ML17319B413
| ML17319B413 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 07/02/1982 |
| From: | Hunter R INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.2.17, TASK-TM AEP:NRC:0440A, AEP:NRC:440A, GL-81-21, NUDOCS 8207080415 | |
| Download: ML17319B413 (8) | |
Text
REGULATORY
]FORMATION DISTRIBUTION SY, M (RIDS)
ACCESSION NOR:8207080415 DOC,DATE: 82/07/02 NOTARIZED: YES DOCKET FACIL:50"315 Donald C ~
Cook Nuclear Power Plant~
Unit li Indiana 8
05000315 50-316 Donald C,
Cook Nuclear Power Plant~
Unit 2< Indiana 8
05000316 AUTH,NAME AUTHOR AFFILIATION
,HUNTERiR ~ ST Indiana 8 Michigan Electric Co ~
REiCIP ~ NAME; RECIPIENT AFFILIATION DENTON/HE RE Office of Nuclear Reactor Regulationi Director
SUBJECT:
Responds to Generic Ltr 82 21~ "Natura) Circulation Cooldown," Review of current plant operation 8.procedural mods L training implemented, DISTRIBUTION CODE:
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TITLE: Response to NUREG "0737/NUREG 0660 TMI Action Plan Rgmts (OL's)
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INDIANA It MICHIGAN ELECTRIC COMPANY P. O.
BOX 18 BO WLING GR E EN ST ATION NEW YORK, N. Y. 10004 July 2, 1982 AEP:NRC:0440A Donald C. Cook Nuclear Plant Unit Nos.
1 and 2
'ocket Nos. 50-315 and 50-316 License Nos. DPR-58 and DPR-74 GENERIC LETTER NO. 81-21; NATURAL CIRCULATION COOLDOWN Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Denton:
As required by Generic Letter No. 81-21 entitled "Natural Circulation Cooldown," we have reviewed our current plant operations in light of the St. Lucie, Unit No.
1 event and the discussions presented in the Generic Letter and have <implemented procedural modifications and training which should enable our operators to avoid as well as recognize reactor vessel voiding if it occurs and to properly react to it during natural circulation cooldown.
As stated in our response to Item II.K.2.17 - "Potential for Voiding in RCS during Transients" of NUREG-0737 contained in our letter No. AEP:NRC:0649 dated December 29, 1981, the Westinghouse Owners Group has performed a study, with supporting analysis, which addresses the potential for void formation in Westinghouse - designed nuclear steam supply systems during natural circulation cooldown/depressurization transients.
This study has been submitted to the NRC by the Westinghouse Owners Group by letter No. OG-57, dated April 20,
- 1981, and is applicable to the Donald C. Cook Nuclear Plant.
In addition, a
generic natural circulation cooldown guideline has been developed by the Westinghouse Owners Group and was submitted to the NRC by letter No.
OG-64, dated November 30, 1981.
The generic guideline takes the results of the study into account so as to preclude void formation in the upper head region during natural circulation cooldown/depressurization transients, and specifies those conditions under which upper head voiding may occur.
The generic guidance developed by the Westinghouse Qmers Group will be utilized in updating, if necessary, our existing natural circulation cooldown procedure as part of the efforts for Item I.C.l of NUREG-0737.
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Mr. Harold R. Denton AEP: NRC: 044 0A It should be noted that our present natural circulation cooldown procedure was revised in October, 1'980 to incorporate.adequate provisions to prevent void formation in the reactor head as a result of the concerns expressed in IE Circular No.'.'80-.'15 and is consistent with the information contained in Generic Letter'No.'1-.21.
As, such, a
controlled natural circulation cooldown, conducted in accordance with our procedure, should not result in reactor, vessel head voiding.
Best-estimate calculations with an approximate 80% condensate storage tank inventory have verified.that sufficient condensate grade auxiliary feedwater supplies exist to support the cooldown method employed in.our natural circulation cooldown procedure.
This calculation assumed a conservatively high constant auxiliary feedwater flow rate representative of the required flow to remove decay heat at reactor trip.
In addition, when credit was taken for decreasing coze decay heat rate, the minimum tank inventory required by the Technical Specifications was found to be sufficient to insure adequate core cooling The revision to our procedure assumed a hot spot (head) 0 temperature of.650 F since void formation has not been observed when the reactor has tripped and the saturation temperature corresponding to the RCS pressure of.2250 psi is approximately 650 F.
Data from St. Lucie and our analysis work was then used to estimate an envelope of cooldown rates.
A "safe" cooldown rate of 25 F/hr was identified and this rate along with the assumed hot spot temperature was used in revising our procedure to guard against a St. Lucie type event.
Appropriate warnings that stagnant reactor coolant could exist in the RCS, which could flash to steam at any time during depressurization, were also incorporated into the procedure.
Finally, training for licensed operators. pertaining to reactor vessel voiding during natural circulation cooldown was performed during requalification exercises.
Very truly yours, R.
S. Hunter Vice President
/md cc:
John'E.
Dolan Columbus R.
W. Jurgensen W. G. Smith, Jr.
Bridgman R..C. Callen G.,Charnoff Joe Williams, Jr.
NRC Resident Inspector at Cook Plant - Bridgman
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STATE OF NEW YORK )
COUNTY OF NEW YORK)
R. S. Hunter, being duly sworq, deposes and says that he is a Vice President of Licensee Indiana and Michigan Electric Company, that he has read the foregoing response to Generic Letter No. 81-21 and knows the contents thereof;,and that said contents are true to the best of his knowledge and belief.
R. S. Hunter
~ 4C Subscribed and sworn to before me this Z,
day of ~m 1982.
otary Public YM's'Hl i:s 'a'4 bAiCiC'tf'OTARY itritLtC, State oi Ncw York No. 41-4606'J92 Qualified in Queens County gorfificate filed in New York County Come ssrorr ap.stares rhcrch 30, l98'8
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