TXX-4413, Forwards Addl Info Re Equipment Adequacy for Mitigation of Steamline Breaks Outside Reactor Bldg Containment.Info Will Be Included in Future FSAR Amend

Forwards Addl Info Re Equipment Adequacy for Mitigation of Steamline Breaks Outside Reactor Bldg Containment.Info Will Be Included in Future FSAR Amend

ML20107A742
Person / Time
Site:	Comanche Peak
Issue date:	02/14/1985
From:	Beck J TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Youngblood B Office of Nuclear Reactor Regulation
References
TXX-4413, NUDOCS 8502200093
Download: ML20107A742 (13)

Text

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Log # TXX-4413 File # 10010 TEXAS UTILITIES GENERATING COMPANY 903.11 clo Marw4T TowEn. io nonTu ouYE MTnEET I..B. MI. DAI.I.AM, TEXAM W '

915.1 clo 1,?,"2.*a.",'.c" February 14, 1985 Director of Nuclear Reactor Regulation

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Attention: Mr. B. J. Youngblood, Chief Licensing Branch No.1 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.

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SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION DOCKET NOS. 50-445 AND 50-446 MAIN STEAM LINE BREAKS OUTSIDE CONTAINENT REF:

B. J. Youngblood to M. D. Spence

. letter of December 21, 1984, concerning Main Steam Line Breaks Outside Containment

Dear Sir:

The referenced letter is a request for additional information on the adequacy of.the equipment necessary for mitigation of main steam Ifne breaks outside the reactor building containment.

The response to this request is enclosed and will be included in a future amendment to the FSAR.

Respec tfully, N 4. b / -

hohn W. Beck DRW/grr Attachment Di s tribu tio n : 10rijiE.131TsNib$ hie 73 u.

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6pl 8502200093 850214 PDR ADOCK 05000445 A

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A DIVIN10N OF TEXAM t*TILITIEN ELECTRIC COME*ANY

h CPSES/FSAR 140-EQUIPMENT QUALIFICATION BRANCH ENVIRONMENTAL QUALIFICATION Q0140.1 Impact of MSLB on qualified equipment outside containment:

1.

TUGC0 discusses the effects of the main steam line break (MSLB) event due to a break area of 1 sq.

ft. Needed are:

a.

A technical justification which supports that a break area of 1 sq. ft. is the worst break, from an operational standpoint, for equipment necessary for break mitigation, and what the worst initial power level is for the 1 sq. f t. break.

b.

The time sequence of events of the worst break.

c.

The assumption used in the analysis of the MSLB with superheat.

d.

Verification that the analysis included the effects of jet impingement.

e.

Identification of the safety-related equipment located in the area affected by a steam line break with superheat.

This should. include:

(1) The Class 1E cables located in areas affected by MSLB, the separation between redundant Class 1E cables or Class 1E' a.nd: non-Class 1E cables which l

are routed in the MSLB area.

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i CPSES/FSAR (2) List of all equipment affected by the MSLB superheat condition with the required operability time.

The required operability time should account for functional operability as well as any subsequent failure which could affect any other safety function, or mislead the operator.

(3)

Qualification test profiles for all equipment affected including the demonstrated operability time for the MSLB with superheat.

(4)

The time margin between the safety equipment performing its safety function and the critical component of

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this equipment exceeding its qualification temperature.

(5)

If the time margin is less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, provide the necessary justification in accordance with Regulatory Guide 1.89, Rev.1.

2.

TUGC0 has analyzed the compartment temperature response following onset of a postulated MSLB using blow down data 2 hat includes superheat effect..The results show that in the break compartment, the temperature profile, which peaks at 3500r', exceeds - the original qualification envelope for about 40 seconds.

Tne analysis also shows that safety functions

.ccur before the surerhtTt effect appears.

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'CPSES/FSAR order to complete its review, the staff requires that TUGC0 provide a copy of the blow down analysis, including the mass and energy release data, and discuss and justify the time following onset of the accident at which safety functions would be completed.

'R140.1 1.a For all rooms except the break room,1.0 ft2 is definitely the most severe case, for more energy is released to these rooms more rapidly than any of the smaller breaks.

Since these rooms do not exceed the qualification temperatures for a 1.0 ft2 break, they will not exceed their temperature for any smaller break.

The only equipment that could be required to operate and that could be in the room where the break occurs are the ventilation dampers.

These dampers close on pressure differential.

Pressure helps keep these dampers closed.

The new temperature spike will not degrade the ability of these dampers to close and remain closed.

Since none of the remaining equipment in the

. area where the break is located is required to operate, the operability of this equipment will not contribute to determining the most severe break from the standpoint of equipment

'operabil ity.

Therefore, based on the impact to equipment in rooms outside the break area, the most' severe break is the break that releases the most energy and generates the highest peak.

That break is the '1.0 f t2 b reak.

CPSES/FSAR The previous environmental analyses for the break areas clearly showed that without

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superheat, full power provided the worst environmental results.

