and international collaborative programmes of research contribute significantly to the UK knowledge base on this type of reactor.
Nuclear safety starts with the production of safety cases by the licensees to justify the safe operation of their Nuclear Plant. These safety cases are based on the original design data and assumptions regarding through-life ageing effects. The operators need to undertake programmes of research work to continue the validation and maintenance of these safety cases by gathering data from the operating nuclear plant and developing predictive mathematical modelling techniques. Without this work the operating nuclear stations would reach the limits of their existing safety justifications and would then need to be shutdown earlier than might be the case otherwise.
In addition to the extant fleet, new build proposals are currently being considered. The new designs employ some innovative technologies and designs, which have not been seen before in the UK nuclear power industry. Research may be needed to better understand the impact on safety that these new designs pose.
The UK nuclear industry is currently in a state of change. The shutdown and decommissioning programme for the Magnox nuclear plant, allied to the requirements to maintain the existing operating fleet and resource the demands of the new build programme has placed a significant demand on the available experienced nuclear resources and personnel. In particular there is a limited pool of suitably qualified and experienced persons (SQEP) and the age profile of these persons is significantly biased towards retirement age. Therefore the maintenance of sufficient numbers of SQEP personnel is a significant challenge.
As operation of the existing fleet continues, systems that provide a nuclear safety function age and gradually become obsolete. Some of the original equipment is now out of date and spares are no longer readily available. Therefore, as part of the justification of continued operation, these systems have to be updated or replaced with equivalent functionality based on modern components. These systems need to be evaluated carefully so as to ensure that they do not have failure mechanisms that would compromise nuclear safety.
The AGR reactors have a number of significant components that are too large and difficult to repair or replace. These components, such as the graphite core, effectively determine the operational lifetime of the reactor. They are subject to a high-temperature, high-irradiation operating environment with significant thermal cycling. This produces through-life ageing effects that need to be monitored. Any significant changes to their condition need to be analysed to ensure adequate levels of safety are maintained.
The analysis of these through-life ageing effects is achieved in part by gathering physical data from inspections and monitoring of the plant and partly by the use of predictive mathematical models. Research work is essential in keeping these techniques and models up to date and verified for use. As modern technologies are developed, their impact needs to be assessed both on plant operations and human performance.
The events at Fukushima in Japan are requiring nuclear operators across the world to re-examine the safety justifications for their own nuclear plant. This involves a significant amount of review and assessment of the existing safety cases.
The regulatory objectives of the research detailed in the NRI are as follows:
The strategy outlined in the topic sections of the NRI is consistent with achieving the regulatory objectives outlined above. Previous research undertaken under the auspices of the NRI has addressed a wide range of operational, analytical, cultural, organisational and design issues. This general theme is maintained, with suitable modification, to reflect the full diversity of research needs for an adequate and balanced programme, whilst reflecting the need for specific information that is generated by changing industrial circumstances. The NRI strategy seeks to achieve effective dissemination and application of data whilst, at the same time, ensuring that fundamental issues are not neglected.
The research programme envisaged by this NRI aims to achieve a balance between work which addresses current operational safety issues and work which will have application over a longer time scale. It also takes into account input from a wide range of academic, international, regulatory and industry sources to capture important cultural and performance issues which need to be addressed over the short, medium and long-term.
Licensees are free to undertake research projects that address commercial operational needs and these are considered to be outside of the scope of the NRI.
The licensees are expected to conduct adequate research to support continued safe operation of their licensed sites. They are free to undertake other research as they see fit, (such as alternative energy production technologies and green transport programmes). However, ONR's interest is in the research that is related to issues of nuclear safety. The licensees are expected to report on the status of such research at least on a yearly basis, so that there is clear evidence that adequate research is being undertaken in this area. In order to achieve this, the licensees must maintain the capability to undertake this essential research which is known as 'Licensee essential research capability’. Essential research capability ranges from the maintenance of key teams and experimental facilities to areas where in-house teams are maintained, though they are not formally declared as essential research capability. Examples of where essential research capability is declared are where the licensees are engaged on maintenance and validation of key UK modelling codes, as well as further refinement of these codes. In other technical areas related to fuel, the in-house teams have access to experimental facilities and sources of information through participation in international programmes. A statement on essential research capability is clearly identified for each technical section in the licensees’ NRS.
Maintenance of essential research capability is critical to the continuing safety of the UK nuclear industry. There is a need to maintain suitable SQEP personnel and appropriate facilities to enable adequate nuclear safety research to be undertaken. This has been recognised by the industry and they are actively supporting apprenticeship courses, university involvement including sponsoring PhD students and post-doctoral researchers.
In-house teams are currently maintained by the licensees, though they are not formally declared as essential research capability. They are engaged on maintenance and validation of key UK codes, as well as further refinement of these codes. These teams have access to experimental facilities and sources of information through participation in international programmes.
The various countries that operate nuclear facilities maintain a global international community with various international fora and networks to pool and discuss nuclear matters. The UK nuclear industry participates in these fora providing nuclear expertise to and gaining learning from a number of significant international research projects.
The interaction with the international community of nuclear operators is of significant benefit to the UK in a number of important topic areas. It allows data to be gathered from large international databases, participation in international collaborative projects (that would be too costly to fund from within the UK alone) and access to a much wider spectrum of knowledge and experience on nuclear matters. The NRI research programme makes explicit provision for monitoring of international nuclear topics and research.
Examples of such international research projects include:
ONR routinely sends delegates to international conferences to gain information first hand and develop/maintain experience.
The 2012 NRI builds on the 2011 issue and all the sections have been considered with respect to the current state of the research issues detailed in them. Some new requirements have been added to capture new research needs arising, including those from the continuing response to the event at Fukushima. The most significant updates are inter alia:-