Energetic Materials and Munitions: Environmental Aspects and Technology Trends

By Adam S. Cumming

Energetic Materials and Munitions: Environmental Aspects and Technology Trends

Armed forces countries possess and use large quantities of munitions. Civil authorities, such as space agencies, also use quantities of energetic materials. The production, use, and disposal of these materials make a contribution to the overall environmental impact. Handling of munitions with energetic materials requires great care and considerable cost. The environmental impact of the processes must be acceptable to an increasingly critical general population to avoid public concern and be acceptable under environmental laws. Significant funds must be used to clean up and restore areas where military activities have polluted the ground or water. Past practices such as dumping at sea or into landfill sites are no longer generally acceptable. There is a need to know and minimize the environmental impact from munitions so that environmental management can be undertaken properly. Governments have a duty of care to the members of their armed forces, and all reasonable precautions must be exercised to ensure safe use of munitions. For example, some weapons systems can spread over 70% of their energetic material, particularly propellant around the shooting range. This is a health risk with the hazard of fires after prolonged use of the shooting range and there is also a work environment hazard. It is also an environmental hazard since a propellant’s environmental hazard assessment is usually based on the final combustion products and not on the propellant itself.

The design of new weapons should include disposal procedures and an environmental impact statement. The understanding of munitions disposal is still lagging behind this design requirement although progress has been made, as is noted in this volume. However, to better meet the requirement, it is important to fully understand the environmental issues so that they do not place undue constraints on the design of weapons. Such understanding can also reduce the costs. To be able to assess the environmental impact of the munitions, we need the right environmental assessment tools. To minimize the impact of manufacture and manage green munitions, it is important to look at all processes governing these activities.

Legislative Impact

Public pressure has led to the implementation of legislation to manage environmental impact. This has gradually evolved from ad hoc national approaches to systematic regulations such as the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) in the European Union (EU) where the law is limiting and controls the availability and use of materials. While such legislation is of prime importance in the nations where it is directly applied, it has an effect elsewhere since import and export of materials is transnational and those imposing the legislation are usually the largest users and hence the largest market for the materials. For example, the imposition of REACH terms affects the sales of energetic materials, etc. to EU nations from outside the EU. The US Environmental Protection Agency (EPA) and the EU have focused on minimizing impact, and in the EU legislation the control of chemicals is being introduced. Therefore, changing public perception and new legislation means that the environmental impact of munitions and their ingredients cannot be ignored. We require understanding of the problems if they are to be dealt with, simply:

(i) What is the impact of manufacturing processes as presently used and how may they be improved? Are there alternatives available or likely to become available?
(ii) What is the effect of use – on humans and on the environment? (a) What are the toxicity effects in handling and use? (b) What are the effects on land – that is managing contamination?
(iii) Are there disposal techniques available using safe methods?
(iv) Can improved disposal methods be devised?
(v) Finally, what are the costs involved? Are there spend‐to‐save options?

It is clear from examining the published literature that no one nation has all the answers and that no one nation has unique problems. While legal requirements do vary, there are common themes affecting all. There is active work ongoing in the United States under the Strategic Environmental R&D Program (SERDP), a joint approach between Department of Defense (DoD), Department of Energy (DoE), and the EPA. There have been studies in the European Defence Agency and also studies in the North Atlantic Treaty Organization (NATO) – Science and Technology area. These legislative requirements are driving research, as has been noted.

New Ingredients and Compositions

It has been argued that changes in materials will answer the requirement and there is evidence that they can improve matters. There is, however, a need to demonstrate that new materials offer significant advantages, and this is shown in several of the reports now in the open literature. An early example of this is the four‐power programme on novel propellants. Again, this is an illustration of the approach and, as detailed later, the area of focus is now materials such as ammonium dinitramide (ADN). This was part of a multinational programme involving the United Kingdom, France, Germany, and the United States. It involved joint studies on the formulation and testing of a smokeless propellant for tactical systems. The aim was proof of principle, but environmental issues did not play a major part in the study. It has interesting aspects, however, as elimination of acid smoke has been a first target for environmental improvement. This is an improvement in many ways, but there are still products, and these may be just as hazardous as the eliminated smoke. In some ways, an invisible product can be more hazardous. Therefore, there is a need for clear demonstration of safety and proven ways of assessing true impact. This needs examination and experimental proof. In short, simple answers can be in error and assumptions need testing before acceptance. These are the constraints that must be addressed. There has also been considerable work on the replacement of metals in pyrotechnics and related systems. The presence of metals, particularly Pb, is both undesirable and dangerous. Work has been under way for some time funded by the US Army with promising results. Detailed toxicity studies are needed to avoid future problems of the kind found in the past. This is perhaps the most advanced study area, although small arms of all kinds are also being developed with the removal of ingredients of known toxicity.

