ML19353A267
| ML19353A267 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 11/24/1980 |
| From: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| LQA8000442, TAC-42227, TAC-47003, TAC-47004, NUDOCS 8101070642 | |
| Download: ML19353A267 (4) | |
Text
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lOf 281980 Mr. Karl V. Seyfrit, Director
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U.S. Nuclear Regulatory Com=ission Office of Inspection and Enforcement Region IV 611 Ryan Pla=a Drive Suite 1000 Arlington, Texas 76011
Subject:
Dear Mr. Seyfrit:
In our October 22, 1980 letter of response to the Confirmatory order issued on October 2, 1980, we informed you that we had installed a level switch on each scram discharge volume.
We also stated that we would consider the installation and use of UT equipment that we had discussed in our September 11, 1980 letter to you.
We have now received all of the UT equipment and conducted extensive tests on this equipment on a mock-up. Our testing program indicated that the equipment can provide accurate and reliable water level in-dication from 1" to 7-3/4" at the sensor location.
The equipment consists of two redundant sensors on the lower end of each scram dis-l charge volume with associated electronics etc., to provide an alarm in the control room at the desired setpoint. We also have a recorder in the control room that can be activated upon receiving an alarm such that the control room operator can follow water level in the volume.
This recorder will provide the operator with timely information such that he can initiate a manual scram prior to losing adequate volume for the full l
insertion of all rods. This equipment has now been installed and tested.
Procedures and actions for its use will be in place prior to December 1, 1980.
We believe this equipment fully meets the requirements of the Confirmatory Order.
l 8101070 4 y g
Mr. Karl V. Se:-frit Nove=ber 24, 1480 Page 2.
We are attaching our system description of the two installed systems.
Please contact L. C. Lessor at the site if you have further questions about the LT installation or this response.
Sincerely, M
J.c.
Pilant Director of Licensing and Quality Assurance JMP:LCL:cg Attachment
l Page 1 of 2 SCRAM DISCHARGE HEADER LEVEL MONITORING SYSTEM DESCRIPTION There are two different means to monitor the Scram Discharge Header vater level. The first means is by float type level switches, desig-nated LS-232 A(B).
The annunciators for these level switches are lo-cated on the 9-5 panel.
Due to the respective dead band of the two instruments and the need to have the reset for the alarm at least a half inch above the empty pipe level, the alarm points are 2" on the north header and 1-7/8" on the south header.
The second =onitoring device is a Multi-point Sub-Sonic Liquid depth monitor (UT).
The system consists of (4) four ultrasonic transducers j
mounted on the 8" horizontal crosstie between the two legs of the horse-shoe shaped scram discharge header, two per header.
Information is gt,hered and compared at two local station modules, one at each header.
The module contains (2) two Sub-Sonic depth measuring circuits with analog outputs, (2) two Switch-settable Digital depth comparator cir-cuits and (2) two Analog Panel meters. There is a local alarm at each station. The alarm point is at 1-1/2" of water.
Due to the spurious signals generated at water depths of 1" and less, a time delay of 16 seconds is set to preclude annoyance alarms. The alarm must be reset j
locally.
In addition to the local indication, the module has a 4-20 ma output to run a recorder that is located in the Control Room. The multi-point recorder has four channels that will indicate water depth from 0 to 7-3/4".
The scale of the recorder is 0-100 and the full range will be utilized.
One inch will correspond to 10 and so on.
The re-corder will be run in automatic and needs no operator input.
The alarms will be set at 1.5" or 15 on the recorder scale.
Due to the spurious signals below 1" of water level, the recorder may print of f and on.
Unless the alarm is in for longer than 10 seconds there will not be an annunciator. The recorder automatically shuts off when all points are below the alarm point.
General Electric recommends approximately 3.3 gallons per CRD for sizing j
the Scram Discharge Header. This corresponds to approximately 2" of water in the Scram Discharge Header.
Tests perforced by General Elec-tric, as referenced in the " Report on the Browns Ferry 3 Partial Failure to Scram Event on June 28, 1980" by the Office for Analysis and Eval-uation of Operational Data, indicates expected responses to scrats with
/arying degrees of water in the Scram Discharge Header. With a 40%
reduction in free volume in the header over varying degrees of seal leakage a full scram is still possible.
The free volume needed that would correspond to a 40% reduction in design requirements is 137 gal-lons per header.
This corresponds to a level of somewhere between 5 and 6 inches.
The following table indicates free volume versus level.
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SCRAM DISCHARGE HEADER LEVEL MONITORING SYSTEM DESCRIPTION (continued)
Level in Inches Free Volume per Header 2"
228.6 gallons 4"
188 gallons 5"
156 gallons 6"
120.5 gallons l
7" 85.2 gallons The above referenced report indicates at low CRD leakage levels a 70%
reduction in required free volume will still allow full insertion of control rods. This corresponds to free volume of 76 gallons or 7 in-
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ches.
Operator actions for System 1, the float type level switches, consists of (1) verifying the SDV vent and drain valves are open, and (2) man-ually starting the sub-sonic level recorder.
Operator actions for System 2 (UT) consists of (1) verifying the SDV vent and drain valves are open, (2) checking alar =s from System 1, (3) reducing power at 4" in either SD header, (4) scramming reactor at 5" in either SD Header, and (5) confirm alarm by performing SDV air test.
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