A. DeVolpi

APSTNG: radiation interrogation for verification of chemical and nuclear weapons

A neutron diagnostic probe system which has the potential to satisfy a significant number of van-mobile and fixed-portal requirements for nondestructive verification of sealed munitions is described. The probe is based on a unique associated-particle sealed-tube neutron generator (APSTNG) that interrogates a treaty-limited item (TLI) with a low-intensity beam of 14 MeV neutrons generated from the deuterium-tritium reaction and that detects the alpha-particle associated with each neutron. Gamma-ray spectra of resulting neutron inelastic scattering and fission reaction identify nuclides associated with all major chemicals in chemical warfare agents, explosives, and drugs, as well as many pollutants and fissile and fertile special nuclear material. Flight times determined from detection times of the gamma-rays and alpha-particles yield a separate tomographic image of each nuclide. The APSTNG also forms the basis for a compact fast-neutron transmission imaging system that can be used along with or instead of the emission imaging system. The small and relatively inexpensive APSTNG exhibits high reliability and can be quickly replaced.<<ETX>>

Proton-Recoil Proportional Counter Tests at Treat

A methane filled proton-recoil proportional counter will be used as a fission neutron detector in the fastneutron hodoscope. To provide meaningful fuel-motion information the proportional counter should have: a linear response over a wide range of reactor powers (space charge effects are minimized); a good signal-to-background ratio (the number of high energy neutrons detected must be maximized relative to low energy neutrons, and the gamma ray sensitivity must be kept small); and a detector efficiency for fission neutrons above 1 MeV of approximately 1%. In addition, it is desirable that the detector and the associated amplifier/discriminator be capable of operating at counting rates in excess of 500 kHz. This paper reports on tests that were conducted on several proportional counters at the TREAT reactor. The goal of these tests was the determination of a set of counter parameters that would optimize fuel motion detection. The results show that a proton-recoil proportional counter with a methane gas pressure of 0.5 MPa, a counter diameter of 25.4 mm, an anode wire diameter of 0.0504 mm, and a length of 200 mm will be able to meet most of the hodoscope detector requirements.

Hodoscope Performance Tests on a 91-Pin Fuel Bundle at PARKA

Joint LASL/ANL studies of the fuel motion performance capability of a fast-neutron hodoscope have been performed on a 91-pin fuel bundle. Optimization of the neutron detectors used in the hodoscope was also investigated. The neutron detectors tested were a Hornyak button and a stilbene detector with pulse shape discrimination. These studies show that a hodoscope can provide useful fuel motion detection capability for large bundles and that the amount of information provided is greatly increased by the use of neutron detectors with high neutron thresholds and high detection efficiency. These measurements indicate that the TREAT hodoscope can be upgraded to meet most of the fuel motion diagnostic requirements of new safety facilities.

New radiation hodoscope developments for arms control treaty verification

It is pointed out that new developments in hodoscope radiation detection technology offer a wide range of capabilities for arms control treaty verification (ACTV) applications. This concept uses an array of radiation detectors to image or detect objects inside opaque containments. Hodoscope systems can detect neutrons and/or gamma-rays. The systems can be based on transmission of radiation through the objects, can detect radiation stimulated in the objects, or can detect intrinsic object radiation. Laboratory measurements to demonstrate a range of potential applications have been performed. Gamma-ray transmission hodoscopes can be used to inspect canisters, rail cars, etc. to monitor objects such as rocket motors. The use of relatively weak isotopic radiation sources makes it unnecessary to employ expensive and high-intensity accelerators. The heavy metal of nuclear warheads is characterized by strong gamma-ray absorption, and these materials could be counted by low-resolution tomography. Absorbers located in line with objects will themselves be detected, and sources located in the object region will be subtracted out as background. Intrinsic gamma-ray radiation from warheads can also be detected in a passive-instrument mode.<<ETX>>

A Proton-Recoil Proportional-Counter Array for Neutron-Image Construction

The fuel-motion measurement capability of the fast-neutron hodoscope has been upgraded by the addition of a 360-detector proton-recoil proportional-counter array, which detects high-energy fission neutrons. The current sensitive amplifier/discriminator module for each detector fits into a 12.7- by 12.7- by 102-mm package and costs less than

Text processing for the professional staff

100 per module. It has a 50-ns rise time, a noise level of 100 nA, and a deadtime per event of 200 ns. Provision has been provided for the independent adjustment of the input current versus discriminator voltage for each module. The new proportional-counters cost approximately

Extended-capacity high-speed-disk recording system for TREAT hodoscope

400 each. Each detector has been tested to have the same gain versus voltage response. A space-charge model relating count-rate changes to space-charge effects has also been developed. The new detector array has been operational for approximately two years and has become the main detector system in fuel-motion analysis. It has significantly improved the linearity, stability, count-rate capability, and setup ease of the hodoscope.

Switchable radioactive neutron source

The use of computer-related devices has resulted in significant improvements in word processing, permitting better accuracy and more efficient turnover of paperwork in an office. A selective combination of these components comprises a computer-assisted writing and editing system for professionals at Argonne National Laboratory, used primarily for technical reports. Text is entered and corrected at a terminal keyboard, viewed on a CRT, and stored on a magnetic disc; camera-ready copy is obtained on an electrostatic printer. Engineers and scientists enter original text and do creative editing; typewriter-qualified personnel quickly learn to handle other editing and corrections; and computer-support personnel provide periodic file-management services.