ML19210E702
| ML19210E702 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/26/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Crouse R OHIO EDISON CO. |
| References | |
| NUDOCS 7912100444 | |
| Download: ML19210E702 (1) | |
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UNITED STATES 8 \\*
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GLEN E LLYN, ILLINolS 60137 Au, a ws Docket No. 50-346 Toledo Edison Company ATTN:
Mr. Richard P. Crouse Vice President Energy Supply Edison Plaza 300 Madison Avenue Toledo, OH 43652 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,
.,m 1 k p tht ~
ames G. Kepp er Director
Enclosures:
1.
IE Circular No. 79-24 2.
Recently Issued IE Circulars cc w/encls:
Mr. T. Murray, Station Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Harold W. Kohn, Power Siting Commission Helen W. Evans, State of Ohio 1533 337 7912100
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Accession No: 7910250492 SSINS No. 6830 UNITED STATES NUCLEAR REGULATORY COMMISSION 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 additioral) 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 r.egative 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.
DUPLICATE DOCUMENT 1533 338 Entire accument previously entered into systam under:
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