The radioactive materials roadshow30 November 2001
The 13th PATRAM conference was held in Chicago on 3-7 September, 2001. Nearly 200 papers were presented, with coverage of a further 50 topics in the poster session. By Michael Price
The 13th PATRAM conference was held together with a trade exhibition in the Chicago Hilton and Towers, Chicago from 3 to 7 September 2001. The conference was sponsored by the US Department of Energy (DoE) and hosted by the Institute of Nuclear Materials Management in cooperation with the International Atomic Energy Agency (IAEA). The significance of the symposium was confirmed by the attendance of about 675 delegates from 23 countries.
The conference ended with a technical visit, about an hour's drive out of Chicago, to the GE Morris Spent Fuel Pool Storage Facility and the Dresden Dry Cask Storage Park close by, which provided the opportunity to compare the benefits and limitations of these methods of spent fuel storage.
In the opening plenary session David Huizenga of the DoE, the General Chairman of the conference, said that the objectives of the meeting were to present the achievements since PATRAM '98 and to exchange information and ideas. The theme of the conference was that safe transport of radioactive material is the 'vital link' in the industry. It had been said at PATRAM '98 that the majority of problems in the USA in clearing up the legacy of the Cold War were at DoE sites where about 5000 surplus facilities had been identified.
Apart from the regulatory challenge, the logistic problems are large. Amongst the achievements he mentioned the clean-up of Rocky Flats in Denver, Colorado. Closure of many of these places is vitally dependent on clean-up and removal of contaminated material for storage and disposal, for example to the Waste Isolation Pilot Plant (WIPP) in New Mexico. At the same time part of the task involves extensive public participation.
WIPP is now open and to date there have been 350 shipments and the total number projected is 19,500. Another example, illustrated in the photograph above, shows a train carrying low level waste commencing the journey from Fernald, Ohio to the Envirocare site in Utah. Transport is also crucial to the return of spent high-enriched nuclear fuel from reactors outside the USA. David Huizenga pointed to the key issues which need to be considered:
• Training and retaining the next generation.
• Continued compliance with the international regulations.
• Ensuring that regulatory changes are risk-based and not overly conservative.
Analysis of the subjects covered by the papers shows that the main topics discussed were regulatory issues, risk assessment, spent fuel packaging, thermal and mechanical behaviour, transport management and operational experience. The aim here is to give the flavour of the meeting but a survey such as this cannot fully cover the 200 or so papers presented, particularly in advance of their publication and given the fact that up to four papers at a time were presented in parallel sessions.
Regulations and regulatory changes
It was an opportune time to review the position on the IAEA's Radioactive Material Transport Regulations which the IAEA is charged with issuing and maintaining. Regulatory changes are also being made to the United Nations Orange Book and by the modal organisations. The latest version of the IAEA Regulations was published in 1996 as Safety Standards Series ST-1 and updated with minor editorial corrections as TS-R-1 (ST-1 revised) in 2000. TS-R-1 was due to come into force in July 2001 but the supporting documents - the Advisory Material, designated as TS-G-1.1 and the Emergency Procedures, TS-G-1.2 - had not been officially published in time to meet the July 2001 deadline. These documents were also not available by the opening date of the PATRAM 2001 conference.
In December 1996 the United Nations Economic and Social Council's Committee of Experts on the Transport of Dangerous Goods adopted a new structure for its 'Recommendations on the Transport of Dangerous Goods'. Subsequently the modal organisations covering transport by air, water, road and rail changed the structure of their regulations to bring them into line with the 11th revised edition of the United Nations Orange Book (1999).
For the last five years the policy of the IAEA advisory body, known as the Transport Safety Standards Committee (TRANSSC), has been to modify the review/revision process timescale to align it with the practice of other international organisations. The consequence is that what has previously been a ten-year process will become a two-year cycle from 2003. Because it took ten years to produce ST-1 (later TS-R-1) there was concern from Lorne Green, Secretary General of the World Nuclear Transport Institute (WNTI), and Felix Kellar of the Nuclear Energy Institute (NEI) that the change to the two-year rhythm might prove difficult. In addition a policy of more frequent revisions would require significant additional effort and the change might not allow sufficient time for discussion and worldwide implementation. It was evident that WNTI and NEI were underlining their industrial 'muscle'.
Pierre Malesys of Transnucléaire drew attention to the trend that the number of countries where the idea of 'unilateral approval' - where approval is only required from the country of origin - is steadily decreasing. This tendency obviously undermines the concept of unilateral approval and will inevitably lead to delays and difficulties in international transport of radioactive material. A paper by Jean-Yves Reculeau and Christel Fasten described the steps involved in elaborating the modal regulations from TS-R-1 via the Orange Book, as shown diagrammatically in the Figure on page 31. Alignment with the IAEA Regulations is not yet complete and some deviations are to be expected because the modal regulations follow the UN format and do not include all of the IAEA's recommendations.
