Indirect Estimation of Radioactivity in Containerized Cargo
Detecting illicit nuclear and radiological material in containerized cargo challenges the state of the art in detection systems. Current systems are being evaluated and new systems envisioned to address the need for the high probability of detection and extremely low false alarm rates necessary to thwart potential threats and extremely low nuisance and false alarm rates while maintaining necessary to maintain the flow of commerce impacted by the enormous volume of commodities imported in shipping containers. Maintaining flow of commerce also means that primary inspection must be rapid, requiring relatively indirect measurements of cargo from outside the containers. With increasing information content in such indirect measurements, it is natural to ask how the information might be combined to improved detection. Toward this end, we present an approach to estimating isotopic activity of naturally occurring radioactive material in cargo grouped by commodity type, combining container manifest data with radiography and gamma spectroscopy aligned to location along the container. The heart of this approach is our statistical model of gamma counts within peak regions of interest, which captures the effects of background suppression, counting noise, convolution of neighboring cargo contributions, and down-scattered photons to provide physically constrained estimates of counts due to decay of specific radioisotopes in cargo alone. Coupled to that model, we use a mechanistic model of self-attenuated radiation flux to estimate the isotopic activity within cargo, segmented by location within each container, that produces those counts. We demonstrate our approach by applying it to a set of measurements taken at the Port of Seattle in 2006. This approach to synthesizing disparate available data streams and extraction of cargo characteristics holds the potential to improve primary inspection using current detection capabilities and to enable simulation-based evaluation of new candidate detection systems.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1001085
- Report Number(s):
- PNNL-SA-62721; RMEAEP; TRN: US1100269
- Journal Information:
- Radiation Measurements, 46(1):10-20, Vol. 46, Issue 1; ISSN 1350-4487
- Country of Publication:
- United States
- Language:
- English
Similar Records
Portable Source Identification Device
Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo
Related Subjects
CARGO
CONTAINERS
DECAY
DETECTION
EVALUATION
GAMMA SPECTROSCOPY
PHOTONS
PROBABILITY
RADIATION FLUX
RADIOACTIVE MATERIALS
RADIOACTIVITY
RADIOISOTOPES
STATISTICAL MODELS
TRADE
nuclear measurements
nuclear monitoring techniques
portal monitoring
gamma-ray spectral analysis
gamma-ray spectroscopy