Getting back on track28 May 1999
Restarting transports of spent fuel from Germany to the United Kingdom. BNFL Transport provides an industry perspective.
[Since the issue of contamination on transport assets came to light in May 1998, and the subsequent suspension of transports of nuclear fuel from Germany to the UK and France, the nuclear industry has undergone a fundamental review. This has been further compounded by a change in the political landscape in Germany with the election of a Socialist / Green government in September 1998.
There has been considerable debate on how the industry should be structured in recent months, culminating in the recent demonstration in Bonn by industry workers supporting the industry’s future. At the time of writing this article, the outcome of the current consensus discussions in Germany is as yet unclear, but the nuclear transport industry has been making significant progress towards restarting transports from a technical and logistical perspective and in terms of demonstrating robust and efficient systems which will reassure both the politicians and the general public. This article examines some of the key history surrounding the transport industry and presents the solutions of British Nuclear Fuels plc (BNFL) to the issues which need to be solved prior to transports restarting.
In essence, BNFL has co-operated with the independent third party experts who have reviewed technical, organisational and reporting systems. BNFL along with its customers, has reviewed the recommendations of the experts and is adjusting its systems to comply with the advice given in order to restore public and political confidence in the transport activities undertaken.
On 6 May 1998, an article appeared in a French daily newspaper, Liberation, claiming that radiological measurements performed on flasks and rail wagons being transported from Gravelines NPS to the La Hague reprocessing facility had shown that higher levels of contamination than were permitted by international regulation had been found. One day later, reacting to this report, SNCF, the French national railway service, called for a suspension of movements of nuclear materials through France as a precautionary measure to safeguard its employees. An immediate inquiry into the issue was launched by the French government. Information was demanded by the French competent authorities (Direction de la Surete Des Installations Nucleaires, DSIN), and Cogema, Transnucléaire and EDF began the task of collating information relating to radiological measurements on flasks transporting spent fuel in Europe.
DSIN’s official report into the matter was published on 13 May 1998, criticising procedures for handling flasks at nuclear power stations and the failure of the French state to control the nuclear industry. On 22 May 1998 this report was passed on to the German authorities (BMU) as it also contained data pertaining to transports from Germany to France. Cogema, along with BNFL, the two reprocessors, and the German utilities were immediately requested by BMU to pass all information pertaining to transports between Germany and the reprocessing plants. As a precautionary measure, until the issue had been resolved, BMU Minister Dr Angela Merkel requested the German utilities to instigate a voluntary suspension of transports of spent fuel until further notice. The utilities complied with this request and transports of spent fuel were suspended and remain so today.
Merkel’s 10 point plan
Following briefings by relevant experts, Dr Merkel’s department in BMU issued a 10 point plan to which the industry needed to adhere before transports could be restarted. The key areas ot the 10 point plan focused on the following:
• BMU contracted Gesellschaft für Anlagen und Reaktorsicherheit (GRS) to provide an expert analysis of the reasons why the contamination had occurred and how it could be avoided in the future.
• Coherent international systems for reporting of all instances of contamination needed to be established.
• Organisational structures within the German nuclear industry needed to be clarified and simplified to ensure greater transparency in the transport organisation and information chain to the public and government.
• Introduction of technical solutions to avoid future possible contamination.
• Publication of all relevant transport monitoring documents to ensure full public access to transport related documentation.
In order to clarify BNFL’s position and to restate BNFL’s excellent record of safe and compliant transports, BNFL, officials from the UK government, and officials from the BMU met in Bonn in early July 1998. At the meeting BNFL presented its views of why contamination occurred on flasks, and indicated also the experience that BNFL has in avoiding contamination on its flasks and rail wagons. BNFL maintained that the low instances and low values of contamination found on BNFL flasks (there have been no instances of contamination on rail wagons transporting spent fuel from Germany) were entirely due to the phenomenon of ‘sweating out’ or ‘weeping’, a phenomenon that is accepted internationally within the IAEA regulations.
GRS Expert Report and Oko-Institut Critique
The GRS Expert Report was published on 11 September 1998 and clearly indicates that BNFL’s system for handling, preparing and unloading flasks within the Receipt and Storage Building at BNFL Sellafield is a robust and effective system which fully complies with all national and international regulations. Nevertheless as a responsible and quality conscious operator, BNFL recognises the need to constantly strive for improvements in its systems to maintain an edge as one of the world’s leading players in nuclear transport.
