April 2002
Under a condition attached to the nuclear site licence, Periodic Safety Reviews (PSRs) are required to be carried out by the licensee of a nuclear installation. In line with international practice NII policy requires licensees to carry out a periodic safety review at least once every 10 years. The reviews are complementary to the day to day regulatory controls which are applied to nuclear installations. They provide the opportunity to undertake a comprehensive study of the safety of plant, taking into account operational history, ageing factors which could lead to a deterioration in safety, and the advances in safety standards since the time of construction or the previous review. From this, the safety of future operation of the installation can be evaluated.
The reviews are submitted to the Health and Safety Executive's Nuclear Installations Inspectorate (NII) for consideration and assessment to evaluate whether an adequate level of safety has been achieved. A nuclear installation such as the Grove Centre has a large number of nuclear plants housed in a number of buildings and each nuclear plant has to be covered by a safety case. For such multi-plant sites it is not practicable to carry out a PSR of all of the safety cases at the same time and therefore the licensee in agreement with the NII, has put in place a rolling programme of periodic reviews such that each plant is reviewed over a ten year period. On such sites it is also important that site wide topics and interactions between plants are addressed for the whole site and therefore the licensee has been required to undertake a 'Site' PSR which is subject to the same arrangements as individual plant PSRs. The 'Site' PSR document prepared by the licensee provides an overview of the plant PSRs.
This report summarises the outcome of the 'Site' PSR for the Grove Centre which has been carried out by the licensee Amersham plc. It describes the current position and background to NII's assessment and our conclusions on the acceptability of continued operation of the site.
We are satisfied that the licensee has carried out a satisfactory rolling programme of PSR's to date to review individual nuclear plants on the site. Improvements to individual plants which the licensee initiated as a result of the reviews have enhanced the safety of the site. The overall outcome of the licensee's reviews provides confidence in the ability of the site to continue to operate safely.
Subject to continuing satisfactory results from the routine monitoring and demonstration of safety required under the nuclear site licensing arrangements and the satisfactory completion of the ongoing rolling programme of PSR's, we expect the site to be able to continue to operate safely.
The Grove Centre site houses a wide range of plants for manufacturing radio-pharmaceutical products for use in medicine and research. The physical scale of the operations is small and they are essentially bench chemistry operations that are enclosed and shielded because of the radioactive content.
Under a condition attached to the nuclear site licence, Periodic Safety Reviews (PSRs) are required to be carried out by the licensee of a nuclear site and NII policy requires licensees to carry out such reviews at least every ten years. The purpose of a PSR is to determine, by means of a comprehensive assessment, whether the plants, processes, management, operations and facilities covered by a safety case are safe so far as is reasonably practicable, as judged against modern standards, at the time the review is carried out, and that ageing and other time related phenomena will not render them unsafe.
For multi-plant sites such as the Grove Centre it is not practicable to carry out a PSR of all of the safety cases at the same time and therefore the licensee in agreement with the NII, put in place in 1990 a rolling programme of periodic reviews such that each plant was reviewed over a ten year period. On such sites it is also important that site wide topics and interactions between plants are addressed for the whole site and therefore the licensee has been required to undertake a 'site' PSR which is subject to the same arrangements as individual plant PSRs. In 1999 Amersham was informed of the requirement to submit a 'site' PSR for its Grove Centre site and it is this review that is the subject of this report.
The 'Site' PSR Report prepared by the licensee provides an overview of the site rolling programme of PSRs and summarises the outcomes from individual PSRs undertaken since 1990. The report also covers site wide topics such as interactions between plants and overall hazards and risks from the site.
This report provides a summary of the NII assessments undertaken and the conclusions arising from it.
Before any new nuclear plant is operated, the licensee must have a valid safety case, which is essentially a written demonstration that the intended operation of the plant will be adequately safe. The safety case therefore needs to confirm that all credible hazards have been identified, appropriate standards have been set and met, adequate safety features are in place, all significant assumptions have been identified, verified and validated, and that all instructions, limits and conditions required to maintain operations within specified margins for safety have been identified.
