ML20151N644
| ML20151N644 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/30/1985 |
| From: | Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Thompson H Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.2, TASK-TM RJR-85-578, NUDOCS 8601030041 | |
| Download: ML20151N644 (5) | |
Text
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esuun SACRAMENTO MUNICIPAL UTILPY DISTRICT O 6201 S Street, P.O. Box 15830. Sacramento CA 95852 183o,(916) 452 3211 RJR 85-578 AN ELECTRIC SYSTEM SERVING THE HEART OF CAllFORNIA December 30, 1985 DIRECTOR OF NUCLEAR REACTOR REGULATION ATIN HUGH L THONPSON JR DIVISION OF LICENSING U S NUCLEAR REGULATORY COMMISSION WASHINGTON DC 20555 DOCKET 50-312 RANCHO SECO NUCLEAR GENERATING STATION UNIT NO. I NUREG 0737 ITEM II.F.2 INADEQUATE CORE COOLING (ICC)
By letter dated April 15, 1983, the District proposed ICC instrumentation to satisfy your Order for Modification of License for Rancho Seco Nuclear Generating Station, dated December 10, 1982.
On June 28, 1984, the District responded to your Request for Additional Information, dated August 24, 1983.
In these submittals, the District identified a heated junction thermocouple system (HJTCS) as the preferred method for reactor vessel coolant inventory trending. A differential pressure (DP) system was identified as an option.
Due to the recent availability of qualified higher accuracy transmitters and procurement difficulties with the HJTCS, the District has reevaluated the options and decided to pursue the DP system.
The attachment to this letter provides a design description for the proposed reactor coolant inventory tracking system (RITS). This information supersedes the reactor vessel level measurement system description provided by the District's At il 15, 1983 and June 28, 1984 submittals.
The previous descriptions of the balance of the ICC instrumentation, including hot leg level, are still valid.
610y0y ho 2
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e RJR-85-570 Hugh L. Thompson. Jr. December 30, 1985 The District remains consnitted to install the balance of the RITS instrumentation during the Cycle 8 refueling outage, as reiterated in our letter of September 30, 1985.
If you have any questions concerning the above, please contact Robert Little at (916) 732-6021.
R.
U ASSISTANT GENERAL MANAGER, NUCLEAR Attachment i
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Attachment REACTOR COOLANT INVENTORY TRENDING SYSTEM The reactor coolant inventory tracking system (RITS) is designed to provide unambiguous indication of reactor coolant inventory trending.
The RITS will provide inventory trending indication with the reactor coolant pumps (RCPs) either running or tripped.
The system is being designed to meet the intent of NUREG 0737 Item II.F.2.
The RITS measures three parameters for reactor coolant inventory trending determination:
differential pressure (DP) across the vertical run of the hot legs (hot leg level);
DP across the upper region reactor vessel (RV level); and RCP motor power.
Hot Lee Level Measurement The hot leg level portion of the RITS is described in the District's submittals of April 15, 1983 and June 28, 1984.
RV Level Measurement The RV level measurement provides an indication of reactor coolant inventory trending when the RCPs are not operating.
The RV level measurement ranges from the top of the reactor vessel (RV) head to the center of the cold leg. The design includes the removal of the central control drive mechanism to provide a penetration in the RV head for location of the top RV pressure tap.
The existing tap on the Loop A cold leg (discharge of RCP P-2108) will be used as a lower pressure tap. Use of the existing cold leg tap provides the following benefits:
elimination of single failure concerns relative to use of the tap on decay heat drop line common with the hot leg DP transmitters; and Iower personnel exposure over installing a new hot leg tap.
Two DP transmitters (one per channel) will be used to provide redundancy.
Each transmitter will be powered independently by Class 1 instrumentation power. The DP transmitters will be located inside containment and will be qualified to withstand the normul, abnormal, and post accident conditions, in accordance with the District's environmental qualification program.
The DP transmitters will be qualified to withstand the overpressure conditions imposed on the diaphragm of the transmitters when the RCPs are running and will be fully recoverable when the RCPs are stopped. The transmitters will be installed in an insulated enclosure to protect them from temperature transients during design basis events and to improve their performance.
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The design includes density compensation for level measurements due to l
temperature offects on process liquid density.
Density compensation on the
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reference legs (vertical runs) is not required because the sensing lines will
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be insulated with 1* thick insulation to maintain the temperature of the i
j reference legs relatively constant.
The maximum temperature rise of the i
reference legs is anticipated to be 10*f above normal containment atmospheric i
temperature (120*F) when subjected to the temperature transients during a design basis event.
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j The output of the transmitters will be connected to the Class 1 multiplexer f
j system for the level indications on the safety parameter display system (SPOS) 1 and the interim data acquisition and display system (IDA05) CRis.
Isolation l
1 for 10A05 is provided in the multiplexers.
IDADS is the primary display system for ICC and has trend recording capability showing the level-time history of representative RV level readings.
l Primary (IDADS) and backup (SPOS) display channels are electrically I
independent.
IDA05 is powered from battery backed Class 2 power source and SPOS will be powered from a Class 1 power source. SPDS modifications will be implemented per the Living Schedule and in accordance with Reg. Guide 1.97 and CROR recommendations.
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j A sketch of the RV level portion of the RITS is shown in figure 1.
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RCP Motor Power _
RCP motor power and pump inlet temperature measurements will be used by the
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t RITS to trend the reactor coolant void fraction when one, or more, of the RCPs j
is operating.
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RCP power measurement requires the use of 3-phase Watt-transducers (Class 2),
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one for each RCP, to provide an analog signal proportional to RCP motor l
power. Watt-transducers will use existing Class 2 current and potential j~
transformer signals and will be self powered.
The transducers will be high l
quality connercial grade components and will be installed in the same i
environment as the existing 6.9kV switchgear supplying power to RCPs.
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The output from the transducers will be fed into Class 2 multiplexers located j
in the same switchgear room.
The Watt-transducers' signals will be processed t
in IDADS (Primary display) to provide percent void indication for each pump j
j via CRT on demand.
IDADS also has trend capability and recording capability j
l on demand. Since 10 ADS is powered from a battery backed Class 2 power source and the RCP motors are powered from a Class 2 power source, the percent void l
I indication will be available on IDADS CRT whenever the RCPs are running.
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