ML20082T163

Forwards Responses to Items 2,3,6,7,8 & 11 of Encl 2 to Re Instrumentation to Detect Inadequate Core Cooling.Void Fraction Calculation Performed Only When Reactor Tripped & Reactor Coolant Pumps Running

ML20082T163
Person / Time
Site:	Davis Besse
Issue date:	12/08/1983
From:	Crouse R TOLEDO EDISON CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
1003, NUDOCS 8312150190
Download: ML20082T163 (8)

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TOLEDO EDISON ,

Docket No. 50-346 RCHARD P. CROUSE Vce Presdent License No.'NPF-3 [,1,,,

Serial No. 1003 December 8, 1983 Director of Nuclear Reactor Regulation Attention: Mr. John F. Stolz Operating Reactor Branch No. 4 Division of Operating Reactors-United States Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Stolz:

This is-in response to your letter dated September 6, 1983 (Log No. 1360),

concerning the instrumentatioc to detect Inadequate Core Cooling (ICC).

' Toledo Edison provided the schedule for the response on August 9, 1983 (Serial No. 993). We have. committed that Item No. 2, 3, 6, 7,'8 and 11 in the Enclosure 2 of your letter will be submitted to you by December 9, 1983. Enclosed is Toledo Edison's response to these items for the Davis-Besse Nuclear Power Station Unit No. 1.

Very truly yours, ff : - = ;

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DB-1 NRC Resident Inspector 8312150190 831208 \\

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THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652

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ATTACHMENT TO LETTER SERIAL NO. 1003 x

? QUESTION: 2. = Describe more specifically the deviations of the TSAT meter from Appendix B requirements.

. RESPONSE: .The TSAT metersLwere built to a B&W Q.A. specification. .A

' comparison of the B&W Q.A. specification with'the require-

? mentscof 10CFR 50 Appendix B shows that the B&W specification E does'not address criteriaLVIII,. Identification and Control of Materials,-Parts cad Components; IX,, Control of Special-Processes; X, Inspection; and XI, Test Control. However, 2 it meets.the intent of Appendix.B in all other areas.

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' QUESTION: 3. It is not clear from-the description and Figure 1 in the March 23, 1983 submittal how the TSAT meter works. Does-

, the TSAT meter-display a computation of-the saturation temperature for the operating pressure,.or.does it give an indication of.the margin-between operating temperature and saturation temperature, i.e. , AT to superheat?

What is the

. range and, type of the display?

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--RESPONSE: -The TSAT meters display margin to saturation temperature or c AT to superheat. .As stated in our March 23, 1983 submittal, each TSAT' meter' channel receives inputs-from one RCS pressure transmitter and two RCS hot: leg RTD's. Also, one of'the eight,incore thermocouples for'the particular channel _can be' manually selected as a temperature input.

One of these. temperature inputs is manually selected at the

-TSAT meter and the' margin displayed is based-on that selected temperature. Mergin to saturation pressure can also be' displayed on the TSAT meter by depressing and holding a" toggle switch at the meter. In the event that

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system temperatures exceed saturation temperature, the TSAT meterLdisplays. degrees of superheat as indicated by.the negative margin light on the meter. ~The-TSAT meters are

. digital: displays. The design ~ range of the wide range pressure instruments is 0-2500 psig. The instrument range for hot leg RTD is 120*-920*F, and 0*-2300*F for. core exit

.thermocouples. The designed range of the TSAT meter display is 4096*F.

? QUESTION: 6. It is-unclear from the description how the core map of core exit temperatures works. Does this display give a continuous indication of all CETs and is this considered the primary

. display?

' RESPONSE: The core map' display for core exit thermocouples as described

.in our-March 23, 1983 submittal referred to our backup display. The core map for the backup display is located at the hand selector switch. It shows the spatial location of the eight thermocouples for that particular channel (see details C & D). The hand switch is used to select one of

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, n these temperatures for display on the temperature indicator

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for that channel.

00ur~ primary display.will-be a video display available for-viewing on the control room CRTs~via the plant computer.

This display will show a core map with temperature readings 0 - for all- of the existing 52 incore thermocouples. The=

_ _ software required for this display will be implemented by

' February 1, 1984. Hard copy computer printout displays are Eavailable for all'52 core exit temperatures at this time.

QUESTION:'7. Where specifically are all the displays located?

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RESPONSE: The core maps / hand selecto'r switches and associated temper-ature indicators'for the backup display are located on the ,

Post Accident Indicating Panels (see figures 1 & 2). The

core exit thermocouples are also available for display via the plant computer and Technical Support Center computer.

QUESTION: 8. The description mentions that core exit temperature alarms are computer generated. What are the alarm criteria?

, RESPONSE: It is expected that.long before the core exit temperatures show any signs of' core uncovery, the plant must be in an-abnormal transient condition where operators are instructed f .to, monitor-the. core exit thermocouple. readings. Therefore, the alarm is.not used-for any specific operator action.

The only criteria on the computer alarn. for core exit temperatures'is to maintain sufficient margin between the

. ',  : alarm setpoint and the normal.operatine temperature-to avoid nuisance. alarms ~during normal operation.

._. . QUESTION: 'll. Describe in more detail how the values for input to the-void fraction calculation in the reactor coolant pump

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. monitor program are obtained. -In particular, how is the effect'of degraded pump performance under two phase flow

conditions-accounted for in the calculation.

RESPONSE: The void fraction calculation is performed on each reactor coolant pump using their respective cold leg wide range temperatures to. define the liquid density (pf) and their respective loop hot leg pressure to define vapor density (pg). A curve fit routine is-developed to correlate the L pump motor power, P, (a computer point) with the pump and

[- motor combined efficiency (q). Therefore, q is defined L' whenever the pump motor power is available. The reference condition for po, Po-and qo are defined with normal operating .

L conditions (no void in the system).

p j The pump performance under.two phase flow conditions is detected by a decrease in pump motor power which can be correlated directly with the density decrease of the fluid

' in the pump. Since RCP is a constant speed pump, the

volume flow rate is assumed as a constant. The decrease'in

. density can-then be translated to void fraction.

lThe calculation is performed only when the reactor is tripped and the RCPs are running. The results ate only valid when t'a e RCS is at relatively steady state conditions and there is no degradation in the RCP impeller. _Since the operators are instructed to trip the RCPs at 20 F subcooling margin during a small break'LOCA, this program conceivably will' never be used when the RCS is in a voided condition.

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