TRANSSC has been overseeing the next revision of the IAEA Radioactive Material Transport Regulations which are due to be published in 2003 leading to these recommendations being incorporated into the 2005 edition of the modal authorities regulatory documents. Possible changes are categorised as Major Changes, Minor Changes and Changes of Detail. Gerry Dicke of the IAEA gave a status report and provided insight into the revision process. He outlined the 12 Major Changes that are going forward to the March 2002 meeting of TRANSSC. Probably those changes that amend the rules for grandfathering of packages and introduce the new training requirements are the most significant for the industry.
New requirement for a RPP
One of the explicit new requirements in TS-R-1 is for a Radiation Protection Programme (RPP) whose task is to provide adequate radiation protection under routine and accident conditions for the workers involved as well as the public. Christel Fasten reported on an EC research project involving GRS, Germany, IPSN, France and NRPB, UK which served as the basis for recommendations on how the RPP requirements are implemented.
New training requirements
A serious gas tank truck explosion took place at a camp site in Spain in 1978, killing over 200 people. It involved a driver who was both untrained and also unaware of the danger of his cargo. This triggered moves to improve safety in the transport of dangerous goods and led to training being specified for drivers. It was then realised that the persons responsible for shipments were also in need of training. Accordingly a directive for the 15 countries of the European Union was issued in 1996 covering the designation and qualifications of Dangerous Goods Safety Officers for road, rail and marine transport of dangerous goods. The success of this initiative at the European level has led to a planned extension of this type of safety officer to the 36 ADR contracting countries. Papers by Odile Kummel and Klaus Ridder gave an overview of the current situation on safety advisors where harmonisation with the Orange Book and the IAEA recommendations is proceeding. One of the proposed 12 Major Changes being put to TRANSSC deals with training, a subject which had not previously been adequately covered in the IAEA Regulations.
Type C packagings
The implementation of TS-R-1 requires that material in a dispersible form, such as plutonium, if transported by air must be in a new packaging which is intended to survive an aircraft accident. This involves a demonstration that the packaging designated Type C will survive impact with a test target at a velocity of at least 90ms-1. Michael Krzaniak of MDS Nordion described the practical problems in designing and transporting high activity Co-60 sources by air in Type C packagings. Gerry Holden of Gravatom Engineering Systems and Jim Pierce of Sandia National Laboratories described the design, development and testing of packages which are capable of complying with the stringent requirements in TS-R-1 for Type C packagings. However, Sebastian Claverie-Forgues of CEA-IPSN suggested that the regulations for Type C packagings containing fissile material need further examination regarding assumed worst-case geometrical configurations.
Uranium hexafluoride packagings
Ben Dekker of Urenco described how an industry working group, formed by the WNTI, had been studying compliance with the test criteria for non-fissile uranium hexafluoride laid down in TS-R-1, the key feature being the valve. During this investigation a new valve protection device was developed for 48-inch cylinders. The 1996 revision of the Transport Regulations contains a new provision that packagings for natural and depleted uranium hexafluoride must survive an 800oC 30-minute fire test without breach of the containment. Tests and analyses over nearly 30 years had failed to resolve the argument with respect to rupture or non-rupture under the fire test conditions. Elisabeth Darrough of the US Enrichment Corporation reported on a risk-informed analysis based on the annual amount of UF6 shipped, the frequency of cylinder rupture, the transport modes and the likelihood of the fire environment occurring. The conclusion was that the 48-inch cylinders containing either depleted or natural UF6 can be safely transported without specific thermal protection.
One widely applicable way of reducing the cost of spent fuel management is to take advantage of burnup credit (BUC), and its role in transport continues to develop. The benefit results from the use of higher enrichments in existing flasks or increasing the carrying capacity of new flasks. It leads to a reduction in the number of flasks required and/or the number of shipments. The session devoted to this subject had five papers presented, coming from the IAEA, Framatome, ORNL, JAERI and JNC. The IAEA has an ongoing programme on BUC which began in 1997 with an Advisory Group Meeting (AGM) to monitor the implementation of BUC in spent fuel management. The proceedings of that AGM were published in 1998 as IAEA-TECDOC-1013.
In July 2000 a Technical Committee Meeting (TCM) was convened to survey progress. Peter Dyck of the IAEA gave an overview of that TCM, the results of which have been published in IAEA-TECDOC-1241. He included a summary showing the countries where BUC is currently approved, under consideration or development. One outcome has been the recognition of the need for a further TCM on requirements, practices and developments. This is planned to take place in April 2002 in Madrid with 30 countries/organisations invited.
As computing capability has grown and improved data has been collected there has been a large growth in assessment studies and re-evaluation of earlier work. The US Nuclear Regulatory Commission (NRC) asked Sandia National Laboratories to re-examine the risks associated with the transport of spent fuel by road and rail. This extensive study which used the RADTRAN5 risk assessment code has been reported in NUREG/CR-6672. It was, justifiably, the subject of a complete session at the conference, involving the presentation of five papers. The results indicate that the accident risks are 103-104 times smaller than the estimate published in NUREG-0170, the NRC environmental impact statement for the transport of radioactive material.
