ML19253C604
| ML19253C604 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 11/26/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| NUDOCS 7912060567 | |
| Download: ML19253C604 (1) | |
Text
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UNITED STATES S'y)e,c\\
NUCLEAR REGULATORY COMMISSION 3\\"
. I 631 PARK AVENUE E
REGION I
% ' .V [e 0, ' N KING OF PRUSSIA, PENNSYLVANIA 19406 9.
Docket No. 50-213 NOV 2 61979 Connecticut Yankee Atomic Power Company ATTN:
Mr. W. G. Counsil Vice Presidect - Nuclear Engineering ana Operations P. O. Box 270 Hartford, Connecticut 06101 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,
/AYK
~
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:
R. Graves, Plant Superintendent D. G. Diedrick, Manager of Quality Assurance J. R. Himmelwright, Licensing Safeguards Engineer 1540 096 7912060
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 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 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 larm was set to trip at 5 psid increasing.
Because of this cold calibration dp instrument then indicated full downscale negative during operation.
Th' 7 gative dp was due to the heat up of the reference leg (Fiqure 1 Connection C which canced tho fi ni ti 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 deflection in a total required deflection of 8.5 p Entire document previously Since the total dp available across the entered into system under:
1540 097 7//gof94L nNO No. of pages: