Text

Proposed Tech Specs 3/4.2.2,3/4.2.3,3/4.2.4,3/4.3.1 & 3/4.3.2,reducing Number of Available Movable in-core Detector Thimble from 70% to 50% Required for Detection Sys to Be Operable
	ML20065T187
Person / Time
Site:	Mcguire, McGuire
Issue date:	12/19/1990
From:	; DUKE POWER CO.
To:	;
Shared Package
ML19310D058	List: ML20065T179; ML20065T187; ML20065T196;
References
	NUDOCS 9012270317
	Download: ML20065T187 (63)
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_ _ _ _ _ _ _ _ _ _ - - _ _ _ .

ATTACHMENT 1 Proposed McGuire Unit 1 and 2 Technical Specifications Changes

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., 3 POWER OISTRIBUTIOH= LIMITS SURVEILLANCE REQUIREMENTS 4.2.2.1 The provisions of Specification 4.0.4 are not applicable.

>4.2.2.2 is withinFor its RA00 operation, 9F (z) shall be evaluated to determine if Fq (z) limit by:

a. Using the movable incore detectors to obtain a power distribution '

map at any THERMAL POWER greater than 5% of RATED THERMAL POWER.

b. Increasing the measured qF (z) component of the power distribution map by 3% to account.for mgg.ufacturing tolerances and further increasing the value by 5% Co account for measurement uncertainties. l Verify the requirements of Specification 3.2.2 are satisfied.

c. Satisfying the following relationship:

M p RTP y Fq Q) 5 0 x K(z) for P > 0.5 /

-P x W(z)

RTP M /

F g (z) < F Q W(z) xx 0.5-K(z) for P~<

0.5 where F (z) is the' measured F (z) increased by the allowances-for 9

manufacturing tolerances'and measurement uncertainty, F RTP is -

the q

Fq limit, K(2) is the normalized F q(2) as a function ,of core height,

$/

/ \

' P is the relative THERMAL-POWER, and W(z) is the cycle dependent

. function that accounts for' power distribution transients encountered

dur_ing normal operation. FhTP, K(z), and W(z) are specified in the .V CORE OPERATING LIMITS REPORT per Specification 6.9.1.9. \

N

d. Measuring Fq (z) according to the following schedule:

1, Upon achieving equilibrium conditions after exceeding by L My p/OTTgoWN 10% or more of RATED THERMAL POWER, the THERMAL POWER at ggg which Fq (z) was last determined," or 1

2. At-least once per 31 Effective -Full Power Days, whichever-occurs first.

During power escalation at the beginning of each cycle, power level may be increased until a power level for extended operation has been achieved and a power distribution map obtained. Y cGUIRE - UNITS 1 and 2 3/4 2-7 Amendment No.1 Unit 1) /\

Amendment No. nit 2)

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rnoje.aa ac jeteu4or &l miles i! gres4er dan &c.9x( l

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[$~% + (% -Tlt1..d(A %).] Jen T i.t f(e. n vAtr &

, ceilaw tRinues.

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y R Nyog ; g Wo POWER DISTRIBUTION LIMITS 0%

SURVEILLANCE REQUIREMENTS (Continued)

e. With measurements indicating maximum [F (z) over z ( K(z) ) N has following the increasedactions since theshallprevious be taken:determination of Fq (z) either of N

1) Fq (z) shall be increased by-2% over that specified in Specifi-cation 4.2.2.2c. or N

2) Fq (z) shall be measured at least once per 7 Effective Full Power Days until two successive maps indicate that N

maximum

[Fn (z) is not increasing, over z ( K(zT)

f. With the relationships specified in Specification 4.2.2.2c. above not being satisfied:

1) Calculate the percent F q (z) exceeds its limit by the following expression: ,

Imaximum M Fg (z) x W(z) } 14 x 100 l

99,7 7 for P > 0.5 x K(z) J

[

f # - :s Imaximum M g

, Fq (z).x W(2) _y , x 100 for P < 0.5 hverz p RTP L .5 x K(z) ))

2) One of the following actions shall be taken:

a) Within 15 minutes, control the AFD to within new AFD limits which are determined by reducing the AFD limits of Specification 3.2.1 by 1% AFD for each percent F (z) exceeds l 9

its limits as determined in. Specification 4.2.2.2f.1). i

? Within 0 hours0 days 0 hours 0 weeks 0 months , reset the.AFD alarm setpoints to these modified limits, or l

p b) Comply with the requirements of Specification 3.2.2 for Fq(z) exceeding its limit by the percent calculated above, or.

! c) Verify that the requirements of Specification 4.2.2.3 for base load operation are satisfied and enter base load operation. ,

McGUIRE - UNITS 1 and 2 3/4 2-8 Amendment No105(Unit 1)

Amendment No.87(Unit 2)

POWER OlsTRIBUTION LIMITS SURVEILLANCE REQUIREMENTS (Continued)

g. The limits specified in SpecifirM ions 4.2.2.2c, 4.2.2.2e., and 4.2.2.2f.

above are 'rA apr.icablo in the foi owing core plane regions:

1. Lower core region from 0 to 15%, inclusive.

2. Upper core region from 85 to 100%, inclusive.

4.2.2.3 Base load operation is permitted at powers above APL"0* if the following conditions are satisfied:

a. Prior to enterirg base load operation, maintain THERMAL POWER above NO APL and less than or e:;ual to that allowed by specification 4.2.2.2 for at least the previous 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . Maintain base lod operation 5' surveillance (AFD within the target band about the target flux f difference of Specification 3.2.1) during this time period. C:se loari operation is then permitted providing THERMAL POWER is M maintained between APL ND and APL OL or between APL ND and 100%

(whichever is most limiting) and FQ surveillance is maintained pursuant to Specification 4.2.2.4. 0l APL is defined as:

RTP s /

APLOL = minimum g0 (p x K(Z) ) x 100%

over Z b

F (Z) x W(I)gt M

where: F9 (2) is the measured Fq (2) increased by the allowances for manufacturing tolerances and measurement uncertainty, F TP is the F q

limit. K(2) is the normalized Fq (z) as a function of core height.

W(z)BL is the cycle dependent function that accounts for limited power distribution transients encountered during base load optration.

TP F

K(I), and W(z)BL are specified in the CORE OPERATING LIMITS REPORT per Specification 6.9.1.9.

b. During base load operation, if the THERMAL POWER is decreased below ND APL then the conditions of 4.2.2.3.a shall be satisfied before re-entering base load operation.

4.2.2.4 During base load operation Fq (Z) shall be evaluated to determine if F (Z) is within its limit by:

q" . Using the movable incore detectors to obtain a power distribution lY A 6 map at any THERMAL POWER above APL ND ,

g . Increasing the measured F (Z) component of the power distribution I

9 l map by 3% to account for m ufacturing tolerances and further in:reasing the value by 5% 0 account for measurement uncertainties. I

{:

Verify the requirements of Specification 3.2.2 are satisfied.

ND

APL is the minimum allowable (nuclear desiga) power level for base load o

> peration in Specification 3.2.1.

Y'S McGUIRE - UNITS 1 and 2 3/4 2-9 Amendment No. Unit 1)

Amendment No. Unit 2) -l

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NO CHANegg yg@ PAGt' N INFORMAT(qq POWER DISTRIBUTION LIMITS ONLY URVEILLANCE REQUIREMENTS (Continued)

c. Satisfying the following relationship:

p RTP M x F (Z) i p 0 for P > APL ND where: F (Z) is the measured F9 (Z). F is the Fq timit.

