Inspection of a LOCA test rod at the Halden reactor project using gamma emission tomography

Conference · Fri Jul 01 04:00:00 EDT 2016

OSTI ID:22764099

Andersson, P. ^[1]; Holcombe, S.; Tverberg, T. ^[2]

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1. Division of Applied Nuclear Physics, Uppsala University, SE-75105 Uppsala (Sweden)
2. Institutt for Energiteknikk, OECD Halden Reactor Project, N-1751 Halden (Norway)

The LOCA test series IFA-650 conducted at the OECD Halden Reactor Project (HRP) has provided unique data on the performance of fuel rods during LOCA transients. One focus of the current investigations is the performance of the fuel in the ballooning stage of the LOCA transient. In this stage, relocation of fuel material is a possibility, in which case pellet fragments fall down to fill the void introduced by the increased volume of the ballooned cladding. This increases the heat load in that region, further promoting corrosion of the cladding. A special concern in the case of high-burnup fuels is the increasing number of small fuel fragments, which may be expected to cause a higher packing fraction in the ballooned region. In this work, a novel technique is presented for assessing the average density of the fuel material in the ballooned region of LOCA test rods. The investigation is based on non-destructive gamma emission tomography measurements, using the dedicated instrument recently developed at the HRP in collaboration with Westinghouse (Sweden) and Uppsala University. In this approach, the gamma radiation field surrounding the test rod has been measured with a narrowly collimated HPGe detector. Tomographic reconstruction of the data was performed, providing the radial gamma-ray source distribution within the measured volume, which reveals the fuel fragment distribution. From this, the density of the fuel in the measured volume (i.e., the packing fraction) may be calculated. The technique has been used to investigate a LOCA test rod of the Halden Reactor Project LOCA series. The LOCA experiment was carried out about one month prior to the gamma tomography examination. The results show that the distribution of the relocated fuel can be imaged using gamma rays from fission products. The reconstructions of the 662 keV rays from {sup 137}Cs and 1596 keV from {sup 140}Ba/La are demonstrated. In addition, the peaks of activation products offer valuable information on the location of the test rig structures, which may be utilized in a quantitative tomographic reconstruction to assess the spatially resolved packing fraction. (authors)

• Research Organization: American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 22764099
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
42 ENGINEERING
BARIUM 140
CESIUM 137
CLADDING
DENSITY
FISSION PRODUCTS
FUEL CANS
FUEL PELLETS
FUEL RODS
GAMMA RADIATION
GAMMA RADIOGRAPHY
HBWR REACTOR
HEATING LOAD
HIGH-PURITY GE DETECTORS
INSPECTION
LOSS OF COOLANT
NUCLEAR FUELS
NUCLEAR INDUSTRY
TOMOGRAPHY