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Title: ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.

Abstract

The Zero Power Physics Reactor (ZPPR) fast critical facility was built at the Argonne National Laboratory-West (ANL-W) site in Idaho in 1969 to obtain neutron physics information necessary for the design of fast breeder reactors. The ZPPR-20D Benchmark Assembly was part of a series of cores built in Assembly 20 (References 1 through 3) of the ZPPR facility to provide data for developing a nuclear power source for space applications (SP-100). The assemblies were beryllium oxide reflected and had core fuel compositions containing enriched uranium fuel, niobium and rhenium. ZPPR-20 Phase C (HEU-MET-FAST-075) was built as the reference flight configuration. Two other configurations, Phases D and E, simulated accident scenarios. Phase D modeled the water immersion scenario during a launch accident, and Phase E (SUB-HEU-MET-FAST-001) modeled the earth burial scenario during a launch accident. Two configurations were recorded for the simulated water immersion accident scenario (Phase D); the critical configuration, documented here, and the subcritical configuration (SUB-HEU-MET-MIXED-001). Experiments in Assembly 20 Phases 20A through 20F were performed in 1988. The reference water immersion configuration for the ZPPR-20D assembly was obtained as reactor loading 129 on October 7, 1988 with a fissile mass of 167.477 kg and a reactivity of -4.626more » {+-} 0.044{cents} (k {approx} 0.9997). The SP-100 core was to be constructed of highly enriched uranium nitride, niobium, rhenium and depleted lithium. The core design called for two enrichment zones with niobium-1% zirconium alloy fuel cladding and core structure. Rhenium was to be used as a fuel pin liner to provide shut down in the event of water immersion and flooding. The core coolant was to be depleted lithium metal ({sup 7}Li). The core was to be surrounded radially with a niobium reactor vessel and bypass which would carry the lithium coolant to the forward inlet plenum. Immediately inside the reactor vessel was a rhenium baffle which would act as a neutron curtain in the event of water immersion. A fission gas plenum and coolant inlet plenum were located axially forward of the core. Some material substitutions had to be made in mocking up the SP-100 design. The ZPPR-20 critical assemblies were fueled by 93% enriched uranium metal because uranium nitride, which was the SP-100 fuel type, was not available. ZPPR Assembly 20D was designed to simulate a water immersion accident. The water was simulated by polyethylene (CH{sub 2}), which contains a similar amount of hydrogen and has a similar density. A very accurate transformation to a simplified model is needed to make any of the ZPPR assemblies a practical criticality-safety benchmark. There is simply too much geometric detail in an exact model of a ZPPR assembly, particularly as complicated an assembly as ZPPR-20D. The transformation must reduce the detail to a practical level without masking any of the important features of the critical experiment. And it must do this without increasing the total uncertainty far beyond that of the original experiment. Such a transformation will be described in a later section. First, Assembly 20D was modeled in full detail--every plate, drawer, matrix tube, and air gap was modeled explicitly. Then the regionwise compositions and volumes from this model were converted to an RZ model. ZPPR Assembly 20D has been determined to be an acceptable criticality-safety benchmark experiment.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
929227
Report Number(s):
NEA/NSC/DOC(95)03/II VOLUME II HEU-MET-MIXED-012
TRN: US0803713
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Technical Report
Country of Publication:
United States
Language:
ENGLISH
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 29 ENERGY PLANNING, POLICY AND ECONOMY; 36 MATERIALS SCIENCE; BERYLLIUM OXIDES; BREEDER REACTORS; CONFIGURATION; ENRICHED URANIUM; FUEL PINS; HIGHLY ENRICHED URANIUM; LITHIUM; MATERIAL SUBSTITUTION; NIOBIUM; NUCLEAR POWER; POLYETHYLENES; REACTOR VESSELS; RHENIUM; URANIUM NITRIDES; ZERO POWER REACTORS; ZIRCONIUM ALLOYS; NESDPS Office of Nuclear Energy Space and Defense Power Systems

