ML20217B572

Supplemental Application for Amend to License NPF-11, Changing Leak & Break Detection Isolation Instrumentation. Util Response to RAI & Rev 1 to Calculation L-001443,encl

ML20217B572
Person / Time
Site:	LaSalle
Issue date:	04/16/1998
From:	Dacimo F COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20217B575	List: ML20217B572 ML20217B592
References
NUDOCS 9804230083
Download: ML20217B572 (22)

Text

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April 16,1998 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555

Subject:

LaSalle County Station Unit 1 Comed Response to NRC Staff Request for Additional Information (RAI) and Supplemental Request for Technical Specification Amendment to Facility Operating License NPF-11; Leak and Break Detection isolation Instrumentation.

NRC Docket No. 50-373

References:

(a) Letter dated November 24,1997 from W.T. Subalusky to the U.S. NRC, Request for Technical Specification Amendment to Facility Operating License NPF-11, concerning Leak and Break Detection isolation Instrumentation.

(b) January 6,1998 Telephone Conference between Comed and NRR involving RWCU leak and break detection. 4 (c) January 15,1998 Telephone Conference between Comed and NRR involving RWCU leak and break detection. l The purpose of this letter is to respond to the NRC staff's questions involving LaSalle Station's Leak and Break Detection changes described in Reference (a) for LaSalle County Station Unit 1. The questions were asked in the telephone conferences in References (b) and (c) above. LaSalle's responses, which provide clarification, are provided as an attachment to this letter.

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In addition, this letter supplements Reference (a) by changing the values and basis for the proposed RWCU Pump Suction Flow - High Isolation l The response to NRC questions, the change proposed to the RWCU Suction Flow - High values and the change basis are consistent with the original Significant Hazards Consideration, which remains valid.

This proposed amendment request is subdivided as follows:

i l 1. Attachment A provides the response to NRC questions and discusses the changes to the RWCU Suction Flow - High Isolation Instrumentation.

2. Attachment B includes the revised pages of the original l' submittal concerning the RWCU Suction Flow - High Isolation Instrumentation, including insert B for the Unit 1 Technical Specifications.

3. Attachment J is Calculation No. L-001443, Rev.1, Dated March 6,1998, Reactor Water Cleanup High Flow Isolation Error Analysis.

4. Attachment K is a summary of Calculation No. L-001384, Rev. O, Dated February 26,1998, Reactor Building Environmental Transient Conditions Following RWCU and RCIC HELBs. i This proposed amendment has been reviewed and approved by Comed Onsite and Offsite Review in accordance with Comed procedures.

Comed requests approval of this license amendment request prior to startup of LaSalle Unit 1 from its current forced outage. The amendment should be made effective upon issuance for Unit 1. Comed willimplement the amendment prior to startup of LaSalle Unit 1.

Comed is notifying the State of Illinois of this application for amendment by transmitting a copy of this letter and its attachments to the designated state official.

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If there are any questions or comments conceming this letter, please refer them to Harold Pontious, Regulatory Assurance Manager, at (815) 357-6761, extension 2383.

Respectfully, A l Fred Dacimo Site Vice President LaSalle County Station Enclosure  ;

I cc: A. B. Beach, NRC Region ill Administrator M. P. Huber, NRC Senior Resident inspector - LaSalle j D. M. Skay, Project Manager - NRR - LaSalle j F. Niziotek, Office of Nuclear Facility Safety - IDNS

I s STATE OF ILLINOIS )

Docket Nos. 50-373 50-374 IN THE MATTER OF )

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COMMONWEALTH EDISON COMPANY )

i LASALLE COUNTY STATION - UNITS 1 & 2 )

AFFIDAVIT l

I I affirm that the content of this transmittal is true and correct to the best of my knowledge, information and belief.

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Fred R. Dacimo Slte Vice President LaSalle County Station Subscribed and swom to before me, a Notary Public in and for the State above named, this lu4 day of Oni 2: # . N97 . My Commission expires on Ii- I , acco .