For the superheat studies, typical mass and energy data are only avail ble for the full power cases.

However, it is fully reasonable to expect that, for the superheat cases, full power will still provide the worst environmental results.

Since equipment operability is not required in the room with the break, minor deviations in the peak temperature will not impact mitigation of the event.

The validity of this expectation will be confirmed when the mass and energy release data are received from Westinghouse.

b.

The time sequence based on a 1.0 ft2 break and an initial. power level of 100% is as follows:

9 seconds Reactor Trip (due to overpower N-16)

Feedwater Isolation (due to

- 11 seconds reactor trip and low Tavg)

Safety Injection Signal' 47 seconds (due to low pressurizer signal)

Steamline Isolation (due to

- 130 seconds low steamline pressure)

Steam Generator Tube Uncovery

- 180 seconds The time sequence for these events will be later for smaller breaks. At some point as the breaks 7

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CPSES/FSAR get smaller, steam generator tube uncovery will occur before Steamline Isolation because the i

break is so small that the tubes uncover before pressure falls below the low steamline pressure setpoint. At lower power levels and break sizes, other events such as low steam generator level will initiate reactor trip.

Such slight deviations in the sequence are not expected to result in a more severe event.

The most important action to mitigate the event, steamline isolation for the unaffected steam generators, will always be possible, c.

The mass / energy releases were calculated by Westinghouse using a modified version of the LOFTRAN code.

The LOFTRAN code is a digital computer code which simulates the behavior of a multi-loop pressurized water reactor. LOFTRAN simulates the neutron kinetics, thermal-hydraulic conditions, pressurizer, steam generators, reactor coolant pumps, ano control and protection system operation. LOFTRAN has been modified to model the heat transfer which may occur in the uncovered portion of the tube bundle of a steam generator and to calculate the resulting superheated steam mass and energy release.

The mass / energy releases are based on a four-loop plant. Conservative assumptions were made in order to result in early tube bundle uncovery and, therefore, the earliest superheat initiation time. Although these sample mass / energy releases are neither generic nor

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CPSES/FSAR necessarily conservative for a given plant, they are representative of the superheated steam phenomenon and will provide a valid estimate of the effects on compartment temperature analyses.

The environmental analysis used to determine the temperature transient due to this break is described in FSAR Section 3.6B.1.2.3.

Additional specific information is provided in the FSAR in the response to question 010.20.

d.

The NRC staff provided that for CPSES, in piping tunnels that contain break exclusion regions of main steam lines, the safety related equipment in these tunnels be designed to withstand the environmental effects of a non-mechanistic crack with a flow area of one square foot.

(See NRC ustaff question 010.20 in the CPSES FSAR).

Therefore, it was assumed that jets are not generated and hence jet loads are not considered.

This criterion ~ was reviewed and accepted in the CPSES SER (NUREG-0797) and SSER 6 (NUREG-0797 Supplement No. 6) in Section 3.6.2.

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e.

Items (2) through (5) are covered in Table 140.1-1.

The Class 1E cables located in the areas affected by the crack are those cables required to? support the ciass.1E equipment in the same areas. All of these cables are qualified for the LOCA/MSLB inside containment for CPSES. As such, these cables are expected to remain fully

O CPSES/FSAR operational throughout this event.

The cable separation in these areas meets the requirements of Regulatory Guide 1.75.

2.

The blow down analysis and the mass and energy release data are based on an analysis performed by Westinghouse and are representative of a four loop plant.

(See the response to item 1.c above.) Since reasonable margins exist in both time and temperature at CPSES for this event, the representative data are adequate for acceptance of the CPSES design. A plant specific blow down analysis will be prepared for CPSES and is expected to be available by about August of 1985.

The time following onset at which safety function would occur does not vary from the previous CPSES analysis of this event.

The assumption that the equipment in the break area fails in its most adverse mode is no more severe than the assumptions made for the previous CPSES analysis of this event.

Therefore, the safety analysis and the crack mitigation / shutdown analysis remain the same.

4

CPSES/FSAR TABLE 140.1-1 (Sheet 1 of 5)

REQUIRED POSTULATED DEMONSTRATED DEMONSTRATED OPERABILITY TEW ERATURE TEW ERATURE OPERABILITY TIME EQUIPMENT T!ME "

PEAK PEAK TIME MARGIN (3)

NOTES MSIV Not required N/A N/A '

N/A N/A (1)

(in room with break) 12 minutes

<3360F 3580F 30 days 29 days (2)

(not in room

.with break)

MSIV Bypass Not required N/A N/A N/A N/A (1)

(MSIVBP)

(in room with break) 12 minutes

<3360F 3650F 30 days 29 days (2)

(not in room with break)

Main Steam Drain Not required N/A N/A N/A N/A (1)

Pot Isolation (in room with Valves break)

(MSDPIV) 12 minutes

<3360F 3460F 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> 168 minutes (4)

(not in room with break)

