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  • Author or Editor: S. Bowyer x
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Abstract  

The detection of neutrons in the presence of significant gamma-radiation is often required in arms control, material accountability, and nuclear smuggling scenarios as well as in basic nuclear research. The new scintillator material LiBaF3 offers the possibility of measuring neutron count rates and energy spectra simultaneously while measuring gamma-count rates and spectra using a single detector. These capabilities derive from the fact that LiBaF3 exhibits a very fast core-valence luminescence under gamma-irradiation whereas this component is missing under neutron irradiation. Relatively simple pulse shape analysis techniques can be used to obtain excellent neutron/gamma discrimination. We present our current results illustrating these capabilities.

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Abstract  

The Comprehensive Test Ban Treaty calls for the monitoring of aerosol radionuclides throughout the globe. Pacific Northwest National Laboratory has developed the Radionuclide Aerosol Sampler/Analyzer (RASA) for the Department of Energy to automatically collect and measure radioactive aerosols from the atmosphere. The RASA passes high volumes of air through a 3MTM Substrate Blown Microfiber Media (SBMF) specifically designated as SBMF-40VF. It then automatically moves the filter media in front of a high-purity germanium detector and collects a gamma spectrum. If further analysis on the filter is desired, the filter is sent to a laboratory and radiochemical analysis is performed. This paper discusses the method of dissolution of the SBMF-40VF filter media and the separation of the radioisotopes of interest.

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Abstract  

Radionuclide monitoring, though slower than vibrational methods of explosion detection, provides a basic and certain component of Comprehensive Test Ban treaty (CTBT) verification. Measurement of aerosol radioactive debris, specifically a suite of short-lived fission products, gives high confidence that a nuclear weapon has been detonated in or vented to the atmosphere. The variable nature of wind-borne transport of the debris requires that many monitoring stations cover the globe to insure a high degree of confidence that tests which vent to the atmosphere will be detected within a reasonable time period. To fulfill the CTBT aerosol measurement requirements, a system has been developed at PNNL to automatically collect and measure radioactive aerosol debris, then communicate spectral data to a central data center. This development has proceeded through several design iterations which began with sufficient measurement capability (<30 μBq/m3 140Ba) and resulted in a system with a minimal footprint (1 m×2 m), minimal power requirement (1600W), and support of network infrastructure needs. The Mark IV prototype (Fig. 1) is currently the subject of an Air Force procurement with private industry to partially fulfill US treaty obligations under the CTBT. It is planned that the system will be available for purchase from a manufacturer in late 1997.

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Abstract  

A Radionuclide Aerosol Sampler/Analyzer (RASA Mark 4) has been developed at PNNL for use in verifying the Comprehensive Nuclear Test Ban Treaty (CTBT). The RASA Mark 4 collects about 20,000 m3 of air per day on a 0.25 m2 filter. This filter is automatically decayed for 24 hours, then advanced to a germanium detector for a 24 hour count. This system has been operated in Richland, WA for a limited period of time in a predeployment testing phase. The germanium-detector gamma-ray spectra have been analyzed by automatic spectral analysis codes to determine Minimum Detectable Concentrations (MDC) for a number of isotopes of interest. These MDC's have been compared to other atmospheric measurements in the field and in the laboratory.

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