K(Z) is the normalized F9 (Z) as a function of core height. P is the relative THERMAL POWER. W(Z)BL is the cycle dependent function that accounts for limited power distribution transients encountered during TP base load operation. F

, K(Z), and W(Z)BL are specified in the CORE OPERATING LIMITS REPORT per Specification 6.9.1.9.

d. Heast/ing F (Z) in conjunction with target flux difference deter-mination according to the following schedule:

1. Prior to entering base load operation after satisfying Section 4.2.2.3 unless a full core flux map has been taken in the previous 31 EFPD with the relative thermti power having been NO maintained above APL for the 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months prior to mapping, and

2. At least once per 31 effective full power days,

e. With measurements indicating F (Z) maximum [ ]

over Z has increased since the previous determination MF (Z) either of the following actions shall be taken:

1. F (Z) shall be increased by 2 percent over that specified in 4.2.2.4.c, or

2. F (Z) shall be measured at least once per 7 EFP0 until 2 F

successive maps indicate that F (Z) maximum [ ] is not increasing, over z

f. With the relationship specified in 4.2.2.4.c above not being satisfied, either of the following actions shall be taken:

1. Place the core in an equilbrium condition where the limit in 4.2.2.2.c is satisfied, and remeasure F (Z), or l

McGUIRE - UNITS 1 and 2 3/4 2-9a Amendment No10![ Unit 1)

Amendment No. 8% Unit 2)

. o

, POWER DISTRIBUTION l!MITS SURVE!LLANCE REQUIREMENTS (Continued) ,

2. Comply with the requirements of Specification 3.1.2 for F (Z) 9 exceeding its limit by the percent calculated with the following l expression:

((max. over z of ( Ff(Z)xW(Z)l))-1)x100forP>APL RTP ND x K(Z) \

g. The limits specified in 4.2.2.4.c 4.2.2.4.e, and 4.2.2.4.f above are not appli W ie in the following core plan regions:

1. Lower core region 0 to 15 percent, inclusive.

9 Upper core region 85 to 100 percent, inclusive, j 4.2.2.5 When Fg(Z) is measured for reasons other than meeting the requirements of specification 4.2.2.2 an overall measured F (z) shall be obtained from a power 9

distribution map and increas d by 3% to account for manufacturing tolerances.

and further increased by 5 o account for measurement uncertainty. l P

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f inecewL -to s1. +-(2 -r/i+,r)(2 %Q wLvs T is rt< wJer E: W Oldfo . M(c.f.

'McGUIRE - UNITS 1 and 2 3/4 2-9b Amendment No (Unit 1)

Amendment No Unit 2)

EO CHANots ygfg p EDR INpOFM% Tion ONLY ,

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This page deleted, l

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i McGUIRE - UNITS 1 and 2 3/4 2-10 Amendment No.42(Unit 1)

Amendment No.23(Unit 2) l

go CHANGEO THl$P^

@R U4FORgATION otM This page deleted.

McGUIRE - UNITS 1 and 2 3/4 2-13 Amendment No.43(Unit 1)

Amendment No.24(Unit 2)

1 l 9 POWER DISTRIBUTION LIMITS 3/4.2.3 RCS FLOW RATE AND NUCLEAR ENTHALPY RISE HOT CHANNEL FACTOR LIMITING CONDITION FOR OPERATION 3.2.3 The combination of indicated Reactor Coolant System (RCS) total flow rate and R shall be maintained within the region of allowable operation s specified in the CORE OPERATING LIMITS REPORT (COLR) for four loop operation: /\e Where:

N F

AH

a. R=

P p (1.0 + MF H (1.0 - P)]

THERMAL POWER

b. P

= RATED THERMAL POWER

c. F g = Measured values of F H obtained by using the movable incore detectors to obtain a power distribution map. The measured values of F g shall be used to calculate R since the figure '

specified in the COLR includes penalties for undetected feedwater venturi fouling of 0.1% and for measurement uncertainties of 1.7% for flow and 4% for incore measurement I of F H' E

d. limit at RATED THERMAL POWER (RTP) specified in the FfH:TheF H COLR, and y

/ %

e. MFAH= The power factor multiplier specified in the COLR.

APPLICABILITY: MODE 1.

ACTION:

With the combination of RCS total flow rate and R outside the region of acceptable operation specified in the COLR: X

a. Within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months either:

lh!S6E T W g,, g gg 1. Restore the combination of RCS total flow rate and R

' to within the above limits, or (AG H512E

2. Reduce THERMAL POWER to less than 50% of RATED THERMAL POWER and reduce the Power Range Neutron Flux - High Trip Setpoint to less than or equal to 55% of RATED THERMAL POWER within the next 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months .

McGUIRE - UNITS 1 and 2 3/4 2-14 Amendment No.MfI(Unit 1)

AmendmentNo.gunit2)

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. _ . . .- .- - - - _ . ..- _ - - --._ ~ _ -__ - __ - - - -.

3 NO CHANGES THIS PAGE.

POWER DISTRIBUTION LIMITS FORIN N M N

, ONt.Y LIMITING _ CONDITION FOR OPERATION ACTION- (Continued) l b. Within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of initially being outside the above limits, verify through incere flux mapping and RCS total flow rate comparison that the combination of R and RCS total flow rate are restored to within the above limits, or reduce THERMAL POWER to less than 5% of RATED THERMAL POWER within the next 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

i

c. Identify and correct the cause of the out-of-limit condition prior to increasing THERMAL POWER above the reduced THERMAL POWER limit required by ACTION a.2, and/or b. above, subsequent POWER OPERATION may proceed provided that the combination of R and indicated RCS total flow rate are demonstrated, through incore flux mapping and RCS total flow rate comparison, to be within the region of acceptable operation specified in-the COLR prior to exceeding the following l THERMAL POWER levels:

1. A nominal 50% of RATED THERMAL POWER,

2. A nominal 75% of RATED THERMAL POWER, and

3. Within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of attaining greater than or equal to 95% of RATED THERMAL POWER.

l SURVEILLANCE REQUIREMENTS 4.2.3.1 The provisions of Specification 4.0.4 are not applicable.

4.2.3.2 The combination of indicated RCS total flow rate determined by process computer readings or digital voltmeter measurement and R shall be within the region of acceptable operation specified in the COLR: l

a. Prior to operation above 75% of RATED THERMAL POWER after each fuel

loading, and

b. At least once per 31 Effective Full Power Days.

4.2.3.3 The indicated RCS total flow rate shall be verified to be within the region of acceptable operation specified in the COLR at least once per 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months l when the most recently obtained value of R obtained per Specification 4.2.3.2, is assumed to exist.

4.2.3.4 The RCS tots' .aw rate indicators shall be subjected to a CHANNEL CALIBRATION at least once per 18 months.

4.2.3.5 The RCS total flow rate shall be determined by precision heat balance measurement at least once per 18 months.

McGUIRE - UNITS 1 and 2 3/4 2-15 Amendment No.109' Unit 1)

Amendment No. 8XUnit 2) '

i NO CHANGEO THIG PAGE, EOil INFORMATION ONLY, This page deleted.

l McGUIRE - UNITS 1 and 2 3/4 2-16 Amendment No,43 (Unit 1)

Amendment No,24 (Unit 2)

s INSTRUMENTATION MOVARLE INCORE DETECTORS LIMITING C0 6 n !0N FOR OPERATION 3.3.3.2 The Movable Incore Detection System shall be OPERABLE with:

, a. At least 75% of the detector thimbles, l

b. A minimum of twoYetector thimbles per core quadrant, and l

c. Sufficient movable detectors, drive, and readout equipment to map these thimbles.

APPLICABILITY: When the Movable Incore Detection System is used for:

a. Recalibration of the Excore Neutron Flux Detection Sys' tem,

b. Monitoring the QUADRANT POWER TILT RATIO, or

c. Measurement of FA and F9 (Z)

ACTION:

With the Movable Incore Detection System inoperable, do not use the system for the above applicable monitoring or calibration functions. The provisions of Specification 3.0.3 are not applicable.

SURVEILLANCE REQUIREMENTS 4.3.3.2 The Movable Incore Detection System shall be demonstrated OPERABLE at least once per 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months by normalizing each detector output when required for:

a. Recalibration of the Excore Neutron Flux Detection System, or

b. Monitoring the QUADRANT POWER TILT RATIO, or c.

MeasurementofFhandF(Z) q

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pse u & I, e.ycle 7, w(es tte.numler o{ an.Mles moquMe. AtAedoe SJsf EE 1- y s~o% ad. t ys % e4 idr. tein( of 400r At%A*r Ole! W

{ustraY i.t regd,rek (w% q ubr=o doaOs-~

& kk$er horiwS* l ' Vt'%i p A rn 4e a n R A ia3 . na((y f o o fe l g u d r o +. d .

Mc0UIRE - UNITS 1 and 2 3/4 3-45 Amendment No. N (Unit 1)

Amendment No. (Unit 2) l

- , - . - - wir'

l I

l NO CHANGES TFils PAGE.

INSTRUMENTATION FOR INFORMATION ONI.Y SEISMIC INSTRUMENTATION LIMITING CONDITION FOR OPERATION 3.3.3.3 The seismic monitoring instrumentation shown in Table 3.3-7 shall be OPERABLE.

APPLICABILITY: At all times.

ACTION:

a. With one or more seismic monitoring instruments inoperable for more than 30 days, prepare and submit a Special Report to the Commission

-pursuant t; Specification 6.9.2 within the next 10 days outlining the cause of the malfunction and the plans for restoring the instru-ment (s) to OPERABLE status,

b. The provisions of Specification 3.0.3 are not applicable.

l SURVEILLANCE REQUIREMENTS 4.3.3.3.1 Each of the above seismic monitoring instruments shall be demon-strated OPERABLE by the $erformance of the CHANNEL CHECK, CHANNEL-CALIBRATION and ANALOG CHANNEL OPERATIONAL TEST operations at the frequencies shown in Table 4.3-4.

4s3.3.3.2 Each-of the above accessible seismic monitoring instruments actuated during a seismic event greater than or equal to 0.01 g shall be restored to OPERABLE status within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months following the seismic event. Data shall be retrieved from accessible actuated instruments and analyzed to determ' Lhe magnitude of the vibratory ground motion. Data retrieved from the tt u.xial time-history accelerograph shall include a post-event CHANNEL CALIBRATION obtained by actuation of'the internal test and calibrate function immediately prior to removing data. CHANNEL CALIBRATION shall be performed immediately.

after' insertion of-the new recording media in the triaxial-time-history accelo-graph recorder. A Special Report shall be prepared and submitted to the-

' Commission pursuant to Specification 6.9.2, with a copy to Director, Office of Nuclear Reactor Regulation, Attention: Chief, Structural and Geotechnical Engineering Branch,'U.S. Nuclear Regulatory Commission, Washington, D.C. 20555, within 10 days describing the magnitude, frequency spectrum, and resultant effect upon facility features important to safety.

McGUIRE - UNITS 1 and 2 3/4 3-46 Amendment No. 87 (Unit 1)

Amendment No. 68 (Unit 2)

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ATTACIIMENT 2 t

Justification and Safety Analysis 3.

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4 2 e Background / Justification:

The Moveable Incore Detector System consists of 58 incore flux thimbles t o permit measurement of the axial and radial neutron flux distribution g within the reactor core. Due to problems during Cycle 6 extensive c1 caning and repairs to the system were performed during the refueling outage. All tubes were flushed with acetone and then flushed twice with water. Subsequent to the flushing, location M-7 could not be accessed.

Af ter suf ficient drying tin.e, it was successfully accessed. Numerous repairs were made to the drive systems, the tubing the drives pass through before enter 2ng the instrument tubes, and the fittings on the ends of the instrument Lubas.

During the final checkout of the system on May 10, 1990 all detector thimbles were accessed normally except for thimbles D3, F3, and 1115. ;

The D3 and F3' thimbles were determined to be bent and 1115 was subsequently accessed during later flux mapping.

The following table illustrates the detector sticking problems encountered so far in McGuire 1 Cycle 7:

Flux Han Date % Power Number of Accessed Thimbles 1 5/21/90 38.42 46*

15 5/24/90 77.21 48*

16 6/14/90 97.77 46*

17 6/28/90 99.75 45*

18 7/25/90 100.00 49 21 8/16/90 99.82 51 26 9/14/90 94.01 47 27 10/11/90 99.92 44 28 11/26/90 100.00 46**

-Note: Maps did not use Detector A due to a detector voltage problem nor Detector F-in emergency due to erratic operation of its 5 path. -These were repaired and uaed beginning with map 18.

- Note: Map 28 was taken following an extended outage during which additional maintenance'was performed on the system.

Map 27 taken on October 11.-1990 originally could only access 43 thimble locations. Instrument and Electrical personnel entered the containment and adjusted clutch settings on detectors C and E and subsequently one additional trace was obtained.

[ The available' detectors fer maps 26 and 27 (see Figure 1) are well distributed-throughout the core and provide a good indication of the coro power distributio:i. At this burnup the core power distribution has been demonstrated to agree very well with the predicted power distribution ae.shown by the relative error in detector response progided in. Figures 2a-c for maps 26-28, respectively. The predicted

'F has already reached its maximum value for the cycle and stays fkYrlyconstantbetween100and200EFPDbeforestartingtodecrease.

l l i. .u. . - ,._.__.._-a.- . _ . _ _ . _ _ . , . . - . . . _ _ - _ . . - , - . _ . ~ _ . . - . . . _ _ _ . . . _ . ~ . , . . - , _ - - - , - . . . - ,

l l

The map taken 10/11/00 showed a margin to the g F surveillgnce limit of

'6.2%. Figure 3 depicts the measured versus predicted F g and Fg values for the cy.:lo to date. Figure 4 shows the maasured versus predicted solubic boron behavior. These figures indicate that the cycle is operating as designed.

On October 11, 1990 McGuire 1 was at a burnup of 126.6 EFPD out of a cycle nominal burnup of 420 EFPD. Based on the above detector sticking history cnd the length of time that the plant is expected to operate before the next scheduled outage, Duke Power proposes to change the Technical Specifications to allow Unit 1 Moveable Incore Detector System operability (and therefore continued plant operation) with less than 75%

of the detecters available for the remainder of Cycle 7.

It should be noted that McGuire Unit i underwent approximately a four-week outage during October - November 1990. During th'.s time, further efforts were made to improve the reliability of thu Moveable Incore Detector System. These effort:. included modification to lessen bending in the thimble tubing, additional soaking of the thimble tubing in acetone and subsequent water flushing, and running the detector probes through the tubing to determino if the locations could be successfully accessed. Also, current plans are to wire brush the tubes ducing.the next refueling' outage. It should also be noted that the magnitude of this' problem is unique to McGuire Unit 1. Neither McGuire Unit 2 nor the two Catawba units have experienced such severe problems.

The problem apparently results from Neolube interacting with the high radiation environment md subsequently clogging the inside of the thimble tubes. This problem is expected to worsen as the unit continues t.o operate.

l\ases/ Safety Analysist As discussed in McGuire FSAR Section 7.7, the Moveable Incore Detection S:. stem is used for confirmatory information and is not required for daily. safe operation of the core (daily core power performance is monitored by the excore detectors). The measured power distribution is

. affected by the "true" power distribution that exists'in the core and the instrenent thimble pattern. The thimbles are distributed nearly uniformly over the core with approximately the same-number of thimbles in each quadrant. The number and lgcation of these thimbics have been chosen to permit measuremont of F g to within 4'I and F to within 5%.