Feedwater Isolation 10 minutes

<3360F 3400F 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 110 minutes (4)

Valves (FIVs)

Feedwater Bypass 10 minutes

<3360F 3460F 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> 170 minutes (4)

Valves (FWBPVs)

Feedwater Sample 10 minutes

<3360F 3460F 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> 170 minutes (4)

Isolation Valves (FW Sample IV)

CPSES/FSAR-TABLE 140.1-1 (Sheet 2) ~

REQUIRED POSTULATED DEMONSTRATED

. DEMONSTRATED OPERABILITY TEW ERATURE TEW ERATURE OPERABILITY TIME EQUIPMENT TIME PEAK PEAK TIME

~ MARGIN (3)

NOTES Turbine Driven Not required N/A N/A N/A N/A (1)

Auxiliary Feedwater Pump Steam Supply Valve (TDAFPSUP)

Main Steam Power Not required N/A N/A N/A N/A (1)

Operated Relief (in room with Valves break)

(MSPORVs) 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (5)

<3360F 3580F 30 days 27 days

- (not in room with break)

Barton Steam Line 12 minutes (6)

<3510F 4200F 2800 hours0.0324 days <br />0.778 hours <br />0.00463 weeks <br />0.00107 months <br /> 2799 hours Provide Pmssure Transmitters (in room with steam ifne break) isolation signal 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (5)

<3360F 4200F 2800 hours0.0324 days <br />0.778 hours <br />0.00463 weeks <br />0.00107 months <br /> 2700 hours (not in room with break)

Rosemount Steam Line Not required (7) N/A N/A N/A N/A Provide Pressure Transmitters (in room with control break) signal for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (5)

<3360F 3500F 30 days 27 days MSPORVs (not in room with break)

Watertight Doors Not required N/A N/A N/A N/A (8) s

n CPSES/FSAR TABLE 140.1-1 (Sheet 3)-

REQUIRED POSTULATED DEMONSTRATED DEMONSTRATED OPERABILITY TEW ERATURE TEW ERATURE OPERABILITY TIME EQUIPMENT TIME PEAK' PEAK TIME MARGIN (3)

NOTES HVAC Isolation

<12 minutes N/A N/A Continuous N/A (9)

Dampers Mechanical Safety Not required N/A N/A N/A N/A Valve Accessory Limit 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

<3360F 3400F 30 days 27 days (3)

Switches for MSIV, MSIVBP, MSPORV, FIV and FWBPV Accessory Limit Not required N/A N/A N/A N/A (10)

Switches for MSDPIV, TDAFPSUP, and FW Sample IV Auxiliary Feedwater Not required N/A N/A N/A N/A (10)

Flow Transmitters

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CPSES/FSAR TABLE 140.1-1 (Sheet 4)

NOTES:

(1)

These valves may. fail in eitbar the open or closed position without increasing the severity of the event beyond the present analysis or decreasing t'ie ability to mitigate the event and safely shutdown the unit.

(2)

These valves will operate to close within the first 12 minutes (the exact time depends on the break size).

Beyond 12 minutes ifor up to.72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while proceeding to cold shutdown) these valves must remain closed.

The qualification testing performed on these valves includes sufficient margin beyond the postulated peak (3360F for 5 minutes) to justify the operability of the valves for well beyond 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

(3)

For no equipment where operability is required does the postulated accident profile exceed the demonstrated qualification profile.

(4)

These valves operate within the first 12 minutes (the exact time depends on the break size). -Operability is not required beyond then for the valves will fail (remain) in a safe position.

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(5) 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> operability time is based on shutdown and cooldown within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> such that the operability'of these items would no longer be required.

(6) : Once the low steamline pressure signal or high negative pressure

. rate signal is provided, the operability of these transmitters is no longer required.

(7)

This transmitter provides an analog signal for the operation of the Main Steam PORY associated with the break.

Since the

CPSES/FSAR TABLE 145.1-1 (Sheet 5) operability of this valve is not required, the operability of this transmitter is not required.

(8)

These are mechanical devices that do not have an active function.

The materials have been analyzed to show that the doors will not

-lose their leak tightness.

(9)

The dampers are mechanical devices.

They are mechanically closed by the pressure buildup from the break and are latched in the closed position (as well 'as being held closed by compartment

pressure).

Failure of the environmentally sensitive components

_ due to this event will not prevent closure of the damper nor cause the damper to reopen.

Therefore, the required operability is

'early in the event (much less than 12 minutes), but the dampers remain continuously operable in spite of the postulated

environment.

The materials have also been analyzed to show that the1 dampers will not lose their leak tightness.

(10) This' equipment is not required to operate to either mitigate the accident or safely shutdown the plant. Output provides status

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information only to be utilized at times much later than during this HELB high temperature periods.

Analyses have been made to verify that the non-metallic-parts of this equipment will

withstand the postulated _ temperature extremes although specific qualification tests have not been performed that envelope this

- scenario.

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