OFFICIAL SEAL DEBRA J.FEENEY J (M NOTARY PUBUC, STATE OF ILUNOIS otah Public

• AT1 ACHMENT A l RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION I

1) RESPONSE TO NRC QUESTIONS l QUESTION:

You plan to add a Pump Suction Flow - High RWCU isolation trip function. The l analytical limit is 600 gpm. It is our understanding that this new trip function l serves to provide rapid isolation for areas where the 45-second delay feature in l the differential fMw trip could cause EQ profiles to be exceeded. Was the l analytical value for this trip function verified by analysis to be adequate for this l purpose (i.e., for breaks less than 600 gpm, will the differential flow trip function i be capable of sensing and isolating the break in time such that EQ limits are not exceeded)?

RESPONSE

l l A 4-inch line is the smallest line size which is postulated to break in the UFSAR Appendix C. 700 gpm is conservatively calculated to be the lowest flow rate l that would result from a 4-inch guillotine break. When considering the high flow break detection instrumentation response time, the break flow rate is reduced to 650 gpm. EQ zone temperature limits are not exceeded as a result of a break flowrate of this magnitude.

The higher analytical value of 650 gpm is based on a new calculation, I summarized in Attachment K. This calculation was performed to establish additional operational margin to avoid spurious isolations due to the new RWCU Suction Flow - High isolation instrumentation setpoints and to validate that EQ temperature limits for affected areas will be maintained within limits for RWCU piping design basis breaks outside of the primary containment.

Flowrates less than the design basis break flowrate, and leak flowrates, are detected by the leak detection system. For the RWCU system, this consists of the high delta-flow sensor (between the flow elements), ambient temperature and differential temperature (T&dT) sensors, floor drain sump monitors and l radiation monitors . T&dT sensors have been added to the plant such that areas containing hot RWCU pipe that could affect safety related equipment necessary to mitigate the consequences of a HELB are protected.

These areas, with the exception of the RWCU Filter-Demineralizer (FID) valve room, are all HELB areas with the ambient temperature isolation setpoint less than the short-term EQ temperature limit. The FID valve room, where a short 1

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e ATTACHMENT A RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION portion of hot piping containing the 1G33-F042, RWCU Return Upstream Stop Valve, a throttle valve, is located, contains no safety-related equipment other than the temperature sensors, which are qualified to the associated HELB environments.

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ATTACHMENT A RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION QUESTION:

It would facilitate our review if you could provide a schematic diagram of the RWCU system that depicts compartment boundaries and RWCU fluid temperatures. A modified version of the figure in LER 97-031 would suffice.

Please identify each enclosed compartment and open space through which the RWCU flow stream passes outside the containment.

RESPONSE

Please see the attached schematic, which is more detailed than the figure supplied in LER 97-031 to show each enclosed compartment and open space through which the RWCU normal flow stream passes outside of the Primary Containment.

Note: A previous version of this schematic was provided by fax earlier and generated the third question, which follows. A copy of the earlier version marked " SUPERSEDED" is also attached for information.

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1 ATTACHMENT A RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION QUESTION:

The sketch shows reactor coolant piping through floor and tunnel spaces for which no leakage detection instruments are indicated. Are other means of monitoring (e.g., radiation, sump monitoring) provided for all (or just some) of such spaces? Is all RWCU piping outside containment monitored for leakage?

Justification is needed for any that is not.

RESPONSE

The following table describes the leak detection methods available for each of the areas shown on the attached figure. All RWCU piping outside containment in the primary flow path is monitored. A secondary flow path, the RWCU Blowdown Line,is not included. The RWCU Blowdown Line branches off of the RWCU return line from the F/Ds prior to the RWCU Regenerative Heat Exchangers. Therefore, the lines only handle cold water (< 140 *F). In addition, these lines are normal!y only used during the following conditions to aid in maintaining reactor water level when steam flow and feedwater flow are too low for the reactor water level control system:

1. Cold Shutdown or Refueling, no steam flow or feedwater flow.

2. Unit Startup prior to the reactor water level control system functioning in l Automatic, at about 10% power.

3. Unit Hot Shutdown after decay heat drops below the capability of the reactor water level control system due to low feedwater flowllow steam j flow.

