ML19253C614
| ML19253C614 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/26/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 7912060579 | |
| Download: ML19253C614 (1) | |
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UNITED STATES y 73 #, c (,g NUCLEAR REGULATORY COMMISSION
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8 KING OF PRUSSIA, PENNSYLVANIA 1940G Nov 2 61979 Docket Nos. 50-245 50-336 50-423 Northeast Nuclear Energy Company ATTN:
Mr. W. G. Counsil Vice President - Nuclear Engineering ard Operations P. O. Box 270 Hartford, Connecticut 0G101 Gentlemen:
The enclosed 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, k
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Boyce H. Grier p
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:
J. F. Opeka, Station Superintendent D. G. Diedrick, Manager of Quality Assurance J. R. Himmelwright, Licensing Safeguards Engineer K. W. Gray, Construction Quality Assurance Lead H. R. Nims, Director of Nuclear Projects 1540 ogg 41208 5 77
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 OETECTION 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 tne 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 (Fia"~
density to decrease as the plant reach was determined to be about 3.5 psid foi discussed below.
DUPLICATE DOCUMENT Adding the 3.5 psi downscale deflectio in a total required deflection of 8.5 p Entire document previously Since the total dp available across the entered into system under:
h ANO 1540 087 No. of pages:
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