Ifthemeasuredpowerpeakingis$argerthanacceptable,reducedpower 9

. capability is indicated. The.75% detector thimble. operability requirement was chosen by the NRC (via Westinghouse Standard Technical-

- Specifications) to allow-a reasonable amount of failures of the incore- _

L detectors, but-to encourage licensees to strivo for as near as 100% as l

possible.. Reduction of opetabic detector thimbles to 50% does not significantly_ degrade the ability-of the detector system to measure core power distributions. However, core peaking factor measurement i

- , , , . .- .---.-,_.m., - - . _ ... ,_,.,_--

m-,-,- - - ....,__ -

. m . _ . . - - - . . . . - - . . - - . . , ,

- - - -. . _ . .. . . - - - - ~ _ . _ - . _ . . _ - - - - . _ . - _ _ . - -

uncertainties will be increased by a reduction in the number of operable detector thimbles from 75% since they were previously determined for the Technical Specifications assuming the 75% criterion.

For Cycle 7, as was the case for Cycle 6. Duke Power commissioned Westinghouse to assess the incremontal peaking factor measurement uncertainties and excore calibration impact associated with a reduction to a minimum of 29 (i.e. 50%) of the 58 moveable detector thimbles in McGuire Unit 1. The study, which is based on a Westinghouse generic thimbledelegionanalysis, indicates that additional uncertainties of 1.0% for F and 2.0% for f are appropriate when the number of instrumentN assemblics is r0duced from 58 to 29. The additional uncertainties should be applied linearly from below 75% to greater than or equal to 50% moveable thimble locations. In addition to the uncertainty. a minimum of four thimbles per quadrant is required (where a quadrant includes both horizontal-vertical quadrants and diagonally bounded quadrants) to establish the bounds of applicability of the study. The study concludes that operation of the moveabic detector system with a minimum of 50% of the thimbles available is acceptable with the above provisions.

Due to the significant database used in the above study Westinghouse intended that the uncertainties derived are to be considered of a generic nature and should be applicable to subsequent cycles with all Westinghouse fuel. The Westinghouse generic thimble deletion analysis portion of the study was originally to support permanent reduction of the detector thimbic operability requirement to 50% (29) in Westinghouse four-loop plants (note that the study also addresses measurement urcertainties for F which McGuire does not use). However, the NRC has previouslydeniedaNemptsforsuchpermanentchanges(referenceBeaver Valley Power Station Facility Operating License No. DPR-66 Amendment No.

73 Safety Evaluation Report) on the grounds that reducing the number to 50% might result in a lack of incentive to keep the system operating as close to 100% as possible which could result in an unacceptably degraded

-ability to detect anomalous conditions in the core. Duke Power has made overy offort to ensure the operability of the system through thimble tubo cleaning and preventive maintenance. Since the NRC has permitted such relaxation of the 75% requirement for the duration of affected reactor cycles (including one for McGuire Unit 1 Cycle 6 an.1 also one for Beaver Valley based on this Westinghouse generic analysis), Duke Power is proposing the Technical Specifications changes be applicable for the remainder of McGuire Unit 1 Cycle 7. Westir.ghouse confirmed the uncertainties are applicable to the McGuire Unit 1 Cycle 7 core. It should be noted that the study usus the INCORE computer code whereas McGuire uses SNACORE. The equivalence of SNACORE and INCORE for i

processing measured power distributions has been previously demonstrated in Duke Power Company's "McGuire/ Catawba Nuclear Station Nuclear Physics Methodology for Reload. Design", DPC-NF-2010A, approved by the NRC SER issued on March 13, 1985. It is also noted that the input factors for l SNACORE are generated by Westinf h ouse using identical methods as used l

l l

N __ . - . - . - . . - -. - - - .--- -._ - -_ - - .-

for INCORE. Therefore, the effects of deleting thimbles from SNACORE are considered as properly analyzed using the results of the generic thimble deletion analysis, i Burnup on Cycle 7 is currently about 5400 MWD /MTU of a 17,500 MWD /MTb cycle. At t'" point in cycle operation, the core characteristics have been well i ' - 'ished and, specifically, core power distribution is well behaved, h .9a rate error distributions from flux map measurement indicate that the core is opgrating as designed. All power distribution surveillance parameters (F ,F currently have sufficient margin to theirlimitsafterthecurNntTbc)hnicalSpecificationrequired uncertainties are applied. FromthefluxmaptakenonOctobergl,1990, (i.e.,

it is calculgted measured F that there is approximately 5.9% margin in Fplus its measurement un TechnicalhocificationLimit)gndapproximately6.2% margin'inF(z).

The predicted peaks (F and F ) decrease in value the remainder9 of the cyclo. ItisalsoexpOctedtbtthecorewillcontinuetobehaveas designed. Therefore, adequate margin exists for implementation of the Westinghouse study additional measurement uncertainties.

Description of Proposed Technical Specifications Changes:

The proposed Technical Specifications changes are based on guidance provided by Westinghouse with the commissioned McGuire 1 Cycle 7 thimble reduction study.

T.S. 3/4.2.2 is modified by adding a footnote to surveillance Specifications 4.2.2.2.b, 4.2.2.4.b, and 4.2.2.5, where the measurement unecrtainties are addressed. The footnotes, which are applicable only for McGuire Unit 1 Cycle 7. for reasons discussed abcVe, instruct that the 5% F (z) measurement uncertainty be increased linearly (with the

, maximum 3%)whenthenumberofavailab:adetectorthimblesislessthan-75% of the total (with the minimum 50%). This additional uncertainty is in accordance with the results/ bounds of the McCuire Unit 1 Cycle 7 Westinghouse study discussed above, and will result in a maximum F (z) measurement. uncertainty of 7% at the 50% available detector thimb1(

level. No other changes to Specification 3/4.2.2 are required for the reduction in the number of availabic moveabic incore detector thimbles.

Note that a footnote is added to Specification 4.2.2.4 which applies for base load operation, even though no base load operation analysis was l performed for-McGuire Unit 1 Cycle 7 and thus the specification would l not be used for Unit 1 Cycle 7. This was done for conservatism in case base load operation is subsequently analyzed and impicmented on Unit 1 .

Cycle 7 for some reason, since failure to increase the measurement uncertainties under the specified conditions (i.e., base load operation L and less than 75% available detector thimbles) would be non-conservative.

l-

~

-- ._R...... . . . . , . _ . _ . _ . , _ . =J.. . _ . _ . . . - - - ,. _. 4

T.S. 3/4.2.3 is modified by adding a footnote to limiting condition for operation Specification 3.2.3.c, where measurement uncertainties are addressed. The footnote, which is applicable only fog McGuire Unit. 1 measurement

' Cycle 7 as discussed uncertainty be increased above, instructs linearly (w!ththat the the 4% F,Y%) when the ntunber maximum of available detector thimbles is less than 75% of the total (with the minimum 50%). This additional uncertainty is in accordance with the .

results/boundsoftheMcGuireUnit1 Cycle 7Westgnghousestudy l discussed abovo, and will result in a maximum F measurement l uncertainty of 5% at the 50% available detectora bimble level. No other changes to Specification 3/4.2.3 are required for the reduction in the numgerofavailablemoveableincoredetectorthimbles. Note that thg FmeasuregtuncertaintywouldbeincreasedbyadjustingtheF)g 1bitofF (linearlyby1%from757. tog 0%thimblesavailable, ratherthabgadjusting the measured value F The method used is equivalent te adjusting the 4% F N measurben.t uncertainty by 14%+(3-T/14.5)(1%)],wherefgis the number of available thimbles, similarly to the method used in Specification 3/4.2.2. This was deemed the best way to accomplish incorporating the additional uncertainty into Specification 3/4.2.3. Specification 3.2.3.cstatesthatthefiggre specifled in the measurement. Core Operating uncertainty. Limits Since both t.heReporg F includes limit of F the N ab F N R

areusedintheRequation(definedinSpobfication3.2b.a)whichy, A utilizedwiththuggurespecifiedintheCoreOperatingLimitsReport, adjusting the F gg valuetoreflecttheadgitionaluncertainty accomplishes the same thing as adjusting F g. No changes to Specification 3.2.3.a or the figure specifted in the Core Operating limits Report (which specify the R equation) are needed since the F 3g N utilized in the equation is defined in Specification 3.2.3.c which includes the additional uncertainty adjustment footnote.