As the individual plant matures modifications are made, ageing effects take place, some components may become obsolete and plant operating instructions may be changed as a result of experience. During all this time the safety case for the plant must remain valid and individual changes will be incorporated in the safety case as appropriate. The PSR process is designed to ensure that in addition a thorough and comprehensive review is made of the whole plant safety case at regular intervals throughout the plant's life. The reviews have become a well established feature in the licensing requirements for nuclear installations, and are intended to be more wide ranging than a restatement of the safety case. They complement the normal day to day operational monitoring of safety, which is further underpinned by thorough inspections and assessment of the condition of plants during normal maintenance and testing.
The objectives of the PSRs are:
In reviewing plant safety cases, which is the first objective, we expect the licensee to reaffirm the validity of the original safety case, reflecting on factors such as:
The second objective, to compare against current standards for new plant requires the review to address all relevant advances in safety standards and practices. Any significant shortcomings should be identified, and any improvements which are reasonably practicable should be introduced.
Another essential element of the review is that we require all structures, systems, or components susceptible to ageing or wear out to be examined, and failure mechanisms, together with any life limiting features, identified. These various factors then have to be evaluated, particularly for aspects which may eventually result in unacceptably reduced levels of safety, and ultimately dictate the safe working life of individual plant.
Finally we expect the PSRs to confirm that the plant safety case will remain valid until the time of the next review, which is normally set at ten years. As we have stated above, the PSRs complement the normal operational monitoring of safety which is also regulated by the NII. Therefore although PSRs may conclude that the safety case is adequate for another ten years, this will be dependant upon continuing satisfactory results from routine inspections and adequate maintenance. Should any safety related factor emerge in the interim period which may throw doubt on the continuing validity of the safety cases, we would require the licensee to resolve the matter to our satisfaction.
The licensee is undertaking a rolling programme of PSR's covering the large number of different plants housed on the site because it would not be practicable to address all the safety cases at the same time. The programme was designed to ensure that all nuclear related site operations were reviewed over a 10 year period. On a multi-plant site such as the Grove Centre we considered that it was important for the licensee to address interactions between plants having safety cases subject to individual PSRs and also to address site wide topics covering the safety infrastructure of the site. We therefore required the licensee to produce a 'Site' PSR report covering these topics and we informed it that site wide issues should also be reviewed at 10 yearly intervals.
The 'Site' PSR Report prepared by the licensee provided an overview of the site rolling programme of individual plant/building safety case reviews and summarised the outcomes from such reviews undertaken since 1990. The report also covered site wide topics such as interactions between plants and overall hazards and risks from the site. The report concluded that the periodic review of safety of the site has demonstrated the basis for continued operation and has, in particular, shown that life limiting effects have been considered and that the risks from plant operation are acceptable.
The report was produced by the licensee's staff assisted by a contractor. The report was peer reviewed by other staff from the licensee's organisation before being submitted to the NII.
Assessment of the licensee's 'Site' PSR Report involved a team of NII inspectors.
The inspectors used the NII's Safety Inspection Principles (Reference 1) as the standard against which to judge the safety of the plants. Since the principles were written primarily for use on new plant, differences between the original standards to which the individual plant were built and the current safety standards may be evident when applying the principles. In such cases the general requirement that all risks must be shown to be either negligible or 'as low as reasonably practicable' is very relevant to the assessment. The age of plants and their projected life are important factors which were considered when making judgements on the reasonable practicability of making improvements.
The Grove Centre site is located about two miles from the centre of Amersham, Buckinghamshire. It was set up in the 1940's and was originally the parent site of The Radiochemical Centre. In 1982 the company was privatised and renamed Amersham International plc. Nycomed Amersham plc was formed in the autumn of 1997 by the merging of Amersham International plc (including the subsidiary Amersham Pharmacia Biotech Limited) and Nycomed ASA of Norway. In July 2001 the company was renamed Amersham plc.
