ML19253C376
| ML19253C376 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1979 |
| From: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | Grier B, James Keppler, James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 7912050284 | |
| Download: ML19253C376 (7) | |
Text
M fA November 24, 1979 MEMORANDUM FOR:
B. H. Grier, Director, Region I J. P. O'Reilly, Director, Region II J. G. Keppler, Director,' Region III K. V. Seyfrit, Director, Region IV R. H. Engelken, Director, Region V FROM:
Norman C. Moseley, Director, Division of Reactor Operations Inspection, IE
SUBJECT:
IE CIRCULAR NO. 79-24, PROPER INSTALLATION AND CALIBRATION OF CORE SPRAY PIPE BREAK DETECTION EQUIPMENT ON BWRs The subject IE Circular is transmitted for issuance on November 26,1979.
The Circular should be issued to all holders of a power reactor operating license or construction permit.
The text of the Circular and draft letter to the licensees and permit holders are enclosed for this purpose.
Norman C. Moseley, Director Division of Reactor Operations Inspection Office of Inspection and Enforcement
Enclosures:
1.
Draft transmittal letter 2.
IE Circular No. 79-24 1503 055 CONTACT:
C. J. DeBevec, IE 49-28180
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WPU/DLM Office:
R A:Xp%:IE 11/14/79 Surname:
e evec Jord n NC ose GCMver Job M Date:
//f/79 11/ /79 11/,,2Y79 1
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7912050 2.7
(Draft transmittal letter for Circular t!c. 79-24 to each holder of a pcwer reactor operating license er construction oermit.)
IE Circular No. 79-24 Addressee:
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, Signature (Regional Director)
Enclosures:
1.
IE Circular No. 79-24 2.
Recently Issued IE Circulars 4
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 ard 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 instrement (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 pipi ig 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 addi,tional) 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 (Figure 1 Connection X) which caused the fluid density to dec* ease as the plant reached hot conditions.
The magnitude of this dp was determined to be about 3.5 psid following completion of the modification discussed below.
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