T.S. 3/4.3.3.2 is modified by adding footnotes to limiting condition for operation Specifications 3.3.3.2.a and 3.3.3.2.b, where the minimum percentage of detector thimbles and minimum number of detector thimbles per core quadrant are specified for operability of the Moveable Incore Detection System. The Specification 3.3.3.2.a footnote states that the minimum percentage of available detector thimbles may be reduced from 75% down to 50%, provided that any necessary adjustments are made to peaking factor measurement uncertainties and the minimum number of detector thimbles per core quadrant 'is appropriately adjusted. This reduction to 50% (with attendant provisions) is in accordance with the results/ bounds of the McGuire 1 Cycle 7 Westinghouse study discussed above. The Specification 3.3.3.2.b footnote states that the minimum number of available detector thimbles per core quadrant,-where quadrant includes both horizontal-vertical quadrants and diagonally-bounded quadrants, must be raised from two to four for a reduction of the number of available detector-thimbles below 75% of the total (with the minimum l

50%). This increased minimum (with quadrant proviso) is in accordance with the results of the Westinghouse study discussed above and is i required to establish the bounds of applicability of the study. Both of the above footnotes are applicable only for McGuire Unit 1 Cycle 7 for

. - ~ . .

i g

reasons previously discussed. No other changes to Specification 3/4.3.3.2 are required for the reduction in the number of availabic moveable incoro detector thimbles.

No other changes to Technical Specifications are required for the reduction in the number of available moveable incore detector thimbios.

The Moveable Incore Detection System is also utilized for Specifications 3/4.2.4 (i.e., surveillance Specification 4.2.4.2) and 3/4.3.1 (i.e.,

Surveillance Tabic 4.3-1 Item 2). While these specifications will be impacted by the reduction (i.e., the changes to Specification 3/4.3.3,2 will allow performance of the surveillances of Specifications 3/4.2.4 and 3/4.3.1 with the Hoveable Incore Detection System having less than 75% of the detector thimbles availabic), there are no peaking factor measurement uncertainties or other factors referenced in the specifications which require changing. The changes to Specification 3/4.3.3.2 are all that are needed to handle the Specification 3/4.2.4 and 3/4.3.1 aspects of the reduction in the number of available moveable incore detector thimbles.. Further, since this is a temporary change which will expire at the end of Unit 1 Cycle 7, the Bases sections of the affected Technical Specifications are not being changed to reflect the temporary provisions. The bases for these temporary provisions will be documented via this submittal and the NRC Safety Evaluation Report approving these proposed amendments.

Conclusions:

This proposed Technical Specifications change would allow an increase in plant operating flexibility (for Unit i Cycle 7) while maintaining sufficient data collection capability to ensure that the operation of the core is within licensed limits. This' change would be utilized only if further failures of the detector thimbios occur. Based upon the preceding-justification, Duke Power Company concludes that the proposed-amendments are necessary to avoid an unnecessary potential shutdown of

- McCuire Unit I which has real benefits in terms of availability, component lifetime (avoiding an unnecessary thermal cycle on the reactor and associated systems), and safety. Based upon the preceding safety analysis, Duke Power Company concludes that the proposed amendments will not be inimical to the health and safety of company personnel or the public. Further, such amendments have been granted by the NRC for McGuire Unit 1. Cycle 6 and for other plants in similar situations in the past (e.g., Yankee Nuclear Power Station, Facility Operating License No. DPR-3 Amendment No. 100; and Beaver Valley Power Station, Facility

. Operating License No. DPR-66 Amendment No. 61),

i l

__ - - ~ . . - - - -. ..~ - . . ._ . __. . .-- - _ - . - - - - . - - . . . - - . - -

4 Figure 1 Recently Accessible and Inaccessible Detector Thimbles McGuire Unit 1 Cycle 7 2

R F 5 M. L K J I G F E D C 3 A

r. n, B

E M 2

og g o g , g ,

M 3

E - E %

4 ^* '

E E

E E O 0 5

5 o' E o. E o'. .E 8

[5 h ,

E ,* 5 E l- O X F 5 '

7 E A o E ,

E -

' ;E *-

h D E -

- 5 0-8 h

e 5 5 o

- 5 o 5

10 11 m

E g

l-

) F E l-A. g g O

X.

~

12 E E .

'E i E 13 ,

y, E . E x

$~ ,E )

14 y g y 3

g ,x *

^

15 O

E h D

E b.

g Thassoccuple (ES)

)

M&

9f b Ybl* O O ( 44) e Movable Detector (51)

A7 Ormkle

mala orrecten um fxswoccorLa LocAtters

f. ; , . . s. - .,

. , - _ . ~ . . . _ .

- - -_.-.__ - ___ -. .- . - _ ___ _ _ . _ _ _ . . .=.

Figure 2a Relative Error in Detector Response

((Calc-meas)/ meas) ~~

McGuire Unit 1 Cycle 7 September 14, 1990 Flux Map X

I b.

3.02'4 I

3 0.023 0.001 l 3- ).009 0.004 4- u.006 0.02C -0.003.

5 0.004 -0.00E D.008 0.038 -

0.003 -

3.011 0.011 0.008 7 -

).010 -0.015 -3.007

\

8 3.046 3.001 -0.010 -

0.022 ).008 0.001 0.008 W 7 9' O.009 -0.001 3.0011 0.033 10 -3.016 -0.009 10 007 11 y.017- .l 0.012 -0.020 0.001

'2

. -0.0 I C -0.022 _

4

'3 0.013 0.008 0.011 g ..

.4 ].020L ).013 -

0.015 l ,

l .5 0.009 0.029 1

i .

R' P N M L K J H G F E D C B A D!S Error Of Inst rumented Locations = 0.0159

_ . . . . _ . _ _ . _ . _ _ _ _ - . _ _ _ _ _ _ _ . ~ . _ . . . . _ . _ _ _ - - - -.

a Figure 2b ,

, Relative Error in Detector Response

((Calc-meas)/ meas)

McGuire Unit 1 Cycle 7 ,

October 11, 1990 Flux Map '

E i

X s ,

1 I l 0.022 I- p.015 0.004 4

3

-0.001 -0.012 e

4 i

0.006 0.007 -0.005 3 , -0.010 - 0.003 0.012 , 0.014 6

0.033 -0.00E 3.002 , -0.002 -

I -0.006 -0.029 -0 .001 8

0.047 -0.019 3.011 0.006 0.009 V Y

i. 9* 0.009 -

0.009 0.027 1

10

-0.014 -0.006 -0.001 11 0.009 "

, -0.003 -

0.020 0.002 12 -0.002 -

0.021

l. 13 0.015 -O 001 0.008 -

l. j .

a 14 g 0.013; 0.025 -

p0.012 l 0.005 0.029 1

1 R p- N L M K J H G y g 3 C

,S' -A 1015 Error Of Instrumented Locations = 0.0156 1

m g wv.. wr wwn- e *werwww w wfueM w-w<-e ,ww--t3-gg. _y-

~

5'w=mrW^t**Y 7747C'"7et'**T ' - v F

w; 1 "*T"' W*

' W"'

, Figure 2e

' Relative Error in Detector Responso

((Cale-meas)/ meas) ~

McGuire Unit 1 Cycle 7 Novmeber 26, 1990 Flux Map X

1:

1.020 2 p.016 1 0.003 0.012 3 -0.002 -

0.016 b 0.005-0.001 -0 . 00 d 5

0.005 6

0.031 0.001 : -

0.009 0.004 0.005 7 0.008 -

0.027 -0.004 0.016l 0 -

).008 -0.014 0.008 3.008 0.020 0.00 g.

