Systems For Nuclear Auxiliary Power Research Articles

Reproducible Benchmark for the SNAP 8 Experimental Reactor at Dry Conditions

This work provides fully reproducible benchmark models of the Systems for Nuclear Auxiliary Power (SNAP) 8 Experimental Reactor. Validation benchmarks of the criticality configuration experiments under dry conditions with no coolant are presented. In addition, relevant reactivity worth experiments, and measurement of power distributions are validated and presented here. Discrepancies between modeled and experimental results are at most 110 pcm for fuel and poison worths, and critical configurations that do not manipulate control elements are within 50 pcm. Larger discrepancies found in reflector element worth experiments are due to experimental methodology which was noted as being simplified due to limited calculational capabilities at the time, while discrepancy in the control element manipulated critical configuration is due the absence of structural components for modeling simplification. Power distributions closely follow what was observed in experiment with expected peaking in reflecting elements. All models are well documented with cited references describing and justifying assumptions, simplifications, and adjustments to reproduce the models with any nuclear safety codes; model inputs and outputs are stored in the snapReactors GitHub repository.

Dismantlement of the TSF-SNAP Reactor Assembly

This paper describes the dismantlement of the Tower Shielding Facility (TSF)-Systems for Nuclear Auxiliary Power (SNAP) reactor, a SNAP-10A reactor used to validate radiation source terms and shield performance models at Oak Ridge National Laboratory (ORNL) from 1967 through 1973. After shutdown, it was placed in storage at the Y-12 National Security Complex (Y-12), eventually falling under the auspices of the Highly Enriched Uranium (HEU) Disposition Program.To facilitate downblending of the HEU present in the fuel elements, the TSF-SNAP was moved to ORNL on June 24, 2006. The reactor assembly was removed from its packaging, inspected, and the sodium-potassium (NaK) coolant was drained. A superheated steam process was used to chemically react the residual NaK inside the reactor assembly. The heat exchanger assembly was removed from the top of the reactor vessel, and the criticality safety sleeve was exchanged for a new safety sleeve that allowed for the removal of the vessel lid. A chain-mounted tubing cutter was used to separate the lid from the vessel, and the 36 fuel elements were removed and packaged in four U.S. Department of Transportation 2R/6M containers. The fuel elements were returned to Y-12 on July 13, 2006.The return of the fuel elements and disposal of all other reactor materials accomplished the formal objectives of the dismantlement project. In addition, a project model was established for the handling of a fully fueled liquid-metal–cooled reactor assembly. Current criticality safety codes have been benchmarked against experiments performed by Atomics International in the 1950s and 1960s. Execution of this project provides valuable experience applicable to future projects addressing space and liquid-metal–cooled reactors.

An Effect of Nuclear-reactor Operation in Space

THERE is considerable development effort towards producing nuclear reactors for SNAP (systems for nuclear auxiliary power) applications. Obviously the performance of these reactors in the space environment is a matter of some concern.

Space power systems state of the art

The state of the art of the space power systems and components and associated technologies in the United States are surveyed. Included are the following: solar power system, chemically fueled power systems, systems for nuclear auxiliary power, dynamic machinery for space power, radioisotope space power, thermoelectric systems, thermionic energy conversion, magnetohydro-dynamic power generation, and batteries and fuel cells.

Solvent Extraction Recovery and Purification of Strontium-90

A solvent extraction process was developed to produce high-purity Sr/sup 90/ from an irradiated U reprocessing waste solutlon. The extractant is D2EHPA diluted with TBP and Shell Spray Base. The process uses an acetic acid-acetate huffered aqueous phsse which is countercurrently contracted with the D2EHPA organic phase. Calcium and some Ce/sup 144/ extract with the Sr/sup 90/; extraction of other contaminants (Zr/sup 95/, Nb/sup 95/, Ru/sup 106/, and inert lead and iron) is prevented by adding either DTPA or EDTA to the feed solution. Decontamination from Ca and Ce/sup 144/ is provided by back extraction of the Sr/ sup 90/ into an aqueous 1M citric acid solution. The process was used to isolate and purify about one megacurie of Sr/sup 90/ for subsequent use in the fabrication of thermoelectric power generators as part of the Systems for Nuclear Auxiliary Power (SNAP) program. (auth)

Static nuclear thermoelectric system for space

A completely static nuclear-powered thermoelectric generator is discussed. The reactor, designed for snap-10 (Systems for Nuclear Auxiliary Power), uses U235-zirconium-hydride fuel moderator and is capable of operating a thermoelectric generator at a hot-side temperature of 1,000 to 1,200 F (degrees Fahrenheit). A prototype thermoelectric generator is described which produced 250 watts of electric power at spacing operating temperatures. Waste-heat radiators for the system, having constant and tapering fin thicknesses, are discussed. Curves are presented of performance versus fin number and length for both tapered and constant-thickness fins. Weight and electric power capability of a present state-of-the-art thermoelectric generator-radiator system is presented in curve form and shows a 245-pound weight for a 250-watt system exclusive of the reactor and shielding.

Nuclear Auxiliary Power - Watts to Megawatts with SNAP

Full utilization of the capability of advanced booster systems can only be realized if adequate auxiliary power units are integrated into the payload vehicle. Nuclear power units offer unique advantages for space application, - included are: compactness, light-weight, long reliable life, elimination of need for secondary batteries and sun orientation requirements, growth potential from hundreds of watts to megawatt range, and development of qualified units on a time scale that is consistent with present expected payload growth capability. Studies have shown solar cells and nuclear isotope auxiliary power systems have application in missions with power requirements up to a few hundred watts, solar dynamic and nuclear reactor systems are competitive for the sub-kilowatt to few kilowatt level; however, beyond this range compact reactor systems are the only feasible way of obtaining the power needs for advanced missions (Fig. 1). Compact reactors and power conversion equipment for space application have been under development for a number of years under AEC, NASA, and DOD sponsorship, where today three SNAP (Systems for Nuclear Auxiliary Power) reactor projects are now progranmed for early orbital flight testing. These are the 500 watt SNAP 10A, the 3Kw SNAP 2, and 30/60 Kw SNAP 8 systems. Advanced space systems capable of producing hundreds of kilowatts with extension into the megawatt range with less than 5 lbs/kw specific weight are now under study.

SNAP-10 experimental thermoelectric generator

An experimental thermoelectric generator for the SNAP-10 (Systems for Nuclear Auxiliary Power) power system is described. Preliminary tests results are presented for a unit mounted on an electrical heat source which simulated a nuclear reactor.