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A gamma-ray-based, active (A) and passive (P) computed tomography (CT) technology has been developed that locates, identifies and quantifies gamma-ray emitting isotopes, transuranic (TRU) and others, in nuclear waste drums. ACT uses a collimated external source and a HPGe detector to measure selected mono-energetic gamma-rays that are attenuated by waste-drum contents; a separate PCT measurement uses the HPGe detector to record the spectra of gamma-rays emitted from within a drum. The ACT attenuation images and the PCT emission spectra are coupled to quantitatively assay drum contents for ∼0.1–200 g of TRU isotopes. Calibration requires a single measurement of a known radioactive standard; construction of waste-drum surrogates is not required. Fixed and mobile systems demonstrated compliance with a DOE quality assurance program via several independent blind tests.

We present an overview of the Long Duration Exposure Facility (LDEF) induced activation measurements. The LDEF, which was gravity-gradient stabilized, was exposed to the low Earth orbit (LEO) radiation environment over a 5.8 year period. Retrieved activation samples and structural components from the spacecraft were analyzed with low and ultra-low background HPGe gamma spectrometry at several national facilities. This allowed a very sensitive measurement of long-lived radionuclides produced by proton- and neutron-induced reactions in the time-dependent, non-isotropic LEO environment. A summary of major findings from this study is given that consists of directionally dependent activation, depth profiles, thermal neutron activation, and surface beryllium-7 deposition from the upper atmosphere. We also describe a database of these measurements that has been prepared for use in testing radiation environmental models and spacecraft design.

Calculations to predict the radiation environment for spacecraft in low earth orbit sometimes ignore the contribution from secondary radiation products. However, the contribution of secondaries, particularly neutrons, on heavy spacecraft or in planetary bodies can be of concern for biological systems. The Shuttle Activation Monitor (SAM) and Cosmic Radiation Effects and Activation Monitor (CREAM) experiments provide valuable data on secondary (as well as primary) radiation effects. Comparisons have been made between induced activity from flight-exposed samples, induced activity in a ground-irradiated sample, and Monte Carlo-derived predictions with and without secondaries. These comparisons show that for a flight-exposed sample, predictions which omit the secondary contribution result in a spectrum that is too low by a factor of 2. The addition of the secondaries results in a predicted spectrum that closely matches the measured data.

The Shuttle Activation Monitor (SAM) experiment was flown on the Space Shuttle Columbia (STS-28) from 8 – 13 August, 1989 in a 57°, 300 km orbit. One objective of the SAM experiment was to determine the relative effect of different amounts of shielding on the gamma-ray backgrounds measured with similarly configured sodium iodide (NaI) and bismuth germante (BGO) detectors. To achieve this objective twenty-four hours of data were taken with each detector in the middeck of the Shuttle on the ceiling of the airlock (a high-shielding location) as well as on the sleep station wall (a low-shielding location). For the cosmic-ray induced background the results indicate an increased overall count rate in the 0.2 to 10 MeV energy range at the more highly shielded location, while in regions of trapped radiation the low shielding configuration gives higher rates at the low energy end of the spectrum.

An experimental system which was used to compare gamma-ray detector materials in a space environment is described. Two 3-in*3-in scintillator detectors, NaI and BGO, were flown on the Space Shuttle Columbia as part of the Shuttle Activation Monitor (SAM) experiment. The goals of this experiment were to compare the performance of the two detector materials in the same environment and to measure the variations in dynamic radiation background as a function of geomagnetic coordinates, amount of shielding, and type of detector material. Twenty-four hours of data in 5-min time bins were recorded with each detector in both high-shielding and low-shielding locations in the Orbiter middeck. The high-inclination orbit (57 degrees , 160 nmi) provided exposure to the trapped charged particles in the South Atlantic Anomaly as well as the electrons in the polar regions. The system used specially adapted off-the-shelf hardware for data acquisition and storage. The multichannel analyzer was a commercially available unit with added circuitry to support an active particle shield. Data during the flight were stored using a cassette tape recorder. A preliminary look at some of the data from the first flight is included. >