I The RWCU Blowdown Line consists of low pressure piping downstream of Motor-Operated Valves (MOVs),1G33-F034, RWCU Reject to Main Condenser Valve, and 1G33-F035, RWCU Reject to Waste Surge Tank Valve, which form a normally closed boundary, isolating the line. The RWCU Blowdown Flow Control Valve,1G33-F033, (normally closed and upstream of the MOVs) closes if the following are true to protect the piping downstream of the MOVs, thus isolating the blowdown line:

1. High pressure between the 1G33-F033 and the downstream MOVs at about 140 psig.

2. Either the 1G33-F034 or 1G33-F035 are not full closed (an interlock being added by DCP 9600300).

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ATTACHMENT A RESPONSE " J HRG QUESTIONS AND SUPPLEMENTAL INFORMATION 1

The Blowdown Flow Control Valve is designed to fail in the closed position on loss of power or loss of air.

The potentially high pressure portion of the RWCU Blowdown Line piping and valves is in the F/D Valve Room and thus are covered in part (not by T or dT) by leak detection for that area when the Blowdown Flow Control Valve is not fully closed. Any leaks associated with the high energy portion of the blowdown piping within the F/D valve room will be detected by the same leak detection methods listed for the F/D area. In addition, blowdown flow indication is provided in the Main Control Room where it can be seen when controlling the Blowdown Flow Control Valve.

l The associated piping and valves up to and including the RWCU Blowdown Line downstream MOVs are ASME Section Ill, Class C, like the rest of the RWCU system downstream of the primary containment outboard isolation valve that is i part of the normal flow path / pressure boundary for the RWCU system. The RWCU system, including the blowdown line valves and the associated blowdown line instrumentation are non-safety-related and are not single failure i proof. Reactor Coolant Pressure Boundary is maintained by the primary l containment isolation valves in the suction line of the system.

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ATTACHMENT A I RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION l

AREAS THROUGH WHICH RWCU PASSES LEAK DETECTION METHODS AVAILABLE*

Hold-up Pipe Area 1, 2 (new), 5, 6, 7 PumpNalve Rooms 1, 2 (new), 5, 6, 7 Heat ExchangerNalve Rooms 1,2,5,6,7 RWCU Pipe Tunnel 1 (between flow elements),4 (heat exchanger room dT - isolation actuation at approximately 165 gpm leak), 5, 6, 7 Filter /Demineralizer (FID) Valve Room 1, 2 (new), 5, 6, 7 FID Area 1, 5, 6, 7 Radwaste Pipe Tunnel 5,6,7 Main Steam (MS) Tunnel 4 (MS isolation), 6, 7

• The numbers represent the following means of leak / break detection:

1 - High Differential Flow 2 - High TemperaturelDifferential Temperature 3 - High Temperature only 4 - High Differential Temperature only 5 - Floor Drain Sump Alarms 6 - Area Radiation Monitors Alarms 7 - High Flow (new)

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ATTACHMENT A RESPONSE TO NRC QUESTIONS AND SUPPLEMENTAL INFORMATION

2) TECHNICAL SPECIFICATION AMENDMENT REQUEST REVISION Attachment B contains pages A-9, A-14, A-17, and B-3 of the Technical Specification Amendment Request, which have been revised to reflect the i higher analyti::al value, instrument setpoint, and allowable values for the RWCU 1 Pump Suction Flow - High isolation actuation signal, as described above. Also included is a revised Attachment J, Calculation No. L-001443, Rev.1, Dated March 6,1998, " Reactor Water Cleanup High Flow isolation Error Analysis, and a new Attachment K, a summary of Calculation No. L-001384, Rev. O, dated j February 26,1998, " Reactor Building Environmental Transient Conditions i Following RWCU and RCIC HELBs". The Attachment J included in this package l supersedes the Attachment J submitted with Reference (a). I The Comparison of the old values to the new is as follows:  !

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Original Value New Value Analytical Value 600 gpm 650 gpm i 1 .

Allowable Value l 550 gpm 610 gpm l

Setpoint 500 gpm 560 gpm Also, due to the transient conditions that occur, for example during RWCU pump starts and changing pumps, a time delay of approximately 0.5 seconds is  ;

j being added to prevent spurious trips. This time delay is bounded in the l isolation response time for the HELB analysis performed for RWCU piping l outside containment (Attachment K). The Technical Specifications do not need i

! to include this time, as the isolation response time for RWCU in Tech Spec Table 3.3.2-3 is not applicable. The time delay relay will be included in a surveillance to periodically calibrate the time delay to maintain the time within l the isolation response time assumed in the calculation (Attachment K).

These are the only sections of the Technical Specification Amendment Request that are affected by the increased values. Neither the responses to the above questions nor the change in setpoint for the RWCU Pump Suction Flow - High l isolation signal affect the Significant Hazards Consideration, Attachment C of Reference 1.

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. 6 ATTACHMENT A DESCRIPTION OF SAFETY ANALYSIS OF THE PROPOSED CHANGES The proposed change to the Technical Specifications changes the setpoints for trip functions A.3.b. and A.3.c. in TS Table 3.3.2-2 and adds new trip functions A.3.f through A.3.1 to TS Tables associated with TS 3.3.2.

The proposed setpoints are as follows for the following revised or added isolation actuation instrumentation functional units for charges to TS Table 3.3.2-2:

A.3 Reactor Water Cleanuo System isolation

b. Heat Exchanger Area Temperature - High, with a setpoint of s 149'F and an allowable value of s 156.8* F.

c. Heat Exchanger Area Ventilation AT - High, with a setpoint of s 33*F and an allowable value of s 40.3' F.

f. Pump and Pump Valve Area Temperature - High, with a setpoint of s 201* F and an allowable value of s 209' F.

g. Pump and Pump Valve Area Ventilation AT - High, with a setpoint of s 86* F and an allowable value of s 92.5* F.

h. Holdup Pipe Area Temperature - High, with a setpoint of s 201* F and an allowable value of s 209' F.

i. Holdup Pipe Area Ventilation AT - High, with a setpoint of s 86* F and an allowable value of s 92.5' F.

J. Filter /Demineralizer Valve Room Area Temperature - High, with a setpoint of s 201* F and an allowable value of s 209" F.

k. Filter /Demineralizer Valve Room Area Ventilation AT - High, with a setpoint of s 86* F and an allowable value of s 92.5* F.

l. Pump Suction Flow - High, with a setpoint of s 560 gpm and an allowabis value of s 610 gpm.

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I j i e i ATTACHMENT A i DESCRIPTION OF SAFETY ANALYSIS OF THE PROPOSED CHANGES The following provides a summary of the results of the analyses performed for the changes to the detection isolation Technical Specifications:

1. The process flow analytical value for the high suction flow instrumentation is .

l conservatively established at 650 gpm. This flow rate was selected to be high l enough to avoid spurious isolations during normal RWCU operations (maximum  !

system flow is approximately 360 gpm) while also being low cough to ensure that the break flow will be detected prior to exceeding EQ limits (see Attachment K). The flow for the postulated bounding RWCU line break is over n000 gpm.

The setpoint calculation (Attachment J) provides the basis for the difference between the setpoint and allowable value. The calculation determined the '

l setpoint to be 560 gpm, with an allowable value of 610 gpm, for the . suction line flow isolation, which ensures a high level of confidence that the analytical limit will not be exceeded under normal or accident operating conditions. A 0.5 i second time delay is included in the instrument circuitry for operational considerations. The delay is designed to reduce the potential for spurious actuations resulting from fluid flow transients, and has been included in the rnargin for the HELB analysis summarized in Attachment K. j i

2. Based on the calculation of changes in AT (Attachment F) in response to a leak, i it was determined that with an established leak rate limit of 25 gpm or less, the AT analytical value will be 41.8* F for the heat exchanger room,94* F for the pump and pump valve rooms,94* F for the holdup pipe room, and 94* F for the F/D valve rooms. The setpoint calculations (Attachment I) provide the basis for the difference between the setpoints and allowable values. The calculations determined nominal setpoints for the differential temperature isolation setpoints, which ensure a high level of confidence that the analytical limit will not be exceeded under normal or accident operating conditions.

3. Based on the calculation of changes in temperature (T) (Attachment F) in response to a leak, it was determined that with an established leak rate limit of 25 gpm or less, the temperature analytical value will be 159.8* F for the heat exchanger room,212* F for the pump and pump valve rooms,212* F for the holdup pipe room, and 212' F for the F/D valve rooms. The setpoint calculations (Attachment l) provide the basis for the difference between the setpoints and allowable values. The calculations determined nominal setpoints for the temperature isolation setpoints which ensure a high level of confidence that the analytical limit will not be exceeded under normal or accident operating conditions.

