ML17326A267
| ML17326A267 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 09/27/1979 |
| From: | Dolan J INDIANA MICHIGAN POWER CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 316, NUDOCS 7910030399 | |
| Download: ML17326A267 (10) | |
Text
REGULATORY INFORNATION DISTRIBUTION SYSTEN (RIDS>
ACCESSION NBR: 7910030399 DOC. DATE: 79/09/27 NOTARIZED:
NO DOCKE
" FACIL-:50-315 Donald C.
Cook Nuclear Power Plantl Unit il Indiana Cc 0500 1
50-3jb Donald C.
Cook Nuclear Power Plantl Unit 2I Indiana 5
05000316 AUTH. NANE AUTHOR AFFILIATION DQLANIJ. E.
& Nichigan Power Co.
REC IP. NANE REC IP IENT AFFILIATION DENTQNI H. R.
Off-ice of Nuclear Reactor Regulation
SUBJECT:
Forwards addi info 'per IE Bulletin, 79-17 re p'otential for cracks in stagnant borated water environ. Due to trained staff shortagel requests forty day extension to fulfill requirements of-IE Bulletin 79-17I Item 6.
DISTRIBUTION CODE:
A001S COPIES RECEIVED: LTR I ENCL Q SIZE:
TITLE: General Distribution for After Issuance o0 Operating Lic NOTES: Wv-H- H m
ALL M 72 RECIPIENT ID CODE/NAME ACTION:
05 BC OgB ~/
COPIES LTTR ENCL 7
7 RECIPIENT ID CODE/NANE
'OPIES LTTR ENCL INTERNAL'2 ICE 15 CORE PERF BR
,18 REAC SFTY BR 20 EEB 22 BR INKNAN 1
2 1
1 1
1 12, 1
1 1
02 NRC PDR 14 TA/EDO 17 ENGR BR 19 PLANT SYS BR 21 EFLT TRT SYS GELD 1
1 1
1 1
1 1
1 0
EXTERNAL: 03 LPDR 23 ACRS 1
1 jh jh 04 NSIC
1 h I th Ir tj I
h
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INDIANA R MICHIGAN POWER COMPANY P. O. BOX 18 BO WLIN G G R E EN STAT ION NEW YORK, N. Y. 10004 September 27, 1979 AEP:NRC:00255A Donald C.
Cook Nuclear Plant Units 1
and 2
Docket Nos.
50-315 and 50-316 License Nos.
DPR-54 and DPR-74 Additional Information Relevant to I.E. Bulletin No. 79-17 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washinoton, D.C.
20555
Dear Mr. Denton:
The Attachment to this letter contains our responses to four questions we received over the telephone from your Staff on September 13, 1979.
These
'questions, which deal with the potential for cracks in a stagnant borated water environment, are part of the Commission's request for additional infor-mation to complete the review of our spent fuel storage cpacity expansion program and were generated in connection with IE Bulletin No. 79-17.
In'addition, we would like to request an extension of 40 days to ful-fill the requirements set forth under Item 6 of'E Bulletin No. 79-17.
This extension, both for the inspection and for the submittal of the sub-sequent written report, is required to accomodate shortage of trained per-sonnel and contractors to perform this task.
Very truly yours, JED:em ohn E. Dolan Vice President cc:
R.
C. Callen G. Charnoff
'D. V. S'hailer-Bridgman R..S.
Hunter; R.
W. Jurgensen gpPX
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ATTACHMENT TO AEP:NRC:00255A
'A lt e
1.
@~serio Are the materials in the spent fuel pool complex at Donald C.
Cook the same as those where cracks were found in TMI-1, that is, 304 stainless steel?
~An ~r The spent fuel racks and the cooling pipe system are constructed of type 304 stainless steel.
The liner is constructed from 304L stainless steel.
2.
~us~tio Are these components, with like materials, immersed in the same environment as at TMI-1?
~Asw r The spent fuel pool is filled with oxygenated, borated water.
Once fuel is placed in the pool, natural circulation takes place within the pool, which is augmented by flow from the pool cooling system.
The spent fuel racks are designed to minimize the possibility for water stagnation within the rack structure.
Therefore, although the chemical make-up of the pool environment is similar to that at TMI-l, the important ingredient of stagnation is missing in the Donald C.
Cook spent fuel pool.
3 9m.WLm If so, what is the potential for the type of cracks identified in IE Bulletin No. 79-17?
~Ansv The potential for cracking, of the type identified in IE Bulletin 79-17, should be quite low for the spent fuel storage racks in the spent fuel pool.
Not only is the water in the spent fuel pool not stagnant, but the metallurgy of the type 304 stainless steel in the racks is controlled during manufacture and fabri-cation to minimize sensitization in the weld heat-affected zones.
The material is procured in the quenched'ondition, and the wel-ding heat input is closely controlled and minimized to reduce the probability of carbide precipitation.
This will increase the material~s ability to resist stress corrosion cracking in the
'eld heat-affected zone.
Potential for cracking is considered to be very low in the liner since it is fabricated from the low carbon version of 304, and all welding at the Cook Plant was performed with interpass temperature control.
Carbide precipitation in the heat-affected zone of the liner has, in this manner, been eliminated or greatly minimized.
Potential for cracking is also considered to be very low for the cooling system piping associated with the spent fuel pit as these lines are not stagnant.
Fabrication was to a specification that required a maximum weld interpass temperature of 350oF so that carbide precip'itation in the heat-affected zone would be minimized and thus reduce the possibility for stress corrosion cracking.
If there is cracking what is the consequence of the loss of func-tion/integrity of the components
~s~w.r The spent fuel storage racks are highly redundant structures as-sembled with many small welds.
Cracking of a small percentage of these welds would not, therefore, have a significant effect on the functional integrity of the racks.
Any crack in the liner would be detected by our leak detection system.
The plant operators are instructed to check for spent fuel pool water leakage daily.
Detection of leakage would occur, therefore, before there was any significant loss of fluid or loss of structural integrity.
Me add here a few comments that are pertinent to the general intent of this attachment.
In our submittal No. AEP:NRC:00213B dated.
September 26, 1979, we pointed out that no cracks had been found during the inspection performed in the cooling systems of the spent fuel pool.
A weekly chemical analysis is performed of the pool water.
This analysis checks for, among other things, the presence of fluorides and chlorides, both of which could be connected with the potential for stress corrosion cracking.
The analysis results have always been below our detectalglity level.
As we also pointed out in our submittal No. AEP:NRC:002133, there is sufficient certainty of our ability to add make-up water to the pool in case such need'rose as a result of cracks in the cooling system.
Finally, no conclusive evidence has been found at this time to identify those chemical species which promoted the intergranular stress corrosion cracking (IGSCC) discovered in Three Mile Island Unit l.
When the precise causes for the IGSCC are discovered, their relevance to the Cook Plant Spent Fuel Pool and associated cooling system will be analyzed.
<a, I.
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