A 7.6-cm*7.6-cm BGO (bismuth germanate) detector was flown in the middeck of the Space Shuttle Columbia August 8-13, 1989, as part of the Shuttle Activation Monitor (SAM) experiment. One of the goals of this experiment was to compare the performance of the BGO to that of NaI in the same environment. Twenty-four hours of data in 5-min time bins were recorded with each detector in each of two locations in a high-inclination orbit (57 degrees , 300 km). Pre- aid post-flight low-background counting was preformed for identification of activities induced by the space radiation environment. A number of isotopes attributed to induced activity from exposure to the space radiation environment have been tentatively identified. >

The technology being proposed by LLNL is an Active and Passive Computed Tomography (A P CT) Drum Scanner for contact-handled (CH) wastes. It combines the advantages offered by two well-developed nondestructive assay technologies: gamma-ray spectrometry and computed tomography (CT). Coupled together, these two technologies offer to nondestructively and quantitatively characterize mixed- wastes forms. Gamma-ray spectroscopy uses one or more external radiation detectors to passively and nondestructively measure the energy spectrum emitted from a closed container. From the resulting spectrum one can identify most radioactivities detected, be they transuranic isotopes, mixed-fission products, activation products or environmental radioactivities. Spectral libraries exist at LLNL for all four. Active (A) or transmission CT is a well-developed, nondestructive medical and industrial technique that uses an external-radiation beam to map regions of varying attenuation within a container. Passive (P) or emission CT is a technique mainly developed for medical application, e.g., single-photon emission CT. Nondestructive industrial uses of PCT are under development and just coming into use. This report discuses work on the A P CT Drum Scanner at LLNL.

A high purity germanium gamma-camera has been developed and is currently being evaluated. This camera incorporates unique performance parameters such as a 2 mm full-width spatial response function with rejection of multiple-scatter in the detector, a 2.2% FWHM energy resolution for 99 mTc, a 180 nsec paralyzable dead-time, and a 2 mu sec non-paralyzable dead-time. Imaging studies demonstrate the superior capabilities of this instrument.

A megachannel pulse-height analysis system using a PDP-8/E computer and two moving-head disk memories has been developed. The system has a storage capacity of 220 memory locations, is capable of processing 1100 events/s, and provides on-line sorting and disk storage. An X- or Y-pulse-height spectrum in coincidence with one or several arbitrary pulse-height windows can be assembled in core for scope display and spectral analysis within 2 to 20 seconds. Reconstruction of a complete X- or Y-pulse-height spectrum requires about 3 minutes.

An x-ray fluorescence system has been designed to make elemental analyses of trace elements in low-Z matrices. It consists of radioisotope exciters, a Si(Li) detector, and a computer-based pulse height analyzer. Qualitative measurements of all elements heavier than phosphorus (Z = 15) and quantitative measurements of all elements heavier than potassium (Z = 19) can be made. For samples fluoresced for 1000 s on 9 mg/cm2 filter paper, the three sigma detection limits range from 10 to 100 ng/cm2. Accuracy is within ±10% and reproducibility is better than 5%. The method often requires no sample preparation and is completely nondestructive. Quantitative information obtained with such a system is useful in monitoring trace element concentrations in air, water, or biological material.

An EPA sponsored field study intercompared the performance of 11 different aerosol samplers. They were operated simultaneously for eight consecutive days by scientific groups having expertise in sampler development and operation. Collection surfaces were changed every 12 h allowing a 16 period intercomparison. Samples were analyzed at each participant's laboratory for one or more of the pollutants mass, nitrate, sulfur or sulfate, lead, and 8 other elements using one or more analysis methods. Most samplers collected two particle-size fractions with the 50% separation for the fine fraction between 2.4 and 4.3 μm. Upper cutoff diameters ranged from 14 to above 30 μm which strongly influenced the total mass collected. Results were intercompared for the total, fine, and coarse size fractions. Agreement to better than 10% was found for the elements Zn, S, and Pb that occur primarily in the fine fraction. Mean sulfate concentration was three times the sulfur concentration, showing that all sulfur occurs as sulfate.

The fluorescent excitation analysis equipment and techniques developed at the University of California, San Francisco are reviewed and the recent advances and their impact on extending the applicability are discussed.

A sample changer designed to process automatically up to 48 2-cc samples is described. Mechanical drive mechanisms, digital electronics logic, and operational flow diagrams are presented. The changer is an integral part of a system consisting of an x-ray exciting source, a turntable changer, a Si(Li) radiation detector, and a preprogrammed pulse-height analyzer. X-ray fluorescence analysis of a sample allows quantitation of selected trace elements after simple spectral integrations are performed by an on-line microprocessor. Selection of the changer's MIX mode will cause each solution sample to be mixed just prior to analysis, thus insuring that representative tracer concentrations are determined.