'd 9' O.010 0.001 0.029 10 .

0.016 -0.008 , -0.001 i

l 11 ,0,005 0.013; -0.018 -0.019 l

12 .

0.013 0.000 -0.014 13 0.007 -0.005 l

l l

l 14 0.007 0.003 151 ---o.002 0.028 l . t e

R P N M L K J H G F E D C B A RMS ERROR OF INSTRUMENTED LOCATIONS = 0.0131

i

(

i FIGURE 3' .

j M1C7 PEAKING FACTORS VERSUS BURNUP -i s

l 1.9 f I !

l l

' 1.8 ~j 1 !

l'-

l -!

i

I

! 1.7 , !

i - 1 [

i tr 1 I. ;

i w .

l *

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w __

l 2-o '

u 1.5 '

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"o'- : WAS FDH I 1.2 PKASFO

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mEDFO i l

t 4

l' , $

L i .1.0 - - - - - -

!' O . 25 50' 75 100 125 150 +

)

j t CORF BURNUp (FFPD) [

t

?

1 -6 1 i l,

?

y -

5 .f_ , .e - .. . , - _ - . . , - . , _ , , ,.

. t i

~'

j FIGURE 4

. BORON CONCENTRATION VERSUS CORE AVERAGE BURNUP.-

4 1400 i

1 s ;

1300 '

i --

% i 5

N i a-1200 w N

N. .

z s j 9

n i i

< i m ;

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z 1100 '

i

un

o

t

, z :

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i O I

z l O

m 1000 ,

O t

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j ; MEAS DORON i

1'

% ; PEDBJRON i

l

1 I g . . . l .

j O 20 40 60 80 100 120 140 !

t

[

BURNUP (EFPD) 1 i

i

. Table 1 McGuire Unit 1 Cycle 7 Zero Power Physics Testing Results Prec1cted Cata and acceptance criterna aere cotained from tee McGuire Nuclear Station Unit t Cycle 7 Startup and Ocerational Aeoort, MCNE-1553.05-00-0005.

Ths value in parentheses incteates tne acceptance criterton.

Drecicted Value/

Paramete* "eesured 'ialue (Accectance criterten)

Point of adding nuclear neat (on N42) 1,7 = 10-6 amos ------

per piccammeter .

ZPpf Range (on N42) 1.0 x 10', g to ,,,,,,

per ptccammeter 1.0 m to amos ARD Boron Endpoint 1746 com 1755 com (1705 to 1905 ccm)

ARD !TC +2.650 cem/*r +3.05 ccm/**

(1.05 to 5.05 ocm/'F)

ARD MTC +4.41B ccm/'F +* . 81 c e m / ' t (2.91 to e.B1 ocm/'F)

Reference Bank (S/0 Bank B) Worth 522 ocm 830 ccm by Dilution (790 to 1070 ccm)

WORTH OF BANKS BY ROL EXCHANGE Control Bank A 227 pcm 332 ccm (32 to 532 ocm>

Control Bank B 729 pcm 730 pcm (517 to 059 ocm)

Control Bank C 745 ocm 759 ocm (532 to 986 ocm)

Control Bann D -96 ocm *B6 pcm (206 to 6B6 ocm)

Shutcown Bank A 304 pcm 290 ccm (90 to 490 pcm)

Shuteown Bank C 449 ocm 435 pcm (235 to 635 ocm)

Shutdown Bank D 449 ocm 435 pcm (235 to 635 ocm)

Shutcown Bank E 429 ocm 402 ocm (202 to 602 pcm)

Total Bank Worth 4850 ccm 4807 pcm

( > 4326 ocm)

NOTES:

1. Control Rec Witherawal Limits were not reoutred.

2. Iero Power Flux Man was not taken.

3. The same chemistry stancare was usec for all ISPT.

4 Ref erence Bank Worth reactivity enange was 230 ccm/hr.

5. All Acceptance Criteria were met.

1

.?

MCGUIRE UNIT 1 EVALUATION OF THIMBLE DELETION ON PEAKING FACTORS Introduction This study was undertaken to assess incremental peaking factor measurement uncer-tainties associated with a reduction to a minimum of 29 of the 58 of the movable detector (M/D) thimbles in McGuire Unit 1. Due to the significant database used in the study, it is intended that the uncertainties quantified herein is to be considered of i. generic nature and should be applicable to subsequent cycles.

Section 1 of this study presents the methodology and results of randomly deleting thimbles from actual INCORE maps to quantify the uncertainties. Section 2 quanti-fies the minimum number of thirbles per quadrant required in order to improve the ability to distinguish between random and systematic thimble deletion events and to establish the bounds of applicability of Section 1.

For McGuire Unit 1 Cycle 7, an evaluation was performed to nonfirm applicability of this cycle to the study described herein. Review of cut.ent cycle flux maps indicate that measurement to predicted peaking factors are well within the re-quired measurement uncertainties and indicate the core is behaving as predicted.

Based on this, it is not anticipated that the core will not perform as expected for the remainder of the cycle. It is not expected that the additional uncer-tainties on the peaking factors will result in any violation of the limits. Even with the increased measurement uncertainty applied as a result of the thimble delection study, the McGuire Unit 1 F, Surveillence Technical Specification will provide additional protection. The Tech. Spec. is designed to reduce the Sperat-ing band (AFD) resulting f rom violations of the lindting condition of operation (LCO).

In order to address thimble deletion in four loop plants, flux maps were chosen from plants with the maximum of 58 thimbles. When referring to percentages in Sections 1 and 2 they refer to the percentage from a total of 50 thirbles unless otherwise specified.

I MCGUIRE UNIT 1 CYCLE 7 PAGE-1

- - - ~ _____ - _-____ __ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ __

{ .

SECTION 1 METHODOLOGY - GENERAL To assess the additional peaking factor measurement uncertainties associated with as few as 50% of the M/D thimbles available, twenty-one full core INCORE flux maps from various plants and cycles were used. The selection of these naps was made to reflect the wide variety of loading pattern types such as annual reload cycles, low leakage, first cores, and eighteen month reload cycles. For each of the INCORE maps, five separate random deletions were made, giving a total of 105 thinble deletion cases with 50% of the thimbles available. Five separate random deletions were also done with this same set of 21 INCORE maps giving 105 thimble deletion cases with 75% of tho thimbles available. The INCORE code was used to randomly delete thimble locations. The measured peaking factors for the thimble deletion maps were then compared with the neasured peaking factors in the refer-ence maps, i.e., the INCORE maps employing all or most of the 58 movable detector thimbles. Figure 1 shows the movable detector (M/D) locations for the four-loop plants considered and Table 1 provides additional information on the twenty-one maps used in the study. For those maps with less than 100% of available thimbles (e.g., 89.7%), thimble deletion cases to 50% of available thimbles were run utilizing 50% of the available thimbles in the reference map (e.g. 44.8%). These cotoparisons yielded the additional measurement uncertainties to be applied to F u, F,, and F n. Thimblo deletion ef fects on the INCORE naasured axial of fset and quadrant tilt were addressed in a similar manner.

