Edgar A. Rhodes

BEHAVIOR OF MODERN METALLIC FUEL IN TREAT TRANSIENT OVERPOWER TESTS

AbstractResults and analyses of margin to cladding failure and prefailure axial expansion of metallic fuel are reported for Transient Reactor Test Facility in-pile transient overpower tests M2 through M7. These include the first such tests on binary and ternary alloy fuel of the Integral Fast Reactor concept and fuel burnups to 10 at. %. The fuel was tested at full coolant flow and subjected to an exponential power rise on an 8-s period until either incipient or actual cladding failure was achieved. Objectives, designs, and methods are described with emphasis on developments unique to metal fuel safety testing. Test results include the following: (a) temperature, flow, and pressure data; (b) fuel motion diagnostic data from the fast neutron hodoscope; and (c) test remains described by both destructive and nondestructive posttest examination. The resulting M-series data base for cladding failure threshold and prefailure fuel expansion is presented. The nature of the observed cladding failure and resultant ...

Fast-Neutron Hodoscope at Treat: Development and Operation

A description is given of a fast-neutron hodoscope to detect fuel motion within test samples inserted in the center of the Transient Reactor Test Facility (TREAT) reactor core. The fuel motion is induced under simulated hypothetical conditions. The hodoscope system includes components necessary to acquire, store, decode, and process the collected data.

Fast-Neutron Hodoscope at TREAT: Methods for Quantitative Determination of Fuel Dispersal

Fuel-motion surveillance using the fast-neutron hodoscope in TREAT experiments has advanced from an initial role of providing time/location/velocity data to that of offering quantitative mass results. The material and radiation surroundings of tha test section contribute to intrinsic and instrumental effects upon hodoscope detectors that require detailed corrections. Depending upon the experiment, count rate compensation is usually required for deadtime, power level, nonlinear response, efficiency, background, and detector calibration. Depending on their magnitude and amenability to analytical and empirical treatment, systematic corrections may be needed for self-shielding, self-multiplication, self-attenuation, flux depression, and other effects. Current verified hodoscope response (for 1- to 7-pin fuel bundles) may be paramatrically characterized under optimum conditions by 1-ms time resolution; 0.25-mm lateral and 5-mm axial-motion displacement resolution; and 50-mg single-pin mass resolution. The experimental and theoretical foundation for this performance is given, with particular emphasis on the geometrical response function and the statistical limits of fuel-motion resolution. Comparisons are made with alternative diagnostic systems.

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>>

Fast-Neutron Hodoscope at TREAT: Data Processing, Analysis, and Results

The fast-neutron hodoscope at the Transient Reactor Test Facility is designed for the determination of fuel motion during the course of brief (0.1- to 30-sec) power transients. During the course of a transient test, data must be recorded from each of 334 hodoscope channels at count rates up to 2 million/sec each, down to millisecond time intervals. This is accomplished in a relatively reliable and inexpensive manner by displaying counts from each detector sequentially in binary code on a lamp panel, which is photographed by a high-speed framing camera, producing a film record of the transient test. After chemical development, the film is examined by a computer-controlled flying-spot scanner, and the position and density of candidate lamp images are recorded on magnetic tape. Through further computer processing, these images are sorted and decoded, and the count rate is recovered for each detector at each instant of collection time. A cathode-ray tube and a plotter, both computer controlled, are used to recreate and analyze the fuel motion history of the experiment. Analysis is directed toward fuel distortion or expansion prior to clad failure, slumping, dispersion, amount and rates of movement, post-scram relocation, and ultimate disposition of fuel.

Associated-particle sealed-tube neutron probe for characterization of materials

A relatively small and inexpensive neutron diagnostic probe system has been developed that can identify and image most elements having a larger atomic number than boron. It has the potential to satisfy van-mobile and fixed-portal requirements for nondestructive detection of contraband drugs, explosives, and nuclear and chemical warfare weapon materials, and for treaty verification of sealed munitions and remediation of radioactive waste.

Fuel motion in overpower tests of metallic integral fast reactor fuel

In this paper results from hodoscope data analyses are presented for transient overpower (TOP) tests M5, M6, and M7 at the Transient Reactor Test Facility, with emphasis on transient feedback mechanisms, including prefailure expansion at the tops of the fuel pins, subsequent dispersive axial fuel motion, and losses in relative worth of the fuel pins during the tests. Tests M5 and M6 were the first TOP tests of margin to cladding breach and prefailure elongation of D9-clad ternary (U-Pu-Zr) integral fast reactor-type fuel. Test M7 extended these results to high-burnup fuel and also initiated transient testing of HT-9-clad binary (U-Zr) Fast Flux Test Facility driver fuel. Results show significant prefailure negative reactivity feedback and strongly negative feedback from fuel driven to failure.

APSTNG: neutron interrogation for detection of explosives, drugs, and nuclear and chemical warfare materials

A recently developed neutron diagnostic probe system has the potential to satisfy a significant number of van-mobile and fixed-portal requirements for nondestructive detection, including monitoring of contraband explosives, drugs, and weapon materials, and treaty verification of sealed munitions. The probe is based on a unique associated-particle sealed-tube neutron generator (APSTNG) that interrogates the object of interest 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 reactions identify nuclides associated with all major chemicals in explosives, drugs, and chemical warfare agents, 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 coarse tomographic image of each identified 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. Proof-of-concept experiments have been performed under laboratory conditions for simulated nuclear and chemical warfare munitions and for explosives and drugs. The small and relatively inexpensive APSTNG exhibits high reliability and can be quickly replaced. Surveillance systems based on APSTNG technology can avoid the large physical size, high capital and operating expenses, and reliability problems associated with complex accelerators.

Advances in associated-particle neutron probe diagnostics for substance detection

The development and investigation of a small associated-particle sealed-tube neutron generator (APSTNG) shows potential to allow the associated-particle diagnostic method to be moved out of the laboratory into field applications. The APSTNG interrogates the inspected object with 14-MeV neutrons generated from the deuterium-tritium reaction and detects the alpha-particle associated with each neutron inside a cone encompassing the region of interest. Gamma-ray spectra of resulting neutron reactions identify many nuclides. Flight-times determined from detection times of the gamma-rays and alpha-particles can yield a separate course tomographic image of each identified nuclide, from a single orientation. Chemical substances are identified by comparing relative spectral line intensities with ratios of elements in reference compounds. The high-energy neutrons and gamma-rays penetrate large objects and dense materials. Generally, no collimators or radiation shielding are needed. Proof-of-concept laboratory experiments have been successfully performed for simulated nuclear, chemical warfare, and conventional munitions. Most recently, inspection applications have been investigated for radioactive waste characterization, presence of cocaine in propane tanks, and uranium and plutonium smuggling. Based on lessons learned with the present APSTNG system, an advanced APSTNG tube (along with improved high voltage supply and control units) is being designed and fabricated that will be transportable and rugged, yield a substantial neutron output increase, and provide sufficiently improved lifetime to allow operation at more than an order of magnitude increase in neutron flux.

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>>