Increased impact sensitivity in ageing high explosives: Analysis of Amatol extracted from explosive remnants of war
Data files
Sep 21, 2023 version files 23.57 KB
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Dataset_160923.docx
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README.md
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Abstract
Millions of tonnes of explosive remnants of war remain in nature, and the volume is continuously growing. The explosive legacy of wars represents an increasing threat to the environment and to societal safety and security. As munitions continue to deteriorate, harmful constituents will eventually leak into the environment, poisoning ecological receptors and contaminating the surrounding soil and groundwater. Deteriorating munitions may also become increasingly sensitive to external stimuli and may be susceptible to accidental detonation. To thoroughly assess how to address these ageing munitions, we must first establish certain threshold values for the safe and secure handling and final disposal of the explosive ordnance. One key factor is to establish how the impact sensitivity of the explosives evolves over time. In the present work, we investigated the high explosive substance Amatol extracted from ageing explosive remnants of war. The results obtained in the analysis indicate that the high explosives in the examined specimens generally were much more sensitive to impact than previously assumed. Furthermore, the analysis revealed that the standardised methodology of impact sensitivity testing was insufficient for estimating the sensitivities in question, and a more careful statistical analysis was required.
README: Increased impact sensitivity in ageing high explosives; analysis of Amatol extracted from explosive remnants of war
Data from impact sensitivity tests using the BAM Impact Apparatus, demonstrating that Amatols extracted from ERW, with the expected exception of the sample of high moisture content, are still sensitive to impact. For only one of the samples studied, the impact sensitivity coincided with what is recorded in the literature as expected values for Amatol. All the other samples studied were on the other hand significantly more sensitive to impact. In the most extreme case, namely substance B, the substance was more nearly than four times more sensitive than expected for Amatol (the estimate value of being only 7.52 J, which is nearly less than a quarter of the expected value of 30 J). Note also that for this substance, we observed reactions with impacts as low as 6.18 J. The study therefore shows that the impact sensitivity of Amatol high explosives extracted from ageing ERW are suasible of becoming increasingly sensitive to impact.
Description of the data and file structure
The impact sensitivity of an explosive substance is its susceptibility to detonation under impact. This parameter characterises the safety of explosives in handling and transportation. To determine the impact sensitivity of a substance, a type of device known as a fallhammer apparatus is normally applied. There are several versions of these types of devices, but the United Nations recommends the Bundesanstalt für Materialforschung und -prüfung (BAM) fallhammer, which has also become the most frequently used standard impact sensitivity measuring device, however, the various apparatuses all operate on the same principle: A sample of assorted sizes of the tested explosive substance are subjected to the impact of falling weights, and the researcher estimates the sensitivity of the explosive based on which heights resulted in explosions.
Depending on the characteristics of the tested explosive substance, the mass of the drop weight and the drop height (the combined product of which is the impact energy), the sample may or may not initiate upon impact. In judging the results, a distinction is made between no reaction, decomposition (without flame or explosion) and explosion (with weak to strong report or inflammation). When assessing sensitivity, our primary interest is in quantiles such as h50, which is the height from which there is a 50% probability of a reaction occurring. We used the existence of a bounded 95% confidence interval (CI) for h50 as a necessary criterion for terminating our fallhammer experiments.
As repeated drops from the same height in a fallhammer will not invariably yield the same result (reaction versus no reaction), the impact sensitivity of an energetic material must be estimated statistically. Hence, the weight is dropped repeatedly from a range of (log) heights, and for each drop, we observe a binary outcome, recorded as a "1" if a reaction occurred and "0" otherwise.
The dataset contains the full data from the impact sensitivity tests using the BAM Impact Apparatus.
The main results are as follows:
- For substance A1, we initially aimed to obtain a single reaction with a 5 kg weight, but when this was not achieved, we proceeded to drop a 10 kg weight to increase the impact energy. After the first five drops, we still had no reactions, and we therefore decided to execute 10 drops from the maximum height of 100 cm with the 10 kg weight. Out of these, only a single drop caused a reaction.
- For substance A2, we did not obtain a bounded 95% CI for h50 after the first 30 drops, and we therefore increased the number of drops in increments by 10 at a time until a valid confidence interval was achieved. This happened after 70 drops.
- For substance B, we decided to stop the experiment after 30 drops, since this proved to be sufficient for obtaining a bounded 95% CI for h50.
- For substance C, as with substance A2, we had not achieved a bounded 95% CI for h50 after the first 30 drops, and therefore decided to augment the dataset by increments of 10 drops until this was achieved. After 50 drops, we had a 95% CI for h50.
- For substance D, since we had not obtained a bounded CI for h50 after 30 drops, we increased the number of drops by increments of 10 until this was achieved. This happened after 70 drops.
- For substance E, since 30 drops were not sufficient for obtaining a bounded 95% CI for h50, we increased the number of drops by increments of 10 until a valid CI was obtained, after 70 drops.
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Methods
In this analysis the OZM BHF 12 BAM impact apparatus was applied. The tests were performed in accordance with the requirements of the test procedure decribed in NATO STANAG 4489, Annex C; BAM impact machine.