ML19210E701
| ML19210E701 | |
| Person / Time | |
|---|---|
| Site: | Marble Hill |
| Issue date: | 11/26/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Shields S PSI ENERGY, INC. A/K/A PUBLIC SERVICE CO. OF INDIANA |
| References | |
| NUDOCS 7912100442 | |
| Download: ML19210E701 (1) | |
Text
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UNITED STATES
$.-e '2-hg/',,E NUCLEAR REGULATORY COMMISSION REGION lli
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0, 799 ROOSEVELT ROAD
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Docket No. 50-546 NOV261979 Docket No. 50-547 Public Service of Indiana ATTN:
Mr. S. W. Shields Vice President - Electric System 1000 East Main Street Plainfield, IN 46168 Gentlemen:
The enclosed IE Circular No. 79-24 is forwarded to you for information.
No written response is required. Should you have any questions related to your understanding of the recommendations on this matter, please contact this office.
Sincerely,
%,.a s.'b N g jJamesG.Keppler Director
Enclosures:
1.
IE Circular No. 79-24 2.
Recently Issued IE Circulars cc w/encls:
Mr. G. N. Brown, Project Director Central Files Director, NRR/DPM Dire: tor, NRR/ DOR PDR Locs7 PDR NSIC TIC LeBoeuf, Lamb, Leiby & MacRae Mr. Dave Martin, Office of the Attorney General 1533
'3" 1533 335 b (,
7912100 1
Accession No: 7910250492 SSINS No. 6830 UNITED STATES NUCLEAR REGULATORY C0h?!ISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 November 26, 1979 IE Circular No. 79-24 PROPER INSTALLATION AND CALIBRATION OF CORE SPRAY PIPE BREAK DETECTION EQUIPMENT ON BWRs Description of Circumstances:
During 1976 the Iowa Electric Light and Power Company identified and corrected a potential problem involving the core spray (CS) pipe break detection system at the Duane Arnold Energy Center (DAEC). The problem relates to the setpoint, function, and installation of the differential pressure (dp) instrument which monitors for a CS pipe 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, range of 0 - 24 psid, was found deflecting downscale (i.e., reading negative psid) during operation.
The licensee's investigation of the downscale deflection revealed that the original piping arrangement and calibration did not adequately take into account the effect of density changes of the water in the pressure leg connection The original installation had the high pressure side of the dp instrument (see attached Figure 1) connected to the reference leg in the vessel (Figure 1 Connection X) and the low pressure side to the core spray piping outside the vessel but inside the drywell (Figure 1 Connection Y).
With the piping intact, this arrangement senses the pressure difference between bottom and top of core. With a break in CS piping in the annulus area the instrument then senses the additional pressure drop across the separators (dp q 7 psi additional) and dryers (dp q 7-inches water).
This installation was in accordance with GE desigr requirements.
Also in accordance with GE instructions the calibration of the dp instrument was performed with the reactor in the cold condition and the alarm was set to trip at 5 psid increasing.
Because of this cold calibration the dp instrument then indicated full downscale negative during operation.
This negative dp was due to the heat up of the reference leg (Figure 1 Connection X) which caused the flui density to decrease as the plant reached hot conditions.
The magnitude of this c was determined to be about 3.5 psid following completion of the modification discussed below.
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