To examine the ef fect of thimble deletion on measurement of of f-normal power distributions, a pseudo dropped rod map was generated with random deletions such that maps with 50 and 75% of the available detector thimbles were obtained. The measured peaking factors from the thimble deletion maps were then compared to the reference map as for the normal operation maps described above.

METHODOLOGY - STATISTICAL The percent error between the reference peaking factor value, F, (Reference), and the thirble deletion case peaking f actor value, P, (T.D.) is defined in Equation 1 as t Error (T.D.) =

[ 1-F, (T.D.) \

l x 100 (Eq. 1)

F, (Reference) where F, is F , P o, or F, and T.D. refers to 75% or 50% of available thimbles in the reference case. A positive value of error implies that the peaking factor from the thimble deletion map is non-conservative relative to the reference. In the following paragraphs the error will be denoted Xy where i refers to one of the 21 flux maps and $ refers to one of the 5 thimble deletion cases for each map. The percent error between the reference value and the thimble deletion case value for quadrant tilt and axial offset are defined in Equations 2 and 3 as MCGUIRE UNIT 1 CYCTE 7 PACE-2

4 Error (T.D.) = (Re f. - Deleted) x 100 for QUAD Tilt (Eq. 2)

Error (T.D.) =

(Ref. - Deleted) for A.O. (Eq. 3)

The mean error for map 1, X; and the percent relative sample standard deviation for map i, S,, at: defined in Equations 4 and 5, respectively.

5 X, a X,3 (Eq. 4) j=1 5 1/2

~

( X, , - X, ) '

= tr,q. 5)

S, $=1 5-1

> Af ter computing 5 and S, for each map, for cach parameter of interest, and for both o0% and 71% thimble deletion cases, the data is combined. The combined mean

!er all maps, X 3,,,, is given by Equation 6 as:

21 X,,,,,,,,= X, (Eq. 6, ial MCGUIRE UNIT 1 CYCL" 7 PAGE-3

, :s.

.e : _ _

i

-.The' combined percent relative sample. standard deviation of all maps is given

.by Equation 7_ s:

r - 1) S', + N, X,)

2 N,

S ,, ,,,,, =

((f(N n-1 N,

X', ,

) N,-

1)1/2 (Eq.'7) ,

where:

' N, = Number of. random deletion cases of each map = 5 and N, = Total number of- datapoints = 21 maps x 5 deletions / map = 105 Equations G and 7 are constructed in such a manner that if one were to directly-compute the-mean and' standard deviation for all 105 datapoints, the same numeric results would'be obtained.

After X,,og,,, and S,, i,,, have been obtained for each parameter of, interest, and for both 50% and 75% thimble ~_ deletion cases

- r 95% confidence / 95% probability one-f Jided upper tolerance limits:are constructed to quantify the th'mble deletion

uncertainty' component..-(See Equation 8), ,

' Thimble' Deletion-Uncertainty Component (%) = Y,,,,,1+ k S ,,,e (Eq. 8) 1 'where k = tho one-sided 95% confidence /95% probability traert.'.ce -limit factor for 104 degrees -_ of freedotr = 1.919. - ,

L ApplicatJhn of:the above_ methodology is presented in the'"Results"nsection of U this re' ort. The' statistical combination of the thimble deletion uncertainty s component'with 1NCORE measurement is discussed in the " Thimble Deletion Unce.

tainty"Lsection.of this. report.

RESULT 5-Table 2a.provides the peaking factors sample mean'(k) _ for each-map (see Equation

{ 4), and -the sample standard deviation;(%) - for each map _ (see - Equation 5)- for :the.

50% ' thimbles available case. The' combined sample mean (%)- and the combined

' standard deviation (%) for each parameter of-interest, as calculated per Equa-

tions 6 and 7, is also shown. Table,2b presents the analagous-information for

.the 75% thimbles-available case. Tables 2c and 2d provide the_ sample mean~and- i

'the sample standard deriation for quadrant tilt;and axial offset over the same-

? database? t O:

i

,- MCGUIRE UNIT 1 CYCLE 7 : PAGE-_4

a Thimble deletion uncertainty components (i.e. the 95% probability, 95% confidence tolerance limit) for F ,, F,,, and F, are calculated in Appendix A using Equation 8 and are based upon the data of Tables 2a and 2b. The Thimble Deletion Uncer-tainty Component (%) is plotted in Figure 2 as a function of Percentage of Thimules Available. This figure is provided for information only and is not directly used in the uncertainty application.

Table 3a and 3b show the pseudo-dropped rod map data and will be discussed in more detail in a later section.

THIMBLE DELETION UNCERTAINTY Current flux map peaking factor measurement uncertainties include allowance for down to 75% thimbles available. Accordingly, an incremental thimble deletion uncertainty component penalty from 75% to 50% of thimbles available could be considered to be appropriate. However, for conservatism and simplicity, the full thimble deletion uncertainty component penalty from 100% to 50% thimbles avail-able will be used. The Thimble Deletion Uncertainty Component (50% T.D.) dis-cussed in the preceding section is combined with the appropriate flux map meas-urement uncertainty to obtain a total uncertainty.

F , UNCERTAINTY, F,"

The appropriate equacion for combining statisticr?ly inCependent uncertainty components is l';

F ,' (50%) =

1 + F, + ( F," -1)2 + (KS)',y (Eq. 9)

T.D. Blas For conaarvatism, a negative value of T.D. Bias will be treated as zero.

Analagous equations apply to F," and F,,8 Evaluating the above expression yields the following result

. (a,c)

For conservatism to support generic application to subsequent cycles, F ,' (50%)

will be rounded up to 1.05. This value can be interpreted as a 95% probability tolerance limit at a high confidence level. This one percent incremental thimble deletion penalty is linearly applied f rom 75% to 50% thimbles available (i.e.,

1.04 at 44 thlebles and 1.05 at 29 thirbles available) .

MCGUIRE UNIT 1 CYCLE 7 PAGE-5

4 F, UNCERTAINTY, F/

. . (a,c)

For conservatism to support generic application to subsequent cycles, F/ (50%)

will be rounded to 1.07 This 2% incremental thimble deletion penalty is line-arly applied from 75% to 50% thimbles available (i.e., 1.05 at 44 thimbles and 1.07 at 29 thimbles available).

F,, UNCERTAINTY, F ,,'

The appropriate F,, Uncertainty for as f 3w as 29 thimbles remaining is (a,c)

For conservatism, to support generic application to subsequent cycles. F, " (50%)

will be rounded to 1.07. This 2% incremental thimblo deletion penalty is' line-arly applied from 75% to 50% thimbles available (i.e., 1.05 at 44 thimbles and 1.07,at 29 thimbles available).

OFF-NORMAL POWER DISTRIBUTIONS Thimble deletion-uncertainty component tolerance limits are constructed in Appen-dix B based upon the pseudo-dropped rod data from Table 3a. It is interesting to note that the pseudo-dropped rod results are generally less limiting than typical flux map results. For example, for F., the thimble deletion uncertainty compo-nent (50%) is [ '(a,c) l' AXIAL OFFSET AND QUADRANT TILT The mean change in quadrant tilt with 29 of the thimbles available was found to be only [

l' Similarly, the mean change in axial offset *(a,c) with 50% of the thimbles available was also quite small at [

3+

(a,c)

. Note that all uncertainties on A.O. and tilt are absolute values and not percent-ages of A.O. nor tilt. These values indicate that thimble deletion has a negli-L gibic impact on the core. average axial power shape measurement. Changes of this l- magnitude are not significant.and will not adversely affect excore detector cali-bration.

t. .

i l

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l L

L MOGUIRE UNIT 1 CYCI E 7 -PAGE-6 l

l:

. 0 CONSERVATIVE ASSUHPTIONS For convenience a summary of conservative assumptions employed in this study are provided below:

1) The total thimble deletion penalty from 100% to 50% of the available thimbles was utilized rather than the incremental penalty from 75% to 50%

of the available thimbles.