A precision study of the decay of134Csg and134Csm has been made, using ordinary Ge(Li) spectrometers and ā Compton-suppression spectrometer. The logft value of the second forbidden nonuniqueβ-decay to134Xe has been measured to be 13.0±0.2. TheM4γ-ray transition in134Csm(8−) decay has been measured to haveαK= 73±7 and a hindrance of 7.0 over the Moskowski estimate. This is discussed in terms of the level configurations and the analogous transition in133Xe. A new intensity limit of 2×10−6 has been set for the zero-phonon transition between the 4+ and 2+ members of the two-phonon triplet. This leads to an upper limit forB(E2)4→2′, greater than 905. This and the more preciseγ-ray intensity values are discussed in relation to presently available nuclear models.

Stable tracers are safe, convenient and readily available, but their use entails the need for involved assay techniques. X-ray fluorescence combines the use of stable tracers with the convenience of radioactive quantitation techniques. An automated system has been developed for use in medicine. Its performance and applications are presented.

We have attempted to find evidence for high energy alpha particles from Malaysian, Madagascan and Indian monazite minerals (rare earth and actinide phosphates) which might indicate the presence of naturally occurring superheavy elements in nature. A silicon surface barrier detector was used to detect alpha particles in conjunction with a cosmic-ray anti-coincidence detector. The results are consistent with no alphas above 12.5 MeV. This agrees with results of Fireman and Brandt 1978 but does not agree with results of Chevalier et al. 1978.

A gamma-ray camera consisting of two 3.2×3.2×1-cm3 HPGe detectors has been assembled. Shallow orthogonal grooves define 512 2×2-mm2 elements. Square hole collimators have been fabricated with design parameters that exploit the unique characteristics of the detector. Intrinsic spatial resolution is a square function with 2-mm width, and energy resolution is approximately 2.5% FWHM at 140 keV. Evidently superior images are obtained when this instrument is compared to state-of-the-art scintillation cameras.

Two Ge(Li) detector systems designed to measure low-level radioenvironmental samples are described. The materials used in the construction of these systems and the effect of these materials on the background radioactivities are discussed. One system, designed to count mid-range specific activities, contains a closed, coaxial, 10% Ge(Li) detector that is housed in electrolytic magnesium and operated within a standard lead cave. Continuum background levels in this system vary from 0.1 c/min keV at 200 keV to 0.01 c/min keV at 1 MeV. The second system, designed for maximum sensitivity, contains a 15%-relative-efficiency Ge(Li) detector housed in electrolytic magnesium and operated in anticoincidence with a large plastic detector. This entire system is placed inside a lead-and steel armor plate shield located in a counting room below ground level. For single gamma-ray emitters from point sources, the maximum continuum suppression factor is greater than 8. Under suppression conditions the background continuum, as well as the usual contaminant peaks, are the lowest yet reported for Ge(Li) environmental counting systems. Continuum values decrease from about 6 × 10 −3 c/min keV at 200 keV to less than 3 × 10 −4 c/min keV at 1 MeV. A 1000 min count of 250 g of soil shows that this system can measure a 137 Cs specific activity of 20 fCi/g with a precision of 15%. The lowest specific activity per gram detectable in a one-week count under threshold conditions (± 50%) for a single gamma-ray emitter with E γ >500 keV is several hundred aCi/g.

FEA is being used in medicine to substitute radiotracers and chemical analysis of stable tracers. Excitation with polarized x-rays reduces tracer working levels: Since they scatter at preferential angles they reduce the number of photons reaching the detector, thus decreasing system dead time and background. The use of a 160KV 19mA x-ray tube for FEA of iodine (and neighboring elements) realizes count-rates of 2.5 cts/sec/ppmI and background reductions from 11.5 ppmI (when using Am-241 excitation) to 5.7 ppmI. These early results indicate that counting time to realize constant quantitation accuracy can be reduced by 90%. Since the use of the x-ray tube results in a 50% increase in the cost of the source-excited automated system, the ten-fold reduction in analysis time makes this a practical approach.

