ML20148Q714

Forwards Supplemental Response to Generic Ltr 85-12 Re Instrument Certainty for Normal & Adverse Containment Conditions for Reactor Coolant Pump Trip Setpoint,Per Util

ML20148Q714
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	01/25/1988
From:	Morgan W COMMONWEALTH EDISON CO.
To:	Murley T Office of Nuclear Reactor Regulation
References
4145K, GL-85-12, NUDOCS 8802010179
Download: ML20148Q714 (11)

Text

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' Commonwealth First N:$onalEdison Plam, Chicago, Illinois I, v Address Reply to: Post Off~cs Box 767 Chicago, Illinois 60690 0767 January 25, 1988 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Zion Stations Units 1 and 2 Supplemental Response to Generic Letter 85-12 NRC Docket No. 50-295/304 Reference (a): G. L. Alexander letter to H. R. Denton dated August 22, 1985.

Dear Mr. Murley,

The referenced letter transmitted Commonwealth Edison's response to Generic Letter 85-12. Additionally, Zion Station committed to a supplemental response providing the instrument certainity for normal and adverse containment conditions for the reactor coolant pump trip setpoint.

The attached documents contain the supplemental response.

Please address any questions that you or your staff may have regarding this response to this office.

Very truly yours,

\l CA y W. E. rgan Nuclear Licensing Administrator cc: A. Bert Davis - RIII l Resident Inspector - Zion I 1 4145K/bs i g 8802010179 880125 PDR ADOCK 05006T95 PER P

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ATTACHMENT A During the 1987 outage, Unit 2 RCS wide range pressure transmitters were replaced with Rosemounts. For Unit 1, this replacement is scheduled for 1988. The instrument and uncertainties for the Rosemounts are shown in Attachment C. Attachment D shows the determination of the RCP termination pressure as calculated for both Barton and Rosemount Transmitters. Zion Station's emergency operating procedures currently use the value calculater for Barton Transmitters, as they were the transmitters in place when the EOP's were written. For Unit 2, this RCP termination setpoint is conservative, because of the smaller uncertainty associated with the Rosemount transmitters.

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.) Attachment B' INSTRUMENT UNCERTAINTIES Reactor Coolant System Pressure - Barton 763 Pa rameter Value(%) Note (see Attachment C) ,

Process Measurenent 0.0  ;

Accuracy (PMA)  !

l' Primary Element Accuracy 0.0  ;

(PEA)

Sensor Calibration 0.53 1 Accuracy (SCA)

Sensor Temperature 0.5 Effect (STE)

Sensor Pressure Effect b.0 (SPE)

Sensor Drift Allowance 1.0 2 (SDA)

Rack Calibration 0.5 Accuracy (RCA)

Rack Drift Allowance 0.5 3 (RDA)

Rack Temperature 0.5 Effect (RTE)

Indicator Accuracy (IA) 1.5 4 Environmental Allowance 10.0 (EA)

Channel Statistical Allowance (CSA)

/( PMA) * +( PE A) * +( SC A+SD A) * +( ST E)' +( S PE )'+( RC A+R D A) #+(RTE l

/(0.53+1.0)'+ 2(0.5)'+(0.5+0.5)#+(1.5)' = 2.47%

i.e. 0.0247 X 3000 PSIG (span) = 74.1 PSIG (normal containment)

Adverse containment:

i = CSA + EA = 2.47 + 10.0 - 1 12.47%

i.e. 1247 X 3000 PSIG (span) - 374.1 PSIG (adverse containment) 11510

Attachment c' INSTRUMENT UNCERTAINTIES Reactor Coolant System Pressure - Rosemount 1154

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Parameter Value(%) Note (see Attachment C)

Process Measurement 0.0 Accuracy (PMA)

Primary Element Accuracy 0.0 (PEA)

Sensor Calibration 0.53 1 Accuracy (SCA)

Sensor Temperature .63 Effect (STE)

Sensor Pressure Effect 0.0 .

