ML20081D862
| ML20081D862 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 10/28/1983 |
| From: | Bradley E PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8311010365 | |
| Download: ML20081D862 (9) | |
Text
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e PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHI A, PA.19101
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EUGENE J. BR ADLEY assoconts esmema6 covesset DON ALD BLANNEN RUDOLPH A. CHILLEMI E. C. M B R M H A LL T. H. M AHER CORNELL October 28, 1983 PAUL AUERB ACH assistant emmanak cousessh EDW A RD J. CULLEN, J R.
THOM AS H. MILLER, J R.
IRENE A. McMEN N A assestant causessh Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Limerick Generating Station, Units 1 and 2 Information for Containment Systems Branch (CSB) on Hydrogen Recombiners
References:
1)
Telecon between CSB & PECO on 10/24/83 2)
Letter J. S. Kemper (PECO) to A. Schwencer (NRC) dated 9/22/83.
File:
COVT l-1 (NRC)
Dear Mr. Schwencer:
Attached are draf t changes to FSAR Sections 6.2.4.3.1.3.2.3, 6.2.5.1, 6.2.5.2 and 6.2.5.4 which are being made as a result of the referenced telecon.
The information contained on these draf t FSAR changes will be incorporated into the FSAR, exactly as it appears on the attachments, in the revision scheduled for November 1983.
Sincerely,
$2 O
J pg Eu ne J Br ley JTR/gra/Q-4 At tachment l
Copy to: See Attached Service List 8
cc: Judge Lawrence Brenner (w/o enclosure)
Judge Peter A. Morris (w/o enclosure)
Judge Richard F. Cole (w/o enclosure)
Troy B. Conner, Jr., Esq.
(w/o enclosure)
Ann P. Hodgdon, Esq.
(w/o enclosure)
Mr. Frank R. Romano (w/o enclosure)
Mr. Robert L. Anthony (w/o enclosure)
Mr. Marvin I. Lewis (w/o enclosure)
Judith A. Dorsey, Esq.
(w/o enclosure)
Charles W. Elliott, Esq.
(w/o enclosure)
Jacqueline I. Ruttenoerg (w/o enclosure)
Zori C..Ferkin, Esq.
(w/o enclosure)
Mr. Thomas Corusky (w/o enclosure)
Director, Pennsylvania Emergency Management Agency (w/o enclosure)
Mr. Steven P. Hershey (w/o enclosure)
Angus Love, Esq.
(w/o enclosure)
Mr. Joseph H. White, III (w/o enclosure)
David Wersan, Esq.
(w/o enclosure')
Robert J. Sugarman, Esq.
(w/o enclosure)
Martha W. Bush, Esq.
(w/o enclosure)
Spence W. Perry, Esq.
(w/o enclosure)
Jay M. Cutierrez, Esq.
(w/o enclosure)
Atomic Safety and Licensing Appeal Board (w/o enclosure)
Atomic Safety and Licensing Board Panel (w/o enclosure)
Docket and Service Section (w/o enclosure) a
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Outboard suppression pool sample and return isolation valves SV-184, SV-185, SV-186, SV-190, and SV-195 are ganged on HS-187.
6.2.4.3.1.3.2.2 Drywell Equipment and Floor Drain Lines The drywell equipment and floor drain lines are provided with two normally closed air-operated spring-closed valves located outside the primary containment.
The inner valve is located directly on the containment.
Both valves are automatically closed upon receipt of a containment isolation signal.
6.2.4.3.1.3.2.3 Containment Purge and Hydrogen Recombiner Lines The high-volume purge lines for the drywell and suppression chamber are each provided with two isolation valves located outside the primary containment.
The inboard valve in each line is a normally-closed, air-operated butterfly valve located as close as practical to the primary containment penetration.
The outboard valve in each line is a normally-closed, motor-operated butterfly valve.
A nonsafety-related north stack effluent high radiation isolation signal is also provided for the containment purge valves (HV-104, 109, 114, 115, 112, 121, 124, 123, 131, 135, 147).
A description of tne type and the arrangement of containment isolation valves used in the low-volume purge exhaust f
lines is provided in Section 9.4. 5.1.2.
Each of these valves receives automatic isolation signals.
