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Abstract  

A beta-gamma coincidence counting system has been developed for automated analysis of Xe gas samples separated from air. The Xe gas samples are contained in a cylindrical plastic scintillator cell located between two NaI(T1) scintillation detectors. The X-ray and gamma spectra gated by coincident events in the plastic scintillator cell are recorded for each NaI(T1) crystal. The characteristic signatures of the131mXe,133gXe,133mXe, and135gXe isotopes of interest for nuclear test-ban verification as well as the procedures and results of absolute efficiency measurements are described. A NaI(T1) crystal with provision for 4 sample cells has been implemented for the system to be deployed in the field. Examples of data on ambient air samples in New York City obtained with the field prototype are presented.

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Abstract  

An anticoincidence-shielded Ge(Li) γ-ray spectrometer incorporating a largevolume, high-resolution coaxial diode inside a large plastic phosphor shield is described. It provides a peak-to-Compton ratio of 245: 1 for137Cs and a significantly improved sensitivity for both low- and high-level radionuclide measurements. Examples of its application to neutron activation analysis, analysis of proton activated sources, and environmental radionuclide analysis are illustrated.

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Abstract  

A seabed nuclear probe has been developed which permits the measurement of up to 33 elements at the parts per thousand to parts per million levels in continental shelf areas. The probe consists of a neutron irradiation source,252Cf, which neutron activates the elements in the minerals of interest. These resulting radioactive elements emit characteristic gamma radiation which is analyzed in situ in 2- to 10 min counting intervals with a Ge(Li) detector system. Details of the irradiation source, the Ge(Li) detector, and spectra taken in situ in a marine environment are discussed with respect to the detection of the minerals at concentrations of economic 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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Abstract  

A large area beta scintillation detector has been developed which is currently capable of determining Sr-90/Y-90 contamination in surficial soils. The detector system employs scintillating fiber optic arrays, with active dimensions approximately 15 cm wide by 100 cm long, both ends of which are coupled to multiple photomultiplier tubes (PMTs). Electronic processing includes coincidence requirements to optimize sensitivity and selectivity for the 2.28 MeV (maximum) beta particle from Y-90. Low energy beta particles and gamma rays are discriminated against using double ended and multi-layer coincidence requirements. The detector system is personal-computer-software controlled and data restored in a format compatible with standard database software for ease of final data reduction. Experimental calibration studies have shown a linear response for Sr-90/Y-90 soil concentrations from 12 to over 500 pCi/g and a discrimination factor of 50 to 1 versus Cs-137.

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The thermal and mechanical behaviour was measured in the U. S.for a polyethylene that had been prepared and highly drawn in the U. S. S. R. The melting point and percent crystallinity were evaluated in this studies as a function of heating rate and recrystallization. The Young's modulus and tensile stress to break in the orientation direction were 4.1 and 0.15 GPa, respectively.The tensile strain to break was about 8%.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Bachelor, J. Friese, C. Aalseth, J. McIntyre, H. Miley, R. Perkins, and G. Warren

Abstract  

In anticipation of a nuclear detonation, techniques to quickly assess the radiation exposure of evacuees should be developed. Based on experience relating neutron radiation exposures to activation products, measurement of activation products can be performed in a few minutes. Personal items exposed to significant levels of radiation allows neutron dose assessment via the activation products. This approach allows prompt collection of important data on human exposure following a nuclear attack. Data collected will facilitate triage decisions for emergency medical treatment to ameliorate the radiation effects on exposed individuals. Activation experiments with everyday items exposed to a neutron source are presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Bowyer, K. Abel, C. Hubbard, A. McKinnon, M. Panisko, R. Perkins, P. Reeder, R. Thompson, and R. Warner

Abstract  

A fully automatic radioxenon sampler/analyzer (ARSA) has been developed and demonstrated for the collection and quantitative measurement of the four xenon radionuclides,131mXe(11.9 d),133mXe(2.2 d),133Xe(5.2 d), and135Xe(9.1 hr), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a Comprehensive Test Ban Treaty (CTBT). Activity ratios of these radionuclides permit source attribution. Xenon, continuously and automatically separated from the atmosphere, is automatically analyzed by electron-photon coincidence spectrometry providing a lower limit of detection of about 100 μBq/m3. The demonstrated detection limit is about 100 times better than achievable with reported laboratory-based procedures for the short-time collection intervals of interest.

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