A further whole session was devoted to five papers which described the development and use of the INTERTRAN2 Transport Risk Assessment suite of computer codes. Ann-Margret Ericsson, who is at the centre of this work, described how INTERTRAN2 was originally developed under an IAEA-coordinated research programme on Probabilistic Safety Techniques Related to the Transport of Radioactive Material. The aim was to enable IAEA Member States to perform transport risk assessments using the DOS operating system on PCs. It has now been upgraded for use with Windows 95/98/2000 and Windows NT in a new version of INTERTRAN2 which was released in 2000.
Spent fuel packagings
Three sessions of the conference were devoted to papers describing flasks for the transport and/or storage of spent fuel from organisations such as Mitsubishi Heavy Industries, the DoE, Transnucléaire and related companies (including a paper with Kobe Steel) and GNB. There was also a Russian contribution by Vitaly Matveev from RFNC-VNIIEF describing a dual-purpose flask for transport and storage of VVER-1000 spent fuel assemblies. The flask is a replacement for the existing design which fails to meet the latest safety requirements.
Several papers described the application of thermal analysis to assess the behaviour of flasks during hypothetical fire accident conditions. The trend has been to carry out verification and validation. Some papers took the opportunity to compare calculations with new experimental data. An ASTM Task Group is preparing a Standard Practice/Guide which deals with methods of satisfying the regulatory requirements. To provide a useful reference for future risk-based studies, Jorman Koski of Sandia National Laboratories reported on an examination of the likelihood of pipeline or railroad fires affecting transport flasks.
Mechanical analysis and impact tests
A joint BAM/GNB paper presented by Peter Zeisler described how the approach to mechanical testing of flasks, as required by the regulations, had become more sophisticated and not bound by the requirements of the regulations. As an example, knowledge of the stresses and strains during tests is useful in case increased carrying capacity is desired at a later date. Another BAM paper by Thomas Quercetti reported on a range of investigations of oblique (or 'slap-down') impacts. Toshiari Saegusa of CRIEPI and Chi-Fung Tso of Ove Arup separately reported on comparisons of regulatory tests with realistic accident conditions. The results indicated both the significant 'real' margin of safety as well as the ability to model these scenarios.
With some prescience one of the sessions was devoted to five papers which described national and international studies of sabotage issues. A principal aim has been to evaluate the risk in terms of damage to a package and the potential radiological release to the environment. No doubt new studies have been launched post September 11.
Event security scale
Following the Chernobyl reactor accident the IAEA and the Nuclear Energy Agency introduced and developed the International Nuclear Event Scale (INES) but this did not fully cover off-site transport events. Stuart Hughes reported on recent work supported by the European Commission in the UK, Germany and France which aims to develop a practical system in which transport events may be given an appropriate rating consistent with the INES system. The important step is to require an INES evaluation as part of the IAEA Emergency Procedures following an incident. It seeks to forestall a reaction that is out of proportion to the actual situation, and is a necessary part of communicating with the public and the media after an incident. The industry has suffered from a lack of transparency in dealing with the public and the media and it is to be hoped that one of the sponsors of this work, the European Commission, will ensure that the results will not be left to gather dust.
Papers from Cogema and Transnucléaire described the catastrophic events which led to the temporary cessation of all transports of spent fuel assemblies from French nuclear plants to the Cogema reprocessing plant at Cap de la Hague. The storm hit Cogema and other stakeholders in late April and early May 1998 just as the delegates to the last PATRAM conference were assembling in Paris. The problem that caused the furore was long standing. Cogema had complained to plant operators about external contamination for some 20 years. It arose during flask unloading operations at nuclear plants when water-soluble products or insoluble particles could be transferred to the surfaces of flasks and transport vehicles. Spent fuel transports, on arrival at the Cogema plant, had contamination levels frequently above 4Bq.cm-2 for beta/gamma emitters, having started their journeys with 'acceptable' non-fixed contamination levels. A great deal subsequently revolved about the 4Bq.cm-2 limit.
Similar shipments from Germany and Switzerland were also suspended. Florentin Lange of GRS described the results of the analysis of the problem by GRS and the Oeko-Institute and the steps taken to prevent its recurrence. The prime causes of the contamination were identified as the handling procedures. Antoine Vardier of Transnucléaire described the technical conditions and administrative procedures involved in the resumption of transports from Germany to Cap de la Hague.
Bernard Lenail of Cogema in the last paper of the conference argued that a limit such as the allowable non-fixed contamination level needs to have a sound radiological basis. 4Bq.cm-2 was not a safety limit, more a distinction between what is clean and what is not clean. It can noted that one the Major Changes being put to the next TRANSSC meeting is the introduction of a new section in the IAEA Regulations on 'Non-Compliance'. Lenail rounded off his presentation with a summary of the results since mid-1998 (see Figure above). The introduction of strict radiological control measures has clearly overcome the past problems and the phenomena are under control. Some 500,000 smear tests have been performed, of which only 29 were found to be above the 4Bq.cm-2 limit.