[en] An extremely sensitive on-line monitor for alpha-emitting aerosols containing uranium and the transuranics has been developed. If the only alpha activity present were that associated with the decay of these aerosols, then monitoring for significant concentrations would be straightforward. There is, however, a naturally occurring source of alpha activity from the decay of radon and thoron daughter products. These background levels may be several orders of magnitude greater than the maximum permissible airborne concentration, MPC/sub a/, of the aerosol that is being monitored. The monitor that is described here incorporates discrimination against background activity that is based on two factors. Firstly, the background activity is associated with small-sized dust particles, while the aerosol to be monitored has most of its activity associated with large-sized particles. Secondly, the alpha energies from the two sources are different. The monitor utilizes virtual impactors to concentrate the large-sized particles into a flow that is a small fraction of the intake flow. The flow containing the large particles is then passed through a filter to collect the particles. The filter is viewed by a solid-state detector for alpha spectroscopy. The monitor is capable of detecting less than one MPC/sub a/ of soluble aerosols containing plutonium, 0.002 pCi/1, in less than one-half hour

No abstract available

[en] The former Strategic Defense Initiative Organization (SDIO) invested significant resources over a 6-year period to develop and build an accelerator to demonstrate the launching of a cw beam with characteristics suitable for a space-based Neutral Particle Beam (NPD) system. This accelerator, the CWDD (Continuous Wave Deuterium Demonstrator) accelerator, was designed to accelerate 80 mA cw of D^- to 7.5 MeV. A considerable amount of hardware was constructed and installed in the Argonne-based facility, and major performance milestones were achieved before program funding from the Department of Defense ended in October 1993. Existing assets have been turned over to Argonne. Assets include a fully functional 200 kV cw D^- injector, a cw RFQ that has been tuned, leak checked and aligned, beam lines and a high-power beam stop, all installed in a shielded vault with appropriate safety and interlock systems. In addition, there are two high power (1 MW) cw rf amplifiers and all the ancillary power, cooling and control systems required for a high-power accelerator system. The SDI mission required that the CWDD accelerator structures operate at cryogenic temperatures (26 K), a requirement that placed severe limitations on operating period (CWDD would have provided 20 seconds of cw beam every 90 minutes). However, the accelerator structures were designed for full-power rf operation with water cooling and ACWL (Argonne Continuous Wave Linac), the new name for CWDD in its water-cooled, positive-ion configuration, will be able to operate continuously. Project status and achievements will be reviewed. Preliminary design of a proton conversion for the RFQ, and other proposals for turning ACWL into a testbed for cw-linac engineering, will be discussed

[en] Measurements of degraded fission-neutron spectra using recoil proportional counters are done routinely for studies involving fast reactor mockups. The same techniques are applicable to measurements of neutron spectra required for personnel dosimetry in fast neutron environments. A brief discussion of current applications of these methods together with the results of a measurement made on the LITTLE BOY assembly at Los Alamos are here described

No abstract available

No abstract available

[en] Virtual impactors are currently being used in a number of instruments to separate an aerosol into different size ranges. The virtual impactor is a variation of the standard impactor in which the impaction surface is replaced by an orifice into which particles can pass and be collected or counted. We have made an experimental study of the collection characteristics of virtual impactors. The parameters varied included: acceleration nozzle-to-collection probe distance, the ratio of the collection probe-to-acceleration nozzle diameters, and the ratio of collection probe-to-inlet flows. Measurements were also made with different collection probe geometries. It was found that it is possible to parameterize much of the data by introduction of the Stokes number and an effective minor flow collection efficiency. One disadvantage of the virtual impactor is that in the transition region particles are collected on the inside walls of the collection probe near the probe tip. The amount that is collected is a sensitive function of the probe geometry

[en] Gas-filled proton recoil proportional counters have been used extensively for the measurement of neutron spectra in degraded fission-spectrum environments. Some considerations relating to the use of these counters for personnel dosimetry are here described. High sensitivity and good accuracy in the determination of dose-equivalent can be obtained if relatively high pressure hydrogen-filled proportional counters are used as the active element in a dosimeter system

[en] Several different fast-neutron based techniques are being studied for the detection of contraband substances in luggage and cargo containers. The present work discusses the accelerator requirements for fast-neutron transmission spectroscopy (FNTS), pulsed fast-neutron analysis (PFNA), and 14-MeV neutron interrogation. These requirements are based on the results of Monte-Carlo simulations of neutron or gamma detection rates. Accelerator requirements are driven by count-rate considerations, spatial resolution and acceptable uncertainties in elemental compositions. The authors have limited their analyses to luggage inspection with FNTS and to cargo inspection with PFNA or 14-MeV neutron interrogation

[en] An extremely sensitive on-line monitor for alpha-emitting aerosols was developed. The monitor incorporates discrimination against background radon and thoron daughter product activity which is based on two factors. Firstly, the background activity is associated with small-sized dust particles, while the aerosol to be monitored has most of its activity associated with large-sized particles. Secondly, the alpha-particle energies from the two sources are different. The monitor utilizes virtual impactors to concentrate the large-sized particles into a reduced flow. This size-selected sample is then collected on a filter which is viewed by a detector. The monitor is capable of detecting less than one maximum permissible airborne concentration, MPC/sub a/, of these hazardous aerosols in less than one-half hour