At the end of September 1998, however, the German elections returned a new Government, a so-called ‘Red-Green Coalition’. The new Environment Minister was named as Jürgen Trittin. The lower Saxony Environmental Ministry commissioned a leading environmental institute, the Oko-Institut, to critique the GRS Report, and to recommend measures that would need to be met before transports of nuclear materials could be restarted.
The Oko-Institut presented its report in early January 1999, laying down precise measures that need to be satisfied before transports of nuclear materials can be restarted. Its 59 points are an amalgamation of Oko-Institut, TÜV and GRS recommendations on which the nuclear transport industry is basing its proposals for restart of transports.
BNFL’s experience in transporting fuel from Germany
Both the GRS Report and the Oko-Institut report have praised BNFL’s systems as being robust and the following is the reason why. On BNFL transports from Sellafield to Germany, only 3% of flasks were found to be contaminated above the derived working limit of 4 Bq/cm2 (mostly around the 20 Bq/cm2 level) and no rail wagons were contaminated in Germany. On transports from the customer to BNFL, only 1% of flasks had been contaminated. This represents one flask in three years. Again, no contamination was found on any of the rail wagons used by BNFL.
It should be noted, however, that the report of the four Competent Authorities, published on 24 October 1998, concluded that “various independent assessments within the four countries have come to the conclusion that, as far as health effects are concerned, the non-compliance with the 4 Bq/cm2 guidance level did not have any radiological consequence”.
Once contamination had been detected on the flask, however, at intermodal transfer points, BNFL cleaned the flask, as is required by international guidelines, to under the regulatory limits and only then were transports allowed to continue.
All flasks operated by BNFL benefit from an excellent record of reliability which is mainly due to the transport system operated by BNFL. The key points of the system are the following:
• For spent fuel transports, BNFL’s policy is to use Multi-Element Bottles (MEB). The MEB is a sealed inner container within the flask which carries fuel. The main reason for using the MEB system is that it provides a means of clean storage of fuel at the Sellafield reprocessing plant. For transport purposes, however, the MEB has the advantage of reducing the opportunity for reactor coolant sediment (so called ‘crud’) which can adhere to the surface of fuel elements to be transported, becoming detached and lodged in the flask cavity. The presence of crud inside a flask can lead to higher levels of internal contamination of the flask body, causing so-called hot spots, a phenomenon which does not affect BNFL type flasks.
An additional benefit is that a new MEB is completely clean on insertion into the reactor pond and therefore it minimises the amount of crud in the vicinity of the flask during flask loading operations.
•The design of the flask surface also plays a major role in the decontaminability of a particular flask. The flat non-porous surface will decontaminate readily. BNFL flasks are designed to optimise access to the outer surface area of the flask for cleaning purposes.
• All external surfaces of BNFL flasks are coated with a paint which was specifically formulated on the basis of extensive research and development to minimise the potential for contamination sweating out from the surface. The paint system is used on all flasks used by BNFL to transport fuel from German reactors to BNFL Sellafield.
In addition, the following operator practices in handling the BNFL flasks also led to a low level of contamination being found on BNFL flasks:
• Minimising flask immersion time in the reactor pond.
• Use of metallic or plastic skirts covering the greater part of the flask surface whilst in the pond and flushing with clean water under positive pressure.
• Avoidance of blind bolt holes in flanges/ drainable and flushable bolt holes wherever possible. Blanking/masking of unavoidable blind bolt holes during pond immersions.
• Careful selection of decontamination fluids and avoidance of harsh solvents which can render surfaces more liable to subsequent contamination.
• Minimising flask transit time.
Continuous Improvement of BNFL systems
BNFL, as a quality conscious operator, does however, recognise the need to strive for constant improvement of systems, and to this end has carried out reviews of operations at the Sellafield Reprocessing Plant and the German nuclear power plants. The following are the new procedures being adopted to minimise the future potential for activity levels being found in excess of the derived limits.
In order to optimise the cleanliness of the Inlet Pond Area of the BNFL Receipt and Storage Plant, the pond water purging system has been modified, increasing the flow volume of clean water through the inlet pond, giving BNFL the capability to purge the entire volume of the inlet pond in approximately 24 hours, more than five times quicker than the current configuration. This new system will ensure that each flask is effectively handled and unloaded in a more controlled water environment, reducing significantly the possibility of contamination ingressing into the flask surface.
A recommendation of the GRS Expert Report and the Oko-Institut was that contact between the flask surface and the reactor pond water was to be minimised in order to reduce to as great an extent as possible the opportunity of contamination absorbing into the flask surface and sweating out during transport. For transports to BNFL, German nuclear power plants have agreed that a physical barrier between the flask and the pond water will be used to ensure that the contaminated pond water does not touch the flask. The barrier will be provided by a combination of contaminated skirts over the fin areas of the flask and other barriers on exposed surfaces (eg tape, strippable paint, film etc). This is a system that BNFL has used highly successfully on transports of LWR spent fuel from Japan, where no instances of contamination have been found on BNFL flasks.