Results are presented of an intercomparison study involving twenty-two investigators who collectively used six different analytical techniques. Synthetic dried solution and particulate deposits were prepared and, together with natural aerosol samples, were used for the study. Analytical techniques utilized by the participants were wavelength dispersive X-ray spectometry, two different energy dispersive X-ray techniques, atomic absorption spectrometry, emmision spectroscopy and neutron activation analysis. Results showed that energy dispersive X-ray spectrometry, is a reliabnle technique for the multi-element analysis of particulate matter collected on filter media. It reported the most elemental determinations per man-hour invested and provided satisfactory accuracy for the quantitative determination of elements pottassium (Z = 19) and above, with somewhat larger errors for elements down to aluminium (Z = 13). The study demonstrated the need for a better understanding and practical application of particle size corrections for lighter elements. The non X-ray techniques were neither well represented nor strongly supported by the study.

There are currently no plans for the commercial reprocessing of nuclear fuel in the U.S. This is not the case in Japan, England, France, Germany, or the USSR. The U.S. does, however, include the reprocessing of spent nuclear fuel as a part of its defense programs. The Office of Safeguards and Security of DOE's Defense Programs has funded the development and optimization of numerous nondestructive analysis techniques including K-edge x-ray fluorescence analysis. This paper reviews some of the implementation efforts resulting from R&D supported by that office.In 1979, the concept of using K-edge x-ray fluorescence analysis (K XRFA) for the analysis of actinide solution concentrations was first presented. K XRFA using small radioactive Co-57 sources has been shown to be a practical way to measure actinide solution concentrations in offline, at-line, or on-line configurations. The experimental methodology is elegant and the hardware is simple.

Radioactivity measurements have shown evidence for long-lived 92Nb and 2.03 × 10 4 yr 94 Nb in natural niobium. The specific activity of 94Nb was observed to be 0.32 ± 0.03 dis/min. kg Nb and that of 92Nb to be 0.058 ± 0.035 dis/min. kg Nb. With t 1 2 taken as ≈ 1.7 × 108yr, the isotopic abundance of 98Nb is 1.2 × 10−10 per cent.

A portable microcomputer has been developed for the IAEA to perform in-field analysis of plutonium gamma-ray spectra. The unit includes a 16-bit LSI-11/2 microprocessor, 32K words of memory, a 20-character display for user prompting, and a 20-character thermal printer for hardcopy output. Only the positions of the 148-keV Pu-241 and 208-keV U-237 peaks are required for spectral analysis. The unit was tested against gamma-ray spectra taken of NBS plutonium standards and IAEA spectra. Results obtained are presented.

The use of non-radioactive tracers for measuring certain clinically significant parameters by x-ray fluorescence analysis (XRFA) is well established at our institution (1,2). Among the technique's advantages are high accuracy, simplicity, cost effectiveness and reduced or eliminated radiation exposure to patients. One of the more versatile tracers is iodine, which has a low body toxicity and desirable chemical properties, e.g. it is easily bound to organic molecules. Other elements of interest are cesium (3), a potassium analogue of low toxicity; and xenon, the highest atomic number, stable, noble gas.

Title of program : (32 characters maximum) Decay scheme program DCSCH3 Catalogue number : ABOF Program obtainable from : CPC Program Library, Queen's University of Belfast, N. Ireland (see application form in this issue) Computer for which the program is designed and others upon which it is operable Computer : IBM 360-50. Installation : North Texas State University Operating system or monitor under which the program is executed : OS MFT II (HASPII) Programming languages used : FORTRAN IV H High speed store required : 32 806 words. No. of bits in a word : 32 Is the program overlaid ? No No. of magnetic tapes required : None What other peripherals are used ? Card Reader; Line Printer; Disc No. of cards in combined program and test deck : 533 Card punching code : EBCDIC

The intense beta spectrum of Au/sup 198/ and the K internal conversion coefficient of the 412-kev transition were measured. The beta spectrum was found to have a nonstatistical shape which can be best fitted with a once-forbidden shape factor of the form 1--0.33 W + 0.074 W/sup 2/. With this shape factor used to determine the total intensity of the beta spectrum and thereby the intensity of the gamma radiation, the K internal conversion coefficient of the 412-kev transition in Hg/sup 198/ is found to be alpha /sub K/ = (282 plus or minus 10) x 10/sup -4/. On the basis of a statistical shape for the beta spectrum a value of 297 x 10/sup -4/ would be obtained. (auth)

