ML20030C852
| ML20030C852 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 08/25/1981 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 13736, NUDOCS 8108280242 | |
| Download: ML20030C852 (3) | |
Text
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o Consumers power James W Cook 0
Vice President - Projects, Engineering and Construction General offices: 1945 West Parnell Road, Jackson, MI 49201 * (517) 788 o453 August 25, 1981 D
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C Harold R Denton, Director AUG 2 718 m-Office of Nuclear Reactor Regulation
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US Nuclear Regulatory Commission
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Washington, DC 20555 4
I MIDLAND PROJECT MIDLAND DOCKET 50-329, 50-330 RESPONSE TO OPEN ITEM OF PRELIMINARY DRAFT SER SECTION 6.3 FILE: 0505.805 SERIAL:
13736 ENCLOSURE: RESPONSE TO OPEN ITEM OF PRELIMINARY DRAFT SER SECTION 6.3 We have reviewed the preliminary draft section of the NRC Staff Safety Evaluation Report 6.3 provided by the R L Tedesco letter to J W Cook dated August 10, 1981.
Enclosed is our response / comments to the open item contained within this draft section.
With the response provided in this letter and based on meeting all current safety and regulatory criteria, we believe the Open Item can be closed out by the Staff.
If you do not agree with our position, we wish to arrange an appeal to the Reactor Systems Branch Chief and any necessary higher levels as appropriate.
A response to our position is requested within two weeks of the receipt of this letter.
JWC/ PEP /fms CC RJCook, Midland Resident Inspector DSHood, US NRC TPSpeis, US NRC DBMiller, "idland Construction (3)
RWHuston, Washington 0
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L oc0881-0212a131 hh2810825 05000329 E
J-EMERGENCY CORE COOLING SYSTEM - PRELIMINARY SER DRAFT SECTION 6.3 RESPONSE TO OPEN ITEM The preliminary draft SER on the Emergency Core Cooling System (6.3) received by Consumers Power Company contains the following NRC Reactor Systems Branch open item.
Open Item Provide modifications to the HPI system so that operator action to throttle HPI flow in a line for which the high flow alarm setpoint is reached is not required following a small break LOCA. This action is necessary for the current Midland design in the event of an HPI line break.
Response
Standard Review Plan 6.3 Section III.19 states
...."The complete sequence of ECCS operation from accident occurrence through long-term core cooling is examined to see that a minimum of manual action is required, and where manual action is used, a sufficient time (greater than 20 minutes) is available for the operator to respond."
B&W analysis for HPI line break shows that the operator has 20 minutes before operator action need be taken. The scenario for the B&W analysis is a small break LOCA (HPI line break) in addition to the single failure of one HPI train to function. Depending on break size and backpressure conditions, a high-flow alarm in one leg of the operable HPI train (leg containing break) may occur with a corresponding low-flow alarm in the other leg of the operable HPI train. Take note that the HPI is still being injected into portions of the non-operable HPI train cold leg lines through the cross-connect lines. With this combination of events, ie, single failure of one HPI train, plus high flow alarm in one leg of the operable HPI train, plus low flow alarm in the other leg of the operable HPI train, the operator isolates the high flow HPI leg.
This will increase the flow in the low flow leg and provide sufficient HPI to the RCS via one leg of the.,perable train and one leg of the non-operable train through the cross-connect. Thus, a minimum of operator action is all that is required. The operator has unambiguous indication from which to determine correct action. Without this combination of events, no operator action is necessary.
Another scenario that could result in a high-low flow alarm combination is blockage of one HPI leg.
This could be the result of a pinch line break or valve / flow element blockage. The pinch line event could become a problem if the length of pipe between the last check valve and the RCS is longer than approximately one foot and the pipe supports are inadequate.
Pipe break locations in the HPI lines are assumed at specific locations in accordance with the high energy line break analysis (FSAR Subsection 3.6).
The pipe at these locations is restrained within the plastic hinge length. The blockage of a valve or flow element in the HPI leg is not considered a credible event in the short-term when taken with an initiating event and the most limiting single active failure in the other HPI train.
In conclusion, CP Co believes oc0881-0212b131
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that the high/ low flow combination due to HPI line blockage is an extremely unlikely occurrence for Midland and therefore poses no threat to the intended performance of the HPI system.
The HPI system flow split is established during preoperational testing of the system.
It is CP Co's intention to also check system responses to simulated HPI line breaks during preop.
CP Co believes that the HPI system at Midland meets all the requirements of the SRP and we do not see the need for any changes to the system.
oc0881-0212b131
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