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NEA-1806 IFPE/DEFEX.

IFPE/DEFEX, Studsvik DEFEX BWR fuel secondary defect formation as a consequence of primary defects

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1. NAME OF EXPERIMENT:  IFPE/DEFEX.
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2. COMPUTERS
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Program name Package id Status Status date
IFPE/DEFEX NEA-1806/01 Arrived 14-APR-2008

Machines used:

Package ID Orig. computer Test computer
NEA-1806/01 Many Computers
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3. DESCRIPTION OF EXPERIMENT

The DEFEX Project started on 1 April 1993. It is an undertaking made in international co-operation, aiming at the study of secondary defect formation as a consequence of primary defects. The experiments were made in the R2 test reactor using a special simulation technique for the primary defects. Test rodlets typical of 8x8 BWR fuel with three different types of Zircaloy-2 cladding were investigated in a total of eleven tests. Standard cladding was compared to zirconium liner cladding as well as to rifled cladding, which has been proposed as a remedy against secondary failure by hydriding. Linear Heat Rate, pellet - clad gap and irradiation time were the principal test parameters. The rodlets were previously unirradiated.
  
The DEFEX Project was preceded by two exploratory test series, financed by Swedish sponsors. Defect Fuel Experiment No. 1 was performed in December 1990 and March 1991. Defect Fuel Experiment No. 2 was performed between June 1992 and January 1993.
  
The non-destructive measurements that were made include on-line elongation measurement, profilometry measurement, eddy current scanning, neutron radiography, gamma scanning, visual inspection and gap squeeze measurement.
  
Destructive examinations included metallography, fuel grain size measurements, determination of fuel porosity distribution, cladding hydrogen determination by SEM, Electron Probe Micro Analysis in one case, mass spectrometry of residual gas and UO2 oxidation determination by X-ray powder diffraction.
  
Four of the DEFEX test rodlets, all with 0.15 micron gap but with different types of cladding, failed in conjunction with extensive hydriding at Linear Heat Rates of 40 and 50 kW/m. For three of these rodlets, with standard and rifled cladding, time to failure varied between 76 and 102 hours. The fourth rodlet, with liner cladding, failed after 216 hours. The hydriding degradation process could be followed by studying the elongation curve. It was observed that those rodlets that failed early exhibited a steeper increase after the initial features than those that did not fail. This fact is ascribed to intensive hydriding of the cladding. For the liner rodlet, which remained intact for the longest time, the elongation curve had a similar shape in the beginning, but after two days' irradiation it levelled off. The ensuing elongation is ascribed to the influence of irradiation growth.
  
The oxidation behavior of the rodlets with liner cladding and those with standard cladding was not very different at the low burnups of the DEFEX Project. However, the liner cladding showed less hydrogen pick-up than the standard cladding.
  
Pre-characterization and details of DEFEX rods 1 - 10
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DEFEX-1, rod 2365, a rod with standard cladding and a gap of 150 microns. The rod was irradiated with water in the extended plenum, simulating a primary defect.
  
DEFEX-2, rod 2364, a rod with standard cladding and a gap of 150 microns. The rod was irradiated without water in the extended plenum.
  
DEFEX-3, rod 2360, a rod with liner cladding and a gap of 150 microns. The rod was irradiated with water in the extended plenum, simulating a primary defect.
  
DEFEX-4 rod 2357, a rod with rifled cladding and a gap of 150 microns, was irradiated with water in the extended plenum, simulating a primary defect.
  
DEFEX-5 rod 2366, a rod with standard cladding and a gap of 150 microns, was irradiated with water in the extended plenum, simulating a primary defect.
  
DEFEX-5X rod 2363, a rod with standard cladding and a variable gap, meaning 150 microns at the bottom and upper part and only 80 pm at the middle part, was irradiated. The rod had water in the extended plenum, simulating a primary defect.
  
DEFEX-6 rod 2359, a rod with liner cladding and a variable gap, meaning 150 microns at the bottom and upper part and only 80 microns at the middle part was irradiated. The rod had water in the extended plenum, simulating a primary defect.
  
DEFEX-7, the rodlet 2368 with standard cladding and a gap of 80 microns, was irradiated with water in the extended plenum.
  
DEFEX-8, the rodlet 2367 with standard cladding and a gap of 150 microns, was irradiated with water in the extended plenum.
  
DEFEX-9, the rodlet 2361 with liner cladding and a gap of 150 microns, was irradiated with water in the extended plenum.
  
DEFEX-10, the rodlet 2362 with liner cladding and a gap of 80 pm, was irradiated with water in the extended plenum.
  
The Final Report gives diagrams of actual rods and dimensions.
  
A summary of the experiments is given in Table 4.1 of DEFEX16 report.
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8. RELATED OR AUXILIARY PROGRAMS
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9. STATUS
Package ID Status date Status
NEA-1806/01 14-APR-2008 Arrived restricted
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10. REFERENCES
NEA-1806/01, included references:
- Mikael Carlsson:
The DEFEX Project - Irradiation Parameters and Elongation Measurements of the
First Three DEFEX Tests (STUDSVIK-DEFEX-7, 1994)
- Mikael Carlsson:
The DEFEX Project - Irradiation Parameters and Elongation Measurements of the
DEFEX Tests Number 4, 5, 5X and 6 (STUDSVIK-DEFEX-12, 1994)
- Mikael Carlsson:
The DEFEX Project - Irradiation Parameters and Elongation Measurements of the
DEFEX Tests Number 7, 8, 9 and 10 (STUDSVIK-DEFEX-16, 1995)
- Christian Graslund:
Final Report of the DEFEX Project (STUDSVIK-DEFEX-21, 1995)
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12. PROGRAMMING LANGUAGE(S) USED

No item found

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15. NAME AND ESTABLISHMENT OF AUTHORS

Studsvik Nuclear AB
SE-611 82 NYKOEPING
Sweden
  
Compiled by: J. A. TURNBULL, U.K.
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16. MATERIAL AVAILABLE
NEA-1806/01
DEFEX Summary.doc   WORD file summarizing the dataset
Description of the DEFEX experiment
Details of DEFEX rods.doc  File providing pre-characterization and test data
DEFEX-x.HIS  Three zone irradiation histories for rods 1, 2, 3, 4, 5, 5X, 6, 7,
8, 9, 10
(Details of PIE should be sought in the Final Report DEFEX21)
QA report for DEFEX Experiments.doc  QA report for compiling dataset
Readme file
Electronic documentation
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17. CATEGORIES
  • Y. Integral Experiments Data, Databases, Benchmarks

Keywords: boiling water reactor, defect, elongation, zircaloy.