Citation Formats

Lell, R., Grimm, K., McKnight, R., Shaefer, R., Nuclear Engineering Division, and INL. ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.. United States: N. p., 2006. Web. doi:10.2172/929227.
Lell, R., Grimm, K., McKnight, R., Shaefer, R., Nuclear Engineering Division, & INL. ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.. United States. doi:10.2172/929227.
Lell, R., Grimm, K., McKnight, R., Shaefer, R., Nuclear Engineering Division, and INL. Sat . "ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.". United States. doi:10.2172/929227. https://www.osti.gov/servlets/purl/929227.
@article{osti_929227,
title = {ZPPR-20 phase D : a cylindrical assembly of polyethylene moderated U metal reflected by beryllium oxide and polyethylene.},
author = {Lell, R. and Grimm, K. and McKnight, R. and Shaefer, R. and Nuclear Engineering Division and INL},
abstractNote = {The Zero Power Physics Reactor (ZPPR) fast critical facility was built at the Argonne National Laboratory-West (ANL-W) site in Idaho in 1969 to obtain neutron physics information necessary for the design of fast breeder reactors. The ZPPR-20D Benchmark Assembly was part of a series of cores built in Assembly 20 (References 1 through 3) of the ZPPR facility to provide data for developing a nuclear power source for space applications (SP-100). The assemblies were beryllium oxide reflected and had core fuel compositions containing enriched uranium fuel, niobium and rhenium. ZPPR-20 Phase C (HEU-MET-FAST-075) was built as the reference flight configuration. Two other configurations, Phases D and E, simulated accident scenarios. Phase D modeled the water immersion scenario during a launch accident, and Phase E (SUB-HEU-MET-FAST-001) modeled the earth burial scenario during a launch accident. Two configurations were recorded for the simulated water immersion accident scenario (Phase D); the critical configuration, documented here, and the subcritical configuration (SUB-HEU-MET-MIXED-001). Experiments in Assembly 20 Phases 20A through 20F were performed in 1988. The reference water immersion configuration for the ZPPR-20D assembly was obtained as reactor loading 129 on October 7, 1988 with a fissile mass of 167.477 kg and a reactivity of -4.626 {+-} 0.044{cents} (k {approx} 0.9997). The SP-100 core was to be constructed of highly enriched uranium nitride, niobium, rhenium and depleted lithium. The core design called for two enrichment zones with niobium-1% zirconium alloy fuel cladding and core structure. Rhenium was to be used as a fuel pin liner to provide shut down in the event of water immersion and flooding. The core coolant was to be depleted lithium metal ({sup 7}Li). The core was to be surrounded radially with a niobium reactor vessel and bypass which would carry the lithium coolant to the forward inlet plenum. Immediately inside the reactor vessel was a rhenium baffle which would act as a neutron curtain in the event of water immersion. A fission gas plenum and coolant inlet plenum were located axially forward of the core. Some material substitutions had to be made in mocking up the SP-100 design. The ZPPR-20 critical assemblies were fueled by 93% enriched uranium metal because uranium nitride, which was the SP-100 fuel type, was not available. ZPPR Assembly 20D was designed to simulate a water immersion accident. The water was simulated by polyethylene (CH{sub 2}), which contains a similar amount of hydrogen and has a similar density. A very accurate transformation to a simplified model is needed to make any of the ZPPR assemblies a practical criticality-safety benchmark. There is simply too much geometric detail in an exact model of a ZPPR assembly, particularly as complicated an assembly as ZPPR-20D. The transformation must reduce the detail to a practical level without masking any of the important features of the critical experiment. And it must do this without increasing the total uncertainty far beyond that of the original experiment. Such a transformation will be described in a later section. First, Assembly 20D was modeled in full detail--every plate, drawer, matrix tube, and air gap was modeled explicitly. Then the regionwise compositions and volumes from this model were converted to an RZ model. ZPPR Assembly 20D has been determined to be an acceptable criticality-safety benchmark experiment.},
doi = {10.2172/929227},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Sep 30 00:00:00 EDT 2006},
month = {Sat Sep 30 00:00:00 EDT 2006}
}

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