ML19260B115
| ML19260B115 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 11/26/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7912070022 | |
| Download: ML19260B115 (1) | |
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UNITED STATES
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- c REGION V gC NUCLEAR REGULATORY COMMISSION 0, i
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1990 N. CALIFORNI A COULEVARD
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SUITE 202. WALNUT CREE K PLAZA
- ,,,a WALNUT CR E E K, CA' lFORNI A 94596 November 26, 1979 Docket Mos. 50-133, 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
The enclosed Circular No. 79-24 is forwarded to you for information.
No written response is required.
Should you have any quenions related to your uncerstanding of the recommendations on this matter, please contact this office.
Sincerely,
[C dih y
R. H. Engelken Director
Enclosures:
1.
IE Circular No. 79-24 2.
Recently Issued IE Circulars cc w/ enclosures:
W. Barr, PG&E W. Raymond, PG&E R. Ramsay, PG&E, Diablo Canyon E. Weeks, PG&E, Humboldt Bay J. Worthington, PG&E 1517 227 7912070 b N
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Accession !!o: 7910250492 SSI!!S '!o. 6330 IP!ITED "TATES flVCLEAR REGULAT0oY C0"/11SSIO'l 0FFICE OF I!!SPECTIo1 Ain E'! FORCE"EtlT 4ASHIrlqT0!!, D.C.
20555 November 26, 1979 IE Circular ?!o. 79-24 PROPER I'!STALLATIO!! Ai4D CALIBRATIO?! 0F CORE SoRAY DIDE BREAK DETECTIn!! EQUIP'1EtlT 01 SWRs Descriotion of Circunstances:
Durino 1976 the Iowa Electric Light and Power Conoany identified and corrected a potential problem involvina the core soray (CS) oine break detection systen at the Ouane Arnold Enerqy Center (OAEC).
The oroblem relates to the setooint, function, and installation of the differential oressure (do) instrument which nonitors for a CS pioe break that is located in the annulus area of the reactor vessel (i.e., located outside the core shroud but inside the reactor vessel).
The installed instrument, rance of 0 - 24 osid, was found deflectina downscale (i.e., readina negative osid) durina operation.
The licensee's investigation of the downscale deflection revealed that the criainal oicinq arrangement and calibration did not adequately take into account the effect of density chanaes of the water in the pressure leg connections.
The criainal installation had the high pressure side of the dp instrument (see attached Fiaure 1) connected to the reference leo in the vessel (Fiaure 1 Connection X) are-che low oressure side to the core sorav oicinq outside the vessel but insi6e the drvwell (Fiaure 1 Connection Y).
With the pioino intact, this arrangenent senses the pressure difference between botton and ton of core. Pith a break in CS cipino in the annulus area the instrunent then senses the additional oressure droo across the senarators (do $7 osi additional) and drvers (dp # 7-inches water).
This installation was in 'accordance with GE desian requirenents.
Also in accordance with GE instructions the calibration of the dp instrument was cerforned with the reactor in the cold condition and the alarn was set to trio at 5 osid increasino.
Decause of this cold calibration the do instrument then indicated full downscale neaative durirq oneration. This neaative do was due to the heat 40 of the reference loo (Finure 1 Connection X) which caused the fluid density to decrease as the niant reached hot conditions. The naanitude of this do was determined to be about 3.5 nsid followino conoletion of the modification discussed below.
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