Identification of UXO using the Associated Particle Neutron Time-of-Flight Technique
MR-1769
Objective
One of the major problems facing the DoD is dealing with unearthed UXO (unexploded ordnance) items at past or present military facilities or munition testing grounds. Range clearance operations must distinguish UXO filled with High Explosives (HE) from inert ordnance. Handling every piece of ordnance as "live" increases disposal and remediation costs to the DoD. Improvements are needed in the technologies for identification and discrimination of UXO to reduce false alarms.
The suitability of the Associated Particle neutron Time-Of-Flight technique (APnTOF) to non-destructively identify previously found UXO as hazardous or benign in a cluttered environment will be demonstrated in this project. This technique uses an electronically collimated tagged neutron beam from a novel compact, portable field-deployable 14 MeV neutron-generator system to simultaneously provide 3-D imaging of objects and their elemental composition. We will inspect a specific element of volume (~ 5cm3 voxel), thus significantly improving selectivity and the signal-to-noise ratio over present neutron-interrogation methods; identification of small ammunition (shells 20-40 mm diameter) will improve. Further, the APnTOF system will generate elemental distribution maps of a voxel, to better identify the type of munition.
Technical Approach
The APnTOF technique uses mono-energetic neutrons produced by accelerating deuterium ions into a tritium target. The subsequent fusion reaction generates nearly back-to-back emissions of neutrons and alpha particles of 14.1 and 3.5 MeV, respectively. A position-sensitive detector recognizes the associated alpha particle,thus furnishing the direction of the neutron. This tagged neutron interacts with the interrogated object’s nuclei, producing element-specific prompt gamma-rays that the gamma detectors recognize. Measuring the delay between detecting the alpha particle and the gamma-ray determines where the reaction occurred along the axis of the neutron beam (14.1 MeV neutrons travel at 5 cm/nanosecond; gamma rays cover 30 cm/nanosecond). The APnTOF’s main advantage is its suppression of the unrelated background signal by imposing conditions on the data-acquisition system. We will undertake experiments to demonstrate the APnTOF’s efficacy under various field conditions for (i) characterizing munitions types from their elemental composition, and, (ii) discriminating hazardous UXO from non hazardous items amongst clutter. Finally, the portable version will be developed and tested in the field.
Benefits
The proposed non-destructive tool affords new solutions to minimize the effects of background signals while identifying UXO that are recovered, partially exposed, or buried near the surface. It vastly improves signal-to-noise ratio for measuring carbon, nitrogen, and oxygen, the major elements of explosives. By reducing false-negative and –positive alarms, the DoD’s mission to efficiently, and cost-effectively remediate munitions will improve.
Points of Contact
Principal Investigator
Dr. Sudeep Mitra
Brookhaven National Laboratory (BNL)
Phone: 631-344-6377
Document Types
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