ML20128B417

Informs That Info Presented by Licensee Re HPCI Reliability Has Been Reviewed & Found Acceptable

ML20128B417
Person / Time
Site:	Monticello
Issue date:	04/26/1972
From:	James Shea US ATOMIC ENERGY COMMISSION (AEC)
To:	Ziemann D US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9212030650
Download: ML20128B417 (2)

Text

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THRU: D. L. Ziemann, Chief, ORB #2, DRL HIGH PRESSURE COOLANT INJECTION (HPCI) RELIABILITY - MONTICELLO (NORTHERN STATES POWER COMPANY)

Af ter the HPCI system initial performance checkout during February 1971 and final acceptance following corrective measures and controller adjust-ments (see references), the HPCI was placed in " operational" status.

On several occasions since the HPCI has been operational, the system has been declared " inoperable" following monthly performance checks.

The problem that persisted was finally understood when test results showed that the steam flow measurements f rom the HPCI turbine steam inlet elbow taps were erroneously high whenever the main steam line flow, to which the HPCI turbine steam line was connected, exceeded 50% of rated flow. This incorrect signal from elbow taps located too close to the main steam line caused the HPCI steam line to isolate because of a false indication that HPCI steam flow to the turbine had exceeded thel 50% steam flow isolation set point. We have reviewed the information presented by NSP and have concluded that the HPCI system would have operated in an emergency in accordance with design expectations because main steam flow would have been near zero during an emergency requiring HPCI, and that the problem identified is merely one of testing the system whenever main steam flow is greater than 50%

rated.

NSP has proposed that Venturi flow meters be installed to replace the elbow pressure taps to provide accurate HPCI turbine steam flow indication during HPCI system tests. We concur with this corrective action. Based on our review of this experience, we have concluded that the health and safety of the public has not been affected by the steam flow error observed during the HPCI system tests and will not be affected by the proposed change to eliminate s team flow measurement errors during tests of the HPCIS. t /

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amesJ.hhba perating Reactors Branch #2 Division of Reactor Licensing

Enclosure:

References l cc w/ enclosure:

DJSkovholt, DRL JJShea, DRL TJCarter, DRL FDDiggs, DRL DLZiemann, DRL 0

9212030650 720426 PDR ADOCK 05000263 D(

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, y REFE:RENCES "Inoperability of the High Pressure Coolant Injection System" - NSP letter dated September 15, 1971.

"Inoperability of the High Pressure Coolant Injection System" - NSP letter dated September.28, 1971.

" Summary of HPCI Problems Experienced During Startup Testing" - NSP letter dated October 18, 1971.

" Planned Modifications to the HPCI System Steam Line Flow Sensing Device" - NSP letter dated March 2, 1972.

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