As a response to the suspension of transports in Germany, a number of Utility Working Groups were set up to examine current monitoring practices and to propose modifications for future transports to ensure that contamination can and will be detected when present.
It is important to note that the GRS Technical Report indicated no major shortcomings in the BNFL system for monitoring transports and that indeed our systems are fully in line with national and international regulations and guidelines.
BNFL does however recognise the benefits of standardising its measuring techniques in order to provide further reassurances of the robustness and effectiveness of BNFL’s systems. The following indicates exactly BNFL’s future procedures regarding monitoring of transport flasks and rail wagons.
BNFL uses a variety of known monitoring techniques to ensure that flasks and rail wagons are, as far as possible, free from any contamination. These techniques include the following:
Direct Probe Contamination Readings
Direct probe readings are taken on empty flasks and rail wagons which give an indication of the total activity present on the surface of the flask, both fixed and non-fixed. If high levels of contamination are found using this method, swab readings can be taken directly on the contaminated area of the flask or rail wagon. Measurements of this kind allow the entire surface area to be monitored, including the fin area of the flask, allowing a high degree of confidence that there are no ‘hot spots’ present.
Scalar Swab Monitoring
Monitoring of non-fixed contamination on the surface of the flask and rail wagon is carried out by using ‘swabs’ (wipe tests) in full accordance with IAEA Regulations. The swab used is a small filter paper of 50 mm diameter which is wiped over an area of 300 cm2. A pick-up factor of 10% (an internationally recognised standard) is used in calculating non-fixed activity present on the surface of the flask or rail wagon that has been transferred to the swab.
This method has recently been introduced by BNFL to monitor a large area of the flask and rail wagon for non-fixed contamination. By this process the flask is wiped with a large surface ‘screening wipe’ and the amount of activity picked up is measured. This technique provides a qualitative indication of the level of activity present on the flask and wagon.
To provide further reassurance, third party witnessing of monitoring activities carried out at Sellafield will be introduced for the initial transports.
Information and Reporting Systems - Competent Authority Consensus
In response to the Merkel 10 point plan, the Competent Authorities of the United Kingdom, Germany, France and Switzerland have been holding regular meetings to determine a Europe wide reporting structure for any possible future contamination of transport assets. The final report, dated 24 October 1998, has been issued by the Competent Authorities noting guidelines to which all transporters must adhere.
The main principles outlined in the report of the Competent Authorities are:
•There were no public health hazards caused due to the non-compliance with the 4 Bq/cm2 guidance level.
•Additional protective measures to protect the flask and transport equipment during loading need to be considered.
•UK domestic transport records were good.
•Reporting systems should be improved to ensure prompt information exchange between the relevant parties involved in spent fuel transports, especially in the case of non-conformities. The reporting system should be implemented between industry, regulator and authorities.
An international database of spent fuel flask movements will be established, maintained, updated and published annually. Regulators will be responsible for collecting the information. This database will serve as a basis for future co-operation and exchange of experience and will be available for public consumption.
•A working group of regulators has been established to assess new measurement procedures proposed by the operators in the long term.
•For the medium and long term, transport flask designers and manufacturers must propose possible improvements of flasks and handling.
•Development of systems to encompass the above recommendations is ongoing.
n Development of New Organisational Systems
A key feature of the Merkel 10 point plan and subsequent critiques was the development of new organisational systems to enable transport of nuclear materials within Germany.
Future developments of the system will focus on the responsibility of the German nuclear power plant, which will be fully responsible for loaded package consignment according to atomic law. A new transport Company will take over the role as Consignor under traffic law. This will flatten the organisational structures within the industry and simplify communication between relevant parties and regulators.
BNFL, as a world leader in transportation of spent nuclear materials, has consistently developed packages in order to, as an absolute minimum, comply with the relevant stringent requirements that apply to the transport of nuclear materials. This approach has resulted in the existing robust and efficient system which has complemented BNFL’s regulatory compliant global business which “did not have any radiological consequence”. In fact outside of continental Europe, BNFL is continuing its global transport activities to the total satisfaction of regulators, politicians, and the general public.
Moreover as a result of events during the last year within continental Europe, BNFL has undertaken a fundamental review of its activities and modified them in conjunction with customers, in order to further improve public and political confidence and acceptance, a necessary prerequisite prior to transports restarting in the near future.