(SPE)

Sensor Drift Allowance .5 2 (SDA)

Rack Calibration 0.5 Accuracy (RCA)

Rack Orif t Allowance 0.5 3 (RDA) 4 Rack Temperature 0.5  :

Effect (RTE)  !

f Indicator Accuracy (IA) 1.5 4 Environmental Allowance 7.2 (EA)

Channel Statistical Allowance (CSA)

/(PMA)#+( PE A) # +( SC A+SD A) #+(STE)#+(SPE)#+(RCA+RDA)#+(RTE)#+(IA)#

/(.53+.5)#+(.63)#+(.5+.5)#+(.5)#+(1.5)# = 12.23%

i.e. 0.0223 X 3000 PSIG (span) = 66.9 PSIG (normal containment) l Adverse containment:

{ = CSA + EA = 2.23 + 7.2 =i9.43%

l i.e. .0943 X 3000 PSIG (span) = 282.9 PSIG (adverse containment) l 11510

Attachment D INSTRUMENT UNCERTAINTIES FOR RCP TRIP NOTES

1. Sensor Calibration Accuracy (SCA) was adjusted to take into

• consideration the uncertainties associated with test instruments used to perform the calibration. (Reference SAMA Standard PMC-20-1-1973.)

2. Sensor Drift Allowance (SDA) errors are included in the calculations. The instrument manufacturers specify a drift value for i their instruments.

3. Rack Drift Allowance (RDA) errors are included in the calculations.

Zion Station has increased its interval for checking rack instruments from monthly to quarterly. An adequate history of rack drift for this longer interval is not available. The value recommended is based on a review of Westinghouse instrument specifications and is considered reasonabie for the quarterly interval.

4. Indicator Accuracy (IA) includes an uncertainty associated with readability errors.

5. Environmental Allowances (EA) agrees witl the values that are given in the transmitter qualification reports.

6. Sensor Temperature Effect (STE) agrees with values given in the transmitter specifications.

7. Sensor Pressure Effect (SPE) was adjusted where required to reflect changes that occur when the observed pressure has changed from the original calibrated pressure. I

8. Process Measurement Accuracy is an allowance for the effects of fluid stratification or changing fluid density, i

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RCP TERMINATION PRESSURE DETERMINATION

'The following items are the necessary elements for determining the Reactor Coolant Pump trip setpoint for Zion Station Emergency Operating Procedures.

1. Decay Heat Level -

The decay heat level given for all plants is 3.5%.

2. Steam Flow Rate - lj The required flow to be vented through the steam generator safety valves in the absence of condenser and atmospheric relief capability can be derived as follows:

0 = QSs + QRCP where:

Q = Heat input per steam generator Q3g = Lg x Decay Heat Pacdon 0

Q = RCP heat input RCP Q 3g = x Decay Heat hacdon 0 L0

= 3250 (0.035) x 3412141 ggfL op

= 9.703 x 10' HR-Loop 7 btu (Refer to Zion Operating Procedures NowORCP = 1.00 x 10 gp PT-0: Appendix M)

Therefore:

0=QSG + ORCP = 1.07 x 10' HR-L op i

, Steam Flow Rate / Loop, M = 0 fg where Hf is the latent heat of vaporization chosen at the lowest safety valve setpoint for P = 1050 psig Hf = 638.05 BTU /lbm M - 1.07 x 10*_ = 1.779 x 105 lbm 638.05 HR-Loop NOTE: The rated steam flow (at 100% power) is 3.497 x 10' lb/hr such that M represent 5.09% of rated flow.

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3. Safety Valve Set Pressure Selection For Safety Valve #1: Setpoint Pressure = 1050 psig Flow Rating = 584,105 lb/hr Assuming 60% capacity for steam relief flow, Fs ,

F3 = 584,105 (.6) = 350,463 lb/hr Since Fs > M, Safety Valve il satisfies the required flow cited in '2' above. .The safety valve parameters are cited in the Zion Technical Specifications Table 4.7-1.

Therefore, setpoint pressure = 1050 psig

4. Uncertainties in the Steam Generator Safety Valve Opening Pressure Assume that the safety valve tolerance is 3% of the setpoint pressure, or Safety Valve Tolerance = (1050 psig) (0.03)

= 31. 5 psi

5. 6P 8etween the Safety Valves and the Steam Generator Shell The major 6P factor (due to the flow limiter) is approximately 14.78 psi at 100% power. At 5.09% rated steam flow, the 6P should 14.78 x

(.0509)2 = 0.04 psi. Since the pressure dif ferential due to f riction losses is negligible,1 psi will be chosen as a boundary value.

