ML19253C629
| ML19253C629 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/26/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 7912060596 | |
| Download: ML19253C629 (1) | |
Text
o.a atg 4'g g'o, UNITED STATES
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NUCLEAR REGULATORY COMMISSION 3 ?\\ %/
E REGION I 0,
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631 PARK AVENUE KING OF PRUSSIA, PENNSYLVANIA 19406 Docket Nos. 50-443 NOV 2 6 7379 50-444 Public Service Company of New Hampshire ATTN:
Mr. W. C. Tallman President 1000 Elm Street Manchester, New Hampshire 03105 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,
_r
/ hfY-Boyce H. Grier Director
Enclosures:
1.
IE Circular No. 79-24 w/ Attachment 2.
List of Recently Issued IE Circulars CONTACT:
W. H. Baunack (215-337-5253) cc w/encls:
John D. Haseltine, Project Manager 1540 078 791206o595
ENCLOSURE 1 Accession No: 7910250492 SSINS No. 6830 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-24 Date:
November 26, 1979 Page 1 of 3 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 monitcrs 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 connections.
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 design 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 (Fig
- density to decrease as the plant reached was determined to be about 3.5 psid foll discussed below.
DUPLICATE DOCUMENT Adding the 3.5 psi downscale deflection in a total required deflection of 8.5 ps Entire document previously Since the total dp available across the entered into system under:
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ANO 1540 079 Jr'geyes:
3 No.