ML19331D739
| ML19331D739 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/29/1980 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19331D738 | List: |
| References | |
| NUDOCS 8009030514 | |
| Download: ML19331D739 (5) | |
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O Ef! CLOSURE 1 PROPOSED CHAT:GES TO TECHilICAL SPECIFICATI0:!S BRO'RIS FERRY !!UCLEAR PLAllT U!!IT 2 DOCKET f!0. 50-260 i
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8009030514
1 TABIE 3.2.F Surveillance Instrumentation Minimum f of Operable Instrument Type Indication i
Channels Instzmment #
Instrument, and Range Notes 2
II H 94 Drywell and Torus 0.1 - 20%
(1) 2 Ilydrogen H M 104 Concentration 2
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PdI-64-137 Drywell to Suppression Indicator
-(1) (2) (5) i PdI-64-138 Chamber Differential O to 2 paid i
pressure -
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LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIRDIENTS 3.7 CONTAINMENT SYSTEMS 4.7 CONTAINMENT SYSTEMS II. Containment Atmosphere 11. Containment Atmosphere Monitoring (CAM) System -
Monitoring (CAM) System -
11 Analyzer H Analyzer 2
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Whenever the reactor is 1.
Each hydrogen analyzer.
not in cold shutdown, two system shall be demon-independent gas analyzer strated OPERABLE at systems shall be operable least once per quarter for monitoring the drywell by performing a CHANNEL and the torus.
CALIBRATION using standard gas samples containing 2.
With one hydrogen analyzer a nominal eight volume inoperable, restore at percent hydrogen balance least two hydrogen nitrogen.
analyzers to OPERABLE status within 30 days or 2.
Each hydrogen analyzer be in at least HOT system shall be demonstrated SIIUTDOWN within the next OPERABLE by performing 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
a CllANNEL FUNCTIONAL TEST monthly.
3.
With no hydrogen analyzer OPERABLE the reactor shall be in IIOT SilUTDOWN within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
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a BASES The occurrence of primary system leakage following a major refueling outage or other scheduled shutdown is much more probable then the occurrence of the loss-of-coolant accident upon which the specified oxygen concentration limit is based. Permitting access to the drywell for leak inspections during a startup is judged prudent in terms of the added plant safety offered without significantly reducing the margin of safety. Thus, to preclude the possibility of starting the reactor and operating for extended periods of time with significant leaks in the primary system, leak inspections are scheduled during startup periods, when the primary system ia at or near rated operating temperature and pressure. The 24-hour period to provide inerting is judged to be sufficient to perform the leak inspection and establish the required oxygen concentration.
To ensure that the hydrogen concentration is maintained less than 4% following an accident, liquid nitrogen is maintained on-site for containment atmosphere dilution. About 2260 gallons would be sufficient as a 7-day supply,.and replenishment facilities can deliver liquid nitrogen to the site within one day; therefore, a requirement of 2500 gallons is conservative. Following a loss of coolant accident the Containment Air Monitoring (CAM) System continuously monitors the hydrogen concentration of the containment volume. Two independent systems ( a system consists of one hydrogen sensing circuit) are installed in the drywell and the torus. Each sensor and associated circuit is periodically checked by a calibration gas to verify operation. Failure of one system does not reduce the ability to monitor system atmosphere as a second independent and redundant system will still be operable.
In terms of separability, redundancy for a failure of the torus system is based upon at least one operable drywell system. The drywell hydrogen concentration can be used to limit the torus hydrogen concentration during post LOCA conditions.
Post LOCA calculations show that the CAD system initiated within two hours at a flow rate of 100 scfm will limit the peak drywell and wetwell hydrogen con-centration to 3.6% (at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) and 3.8% (at 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />), respectively.
This is based upon purge initiation after 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> at a flow rate of 100 scfm to maintain containment pressure below 30 psig. Thus, peak torus hydrogen concentration can be controlled below 4.0 percent using either the direct torus hyorogen monitoring system or the drywell hydrogen monitoring syste'm with appropriate conservatism (si 3.8%),
as a guide for CAD / Purge operations.
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9 ENCLOSURE 2 e
TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT PRIMARY CONTAINMENT HYDROGEN MONITORING SYSTEM Zach reactor is equipped with two totally independent systems for monitoring hydrogen concentrations in the drywell and the torus. Each system includes a Hays Republic Division, Milton Roy Company, Model 643D Condu-therm thermal conductivity type gas analyzer, sample pumps, sample moisture removal equipment, and associated valves and controls, all mounted in a cabinet external to the primary containment.
Gas samples are withdrawn from either the drywell or the totus for analysis.
The hydrogen analyzers use.the principle of thermal conductivity to analyze the concentration of hydrogen in a gas mixture containing primarily i
nitrogen. The thermal conductivity of the sample changes linearly with i
the change in hydrogen concentration. The analyzer assembly consists of two identical electrically self-heated, glass-covered, temperature-sensitive resistors which are mounted in separate chambers in the analyzer cell block. These resistors form two legs of a Wheatstone bridge. A reference gas with known thermal conductivity diffuses into one of the cell chambers (the reference cell), and the drywell or torus sample dif fuses into the other chamber (the measuring cell). The reference gas abscrbs heat from the reference resistor in direct ratio to its thermal conductivity. The amount of heat absorbed remains constant since the reference gas has a constant thermal conductivity, maintaining the temperature and the resistance of the reference resistors constant. The sample gas absorbs heat from the measuring resister in direct ratio to its thermal conductivity. As the composition of the sample gas changes, its thermal conductivity changes. This causes the amount of heat absorbed by the measuring resistor to change, changing the resistance of the measuring resistor. The Wheatstone bridge is calibr'ated so that 0 percent hydrogen balances the bridge, producing no electrical output.
As the resistance of the measuring resistor changes, the bridge becomes unbalancel, producing an electrical output that is projortional to the hydrogen concentration in the gas sample. This signal is transmitted to a recorder in the control room.
l Monitoring is continuous with an accuracy of 2 percent.
No special operating procedures are required.
Each system is qualified for samples at 340 F, 45 psig, 100 percent RH, and post-LOCA fission product activity. All piping,, cabling, the equipment cabinets, valves, rendouts, and recorders are seismic Class I.
Each system is powered from separate electrical fuses. All sample lines which penetrate the primary containment a're equipped with one inboard and one outboard isolation valve per line.
Each system is designed to fully comply with the requirements of NUREG 0578 and Regulatory Guide 1.7 for primary containment hydrogen monitoring.
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