Status of High Flux Isotope Reactor (HFIR) Post-restart Safety Analysis and Documentation Upgrades
Status of High Flux Isotope Reactor (HFIR) Post-restart Safety Analysis and Documentation Upgrades

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Published: 1990

Total Pages: 15

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The High Flux Isotope Reactor (HFIR), an experimental reactor located at the Oak Ridge National Laboratory (ORNL) and operated for the US Department of Energy by Martin Marietta Energy Systems, was shut down in November, 1986 after the discovery of unexpected neutron embrittlement of the reactor vessel. The reactor was restarted in April, 1989, following an extensive review by DOE and ORNL of the HFIR design, safety, operation, maintenance and management, and the implementation of several upgrades to HFIR safety-related hardware, analyses, documents and procedures. This included establishing new operating conditions to provide added margin against pressure vessel failure, as well as the addition, or upgrading, of specific safety-related hardware. This paper summarizes the status of some of the follow-on (post-restart) activities which are currently in progress, and which will result in a comprehensive set of safety analyses and documentation for the HFIR, comparable with current practice in commercial nuclear power plants. 8 refs.

Upgrading Scientific Capabilities at the High Flux Isotope Reactor
Upgrading Scientific Capabilities at the High Flux Isotope Reactor

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Published: 1997

Total Pages: 6

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Following termination of the Advanced Neutron Source (ANS) Project, a program of upgrades to the Department of Energy's High Flux Isotope Reactor (HFIR) was devised by a team of researchers and reactor operators and has been proposed to the department. HFIR is a multipurpose research reactor, commissioned in 1965, with missions in four nationally important areas: isotope production, especially transuranic isotopes; neutron scattering; neutron activation analysis; and irradiation testing of materials. For neutron scattering, there are two major enhancements and several smaller ones. The first is the installation of a small, hydrogen cold neutron source in one of the four existing beam tubes: because of the high reactor power, and the use of new design concepts developed for ANS, the cold source will be as bright as, or brighter than, the Institute Laue Langevin liquid deuterium vertical cold source, although space limitations mean that there will be far fewer cold beams and instruments at HFIR. This project is underway, and the cold source is expected to come on line following an extended shutdown in 1999 to replace the reactor's beryllium reflector. The second major change proposed would put five thermal neutron guides at an existing beam port and construct a new guide hall to accommodate instruments on these very intense beams.

A Review of Proposed Upgrades to the High Flux Isotope Reactor and Potential Impacts to Reactor Vessel Integrity
A Review of Proposed Upgrades to the High Flux Isotope Reactor and Potential Impacts to Reactor Vessel Integrity

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Published: 2001

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The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) was scheduled in October 2000 to implement design upgrades that include the enlargement of the HB-2 and HB-4 beam tubes. Higher dose rates and higher radiation embrittlement rates were predicted for the two beam-tube nozzles and surrounding vessel areas. ORNL had performed calculations for the upgraded design to show that vessel integrity would be maintained at acceptable levels. Pacific Northwest National Laboratory (PNNL) was requested by the U.S. Department of Energy Headquarters (DOE/HQ) to perform an independent peer review of the ORNL evaluations. PNNL concluded that the calculated probabilities of failure for the HFIR vessel during hydrostatic tests and for operational conditions as estimated by ORNL are an acceptable basis for selecting pressures and test intervals for hydrostatic tests and for justifying continued operation of the vessel. While there were some uncertainties in the embrittlement predictions, the ongoing efforts at ORNL to measure fluence levels at critical locations of the vessel wall and to test materials from surveillance capsules should be effective in dealing with embrittlement uncertainties. It was recommended that ORNL continue to update their fracture mechanics calculations to reflect methods and data from ongoing research for commercial nuclear power plants. Such programs should provide improved data for vessel fracture mechanics calculations.

High Flux Isotope Reactor Power Upgrade Status
High Flux Isotope Reactor Power Upgrade Status

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Published: 1997

Total Pages: 9

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A return to 100-MW operation is being planned for the High Flux Isotope Reactor (HFIR). Recent improvements in fuel element manufacturing procedures and inspection equipment will be exploited to reduce hot spot and hot streak factors sufficiently to permit the power upgrade without an increase in primary coolant pressure. Fresh fuel elements already fabricated for future use are being evaluated individually for power upgrade potential based on their measured coolant channel dimensions.

The Use of PRA (Probabilistic Risk Assessment) in the Management of Safety Issues at the High Flux Isotope Reactor
The Use of PRA (Probabilistic Risk Assessment) in the Management of Safety Issues at the High Flux Isotope Reactor

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Published: 1990

Total Pages: 9

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The High Flux Isotope reactor (HFIR) is a high performance isotope production and research reactor which has been in operation at Oak Ridge National Laboratory (ORNL) since 1965. In late 1986 the reactor was shut down as a result of discovery of unexpected neutron embrittlement of the reactor vessel. In January of 1988, a level 1 Probabilistic Risk Assessment (PRA) (excluding external events) was published as part of the response to the many reviews that followed the shutdown and for use by ORNL to prioritize action items intended to upgrade the safety of the reactor. A conservative estimate of the core damage frequency initiated by internal events for HFIR was 3.11 x 10−4. In June 1989 a draft external events initiated PRA was published. The dominant contributions from external events came from seismic, wind, and fires. The overall external event contribution to core damage frequency is about 138% of the internal event initiated contribution and is dominated by wind initiators. The PRA has provided a basis for the management of a wide range of safety and operation issues at the HFIR. 3 refs., 4 figs., 2 tabs.

External Event Probabilistic Risk Assessment for the High Flux Isotope Reactor (HFIR).
External Event Probabilistic Risk Assessment for the High Flux Isotope Reactor (HFIR).

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Published: 1989

Total Pages: 24

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The High Flux Isotope Reactor (HFIR) is a high performance isotope production and research reactor which has been in operation at Oak Ridge National Laboratory (ORNL) since 1965. In late 1986 the reactor was shut down as a result of discovery of unexpected neutron embrittlement of the reactor vessel. In January of 1988 a level 1 Probabilistic Risk Assessment (PRA) (excluding external events) was published as part of the response to the many reviews that followed the shutdown and for use by ORNL to prioritize action items intended to upgrade the safety of the reactor. A conservative estimate of the core damage frequency initiated by internal events for HFIR was 3.11 x 10−4. In June 1989 a draft external events initiated PRA was published. The dominant contributions from external events came from seismic, wind, and fires. The overall external event contribution to core damage frequency is about 50% of the internal event initiated contribution and is dominated by seismic events.