Nuclear Transmutations in HFIR's Beryllium Reflector and Their Impact on Reactor Operation and Reflector Disposal

Journal Article · Sun Jan 01 04:00:00 EST 2012 · Nuclear Technology

OSTI ID:1042793

Chandler, David ^[1]; Maldonado, G Ivan ^[1]; Primm, Trent ^[1]; Proctor, Larry Duane ^[1]

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1. ORNL

The High Flux Isotope Reactor located at the Oak Ridge National Laboratory utilizes a large cylindrical beryllium reflector that is subdivided into three concentric regions and encompasses the compact reactor core. Nuclear transmutations caused by neutron activation occur in the beryllium reflector regions, which leads to unwanted neutron absorbing and radiation emitting isotopes. During the past year, two topics related to the HFIR beryllium reflector were reviewed. The first topic included studying the neutron poison (helium-3 and lithium-6) buildup in the reflector regions and its affect on beginning-of-cycle reactivity. A new methodology was developed to predict the reactivity impact and estimated symmetrical critical control element positions as a function of outage time between cycles due to helium-3 buildup and was shown to be in better agreement with actual symmetrical critical control element position data than the current methodology. The second topic included studying the composition of the beryllium reflector regions at discharge as well as during decay to assess the viability of transporting, storing, and ultimately disposing the reflector regions currently stored in the spent fuel pool. The post-irradiation curie inventories were used to determine whether the reflector regions are discharged as transuranic waste or become transuranic waste during the decay period for disposal purposes and to determine the nuclear hazard category, which may affect the controls invoked for transportation and temporary storage. Two of the reflector regions were determined to be transuranic waste at discharge and the other region was determined to become transuranic waste in less than 2 years after being discharged due to the initial uranium content (0.0044 weight percent uranium). It was also concluded that all three of the reflector regions could be classified as nuclear hazard category 3 (potential for localized consequences only).

• Research Organization: Oak Ridge National Laboratory (ORNL); High Flux Isotope Reactor
• Sponsoring Organization: NNSA USDOE - National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1042793
• Journal Information: Nuclear Technology, Journal Name: Nuclear Technology Journal Issue: 3 Vol. 177; ISSN 0029-5450; ISSN NUTYBB
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
BERYLLIUM
BUILDUP
Be
CONTROL ELEMENTS
DECAY
HELIUM 3
HFIR
HFIR REACTOR
He-3
INVENTORIES
LITHIUM 6
NEUTRONS
ORNL
RADIATIONS
REACTOR CORES
REACTOR OPERATION
SPENT FUELS
STORAGE
TRANSMUTATION
TRU
URANIUM
VIABILITY
WASTES
beryllium
disposal
hazard category
helium
reactivity
transuranic
waste