ML17324A947
| ML17324A947 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 06/13/1986 |
| From: | Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AEP:NRC:0976, AEP:NRC:976, NUDOCS 8606190320 | |
| Download: ML17324A947 (6) | |
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ACCESSION NBR: 8606190320 DOC. DATE: 86/06/13 NOTARIZED:
NO DOCKET FACIL: 50-315 Donald C'.
Cook Nucleav Po~er Plant>
Unit 1.
Ind iana ic 05000315 50-316 Donald C.
Cook Nucleav Power Plant> Unit 2>
Ind iana 0
05000316 AUTH. NANE AUTHOR AFFILIATION ALEXICH>N. P.
Indiana 5 Michigan Electric Co.
RECIP. NANE RECIPIENT AFFILIATION DENTQN> H. R.
Office of'ucleav Reactor Regulation>
Direc tov'post 851125 SUB JECT:
InForms of-v emoval of. automatic tv'ip on low suction pv essuv e in aux iliav g Feedwater (AFN) sos. Tv ip does not enhance capabi 1 itg of-AFW sos. Alarm/opev ator-action wi1 I rep lace tv i p Punct ion.
DISTRIBUTION CODE:
AO01D Co< IES RECEIVED: i TR ENCL SIZE:
TITLE:
OR Submittal:
General Distv ibution NOTES:
REClPIENT ID CODE/NAI'IE PNR-A EB PNR-A FOB PNR-A PDO PD 01 PNR-A PSB INTERNAL: ADN/LFNB NRR DHFT/TSCB Q F 04 EXTERNAL:
EQ8 S NRC PDR 02 COPIES LTTR ENCL 1
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RECIPIENT ID CODE/MANE PMR-A EICSB PNR-A PD4 LA 4lIQGI NQTQN> D PWR-A RSB ELD/HDS3 NRR/GRAS RGN3 LPDR NSIC COPIES LTTR ENCL 2
2 1
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1 TOTAL NUNBER QF COPIES REQUIRED:
LTTR 24 ENCL 20
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INDIANA8 NICHIGAN ELECTRIC CONPANY P.O. BOX 16631 COLUMBUS, OHIO 43216 Donald C.
Cook Nuclear Plant Unit Nos.
1 and 2 Docket Nos.
50-315 and 50-316 License Nos.
DPR-58 and DPR-74 AUXILIARYFEEDWATER SYSTEM LOW SUCTION PRESSURE PUMP TRIP June 13, 1986 AEP:NRC:0976 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.
C.
20555 I
Dear Mr. Denton:
Pursuant to our discussion with the NRR staff on May 5, 1986, this letter is to inform you that we are revising our response to long-term recommendation GL-4 contained in Mr. D.
G. Eisenhut's letter of October 30, 1979.
In the attachment to our letter of December ll, 1979 (AEP:NRC:00300),
we stated that we had decided to install an automatic trip on low suction pressure in the auxiliary feedwater (AFW) system.
We have decided to remove this automatic trip, as we have determined that this trip does not enhance the capability of the AFW system, but may in fact detract from the system's reliability.
This determination is supported by industry experience as well as an INPO report on the operational performance of AFW systems in U.S.
PWRs (INPO 85-036, September 1985).
It is our intention to use an alarm/operator-action combination in place of the automatic trip function.
Our decision to remove the low suction pressure trip function is based on the following points:
(1)
The primary sources of water for the AFW systems are the condensate storage tanks (CSTs).
These tanks are qualified to withstand an operating-basis earthquake and have also been analyzed to show that they are capable of withstanding a design-basis earthquake (DBE).
The suction piping from the tanks to the pumps has been analyzed to withstand the loads due to a DBE.
(2)
The probability of a tornado (or a tornado-generated missile) causing damage to the CSTs is very low.
Section 2.2 of the Cook FSAR cites a recurrence frequency for a tornado at the site itself of over 1,000 years.
(3)
The Cook Plant has several indications which alert the reactor operators to low level in the CST.
Even in the extreme case in which the tank water level drops to the low suction pressure alarm level (612'-0") and the AFW system is at full-flowconditions, there is approximately a 14-minute time period before the tank water level drops to the centerline of the CST outlet pipe (610'-3").
(The pump 8~oggqOSaO Sbo~o>~~~ ~
ADOCK 00o PDR p
Mr. Harold R. Denton AEP:NRC:0976 suction centerline is at 593'-2".)
This enables the operators to take appropriate measures to ensure an adequate supply of water for the AFW pumps.
The attachment to this letter shows the estimated times for the tank level to drop from alarm to the CST outlet centerline as well as the dimensions of the tanks.
This document has been prepared following Corporate procedures which incorporate a reasonable set of control to insure its accuracy and completeness prior to signature by the undersigned.
Very truly yours, M.. Al ich Vice President MPA/pm Attachment cc:
John E. Dolan W.
G. Smith, Jr.
- Bridgman R.
C. Callen G. Bruchmann G. Charnoff NRC Resident Inspector
- Bridgman
10"- OVERFLOW PIPE
%, 640'-9" CONDENSATE STORAGE TANK 52'-0" DIA x 34'-51/2" HT LO LEVEL 628'-9'O LO LEVEL 614'-0" LO SUCTION PRESSURE 61 2'-0" 12" OUTLET PIPE,
% 610'-3" TIME REQUIRED FOR TANK LEYEL TO DROP FROM ALARM TO OUTLET CENTERLINE ALARM TlMF (MINUTES)
LO SUCTION PRESSURE LO LO LEVEL LO LEVEL 13.9 29.8 123.1 TIME ESTIMATE IS BASED ON A CONSERVATIVE TANK OUTFLOW OF 2000 GPM
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