Transporting plutonium by air

Standards governing the integrity of packages used to convey plutonium were first established nearly 50 years ago. They were based on the safety requirements to protect the public from nuclear radiation and maintain a sub-critical condition. This required the packaging to be a containment system (see panel). There was an exception for small quantities, though in this case it was necessary to demonstrate that any release did not pose a significant safety hazard. The International Atomic Energy Agency (IAEA) has played a major role in the development of the standards, publishing in 1961 the first edition of the “IAEA Regulations for the Safe Transport of Radioactive Material”.

Recently, the issue of transporting plutonium by air has entered the public arena. Last June, concerns were raised in the UK Parliament when an MP, Denis MacShane, issued a news release calling for a halt to the air transport of plutonium waste to Europe. This was followed over the next six weeks by a series of questions to the government by MPs who began receiving letters from the public on the issue.

EVOLUTION OF THE REGULATORY SITUATION

In June 1975, the US Nuclear Regulatory Commission (NRC), having only recently been set up following the reorganisation of the US Atomic Energy Commission (AEC), announced that it was initiating a review of the rules applying to the transport of all radioactive materials by air. During the same month this was overtaken by political fiat when Congressman Scheuer, who considered the NRC to be insensitive to the risks involved, used the ploy of an amendment to the NRC appropriations bill, to propose restriction of the transport of plutonium by air. Scheuer cited two accidents which led to plutonium contamination – the crash of US bombers carrying nuclear weapons at Thule in Greenland and at Palomares in Spain. The NRC objected to the amendment on the grounds that its own rulemaking process was underway and that it implied an absolute guarantee of safety which was undesirable from both practical and social standpoints. In spite of this the US Congress enacted Public Law 94-79 which placed the following restriction on the NRC:

The Nuclear Regulatory Commission shall not license any shipments by air transport of plutonium in any form, whether exports, imports, or domestic shipments; provided, however, that any plutonium in any form contained in a medical device designed for individual human application is not subject to this restriction. This restriction shall be in force until the Nuclear Regulatory Commission has certified to the Joint Committee on Atomic Energy of the Congress that a safe container has been developed and tested which will not rupture under crash and blast-testing equivalent to the crash and explosion of a high-flying aircraft.

The discussion of this amendment in the House of Representatives lacked the technical detail which can be marshalled in a proper regulatory review. The Energy Research and Development Administration (ERDA, also set up in the restructuring of the AEC), argued that the appropriate way to develop the rules was to give the task to the agencies which had been set up by the US Congress for this purpose, namely the NRC and the Department of Transportation. In spite of this, a similar restriction was placed on ERDA.

It is important to realise that the changes in the US regulations which flowed from the Scheuer amendment were not the product of any new safety information. The NRC had to comply in order to get its overall annual budget authorised. It can also be noted that in respect of the regulatory changes the NRC was not subject to specific economic constraints.

Military weapons were exempt from the provisions of the Scheuer amendment. The nuclear devices involved in the two bomber crashes cited above had almost certainly not been designed as radioactive material transport packages.

In response to Public Law 94-79, the NRC initiated a three-pronged certification programme consisting of:

• Evaluation of the conditions produced in severe aircraft accidents.

• Development of appropriate qualification criteria and acceptance standards.

• Demonstration tests and engineering studies to show that the acceptance criteria had been achieved.

A principal output from the NRC studies was the publication in January 1978 of the Qualification Criteria to certify a package for air transport of plutonium (NUREG-0360). The qualification tests specified, which are given in the table, are severe and conservative in that they are required to be carried out sequentially. They can be viewed as seeking virtually absolute protection, irrespective of the probability of occurrence of an accident. Peer reviews have concluded that packages conforming to these criteria are likely to survive the majority of accidents during take-off, landing or ground operations but it is not possible to guarantee that a package will endure an accident.

The crystallisation of these criteria was closely shadowed by the development of the plutonium transportable package, termed PAT-1 for which a Certificate of Compliance was issued by the NRC in September 1978. A smaller lightweight packaging was then developed for use in the air transport of plutonium for non-proliferation treaty verification work.

The regulations in the USA were tightened further in December 1987 when Senator Murkowski of Alaska piloted an amendment through the US Congress which became Public Law 100-203. It prohibited the passage of plutonium through US airspace unless the NRC certified that the package could withstand both an aircraft crash test and a drop from the aircraft’s maximum cruising altitude.

IMPACT ON INTERNATIONAL CONSENSUS

The passage of the two Public Laws by the US Congress represented a considerable departure for the USA and perturbed the aims of the IAEA which were to achieve international consensus in the radioactive material transport regulations and to set standards which were, as far as possible, independent of the mode of transport. At first, some countries were initially inclined to accept the requirements of NUREG-0360 but others wanted to study the problem by means of in depth discussion through the IAEA.