This is not as simple as might be supposed, as a recent Norwegian study has shown. A round was introduced which seemed to offer improved environmental impact, but in use several Norwegian servicemen were taken ill prompting a detailed investigation. The results indicated that the new materials were less benign than originally thought. This illustrates the problems with the introduction of new materials where less is understood of their behaviour. The development of national and international policies for the manufacture and use of less sensitive materials (insensitive munitions) led to the introduction and use of new polymer‐bonded materials. While related to composite rocket propellants and themselves not possessing any significant problems, their manufacture makes extensive use of isocyanates for curing the polymer. Many isocyanates are known carcinogens and therefore require careful handling, if not complete avoidance. To this can be added concerns over phthalates often used as plasticizers, which are now being banned in the EU.

Trinitrotoluene (TNT) has been used and is being used extensively and has been studied in depth by the US Army Corps of Engineers. It is toxic but can be rendered non‐available through immobilization in soils. It has useful explosive properties and ease of handing in preparation. This has prompted renewed research into similar materials to avoid some of the problems with polymer bonded explosive (PBX) while offering reduced sensitivity, and also to offer cost savings. However, recent studies have shown that it will leave more residues in use, and, more particularly, field disposal methods do not operate efficiently.

Toxicology

It is hard to introduce new materials into use if there are uncertainties over their toxicity. Existing materials may well be toxic; but as the understanding of toxicity develops, their use may also be called into question. For example, knowing how 1,3,5‐trinitro‐1,3,5‐triazine (RDX) acts as a neurotoxin helps manage the risk and should help devise treatment where possible. This is a very active area and the likely main area of activity is in integrating this with other activities such as synthesis and formulation, as well as the study of the combustion and detonation products. It is often assumed that energetic materials are completely consumed when used in a design mode. However, forensic studies of explosives as detailed in the International Symposia on the Analysis and Detection of Explosives indicate that residues are left.

Life‐Cycle Analysis

Environmental impact is part of the whole life of a munition and its ingredients. Experience elsewhere has shown that the whole life needs to be examined to understand and optimize the behaviour and so reduce the environmental impact. One of the areas identified for further immediate action within NATO was that of greener munitions. This formed the basis of a further study. At the outset of this study, the group identified several key issues that appeared to need examination: Ingredients, Manufacturing, Use, Whole life‐cycle management, Disposal, Impact on environment. It became clear that the concept of greener munitions is far from simple. Not only are the individual aspects more complex but their interactions are also important and equally complex.

Recycling

Recycling is often seen as a way of covering the costs of disposal. However, experience has shown that at best it can be a disposal–cost offset. Metal parts can be recycled once certified free of explosives and the recovered energetics can possibly be reused for civil and military applications. Techniques such as supercritical fluid extraction or liquid ammonia can produce recovered material which may be acceptable for use. However, a major drawback is the need to satisfy authorities of the consistency, and safety of the recovered materials. These materials need to be demonstrated to be safe in themselves and that no contaminants remain which will prevent safe use. This adds significantly to the cost. However, not all nations see this as an issue. It is likely to become more common especially with rare or expensive ingredients. It will require processes capable of producing a consistent product, or of making a consistent product from variable ingredients and hard evidence will be required to validate any such claims!

Conclusions

This is intended to provide an introduction to the technical area and to provide sufficient information to help manage environmental issues associated with munition systems. In summary, to manage the potential environmental impact of energetic systems we need a range of approaches. Firstly, while it is not merely a matter of using new materials, they do offer sound options. However, they need to be understood well enough to deliver all the requirements placed upon them. This requires an understanding of likely toxicology and environmental and human impact as well as performance, ageing, and vulnerability. Since value for money also needs consideration, it may be that better specified and understood versions of existing materials will be more rapidly and effectively employed. New processes can reduce manufacturing impact. Many processes were designed when there was less understanding of the effects and new approaches can be more efficient with reduced cost. New‐range management methods avoid damage and remove old damage. This is not limited to test ranges but also to manufacturing plants and storage facilities. Overall, therefore, systems design for life minimizes overall impact! These constraints and requirements should be considered a major driver for research and a scientific and engineering challenge. They require the following: a. New methods for analysis; b. New or re‐engineered and well‐characterized materials for use; c. New methods for disposal.

 

 

 

This is an excerpt of the introductory chapter of the book: Energetic Materials and Munitions: Life Cycle Management, Environmental Impact, and Demilitarization. By Adam Stewart Cumming and Mark S. Johnson (eds.), April 2019, 264 Pages, ISBN: 978-3-527-34483-3. Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission. 

Adam S. Cumming
Associate Editor at Propellants Explosives and Pyrotechnics

Dr. Adam Cumming is currently Honorary Professor at the University of Edinburgh. He joined the Ministry of Defence (MOD) research in 1976 and has worked on energetic materials since then. He was Capability Advisor to MOD, based in the Defence Science and Technology Laboratory (DSTL) until 2014 and involved with NATO Science and Technology, leading teams examining Demilitarisation, the Environment and Greener Munitions. He is an established world expert in the field with current particular interests in environmental issues and in the design of new materials.