For this calculation, let Steam Line 6P = 1 psi

6. AT Across the Steam Generator Tubes in order to determine the log-mean 6T (Primary to Secondary) at 3.5%

power on a steam generator, use the following relation:

LMTD 3.5% power = 1.443 AT 3.5% power l

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N w: AT 3.5% power = AT full power (Power Fractionj Where:

Power Fraction , NSSS Power at 3.5%

NSSS Power at 100%

, 3.5% Core Power + RCP heat inDut 100% Core Power + RCP heat input 0 U

=(3250MWth)(.035)(3412141

) + 4.00 x 10 7 th 0 I (3250 MWth)(3412141 ) + 4.00 x 10 R th

= .0385 Using a full power 6T of 64F', we get:

LMID 3.5% power = (1.443)(64)(.0385)

= 3.56F' At 1081.5 psig (lowest steamline safety valve setpoint plus 3% accumulation),

each 1.14F' corresponds to a AP of 10 psi (per ASME Steam Tables). Thus a 3.56F' change corresponds to a 6P between Primary to Secondary of:

6P = 3.56 (10) = 31.2 psi 1.14 l

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7. AP Between the Wide Range Pressure Instrument and the Top of the Steam Generator Tubes -

There are two f actors to determine the 6P between the pressure tap in the hot leg and the entrance of the steam generator.

a) Steam generator design pressure drop, 6Psg 6PSG = 30.1 psi (from Zion Statior FSAR fable 4.1-9)

Assuming that this value is equal to 1/2 of the total steam generator loss during nornal operation, then the AP contribution is:

6P 1 = 1/2 PSg = 15.05 psi i

b) Elevation change pressure drop. 6P2 An estimate of the elevation difference between the Wide Range RCS pressure transmitter (located on 568' elevaticit) and the top of the steam generator tubes (= 627') is approximately 59 ft.

Specific gravity = .731 (at 555.9'F)

Such that.

1 psi = 3.16 f t H 2 O @ 555.9'E Thus, AP = 59/3.16

= 18.66 psi The total AP contribution of this section is:

6P = AP) + 6Pg = 15.05 + 18.66

= 33.71 psig

8. Any Other Factors There are no known other factors.

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,. .$. _ Summary of Calculation In order to determine the channel uncertainty which should be added, the preceding factors in item 3 through 8 should be collected together to give the set pressure 'seen' by the instrument channel,

a. Set Pressure of chosen Stm. Gen. Safety valve 1050 psig

b. Other Factors

1) 3% Accumulated Pressure (Item 4) 31.5 psi 1.0 psi ii) Steam Line AP (Item 5) iii) AT Primary to Secondary AP (Item 6) 31.2 psi  :

iv) RCS Pressure Instrument to Sim. Gen. AP (Item 7) 33.7 psi '

v) Other Factors (Item 8) 0.0 psi TOTAL 97.4 psi By adding this 97.4 psi to the 1050 psig safety valve setpoint, an RCP trip pressure of 1147.4 (without instrument uncertainty) is reached.

10. RCP Trio Pressure (with instrument uncertainties included)

a. Calculation for Barton Transmitters:

Using the instrulaent uncertainties for wide range RCS pressure, (as given in Attachment A for Barton 763 transmitters), the RCP trip pressures are now calculated:

Normal Adverse Containment Containment l RCP Trip Pressure (no instrument uncertsinty) 1147.4 1147.4 Instrument Uncertainty 74.1 374.1 _,

Totals 1221.5 psig 1521.5 psig Since the main control board recorder for wide range RCS pressure has 50 psi increments, the following RCP Trip Setpoints will be used:

RCP Trio Pressure (PSIG)

NORMAL CONTAINMENT 1250 ADVERSE CONTAINMENT 1550 11510

b. Calculation for Rosemount Transtitters:

Using the instrument uncertainties for wide range RCS pressure, (as given in Attachment B for Rosemount 1154 transmitters), the RCP trip pressures are as follows:

Nonaal Adverse Containment Containment RCP Trip Pressure (no instrument uncertainty) 1147.4 1147.4 Instrument Uncertainty 66.9 282.9 Totals 1221.5 psig 1430.3 psig Since the main control board recorder for wide range RCS pressure has 50 psi increments, the following RCP Trip Setpoints will be used:

RCP Trip Pressure (PSIG)

NORMAL CONTAINMENT 1250 ADVERSE CONTAINMENT 1450 These trip pressures are appropriate for use on Unit 2, which has Rosemount 1154 transmitters. On Unit 1, the exis6ing Barton transmitters are scheduled for replacement with Rosemounts during the 1988 refueling outage. Until this replacement is performed, the RCP trip setpoint for Barton transulitters will be used in Zion's E0P's. This value is conservative for Unit 2 because of the snaller uncertainty associated with Rosemount transmitters.

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