The disparity between the IAEA regulations and those in force in the USA, allied to a suggestion in a 1986 Report of the UK House of Commons Environment Committee, led the UK Government Advisory Committee on the Safe Transport of Radioactive Material (ACTRAM) to review the subject. ACTRAM reported in 1988, suggesting that the difference between the two sets of regulations should be reconciled by the IAEA with the aim of achieving a consensus. ACTRAM predicted that some tightening of the (IAEA) Regulations might be appropriate some five years later when the Thermal Oxide Reprocessing Plant (Thorp) at Sellafield became operational and the number of relevant export flights from the UK was then expected to increase from 4 to 30 per year. It is worth adding that the expected increase in flights has not occurred.

When the Technical Committee on the Continuous Review of the IAEA Regulations met in June 1987 it pointed to the need for the Standing Advisory Group on the Safe Transport of Radioactive Material (SAGSTRAM) to examine the risk posed by air transport of plutonium. After SAGSTRAM had discussed the matter in November 1987 the scene was set to inaugurate an extensive series of Working Groups, Consultants’ Meetings, Advisory Groups and Technical Committee Meetings (TCMs) to study the subject and ensure internal consistency. These took place over the period 1988 to 1990. A TCM was convened to formulate proposed regulatory changes and draft an IAEA-TECDOC documenting the recommendations. The TCM was involved in sifting through a wealth of detail and this led to some 24 recommendations including designating the Air Qualified Package as Type C, setting exemption levels, defining the velocity at impact onto a hard target as not less than 85 ms-1 and the inclusion of a puncture/tearing test followed in sequence by a fire test.

When IAEA-TECDOC-702 was issued, in April 1993, it was a landmark in that, as indicated in its title – “The air transport of radioactive material in large quantities of with high activity” – the IAEA had prepared text for one specific mode of transport for the first time in its history. The actual drafting of revised regulations was entrusted to a large group of experts, known as the Revision Panel. As part of this process, many of the recommendations in TECDOC-702 were accepted into the first version of the Draft Revision to the Regulations. Of the issues, specific to air transport, which remained, the most important was the definition of the minimum velocity for the impact test on a Type C package. Values between 85 and 129 ms-1 had been proposed. The Third Revision Panel raised the recommended impact test velocity to 90 ms-1. The data available indicated that beyond

90 ms-1 even relatively large increases in impact velocity will cover very few additional real accidents. The Fourth and Final Revision Panel reviewed, inter alia, the data provided by France and the USA on the consequences of impact accidents for plutonium transport by air. It was eventually agreed that both sets of data support an impact velocity of 90 ms-1. The final draft was issued late in 1996 as part of IAEA Safety Standards Series No ST-1, Regulations for the Safe Transport of Radioactive Material 1996 Edition. The secretariats of the relevant international modal organisations, such as the International Maritime Organization, are likely to recommend a common implementation date for the provisions of ST-1 of 1 January 2001.

Other developments

In the UK, as a result of a meeting between the Minister of Transport and Denis MacShane, there has been some discussion regarding the possibility of ensuring that overflights of urban areas are avoided as far possible. The comment has subsequently been made via the UK Civil Aviation Authority (CAA) that British Nuclear Fuels (BNFL) has procedures in place which specify that flights should be made over water as far as possible, avoiding large conurbations. In addition, air traffic services are made aware of what is being carried on the aircraft. The CAA is establishing a liaison with other shippers to ensure that similar procedures apply to flights carrying similar material in the UK. The CAA will also check compliance with the specified procedures as part of its normal enforcement activities.

However, it will be appreciated that if an aeroplane does get into difficulties where it eventually finishes up may be a considerable distance away, possibly even in an urban area. Furthermore, Western Europe has a relatively high population density, averaging about 150 persons per km2 compared with an average of 3 persons per km2 for Canada. Questions have been raised regarding the specification of packaging for the transport of radioactive material by air compared with the specifications for flight data recorders such as the European Organisation for Civil Aviation Equipment Specifications ED-55 of May 1990 and ED-56A of December 1993, both entitled “Minimum Operational Specification for Flight Data Recorder Systems”. Some work had been carried out in this area in 1975. A French study presented to the IAEA Advisory Group Meeting on Modal Issues in the Safe Transport of Radioactive Material which met in Vienna in November 1996 stated that because the acceptance criteria for a flight data recorder are fundamentally different from those for a Type C package they cannot be compared, a conclusion which is now generally accepted.

