Nodular corrosion of the Zircaloys

Conference · Sun Aug 01 04:00:00 EDT 1976

OSTI ID:7336832

Johnson, Jr., A. B.; Horton, R. M.

Oxide nodules form on Zircaloy nuclear components under irradiation. Similar nodules were observed on Zircaloy coupons in cold rolled or extended conditions after autoclave treatments at 475 and 500/sup 0/C in steam at 1500 to 1700 psi. Stages of nodular corrosion in the autoclave were nodule nucleation, growth, coalescence, propagation to accelerated uniform corrosion, and complete specimen oxidation. Observations on BWR fuel rods suggest that a similar progressive attack has occurred; however, in no case has the in-reactor attack progressed to the stage of complete fuel rod failure. Recent autoclave tests confirmed the nodular character of the attack on cold-worked materials. Alpha anneals (up to 790/sup 0/C) did not consistently suppress the nodular attack. However, alpha + beta (840/sup 0/C) and beta (1010 and 1040/sup 0/C) anneals did suppress the attack if followed by a fast cool. The efficacy of the anneals applied similarly to Zircaloy-2 and Zircaloy-4. Stresses associated with U-bend specimens and heavy (86 percent) cold work did not enhance the nodular attack before stress relief occurred. The nodular attack on reactor components appears to depend on nuclear flux, and develops in oxygenated reactor coolants, principally in the vicinity of fuel rod spacers. Experience with irradiated specimens in reactor loops suggests that uniform concentrations of dissolved oxygen alone do not initiate nodular attack. Localized water chemistry associated with flow disturbances or, in some cases, dissimilar metals in fuel spacers, may be factors in the nodular attack in-reactor.

• Research Organization: Battelle Pacific Northwest Labs., Richland, Wash. (USA)
• DOE Contract Number: E(45-1)-1830
• OSTI ID: 7336832
• Report Number(s): BNWL-SA-5735; CONF-760858-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
360106 -- Metals & Alloys-- Radiation Effects
ALLOYS
ANNEALING
CHEMICAL REACTIONS
CHROMIUM ADDITIONS
CHROMIUM ALLOYS
COLD WORKING
CORROSION
FABRICATION
FUEL CANS
HEAT TREATMENTS
IRON ADDITIONS
IRON ALLOYS
MATERIALS WORKING
NUCLEATION
REACTOR MATERIALS
TIN ALLOYS
ZIRCALOY
ZIRCALOY 2
ZIRCALOY 4
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS