ML20084D323
| ML20084D323 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, 05000000 |
| Issue date: | 05/21/1975 |
| From: | Abel J COMMONWEALTH EDISON CO. |
| To: | Zieman D, Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20084D320 | List: |
| References | |
| 5752, NUDOCS 8304110072 | |
| Download: ML20084D323 (7) | |
Text
Comm vnith Edison
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[C y Address heply to: Post Offica Box 767 Chicago, lilinois 60690 y.-
May 21, 19 75
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f c4 Mr. D. L. Ziemann, Chief I a; ' 7 1976 - i,
I" Operating Reactors - Branch 2 Division of Reactor Licensing hk u
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U.S. Nuclear Regulatory Commission
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Subject:
Dresden and Quad-Cities Stations Reactor Water Recirculation 4-Inch Diameter Piping Crack Investigation
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Program, NRC Dkts.
50-249, 50-254, and 50-265
Dear Mr. Ziemann:
In a letter to Mr. Case dated February 10, 1975, one of the Further Investigations identified was additional strain rate testings of the piping material by Battell.e Columbus Laboratories.
The tests have been completed, and a report describing the results is attached for your information.
These results in conjunction with the results in the Battelle Columbus Laboratories report dated November 26, 1974 attached to the February 10, 1975 letter to Mr. Case, completes the strain rate studies.
The coastant strain rate studies indicate that
" lightly and heavily sensitized specimens from Dresden II (Unit 2) and Quad-Cities II (Unit 2) piping are more susceptible to stress-corrosion cracking in oxygenated high temperature water than are similarly treated specimens from a heat of Type 304 stainless steel used in previous Battelle studies".
The Dresden Unit 2 and Quad-Cities Unit 2 specimens were obtained from portions of the Reactor Water 4-Inch Diameter Piping which was removed for repairs during September and October 1974.
As committed in a letter to Mr. Case dated December 27, 1974, all 4-inch diameter recirculation system piping has been replaced,or in the case of Dresden Unit 3, is being replaced during the current refueling outage.
The heat of piping material represented by the Dresden Unit 2 and Quad-Cities Unit 2 specimens in the Battelle tests is no longer in service at any of the fcu r subject units.
One signed original and 39 copies of the report are provided for your use.
'b Very truly 'ours, hg3 o$2 y
8304110072 750604 S
Abel
'b PDR ADOCK 05000237 f>E?
p PDR Nuclear Licensing Administrator Boiling Water Reactors 00PY SENT REGION '
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Columbn Laboratories l
SC5 king Avenue Columbus, Ohio 43201 l
Telephone 16141299-1151 Telex 24-5454 j
February 28, 1975 i
Mr. D. D. Galle Engineering Department Commonwealth Edison Company P.O. Box 767 Chicago, Illinois 60690
Dear Mr. Galle:
We have completed the chree adcitional constant-strain-rate tests as dis-cussed in our January meeting. The initial results of the study, together dith~the procedures, were detailed in my letter to you dated November 26, 1974.
The additional tests have been made on lightly sensitized specimens from the Dresden-II and Quad Cities II piping and the Battelle heat of Type 304 stainlesssthel.
The tensile-type specimens were sensitized 7 hr at 1150 F i
to produce intermittent chromium carbide precipitation at grain boundaries.
(This structure appears similar to that obtained in the heat-affected zone when welding Type 304 stainless steel.)
The specimens were then pulled to tensile rupture at a constant strain rate of 3 x 10-6 in./in.-sec in 550 F deionized water containing 100 ppm dissolved oxygen at start-up.
The pro-cedures and theory for this test procedure also were described in my letter to you dated November 26, 1974.
f The results of these tests are included in Table 1 together with the results from the previous study. Note that the time-to-failure and reduction in area were less for the Dresden II and Quad Cities II specimens than for the i
Battelle specimen given the same 7 hr/ll50 F sensitization treatment. Thus, the results continue to suggest that the material used in the Dresden II and i
Quad Cities II piping is more susceptible to stress-corrosion cracking than the Battelle heat of material.
This might be related to the quality of the original mill-annealed microstructure, although the constant-strain-rate tests with mill-annealed material revealed no difference among the three specimens.
(No specimen exhibited stress-corrosion cracking and all had about the same time-to-failure and reduction in area--see Table 1.)
The appearance of the lightly sensitized specimens af ter test tends to support the data presented in Table 1.
Photographs of the two halves of the broken tensile specimens are presented in Figures 1 and 2.
These photographs suggest severe cracking.
However, the metallographic examina-tion of longitudinal cross sections through these specimens _ revealed many
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February 28, 1975 TABLE 1.
SU10!ARY OF RESULTS FROM THE CONSTANT-STRAIN-RATE TESTS (3 x 10-6 In./In.-Sec in 550 F Water Containing 100 Ppm Dissolved Oxygen)
Time to Failure, Elongation, Reduction in M:tallurgical Condition Material (")
hr in.
Area, percent As-received (mill-annealed)
Battelle 53.1 0.287 54 Battelle 62.4 0.337 61 Dresden II 54.1 0.280 67 Quad Cities II 55.9 0.320 72 Sensitized 4 hr/1250 F Battello 26.4 0.141 15 Dresden II 9.2 0.059 9.7 Quad Cities II 9.4 0.052 14 Sensitized 7 hr/1150 F Battelle 56.3 0.315 60 Dresden II 45.4 0.254 37 Quad Cities II 45.7 0.258 38 (a)
Dresden II and Quad Cities II specimens cut from as-removed piping.
Battelle specimens obtained from bar stock with following composition and properties:
0.07 C 35,000 psi YS 20.0 Cr 98,000 psi UTS 8.5 Ni 100% elongation in 2 in.
1.85 Mn 84% reduction in area 0.20 Cu s
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Q February 28, 1975
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FIGURE 1.
APPEARANCE OF LIGliTLY SENSITIZED TENSILE SPECIMENS FROM i
DRESDE.N II AND QUAD CITIES II PIPING AFTER PULLED TO l
FAILURE AT 3 x 10-6 IN /IN.-SEC STRAIN RATE IN 550 F WATER CONTAINING 100 PPM DISSOLVED OXYCEN
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j Note the many secondary cracks. Comparc with l
Figure 2.
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February 28, 1975 i
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FIGURE 2.
APPEARANCE OF LIGHTLY SENSITIZED l
TENSILE SPECIMEN FROM A BATTELLE IlEAT OF TYPE 304 STAINLESS STEEL AFTER PULLED TO FAILURE AT 3 x 10-6 IN./IN.-SEC STRAIN RATE IN
- i 550 F WATER CONTAINING 100 PPM DISSOLVED OXYCEN
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Note secondary cracks and l
ductile necking at the fracture.
Compare with Figure 1.
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February 28, 1975 l
i shallow secondary intergranular cracks with an occasional transgranular l -
wedge.
(The latter are often found on crack-resistant mill-annealed i
material after test.)
The Dresden II and Quad Cities II specimens ap-l peared to have more and slightly deeper secondary cracks than the Battelle l
specimen.
Photomicrographs of typical areas are shown in Figure 3.
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In summary, the results of the constant-strain-rate studies indicate that lightly and heavily sensitized specimens from the Dresden II and Quad l
Cities 11 piping are more susceptible to stress-corrosion cracking in oxygenated high-temperature water than are similarly treated specimens from a heat of Type 304 stainless steel used in previous Battelle studies.
l However, constant-strain-rate tests on as-received material show no dif-ference in susceptibility to stress-corrosion cracking that can be related to the behavior of these materials when subsequently sensitized.
Please contact me if you have any questions or comments.
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Best regards, A
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Warren E. Berry Associate bbnager Corrosion and Electrochemical Technology Section t
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Battelle Heat b.
Quad Cities II Piping Etchant: Electrolytic 10 Percent Oxalic Acid yeo-FIGURE 3.
PHOTOMICROGRAPHS OF SECONDARY CRACKS SHOWN IN FIGURES 1 AND 2 (LONGITUDINAL SECTIONS) 2o r1 Note shallow depth of penetration.
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