Investigation of cooling coil corrosion in storage tanks for radioactive waste

Conference · Sun Jan 01 04:00:00 EST 1978

OSTI ID:5203542

Ondrejcin, R. S.

The high frequency of cooling coil leaks observed in high-heat waste storage tanks soon after sludge removal operations is attributed to pitting, according to laboratory corrosion studies. Experiments show that the most likely series of events leading to coil leakage is (1) excessive dilution of basic nitrite in the supernate, (2) initiation of attack in crevices due to oxygen depletion cells, and (3) acceleration of the attack by sulfate dissolved from the sludge. When sludge was slurried with water, the interstitial liquid was diluted. Nitrite, the anodic inhibitor that prevented attack on coils and tanks in normal operation when its concentration was 0.5 to 3.0M, could accelerate attack when diluted to 10/sup -4/ to 10/sup -3/M. Attack was presumably initiated at oxygen depletion cells. The presence of sulfate, leached from the sludge, produced a conductive solution that could produce high current densities at the corroding steel surface. The proposed series of events leading to coil leakage agrees with the observations previously made on one leaking coil removed from Tank 2F after sludge removal in 1967. Examination revealed pitting that had originated on the outside of the coils. This pitting was attributed to oxygen depletion cells in coil crevices. To prevent recurrence of pitting attack on cooling coils during future sludge removal operations, the sludge should be slurried (1) with waste diluted less than one hundredfold with water, or (2) with a 500-ppm nitrite-H/sub 2/O solution at pH 12. Either method should preclude pitting damage to the coils.

• Research Organization: Du Pont de Nemours (E.I.) and Co., Aiken, S.C. (USA). Savannah River Lab.
• DOE Contract Number: EY-76-C-09-0001
• OSTI ID: 5203542
• Report Number(s): DP-MS-77-109; CONF-780308-2
• Country of Publication: United States
• Language: English

Related Subjects

052002* -- Nuclear Fuels-- Waste Disposal & Storage
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
CHEMICAL REACTIONS
CONTAINERS
COOLING SYSTEMS
CORROSION
IRON ALLOYS
IRON BASE ALLOYS
LEAKS
MANAGEMENT
MATERIALS
RADIOACTIVE WASTE STORAGE
STEELS
STORAGE
TANKS
WASTE MANAGEMENT
WASTE STORAGE