The group has two principal lines of business: Health and the Biosciences. The Health activities focus on the development and manufacture of radiopharmaceuticals for diagnosis and treatment of disease including cancer. The Biosciences activities provides hundreds of specialised products, some of which are radioactive, for use in medical and biological research world-wide in the investigation of the fundamental processes of living cells. Amersham also manufactures and distributes products at the Grove Centre for Amersham Biosciences UK Limited.
The site currently manufactures a range of imaging diagnostic and therapeutic products, such as technetium 99m generators and iodine 125 seeds, and bioscience products, such as nucleic acids labelled with carbon 14. Some shorter lived imaging nuclides such as Gallium 67 are produced in the two cyclotrons on the site.
A large number of different plants are operated on the site but the quantity of radioactive material used in each plant is relatively small. The isotopes used are distinct from those encountered in the nuclear power industry. They are mainly of low toxicity and tend to be those that decay relatively quickly i.e. of short half life. The majority of plants are housed in small enclosures such as glove or tong boxes of typical dimensions 1.5m x 1.0m x 1.0m. Some plants are housed in larger shielded facilities or cells. In all cases the physical scale of the plant operations is small and they are essentially bench chemistry operations enclosed and shielded because of the radioactive content.
Typically operations undertaken involve a chemical process to extract the product nuclide from the cyclotron target or other source followed by conditioning and purification. The product is diluted to the required concentration and dispensed into small vials of the order of 10 mls in volume which are packaged for sale.
Decommissioning operations are also being carried out on the site principally to deal with historic liabilities which were inherited at the time of privatisation in 1982. In addition decommissioning of redundant plant is required as products change and the site is developed.
In carrying out our assessment we were looking at a particular point in time with some plant PSR's having been completed and others still needing to be done in accordance with the licensee's rolling programme. The 'Site' PSR produced by the licensee reflects this point in time and describes the PSR programme and principal findings to date. It also addresses site wide topics and interactions between plants. The NII assessment primarily concentrated on the 'Site' PSR but a sample of individual plant PSRs covering both older and newer plant housing higher hazard operations was also considered.
A summary of our assessments are given under the headings below.
The licensee's review process involves a review team drawn from the manufacturing, engineering and safety groups engaging in detailed inspection and analyses of plants and their associated safety cases. The reviews consider, in particular, temporal aspects such as changes in safety criteria, assessment methodology, plant and safety technologies, manufacturing programmes and the potential for plant deterioration due to physical ageing. The review information is collated into a report and after peer review the report is presented to the Site Nuclear Safety Committee. Any recommendations arising from the report are put forward in an action plan and this is monitored by safety groups and the Site Nuclear Safety Committee.
We have reviewed the licensee's PSR process and we are satisfied that it considers the key safety areas but we consider that the documentation describing the process requires further development so that all aspects of the review process are transparent. We have required the licensee to develop better documentation and this will be undertaken as part of the it's ongoing review of site safety documentation.
The licensee first set up a programme of rolling plant reviews in 1990 and by 1996 a review of all facilities and services significantly affecting safety had been completed. A second round of reviews was started in 1996 and this is planned to be completed by 2003. The licensee's programme to date has raised several hundred principal recommendations. Examples of these are the requirement to refurbish the thallium plant in the cyclotron operations building and the need to ensure that mechanical and electrical services and the liquid effluent systems in cyclotron products building are replaced to a specified programme. A small number of the recommendations are outstanding and the majority are scheduled to be completed by the end of the year. Those not scheduled to be completed until later are being programmed into plant refurbishment and decommissioning operations. We will continue to monitor the licensees progress in bringing the small number of outstanding recommendations to a satisfactory conclusion.
The future rolling programme of PSRs has been discussed and we have required the licensee to submit a detailed programme to us. We have also required the licensee to have the programme reviewed annually by the Site Nuclear Safety Committee. Overall we are satisfied that all plants over 10 years old significantly affecting safety have been subject to periodic review and that the licensee's forward programme will ensure that all of the relevant plant safety cases will be addressed over a 10 year period.
Radioactive wastes from the Grove Centre site are handled in different ways according to the type and level of radioactivity involved. Solid non-combustible waste with low levels of radioactivity is temporarily stored on site prior to eventual disposal to the British Nuclear Fuels plc site at Drigg in Cumbria. Solid combustible low level waste can be incinerated at approved facilities. Liquid wastes are either incinerated or discharged through an authorised route. Solid waste with intermediate levels of radioactivity is stored on site.
The licensee has developed a Radioactive Waste Strategy for dealing with wastes. We have examined the waste management strategy documentation and have concluded that it provides an adequate framework for dealing with waste generated on the site. The nature of the licensee's business is such that much of the intermediate level solid radioactive waste is made up of short half life isotopes (less than 3 years) and where practicable this material is segregated and then allowed to decay to levels where it can be freely released or disposed of as low level waste. We note that there are only relatively small amounts of solid intermediate level radioactive waste needing to be stored and this is contained in high technical specification packages consistent with the requirements of NII guidance on the management of radioactive materials and radioactive wastes on nuclear licensed sites (Reference 2). A new waste storage facility was built in 1997 and this should provide sufficient capacity for operational or decommissioning generated waste if storage continues for the next 40 years provided that management standards are maintained.
The licensee has updated and modernised facilities for the temporary storage of solid waste with low levels of activity and the site effluent system for dealing with the discharge of liquid wastes has undergone a major refurbishment over the last ten years.
The licensee has a policy of minimising waste arisings at source and we will continue to monitor this aspect of waste management.
We are satisfied that the licensee has considered ageing effects on the site waste facilities and that time related effects should not render the facilities unsafe before the next round of periodic reviews. Overall we are confident that the licensee is seeking to maintain a satisfactory waste management strategy.
Radioactive materials have been used on the licensee's site since the 1940's and a number of liabilities pre-date privatisation in 1982. These historic liabilities are either being decommissioned or are under a care and maintenance regime awaiting decommissioning. In addition to the historic liabilities decommissioning is required as a result of the site being developed and businesses being transferred off the site.
Following the Department of the Environment's White Paper, Radioactive Waste Management Policy, Cmnd 2919 (Reference 3) the licensee put together a Decommissioning Strategy for dealing with its decommissioning liabilities on the site. It has a rolling 5 year decommissioning programme which is executed by a combination of in house and external expertise.
Cmnd 2919 requires the HSE in consultation with the Environment Agency to carry out Quinquennial Reviews of nuclear site licensee's decommissioning strategies. The first review of the licensee's Decommissioning Strategy has just been completed. From our review we are satisfied that overall decommissioning activities have progressed over the last few years and there is now in place a process for the continuous reduction of such liabilities. A number of relatively minor points have been taken up with the licensee and these are currently being addressed.
The licensee has carefully integrated its waste and decommissioning strategies such that storage capacity for decommissioning wastes that may arise over the next 40 years of operation will be available.
Overall we are confident that the licensee has a satisfactory decommissioning strategy and we shall continue to regulate its implementation.
(i) General
Annual statutory dose limits for exposure to ionising radiation arising from sources other than medical and natural background are set at levels which ensure that the risk of harm to any person receiving such doses is low. The current annual statutory dose limit for classified workers is 20 mSv and that for the public is set 20 times lower at 1 mSv. For comparison, the average dose received in a year from radiation of natural origin in the UK is 2.2 mSv (Reference 4), though in some parts of the country it can exceed 5 mSv. There is a further statutory duty on employees to restrict the exposure of workers and other persons to ionising radiation, so far as is reasonably practicable. Advisory bodies such as the International Commission on Radiological Protection (ICRP), and the National Radiological Protection Board (NRPB), monitor and research national and international information on radiation on a continuing basis, and issue advice about keeping doses as low as reasonably achievable. They also issue updated recommendations on maximum doses from time to time, as additional or new information comes to light.