The hydrogen recombiner lines connect to the high-volume purge lines between the containment penetration and the inboard isolation valve in the latter lines.
Each of the recombiner lines is provided with a normally-closed, motor-operated butterfly valve that can be manually actuated from the control room.
These isolation valves each receive automatic isolation signals.
For operation of the recombiners after a LOCA, the isolation signals to these valves are overridden by using keylocked bypass switches. Rtureur, v
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The engineered safety feature recombiner syst.e.m (Section 6.2.5) i constitutes a closed system outside containment which is' employed as a second containment isolation barrier.
The use of single isolation valves on the recombiner supply and return lines ensures maximum system reliability (i.e., the use of additional isolation valves would decrease system reliability).
The containment isolation provisions for the recombiner lines meet all of the relevant design criteria in Regulatory Guide 1.141, ANSI Standard N-271, and Standard Review Plan 6.2.4, as described below:
a.
The closed system does not communicate with either the secondary containment atmosphere or the environment.
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The closed system has been designed, fabricated, and
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installed,in accordance with ASME Section III, Class 2 requirements.
c.
The closed system has a design temperature and pressure a,( Igst,egual (,,ge,g,gnjafpme,nt y ign conditions..
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d.
The closed system is designed as seismic Category I.
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The system is designed to withstand the loads and s vu o4 environmental conditions accompanying a loss-of-coolanta,,,,,y, accident.
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High energy and moderate energy pipe break effects will
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not affect hydrogen recombiner system continuity when f3' the closed system is needed for containment isolation
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The recombiner system is designed to be leaktight and nove t
will be periodically leaktested at the containment peak accident pressure.
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Any leakage from the system will be confined within the secondary containment and will be diluted and filtered prior to release.
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1.
The closed system is protected from missiles 3
(Section 3.5).
The high-volume purge lines are provided with debris screens located at the point where each purge line terminatis inside the primary containment.
The debris screens ars designated as seismic Category I and are designed to withstand the maximum differential pressure across the screen that could result from a LOCA.
6.2.4.3.1.3.2.4 RCIC and HPCI Turbine Exhaust Vacuum Breaker Lines These lines are provided with two normally open motor-operated remote manually actuated gate valves.
The valves are automatically closed on receipt of an RCIC or HPCI i' solation signal.
6.2.4.3.1.3.2.5 Traversing Incore Probe (TIP)
The TIP system purge line is equipped with a normally open air operated globe valve outside containment and a check valve inside containment.
The TIP system purge line air operated valve is normally open in order to provide a continuous supply of dry gas to the indexing mechanisms.
Upon receipt of a containment isolation signal, the TIP system purge line air-operated valve is
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automatically closed.
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The controls for containment isolation valves on Jinos associated with post-LOCA combustible gas control and monitoring are designed so that the valves may be re-opened by utilizing keylocked bypass switches to override the isolation signals.
e.
The containment hydrogen recombiner subsystem, the combustible gas analyzer subsystem, and the safety-related portions of the drywell air cooling system are designed to remain functional after an SSE.
f.
The containment hydrogen recombiner subsystem, the combustible gas analyzer subsystem, and the safety-related features of the drywell air cooling system are designed so that a single failure of an active component, assuming loss of offsite power, cannot result in the loss of a safety function.
g.
The containment atmospheric control system is designed to permit a controlled purge of the primary containment atmosphere following a LOCA, as a backup means of combustible gas control and as an aid in cleanup.
h.
The containment hydrogen recombiner subsystem, the combustible gas analyzer subsystem, and the portions of the containment atmospheric control system that are related to post-LOCA purging are designed to facilitate periodic inspection and testing of safety-related features.
1.
The containment hydrogen recombiner subsystem, the combustible gas analyzer subsystem, and the safety-related portions of the drywell air cooling system are designed to remain operable in the environments existing in their respective areas following a LOCA.
6.2.5.2
System Description
6.2.5.2.1 Containment Hydrogen Recombiner Subsystem The containment hydrogen recombiner subsystem is part of the containment atmospheric control system, which is discussed in Section 9.4.5.1 and shown schematically in Figure 9.4-5.
The recombiner subsystem consists of two redundant hydrogen recombiner packages, each of which has adequate processing capacity to control the quantity of oxygen postulated to be generated in the primary containment after a LOCA.
