ML20023B314

Forwards Addl Info Requested at 821118-19 Meetings Re Instrumentation (Chapter 7).Amended PSAR Pages Will Be Incorporated Into Amend 75 of PSAR to Be Submitted in Jan 1983

ML20023B314
Person / Time
Site:	Clinch River
Issue date:	12/23/1982
From:	Longenecker J ENERGY, DEPT. OF, CLINCH RIVER BREEDER REACTOR PLANT
To:	Check P Office of Nuclear Reactor Regulation
References
HQ:S:82:163, NUDOCS 8212270229
Download: ML20023B314 (8)

Text

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O Department of Energy Washington, D.C. 20545 Docket No. 50-537 HQ:S:82:163 DEC ~93 1982 Mr. Paul S. Check, Director CRBR Program Office Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Co.nmission Washington, D.C. 20555

Dear Mr. Check:

INSTRUMENTATION (CHAPTER 7) WORKING MEETINGS - ADDITIONAL INFORMATION FOR Tile CLINCH RIVER BREEDER REACTOR PLANT Re ferences : 1) Letter HQ:S:82:095, J. R. Longenecker to P. S. Check,

" Meeting Summary for Instru.untation (Chapter 7)," dated September 24, 1982

2) Letter HQ:S:82:126 J. R. Longenecker to P. S. Check,

" Meeting Summary for Instrumentation (Chapter 7) Working Meeting, November 18 and 19,1982," dated November 29, 1982 Enclosed is the remaining information requested during the subject meetings.

The amended Preliminary Safety Analysis Report (PSAR) pages will be incorpo-rated into Amendment 75 of the PSAR scheduled for submittal in January 1983.

Item 77 of reference 1 stated that detailed information about Sodium Water Reaction Pressure Relief System (SWRPRS) interlocks would be provided. PSAR section 7.3.6.1.3 provides preliminary information about those interlocks. As the SWRPRS instrumentation and control system is still being designed, more detailed information cannot be provided at this time. More information about SWRPRS interlocks will be provided in the Final Safety Analysis Report along with justification as to whether or not the interlocks need to be Safety Classification lE. The current design has no requirements for Safety Classification IE SWRPRS interlocks.

Any questions regarding the information provided or further activities can be addressed to Mr. R. Rosecky (FTS 626-6149) or Mr. A. Meller (FTS 626-6355) of the Project Office Oak Ridge staff.

Sincerely, h .h(n rni Lit

(~ 8212270229 821223 John R. Longene er

, PDR ADOCK 05000537 Acting Director Office of A PDR Breeder Demonstration Projects Enclosure Office of Nuclear Energy cc

Service List Standard Distribution Licensing Distribution hv lf . _ . . __ ._

Enclosure =~

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September item 54, November item 4 Auxiliary Tsedwater System j NRC CONCERN ,

i Amend the Q421.4 response to provide a description i rationale defining why the AFWS valves have nc realistic .

common mode failures, discuss over voltage and under voltage conditions and alarms. Consider a steam or i feedline break in one loop. Provide valve qualification j and design details. The concern is failure of valves in

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the same power division to assume their deenergized position when required.  ;

Reference and confirm PSAR Section 5.6.1.2.3.4.e which refers to "normally open electro-hydraulic control j valves".

Resolution Discussion of the AFW valve failure modes is provided in the revised response to question CS421.4.

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ODESTIOM CS421.4 The applicant should formally submit a diagram of the auxiliary feedwater system showing the division assignments for all valves and safety grade instrumentation and controls. A discussion should be included to indicate the normal position and position

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upon loss of power of each valve. In your presentation, and in Section 7.4.1.1.6, credit is taken f or the feedwater isolation valve to f ail-safe in the open position upon loss of electrical power. Justify this f ail-saf e analysis f or all incidents (i.e.,

r hot shorts, power supply overvoltage, etc.) that could prevent E operation of this isolation valve.

I Resconse

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- Figures 5.1-5 and 5.1-Sa of the PSAR (attached) have been

[ marked-up (Figure QCS421.4-1, 2) to show the power division E assignments for all valves and safety grade ir.strumentation of the au::iliary fee 6 water system. The controls for the devices are not shown. However, the power assignment is the same as that of

the valves, louvers, and f an blade pitch control being actuated.

The normal position and f ailure position.of the valves are shoun g in Figures 5.1-5 and 5.1-Sa.