Finite solid-angle corrections have been calculated for Ge(Li) detectors. Planar detectors considered vary from 4 to 20 cm 2 and from 6 to 16 mm in depletion depth. True circular coaxial detectors vary from 26 to 50 mm in diameter with depletion depths from 7 to 20 mm and lengths from 22 to 57 mm. Five-sided detectors of both trapezoidal and circular cross sections are included, and these range from 20 to 70 mm in length and from 8 to 20 mm in depletion depths. The corrections are calculated for source distances of 3.0, 5.0, 7.0 and 10.0 cm. Results are presented in tables rather than as graphs for greater accuracy. Interpolation is easy and accurate for configurations and distances other than those given. Finite size sources cause small reductions in the point source corrections. Graphs and formulas are presented which allow the reductions to be calculated for spherical or cylindrical sources.

High purity germanium offers excellent potential for use in nuclear medical imaging cameras. A position and energy readout technique using two inexpensive delay lines has been developed for these cameras. Results obtained with a 1-cm2 , 4 mm deep, 5×5 strip high purity germanium detector are 2.1 mm full width spatial resolution, a measured single strip resolution of 0.65 mm full width half maximum (FWHM), a 25 element uncollimated energy resolution of 2.95 keV FWHM, and 2.65 keV FWHM for a single central element at 140 keV.

The intensities and energies of the 346.93-, 826.28-, and 2158.77-keV transitions, and intensity limits for the 467.4- and 1293.7-keV transitions in the decay of $^{60}\mathrm{Co}$ were measured using a new improved Compton suppression spectrometer. The spectrometer yields a maximum Compton continuum suppression of 28 and a peak-to-minimum Compton ratio of 550/1 for the 1332.5-keV transition of $^{60}\mathrm{Co}$.RADIOACTIVITY $^{60}\mathrm{Co}$ [from $^{59}\mathrm{Co} (n,\ensuremath{\gamma})$]; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$; deduced $log\mathrm{ft}$. $^{60}\mathrm{Ni}$ deduced energy levels. Compton suppression spectrometer.

Using a Compton-suppression spectrometer with a central Ge(Li) detector, we have observed a 346.95-ke V gamma-ray transition between the ${4}_{1}^{+}$ and ${2}_{2}^{+}$ states in $^{60}\mathrm{Ni}$. According to the simple vibration model, this so-called zero-phonon transition is strictly forbidden. A lower limit of 0.174 is placed on the ratio of the observed to the single-particle rates.

X-ray analysis has traditionally been wavelength dispersive, manpower intensive, and an analytical laboratory tool employing massive and costly x-ray generators and diffraction spectrometers. Following the development of the lithium drifted silicon and germanium [Si(Li) and Ge(Li)] semiconductor radiation detectors in the mid 1960’s, and more recently the high purity germanium detector [HPGe], the analytical technique of energy dispersive x-ray fluorescence analysis (XRFA)1 matured during the 1970’s.

In response to Task A.63 of the International Safeguards Project Office (ISPO), to upgrade measurement technology used by the International Atomic Energy Agency (IAEA), a portable data-reduction microprocessor was designed and programmed which allows in-field reduction of gamma-ray spectra and interfaces with the IAEA's multichannel analyzers - the 1000 or 2000-channel memory Silena BS27/N. This report describes the components used in assembling the microprocessor unit: hardware, software used to control the unit, and the mathematical formulation used to obtain isotopic ratios from the gamma-ray data. A simple overview is presented of the unit's operation and the results of tests on gamma-ray spectra that sought to verify the unit's operating characteristics and to determine the precision and effectiveness of the software developed for data reduction.

In one plan for reprocessing LWR spent fuel, after separation from fission products and transplutonics, part of the U and all of the Pu in a nitrate solution will form a coprocessed stream which is then evaporated and sent to a hold tank for accounting. The remaining U fraction will be purified and sent to a separate storage tank. These two streams can be monitored using x-ray fluorescence analysis. This report discusses equipment, spectra, cell calibration, and dynamic concentration measurements. 7 figures. (DLC)

The use of stable tracers assayed by x-ray fluorescent excitation analysis has proven advantageous over other stable or radioisotopic techniques in a number of clinical and investigative situations. An automated fluorescent excitation analysis system for medical application has developed. Its design parameters and performance are described.

This letter discusses additional corrections needed for solid angle correction factors for coaxial detectors.