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recombiners are of the thermal recombination type, manufactured l
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The recombiners are similar in design and construction to those described in Ref 6.2-9 and are identica] to those described in Ref 6.2-10.
A schematic diagram of one recombiner package is shown in Figure 6.2-37.
Each hydrogen recombiner package consists of three modules: the recombiner skid assembly, the power cabinet, and the control cabinet.
The recombiner skid assembly, which is shown in Figure 6.2-38, consists of the process components.
The process components include flow contro) valves, canned motor / blower assembly, gas heater pipe, reaction chamber, water-spray cooler, and water separator.
The gas heater pipe and the reaction chamber are located within an insulated enclosure that also contains electric heater elements.
The recombiner skid assembly is located outside the primary containment in the reactor enclosure.
The power cabinet houses the power distribution components for the recombiner package.
The cabinet is located adjacent to its associated recombiner skid assembly and contains the 480V power supply, control transformer, blower motor starter, circuit breakers, control relays, and the silicon-controlled rectifiers (SCRs) that control electrical power to the heater elements.
The control cabinet contains all of the instrumentation, annunciators, lights, and switches necessary for operation of the recombiner package.
The control cabinet is located in the control room.
Each recombiner package is designed to process 60 scfm of gas (inlet flow) containing 5% oxygen, or up to 150 scfm of gas (inlet flow) containing 2% oxygen, with the balance consisting of unlimited amounts of hydrogen, nitrogen, and water vapor.
The system will also process 150 scfm of air containing 4% hydrogen.
The recombination process is accomplished by increasing the temperature of the process stream to approximately 13000F,'at which temperature the hydrogen and oxygen combine ~ spontaneously to form water vapor by the reaction 2H, + 0, --> 2H,0.
Virtually complete recombination occurs, so that the oxygen concentration in the effluent from the recombiner package is negligible.
Duringrecombineroperation, gas'fromthedrywellflows"t['hrough the high-volume purge piping of the containment atmospheric control system to_the gas inlet piping of the recombiner package.
The effluent from the recombiner package flows through the, gas outlet piping to the high-volume purge piping associated with the suppression chamber, and then into the suppression chamber. IBy taking cuction-from the drywell and discharging to.the.
suppression chamber, a differ.ential pressure is created between these two volumes.
This differential pressure is limited ~to 0.5
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(d'escribed in Section 9.4.5.1), that open to allow air to flow from the suppression chamber back into the drywell.
The recombiner gas inlet and outlet lines are each provided with a normally-closed butterfly valve for containment isolation.
i These valves can be operated by hand switches in the control room, and are automatically closed upon receipt of a containment isolation signal.
The isolation signals can be overriden by using keylocked bypass switches.
Containment isolation is discussed further in Section 6.2.4.
The process stream entering the recombiner skid assembly flows first through a control valve that is used to regulate the flow rate through the recombiner.
Next along the' process path is the blower, that provides sufficient head to overcome the system flow losses and also the 0.5 psid maximum differential pressure between the drywell and the suppression chamber.
From the blower, the gar flows through the gas heater pipe that spirals around the reaction chamber.
The gas is heated as it flows through the' gas heater pipe, due to radiated heat from the electric heater elements and the reaction chamber.
Next, the gas flows into the reaction chamber, where the exothermic recombination of hydrogen and oxygen occurs.
The flow field in the reaction chamber is highly turbulent, with sufficient mixing to rapidly bring the inlet gas temperatures to a level where virtually complete recombination occurs.
Reaction chamber temperature is not critical, and considerable deviation from the nominal operating temperature of 13000F ma without seriously affecting recombiner performance.y be tolerated
.The geometric configuration and volume of tie reaction chamber provide gas flow movement and transport times so that recombination is completed over a varied range of hydrogen-czygen concentrations.
Recombined gas flows from the reaction chamber to the water-spray cooler where it is cooled to less than 250*F.
The hot process gas is mixed with water spray in the throat region of a venturi, and the hot gas is cooled by vaporization of the water and by direct contact with the water droplets.
The cooling water is supplied to the recombiners from the RHR system.
Cooled gas flowing from the cooler is passed through a water separator that prevents any remaining water droplets from entering the gas recirculation line.
The separated water drains down to the supp'ression' pool through the recombiner gas outlet piping.
Recirculation (dilution)l gas is drawn from the top of the water separator and is routed to tht'recombiner gas inlet piping.
U Operation of the hydrogen recombiner, package is initiated manually from the control cabinet.
When' Gas flow has been established and the water inlet valve is fully open, the heater l,
elements are energized.
Approximately 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> are required for E
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As the temperature ci the heated enclosure increases, t1e gas being circulated through the recombiner is heated.
The recombination reaction begins to occur at the outlet of the gas heater pipe when the temperature at that location reaches approximately 11500F.
When the temperature at the gas heater pipe outlet reaches 13000F, power to the heater elements is automatically turned off.
When the gas heater pipe cools to the point at which it can no longer sustain the reaction, the reaction moves into the reaction chamber.
When the temperature at the gas heater pipe outlet falls below 13000F, an interlock is cleared and power is returned to the heater elements at a lower level than during startup.
Temperatures in the gas heater pipe stay below those required for reaction, so the reaction stays in the reaction chamber.
A temperature controller located in the control cabinet is used to maintain reaction chamber temperature'at about 13000F.
6.2.5.2.2 Combustible Gas Analyzer Subsystem The combustible gas analyzer subsystem is part of the containment atmospheric control system, which is diccussed in Section 9.4.5.1 and shown schematically in Figure 9.4-5.
The combustible gas analyzer subsystem consists of two analyzer packages, each of which contains a hydrogen analyzer cell and an oxygen analyzer cell.
One of the analyzer packages normally samples gases from the suppression chamber and the other normally samples gases from the drywell.
However, sufficient sample points are provided so that both analyzer packages can take samples from either the drywell or the suppression chamber.
Each analyzer package consists of a sample cabinet located in the reactor enclosure and a remote control panel located in the control room.
Sample points in the primary containment are located as follows:
a.
Drywell 1.
El 291 feet, azimuth 100; 15' feet,from containment centerline 2.
El 255 feet, azimuth 2150; 25 feet from containment centerline I
3.
El 242 feet, azimuth 2140; 1.5 feet from inside wall of reactor pedestal.
b.
Suppression chamber 1.
El 222 feet, azimuth 700; at inside of containment wall l
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in Tables 6.2-20 and 6.2-21, respectively.
Each combustible gas analyzer sample line penetrating the primary containment is provided with redundant isolation valves powered from different divisions of Class IE power.
Since the isolation valves are of a type that fail closed upon loss of power, loss of l
power to any individual valve or to all valves powered from the same division does not disable the containment isolation function.
In the event of a failure of any single valve to close when required, the redundant valve on the same line provides the isolation function.
The bypass of an isolation signal to any valve is annunciated in the control room.
Containment isolation provisions for piping used in conjunction with hydrogen recombination and post-LOCA purging are discussed in Section 9.4.5.1.
The design pressures and temperatures for process components of the hydrogen recombiner packages are as follows:
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-Stainless steel components 30 psig/14000F (gas heater pipe, reaction chamber, and water-spray cooler) 55 ylo sk.
-Carbon steel components 4M4 psig/&OOoF (inlet piping, water separator, and outlet piping)
Since the post-LOCA primary containment pressure-temperature transient stays well below these design parameters for the time period greater than 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after the LOCA (as discussed in Section 6.2.1), no restrictions exist on recombiner operation after this 6-hour period.
As shown in Figures 6.2-44, 6.2-45, and 6.2-46, the operation of one hydrogen recombiner package is sufficient to maintain post-LOCA oxygen concentrations in the containment bel,ow 5 volume percent.
The analysis to determine post-LOCA oxygen concentrations assumes that hydrogen-oxygen recombi' nation begins at 39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br /> after the LOCA.
Since the recombiner requires a 1.5-hour heatup period before completa recombination of oxygen in the process stream occurs, one recombiner package is activated at or prior to 37.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after a LOCA.
In the extremely unlikely event that a LOCA occurs and both recombiner packages fail to function properly, purging may be utilized to control the oxygen concentration inside the containment.
Since the purging of any amount of containment atmosphere after a LOCA is undesirable, operation of the Ile N
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