Data collection

During the development of the 1996 Edition of ST-1, it was recognised that additional data collection and accident analyses building on the existing knowledge of aircraft accidents could be useful in the continuing evolution of the regulations. Early in 1996 the newly constituted IAEA Transport Safety Standards Advisory Committee suggested the establishment of a Coordinated Research Programme (CRP) dealing with issues arising from air transport. The Advisory Group on Modal Issues, referred to above, recommended that the CRP consider research on the frequency and severity of aircraft accidents. The ICAO was invited to participate in this effort and has confirmed the intention to take part.

The information to be collected and analysed will include frequency and severity information related to:

• Impact: aircraft velocity; orientation of aircraft on impact; angle of impact; target hardness; rotation of aircraft on impact etc.

• Fire: duration; temperature, effect of impact velocity on fire characteristics etc.

• Crushing forces from the aircraft structure and other cargo.

• Other relevant environment forces which may be imparted to packages.

It is anticipated that the work under this will span the period 1998 to 2001/2 and that the output will be used in the regulatory development process.

CURRENT IAEA REGULATORY POSITION

Apart from the USA where Congress has, as described earlier, unilaterally imposed special regulations for the transport of plutonium by air, the current IAEA “Regulations for the Safe Transport of Radioactive Material” Safety Series No 6, 1985 Edition (as amended 1990) apply to all modes of transport and serve as the model for national regulations. They are supported by explanatory and advisory material in Safety Series Documents Nos 7, 37 and 80. All the relevant requirements of the IAEA Regulations are included in the “Technical Instructions for the Safe Transport of Dangerous Goods by Air” which are issued biennially by the ICAO1 and are required to be complied with for international air transport.

RESPONSE OF INDUSTRY

Following the issue of NUREG-0360 the industry studied designs for the transport of plutonium by air. As a consequence, one session of the PATRAM ‘89 Conference was devoted to the shipment of plutonium by air. At that time there was the potential to return plutonium from the British and French reprocessing plants to Japan by air, but in the end it was decided to transport it by sea.

The extent of current transport of plutonium by air can be judged from the exchanges in the UK House of Commons, referred to earlier, during which the government minister involved stated that MOX fuel has been transported by BNFL since 1973 and that currently there are some six flights a year to European destinations. The transport packages used on such flights are Type B conforming to the current IAEA Regulations for the Safe Transport of Radioactive Material, Safety Series 6.

With the issue of the revised IAEA regulations in 1996 as Safety Standard ST-1 the industry began to study the two new concepts proposed therein, with a view to having suitable responses available ahead of the implementation date, viz:

• The Type C package.

• The introduction of the ‘low dispersible material’ category (LDM) with such material able to be transported in a Type B package.

The new standard for LDM requires that the material must be demonstrated to meet very stringent criteria for non-dispersibility under accident conditions and to have a low level of external radiation. MOX fuel is a candidate for classification as LDM because, post implementation of ST-1, it would then be able to be transported in a Type B container. Although the performance standards have been established, the methods used to demonstrate compliance are under development.

Thus a group of some of the European organisations (eg BNFL, GRS, Belgonucléaire and Cogema/Transnucléaire) is studying, with some additional funding from the European Union, the possibility of classifying MOX fuel assemblies as an LDM product.

One company is designing a Type C container for transport of MOX fuel assemblies. Preliminary scale models of such a packaging have already been tested and the concept is planned to go forward for licensing but details have not yet been released.

THE OUTLOOK

In the immediate future the main transport of plutonium by air will be in the form of MOX fuel assemblies. Except for the USA, such material can be transported in Type B containers. The current regulations governing air transport of radioactive material are likely to be superseded by 1 January 2001. The expectation of the industry is that MOX fuel assemblies will be licensable as LDM, under the terms of IAEA Safety Standard ST-1, though it should be noted that this will have to be approved by the individual competent authority in each country. If this is the case the MOX assemblies will be transported in Type B containers. Type C containers may be developed as an insurance policy and could have a future for use in the transport of dispersible material such as powders or other material should they not qualify as LDM.

The position of the USA remains anomalous and does not reflect the international consensus but since the NUREG-0360 regulations were imposed by the US Congress this situation can only be changed by annulment of the appropriate laws, which, in the short term, seems unlikely. The US stance is not assisted by requiring differing standards for air shipments between foreign countries overflying US territory and for the import-export or domestic shipment of plutonium. It does underline the problems caused by such unilateral action. When the results of the recently announced IAEA Coordinated Research Programme have been digested there could be an opportunity to resolve the differences between the provisions of ST-1 and NUREG-0360 for air transport of radioactive material.