TABLE 5 - 22 CONDITIONS OF RUNS TO INVESTIGATE STRESS-CORROSION CRACKING IN CHLORIDE-CONTAINING URANYL SULFATE SOLUTION
Run no .
ChloTime, Temp ., U02SO4, ride Oxygen, hr 째C m ppm pp m
Remarks
H-103 H-104a H-104b
98 143 250
250 250 250
0 .17 0 .17 0 .17
H-104c H-104d
260 111
250 250
0 .17 0 .17
H-105a
211
200
0 .17
0 1000 Pretreatment 40 1500-1800 40 1500-1800 Same solution as H-104a 60 20-170 New solution 50 0-40 Oxygen exhaustion occurred and U precipitated 50 1000-3000
H-105b 200
200
0 .17
50
0-25
Cracking results
No cracks No cracks No cracks Pits, but no cracks
One crevice crack Oxygen exhaustion All five specimens occurred and cracked U precipitated
Several of the cracks were parallel rather than normal to the applied tensile stress, and most were in the regions where the identification numbers were stamped on the specimens rather than in the areas of maximum elastic stress . The aggressive stress cracking encountered in the oxygen exhaustion run at 200 째C raised the question whether similar effects might be produced in the absence of chloride . Consequently, oxygen exhaustion studies were carried out in loop runs with 0 .17 M uranyl sulfate solutions containing < 3 ppm of chloride ions . Stress specimens exposed in such runs at 200, 250, and 280 째C showed no stress-corrosion cracks on metallographic examination [162] . In-pile experience has of necessity been substantially less extensive ; however, the results have been consistent with the negative experience encountered with out-of-pile loops . Over a period of 22 years, about 17,000 operating hours have been accumulated in fifteen type-347 stainlesssteel in-pile loop experiments without encountering evidence of stress cracking . Also, stress specimens were exposed in the pressurizer vapor and liquid locations in one 1700-hr experiment . Subsequent microscopic and metallographic examination revealed no evidence of cracks . Stress speci-