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. J ATTACHMENT A DESCRIPTION OF SAFETY ANALYSIS OF THE PROPOSED CHANGES The following is the primary basis for the proposed changes to the detection isolation Technical Specifications:

1. The proposed Technical Specification adds new trip functions A.3.f, A.3.g, l A.3.h, A.3.1, A.3.j, and A.3.k. for Area Temperature - High and Area Ventilation AT - High !n RWCU pump, pump valve, holdup pipe, and FID l valve rooms, and new trip function A.3.1 for the RWCU Pump Suction Flow l

- High, with associated requirements for Tables 3.3.2-1, 3.3.2-2, 3.3.2-3, I and 4.3.2.1-1. The bar,is for the addition is the safety design basis for the primary containmer.t isolation control system of UFSAR section 7.3.2.1,  !

which has been quoted above in " Bases for the Current Requirements".

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2. The proposed Technical Specification setpoint for Table 3.3.2-2, for the RWCU Pump Suction Flow - High, will be 560 cpm with an allowable value of 610 gpm based on the results of setpoint calculations (Attachment J) and the analytical values for the process flow rate resulting from a pipe l break (Attachment K).

3. The proposed Technical Specification setpoints for Table 3.3.2-2, for the RWCU Pump, Pump Valve Area Temperature - High will be 201' F with allowable values of 209' F, and for the RWCU Pump and Valve Area Ventilation AT - High will be 86* F with an allowable value of 92.5' F based on the results of setpoint calculations (Attachment 1) and the analytical values from calculations (Attachment F) of the area temperature and differential temperature resulting from an established leak rate limit of 25 gpm.

4. The proposed Technical Specification setpoints for Table 3.3.2-2, for the RWCU Holdup Pipe Area Temperature - High will be 201' F with an allowable value of 209' F, and for the RWCU Holdup Pipe Area Ventilation AT - High will be 86' F with an allowable value of 92.5' F based on the results of setpoint calculations (Attachment I) and the analytical values from calculations (Attachment F) of the area ta mpe,::ture and differential temperature resulting from an established lealt rate limit of 25 gpm.

5. The proposed Technical Specification setpoints for Table 3.3.2-2, for the RWCU F/D Valve Area Temperature - High will be 201' F with an allowable value of 209' F, and for the RWCU FID Valve Area Ventilation AT - High will be 86* F with an allowable value of 92.5' F based on the results of A-17

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4 ATTACHMENT K

SUMMARY

OF THE REACTOR BUILDING ENVIRONMENTAL TRANSIENT CONDITIONS FOLLOWING RWCU AND RCIC HELBs CALCULATION Calculation L-001384, Revision 0, " Reactor Building Environmental Transient l Conditions Following RWCU and RCIC HELBs," dated February 26,1998 determines short-term environmental conditions, specifically temperature and relative humidity, in the general floor areas of the Reactor Building that result from postulated RCIC and RWCU HELBs, short-term ECCS room transient temperatures that result from l

postulated RCIC HELBs, short-term RCIC Turbine Room transient temperatures that result from postulated RCIC HELBs. In addition, Calculation L-001384, Revision 0 determines the upper bound of the analytical limit for the high RWCU flow ,

instrumentation based on the system volumetric flow rate which would result from a I postulated guillotine pipe break in the RWCU system during normal RWCU operation.

l The calculation results indicated no impact to the existing RCIC Technical Specification setpoints. Therefore, this calculation summary only discusses the RWCU portion of the calculation.

A postulated HELB for the purpose of Calculation L-001384 is considered to be guillotine rupture of a pipe with the ends offset and an assumed break opening time of 1 msec. Per FSAR Section C.2, pipe breaks are postulated for lines of 4-inch diameter or larger. Mass and energy releases from the postulated pipe breaks are determined based on the methodology outlined in ANSI /ANS-58.2-1980. Mass and energy releases from selected pipe break locations are calculated by considering blowdown flow from both ends of the guillotine pipe break. The blowdown of the fluid l downstream of the pipe break is determined based on the removal of all fluid l inventory between the pipe break and the first check valve downstream of the pipe break at a choked flow rate. The initial blowdown of the fluid inventory upstream of l

the pipe break is determined based on the removal of all fluid inventory between the Reactor Pressure Vessel and the pipe break at a choked flow rate. Following the removal of the inventory upstream of the pipe break, a steady-state blowdown is calculated until the pipe break is isolated from the Reactor Pressure Vessel.

! RWCU pipe breaks are postulated in each area of the Reactor Building through which the RWCU piping is routed. RWCU pipe breaks are considered to be detected by the high RWCU flow instrumentation. The time required to isolate the RWCU break from the Reactor Pressure Vessel is determined based upon the time required to accelerate the flow above the high RWCU flow setpoint limit, the high RWCU flow instrument response time including any time delay incorporated to limit spurious isolations resulting from operational transients, and the time required to stroke the RWCU f

K-1

ATTACHMENT K isolation valves closed. Bounding RWCU mass and energy releases based upon high RWCU flow detection and isolation are considered into each respective area of the Reactor Building containing RWCU pipe.

A model of the Reactor Building is generated by dividing the Reactor Building into nodes, which represent rooms. The boundaries of rooms are based on features such as walls, doorways, blowout panels, hallways, and grating. The rooms are connected via a system of" room junctions" that provide paths for mass and energy to travel to surrounding rooms. The " room junctions" consist of stairways, equipment hatches, doorways, hallways, open areas above walls that do not extend to the top of the ceiling (wall-top slots), blowout paths, and other open areas providing a means of communication between rooms. Blowout paths are junctions such as doors and blowout panels that are initially closed, yet are assumed fully open when the difTerential pressure across the junction is greater than its specified blowout limit.

Flow between room via the room junctions are a function of the cross-sectional area available in each room for flow to travel (usually occurring at the actual junction between rooms), the effective inertia for each flow path, and the hydraulic loss coefficients associated with flow from one room to the next. The heat loads l

associated with normal plant operation and heat transmission between Reactor Building rooms at different temperatures are included in the model. The effects of steam condensing on the concrete and steel surfaces have also been accounted for in the Reactor Building Model. The concrete heat sinks include the surface area of the interior side of block and concrete walls, slabs, and beams. For certain areas, cable trays, HVAC ducts, galleries & stairs steel surface area are included. When the surface temperature of a heat sink is equal to or greater than the room temperature, a natural convection heat transfer is considered. Finally, heat transfer via natural l

convection through various equipment hatches, stairway openings, hallways, and tunnels has been incorporated into the model during the post-HELB period.

Using the Reactor Building model developed and the mass and energy releases l calculated for the postulated RWCU and RCIC HELBs, transient analyses are performed using the COMPARE computer program. This code was developed by Los Alamos National Laboratory under contract for the US NRC to perform subcompartment analysis. In addition. COMPARE is cited in Section 6.2.1.2 of the Standard Review Plan "Subcompartment Analysis

" as the applicable tool used by the NRC for review of subcompartment analysis. COMPARE /MODT-PC supplements the original COMPARE / MODI code to permit compliance with the requirements of Appendix B of NUREG 0588 for environmental qualification calculations. The COMPARE model is used to determine the room temperatures and junction flow rates.

The COMPARE /MODT-PC model is run, and the results include the transient room K-2

l 'X ATTACHMENT K l

1 temperatures and relative humidities for each room in the model. From the results, the l l

maximum room temperature and relative humidities is determined for the various line breaks considered.

The results of this calculation indicated the following peak room temperatures:

l Room Peak Break Location l

Temperature Main Room (761'0") (General 144.1 RWCU Pump Valve Room Access Area) l Main Room (786'0") (General 142.2 South RWCU Heat Exchanger Access Area) Valve Room i Main Room - East Side (820'6") 112.8 South RWCU Heat Exchanger (General Access Area) Valve Room The upper bound of the analytical limit for the high RWCU flow instrumentation is determined based on the system volumetric flow rate which would result from a postulated guillotine pipe break of the smallest size postulated in the FSAR in the RWCU system during normal RWCU operation. Larger breaks would result in higher flows and detection / isolation. Based on the normal mode of RWCU operation. it is determined that a minimum of 700 gpm can pass through the RWCU system as a result of the smallest postulated RWCU pipe break. An upper bound for the high-flow sensor analytical limit is determined based on the instrument response time including time delays to be 650 GPM. The peak room temperatures listed in the table above are bounding for all postulated RWCU breaks detected by the high flow instrumentation.

K-3