ML19263E770
| ML19263E770 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 05/11/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19263E769 | List: |
| References | |
| TAC-11005, NUDOCS 7906250162 | |
| Download: ML19263E770 (2) | |
Text
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UNITED STATES 3#
NUCLEAR REGULATORY COMMisSloN
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j WASHINGTON, D. C. 20555
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SAFETY EVALUATION DESIGN OF REDUNDANT INSTRUMENT SENSING LINES FOR REACTOR COOLANT FLOW CRYSTAL RIVER UNIT 3 I.
INTRODUCTION The Licensee, Florida Power Corporation, in its submittal of March 29, 1979, has proposed certain modifications to the Reactor Protection System, (RPS), of Crystal River Unit 3 plant to correct a single failure deficiency which was identified as Condition 2.C.(7) to its operating license.
The present RPS overpower trip based upon reactor coolant flow differential pressure and axial power imbalance utilizes a comon set of instrument sensing lines for the four reactor protection channels (delta P transmitters) in each of the two reactor coolant loops. As stipulated in the condition to the operation license, this deficiency was to be corrected before the Crystal River Unit 3 plant returns to power following its first refueling shutdown.
In eac.h primary loop, reactor coolant ficw is detected by measuring delta'P developed across a flow tube that is an integral part of the outlet piping of the loop.
Each flow tube has a high pressure (HP) tap and a low pressure (LP) tap.
Connections to the taps are made with 1-inch lines.
The 1-inch lines are terminated at root valves located inside the secondary shield wall.
From the root valves,1/2-inch tubing runs through the secondary shield wall to HP and LP headers.
Four delta P transmitters are connected between the two headers.
Each of these transmitters provides flow information directly to one of the Reacto.r. Protective System channels.
The buffered signals of flow are utilized in the Non-Nuclear Instrumentation (NNI) System and are monitored by the~ plant computer. The operator is provided with flow indication and..
alarms at the control console to be alerted of trends or abnormal conditions.
II.
EVALUATION The licensee's proposed design includes the installation of a second set of instrument sensing lines from the differential pressure taps in each of the primary loops to the differential pressure transmitters.
The new design begins immediately downstream of existing pressure tap root valves located inside the secondary shield wall where a one inch tee will be welled in place.
Downstream of the tee tne pipes will be reduced to half inch and manual shutoff valves installed.
The present tubire run will be attached to one of 7 9 0 6 25 ol@-
A
.. these valves and the new redundant sensihg line will be connected to the other new valve.
This modification will be performed on both the high pressure and icw pressure sensing taps.
The redun-dant sensing lines will be routed in the opposite direction from the existing sensing lines to the new location for two of the differ-ential pressure transmitters.
The sensing lines will be stainless steel material and seismically mounted. The system will meet the seismic and separation requimments of the reactor protection system.
The location for the two relocated transmitters is approximately 50 to 75 feet from the present location.
The electrical circuits to these redundant transmitters will be seismically installed and the channel identity maintained in accordance with the requirements of the present reactor protection. We find this acceptable.
III. CONCLUSION Based on our review of the licensee submittal we conclude the design of the installation of the redundant instrument sensing lines to measure flow in each of the primary loops satisfies the requirements for seismic qualification, and separation and iso-lation. We, therefore, conclude with the completion of the installa-tion, the reactor coolant flow sensing system will satisfy our re-quirement for meeting the single failure criterion.
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