1 As shoun in Figure 5.1-5 there are six isolation valves, two in parallel to each steam drum. One valve supplics water f rcm the electric driven pumps, the other f rom the turbino drive pump, each capable of supplying 100 percent water flov to the steam.

drum. These tuo valves are supplied with power f rom separate Class 1E power divisions. The failure of one valve to open on

demand would not result in the loss of water to a stenn drum, as g the required water would be supplied by the parallel line. .

Theiholationvalves (52AFV103A-F) are closed in normal

operation. They open automatically on SGAHRS trip or when the steam drum level drops to 8" below normal water level (IML) .

Automatic closing occurs when the steam drum level rises to 8"

_ ebove rmL for the motor driven pump AFM supply an612" above

= normal water level for the turbine driven pump An? supply.

E Each isolation valve is cupplied f rom a regulated 480 VAC power R supply and is designed to operate uithin the over voltage tolerance allowed f or that pouer supply.

I In addition, Figure 5.1-5 shows that there are flow control i

valves in series with these isolation valves. Each of the flow control valves is supplied with power f. rom a Class 1E power division dif f erent f rom the Class lE pouer division supplied to the isolation valve in the same line.

The flou control valves ( 52 AIV104 A-F) are open during normal plant i operatien. They modulate to control the auxiliary feedwater flow to r.ointain steam drum 1cvel.

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l l Each flow control valve is supplied f rom a 135 VDC power supp1r-and is designed to operate with the voltage tolerances allowed f or that power supply.

The design provides for failure of the control power to result in a " fail-safe" position (open) for the isolation valve, and an "as-is" position for the flow control valve; therefore, the capability to maintain the AFU supply has been assured.

The wiring and controls f or the isolation or flow control valves in the line supplying water to any ' steam drum are in separate Class lE power divisions and separation is provided in accordance with IEEE-3 83. Hot shorts between the two valves supplying the The only hot short which could same steam drum will not occur.

occur would be within the same pouer division between the valve

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and control circuits. This could result in tuo of the six isorction valves not opening when called upon. The two valves that fii'l' being in the same pouer division supply separate steam drums,5ince there is a 100 percent redundant water supply to each stehm drun, a failure of two of the six isolation valves vould not igz' ult in the loss of uater to any of the three stean drums.

A short between two Class 1E power divisions is not a credible event because of the separation between divisions.

Any hot short within a given division in the local panel will not af f ect the control elements in the main control roca area, and vice versa, because isolators are located between them. Shorts or voltage spikes might cause circuit current to e;:ceed the current linitations of the control circuit fuse and consequently the f ailed (open circuited) power supply would result in a

" fail-safe" (open) position of the AR1 isolation valve. The flcu control valve in the same power division would f ail as-is (open) at this time because of the failure in the control circuit.

Upon the loss of power the isolation valves are driven to their f ail-saf e de-energized positions by accumulator pressure, which is released and applied to the bottom of the actuator cylinder.

The flou control valves fail in the as-is position. In the unlikely event of a velve, .o'r the even nore enlikely event of all valves, in a pouer divisioh %s f ailing to. assume their de-energized positions, the operator can nanually operate these valves to accomplish a saf e shutdoun under any set of conditions.

The above has discussed the ability to provide water to the steam drums with the loss of a division of pouer; however, if there is a break in the feedwater line to a steam generator or a stean line in a steam generator loop, the operator has the cap:LAlity to remotely close the flow control valve in series with the In addition, isolation valve that f ailed in the open position.

the operator could also Danually operate the velves to isolate the AFW supply from the pipe break.

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INSERT A If there.is a break in the auxiliary feedwater line to one steam generator and a failure in the division of power that does not feed the affected loop, the loop would isolate the break. The other loops would continue to supply feedwater to the steam drums as the isolation valve affected by the power failure would go to its failure position (open) and the affected ficw control valve would remain in its normal pasition (open). If the power failure is such that it prevents an isolation valve from obtaining its failure position, the affected flow control valve on the parallel line would remain in its normal position (open), and flow would be controlled by the opening and closing of the isolation valve on the other division of power. The flow would be maintained to the steam drum by either tre motor driven or turbine driven pumps.

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l Pi The Anis valves are saf ety-related and are qualified to perb their function in the wortt accident environmental conditionThe is ,

they are e::pected to exper* ence. flow control valves are provided by dif feren dif f erent types of actuators. The isolation valves are gate valves with electro-hydraulic actuators that have internal accumulators to provide the reserve energy to take the valves to their failure position. The flow control valves have internal trim designed to permit These throttling valves the have flow an as uoll ac providing electro-hydtculic shutoff capability.

actuator that permits modulation of the valve pocition and f ails in position.

Because of the different valve cuppliers and the dif f erent type of actuatorn y w  % common failure code is anticipated.

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