The most recent relevant recommendations of the ICRP were published in 1990 (Reference 5). The NRPB gave its advice on the application of the ICRP's recommendations to the UK (Reference 6). These effectively recommend a reduction of the then current annual dose limit for classified workers from 50 mSv to 20 mSv, and that for members of the public, from 5 mSv to 1 mSv. These recommendations were incorporated into NII's Safety Assessment Principles (Reference 1). The revised Euratom Basic Safety Standards Directive incorporating the new limits was adopted in May 1996, with a lead in period for their implementation. HSE revised the Ionising Radiation Regulations 1985 to bring the Directive into effect in January 2000. The new Ionising Radiation Regulations, 1999 specify the statutory dose limits that have legal force in the UK.
(ii) Doses to on-site workers
Individual radiation dose rates to classified workers at the Grove Centre continue to be controlled to levels averaging around 1 mSv per year. This is well below the current statutory limit and the level for statutory investigation. A small group of workers on the site who are involved with the operation of the cyclotrons receive doses that are higher than the average for the site. This group receives doses that typically average around 5 to 8 mSv per year. We are satisfied that the licensee adequately monitors and reviews the maintenance work that gives rise to these doses to ensure that they are as low as is reasonably practicable.
A number of operations at the site result in some operators receiving skin doses to the extremities, principally the hands. The average extremity dose to those workers carrying out such operations is 22 mSv per year which is also well below the statutory dose limit of 500 mSv. We have required the licensee to review it's working practices involving the direct handling of radioactive materials so as to restrict skin doses to being as low as is reasonably practicable.
(iii) Doses to the public
In order to assess the exposure of members of the public to direct radiation from the site, the licensee monitors radiation levels at the perimeter of the site. The licensee has achieved significant reductions in perimeter fence dose over the past few years by the relocation of low and intermediate level waste and improvements to shielding on the site. The licensee's radiological assessment has determined that the annual dose to the critical group from direct radiation from the site does not exceed one quarter of the statutory limit of 1 mSv. The Amersham site is included in the NII's five year rolling programme (Reference 7) to check independently the dose rates, and the associated exposure of members of the public reported by licensees. To date, the results from our independent checks in the vicinity of the site are in broad agreement with the licensee's results. We have examined the licensee's arrangements for determining the dose to members of the public and consider them to be acceptable.
Under the terms of the site discharge authorisation, the licensee measures liquid and gaseous discharges and monitors the environment in the vicinity of the site on a regular basis. The Environment Agency checks the results of the monitoring programme. The monitoring programme confirms that the radiation exposure of members of the general public arising from authorised discharges of gaseous and liquid radioactive waste remains low.
The manufacturing facilities on the site are not particularly complex and generally consist of fume cupboards, gloveboxes and heavily shielded boxes with remote manipulators. The principal safety functions that these facilities provide are containment of relatively small amounts of radioactive materials and shielding to the workers from these materials. An integral part of the containment system on many plants is the ventilation system which is used to maintain multiple containment barriers, remove radioactive gases and particulate matter. We have discussed the standards for ventilation and containment system design and we are satisfied that the licensee has in place satisfactory procedures and standards for specifying the appropriate containment for a particular manufacturing facility.
Individual plant PSR's have highlighted areas for improvement to plant ventilation systems and the licensee has carried out significant upgrades to a number of plant ventilation systems across the site over the past 5 years. On the basis of NII specialist inspection and document review we are satisfied that the licensee is following modern practice with regard to the standard of physical containment and the enhancement of the containment by appropriate ventilation systems.
The site electrical supplies are important principally for the continued ventilation and containment of plant but also for safety related systems such as radiation monitoring and the provision of lighting. The main electrical supplies are backed up by a site standby diesel generator system. The licensee has carried out significant upgrades to the site electrical distribution system and we are satisfied that it meets modern standards.
The licensee has considered the unlikely scenario where all electrical supplies to the site are lost and it has concluded that there are no safety critical systems which would be affected and the site would remain safe until supplies were restored.
The licensee has considered the potential impact on the public of the worst credible accident that could occur in any plant or building, namely a major fire. From this consideration it has devised an index of the dose to the public from inhalation and direct radiation as a result of a release of radioactive material following a fire which involves the maximum inventory in a given building. The licensee has set as a target for all buildings on the site an index level such that the dose to the public would be below the lower Emergency Reference Level of dose for the introduction of countermeasures to protect the public as recommended by the National Radiological Protection Board. To achieve this it uses the following methods: limitation on the activity holding in a building, the provision of multiple fire barriers using compartmentation and the use of fire proof containment where necessary. To restrict the activity holdings in particular plant the licensee imposes a system where each plant is licensed to hold a particular inventory. Where changes to plant in a building are necessary or new plant is introduced to a building the index is reviewed to ensure that the activity holding is below the licensed value. NII is satisfied that the licensee has in place a robust system for minimising the potential impact on the public from its site operations and this will be kept under scrutiny.
The licensee has in place arrangements for dealing with all aspects of the effective control of radiological emergencies. The adequacy of the emergency arrangements is demonstrated in an annual emergency exercise which involves Amersham personnel and outside emergency services such as the local fire brigade. The licensee's performance of the annual exercise is monitored by the NII.
As part of the PSR process the licensee identifies those facilities that require refurbishing or replacing over the next review period due to physical degradation. In addition plant wear-out is identified by routine maintenance. The licensee has recently started to review its engineering maintenance arrangements with a view to improving the linking of safety critical plant and equipment identified in a safety case to the plant maintenance schedule. We will continue to monitor the licensee's progress in this area.
The type and amounts of radioactive materials handled are such that plant ageing caused by radiation damage is negligible in the majority of the facilities. Plant components and systems that are susceptible to radiation damage are easily replaced because of the relative simplicity of the plant involved.
We are satisfied that the licensee has in place systems for monitoring the process of plant ageing and wear out.
The 'Site' PSR has provided an overview of the rolling programme of plant PSRs undertaken so far and has summarised the outcomes from individual PSRs.
From this we conclude that the licensee has carried out a satisfactory rolling programme of PSRs to date to review individual plants on the site. The follow up work arising from these PSRs will re-enforce the individual plant safety cases for longer term operation. We are also satisfied that the licensee has considered site wide issues which may affect safety on the site.
We have discussed the future programme of PSRs with the licensee and we are satisfied that all relevant safety cases, including the site wide PSR will continue to be reviewed within a 10 year period.
Finally NII expect the site to be able to continue to operate safely until the next site wide PSR is required. Our conclusion of course is subject to the continuing satisfactory results from the ongoing programme of plant PSRs, inspections and justifications of safe operation which are required under the current licensing arrangements.
1. Safety Assessment Principles for Nuclear Plants, HSE Books 1992 ISBN 011882043 5.
2. Guidance for Inspectors on the Management of Radioactive Materials and Radioactive Waste on Nuclear Licensed Sites, HSE Web Site, Issued 13 March 2001.
3. Review of Radioactive Waste Management Policy - Final Conclusions, UK Government Cm2919, HMSO 1995.
4. Radiation exposure of the UK population - 1993 Review, NRPB report R263, HMSO ISBN 0 85 951364 5.
5. 1990 Recommendations of the International Commission on Radiological Protection, ICRP publication 60. ISBN 008 0411444.
6. NRPB report 'Board statement on the 1990 recommendations on the ICRP' Documents of the NRPB Vol. 4 No 1 (1993) ISBN 0 85 9513602.
7. The NII programme of checking monitoring of direct radiation doses to members of the public from nuclear sites. Bacon, M L & McCullough, E A in Portsmouth 1994. Proceedings of 17 th IRPA. Regional Congress pp 81-84, June 1994, ISBN 1 87096532.9 6-10.
Published on the HSE web site 13 August 2002