2) Thimble deletion uncertainty results were rounded up and negative bias values were set to zero.

~~ ~~

(a,ci 4) 5)

9 MCGUIRE UNIT 1 CYCLE 7 PAGE-7

SECTION 2 This section quantifies the number of thimbles per quadrant required for McGuire Unit 1 in order to improve the ability to distinguish between random and system-atic thimble deletion events and to establish the bounds of applicability of the incremental peaking factor uncertainties.

The current Technical Specification requirement of a minimum of 2 M/D thimbles per core quadrant is not sufficient to distinguish between random and systematic deletion events with high confidence. By incrcasing the required ml.'imum number of M/D thimbles per quadrant, and by defining quadrant in such a manner as to essentially place a requirement on each 1/8th core, the ability to distinguish between random and systematic events will be significantly enhanced.

I f, for example, for 50% thimbles remaining, the requirement of 4 or more thimbles por quadrant is satisfied, then in all likelihood a random deletion occurred and incremantal thimble deletion peaking factor measurement uncertain-ties are appropriate. On the other hand, if there are less than four thimbles per quadrant, then it is possible that a systematic thimble deletion occurred and that the impact on measured quadrant peaking factors, may be larger than quanti-fled in Section 1.

METHODOLOGY - ANALYTIC SOLUTION Recall that the number of combinatiars of n events taken r at a time, C/, is the number of ways of selecting r out of n elements without regard to ojder. For example, the number of ways of selecting 29 elements out of 58 is C , = 3.01 x 3

10". Ratios of different combinations can be interpreted as probabilities. For convenience the notation C(n,r) will be used to represent C/.

In the actual thimble deletion problem of interest soms thimbles lie on the axis or diagonals and hence are common to two quadrants. Solving this type of problem analytically is quite complex. A somewhat simpler problem type that can be solved exactly is described below.

(a, c) l l:

p

~~

t l

l MCGUIRE UNIT 1 CYCLE 7 PAGE-B l

(

, , . , , , , . , , . , , d} , , ,,

~

"""' (a,c)

The total probability of 0 through ' .nimbles remaining in a particular quadrant is of course 1.0. Thic sthod will be applied to the test protlem described later in this repor i

MCGUIRE UNIT 1 CYCLE 7 PAGE-9

METHODOLOGY - COMPUTER SIMULATION A < = ort computer program for determining the probability distribution of thimbles ren_ining was written. The program allows for different number of thimbles per quadrant and keeps track of interior, axis, and diagonal thimbles (see 4-loop description).

Starting with n, thimbles in the core and randomly deleting down to r, nimbles constitutes one case. Af ter deleting n, - r, thimbles f rom the core, the number of thimbles remaining in each of the eight quadrants is determined. The minimum number of thimbles remaining over all 8 quadrants is then found. A large number of cases is run in order to determine the probability distribution of thimbles remaining.

TEST PROBLEM DESCRIPTION The test problem selected was chosen to be sufficiently complex so as to ade-quately test the simulation code, but also simple enough as to permit an exact analytic solution.

The. problem consisted of a core with an initial compliment of 60 thimbles total with 15 thimbles in each of the 8 quadrants. All thimbles are defined to be in interior locations, i.e. no common thimbles exist within the four vertical-horizontal quadrants and no common thimbles exist within the four diagonally bounded quadrants. Thirty (30) thimbles are randomly deleted for each case. The above information is depicted in Figure 3.

TEST PROBLEM RESULTS For the analytic solution the method described earlier in the text was used to calculate the percent probability of 0 thimbles left in a particular quadrant, 1 thimble left, etc. up to 15 thimbles left. Results are summarized in Table 4.

The computer simulation was performed using two different methods. Method 1 is analogous to the "real" 4-loop problem in that the minimum number of thimbles left over all 8 quadrants was used to obtain the probability distribution. Method 2 is the computer analog to the analytic solution in that the probability distri-bution for a particular quadrant was obtained. Results for both of these methods are provided in Table 4.

TEST PROBLEM CONCLUSIONS

1. For Method 2 (count cases for Q1'only) the computer simulation and analytic solution using ratios of combinations agree very well. Therefore, for this type of problem, the program can be considered to be verified.

2. For the problem type of actual interest (Method 1) the program must calculate the minimum number of thimbles over all 8 quadrants.

The probability distcibution from the Method 1 simulation is skewed more toward fewer numbers of thimbles remaining. Intuitively this makes sense.

For small number of thimbles remaining, if the analytic probabilities for Method 2 are multipliec by 4, the resulting values are close to the Method 1 simulation.

I MCGUIRE UNIT 1 CYCLE 7 PALE-10

5 Because an exact analytic solution for Method 1 it very complex the computer simulation results are relied upon to determine the minimum number of thimbles per quadrant for the 4-loop core problem.

P 4-LOOP PROBLEM DESCRIPTION The maximam possible number of available thimbles for a 4-loop Westinghouse PWR is 58. The initial distribution of these thimbles is provided in the following table. Figurea 4 and 5 should also help in visualization.

No. of Interior Thimbles in Q1 11 No. of Interior Thimbles in C2 10 No. of Interior Thimbles in 03 11 No. of Interior Thimbles in 04 11 No. of Axis Thimb)es Ql c' 4 No. of Axis Thimblis Q2-v3 4 No of Axis Thimbio. ru-04 3 No of Axis Thimbles 04-01 _A 08 Total No. of Interior Thimbles in QA 11 No. of Interior Thimbles in QB 14 No. of Interior Thimbles in OC 12 No. of Interior Thimbles in QD 12 No. of Diagonal L.!: ?ss QA-QB 1

's 0B-QC

~

No. of Diagonal Thi No. of Diagonal Thit. es OB-QD 2 No. of Diagonal Thimules QD-QA _2 58 Total Note that all thimbles nre counted as whole values even if they lie on an axis or diagonal. Provided t'.a technical specification value and computer simulation are consistent this is appropriate. Twenty-nine (29) thimbles are randomly deleted from each case.

4-LOOP FROBLEM RESULTS l AL3000 case simulation was run to obtain the probability distribution of the IL minimum number of thimbles left af ter having reduced to 29 thimbles available.

- Results are summarized in Table 5.

l-J Therefore, a re-

(a,c) l quircrant that 4 or more thtmbles per quadrant be available is appropriate.

As s ur. r, .ndom thimble deletion, it is unlikely that with 29 thimbles remaining-overal ?;wer than 4 thimbles will be available over the 8 quadrants.

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l MCGUIRE UNIT 1 CYCLE 7 PAGE-11 l

l

d CONCLUSION With the inclusion of the additional peaking factor uncertainties, it is con-cluded- that operation of the movable detector system with a minimum of 50% of the thimbles available is acceptable provided that an additional 1.0% for F ,and 2.0% for F, and F,, be applied to the INCORE measured peaking factors. However, when fewer than 75% of the thimbles are availabic there should be a minimum of 4 thimbles per quadrant where quadrant incisdes both horizontal-vertical quadrants and diagonally bounded quadrants, This requirement increases the ability to distinguish between random and systematic thimble deletion events. In addition, the confidence on the appropriateness of the incrcmental thimble deletion peaking factor uncertainty values is increased provided that 4 or more thimbles por quadrant are observed to be available, and counting thimbles on the axis and diagonal as whole values.

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l MCGUIRE UNIT 1 CYCLE 7 PAGE-12

. . . . . . . . . - . .. .~ _ . _ _ - . - - . . - . - ~ . . - . - -

l l

1 TABLE 1 INCORE DETECTOR THIMBLE REDUCTION STUDY MAPS Burnup Core Power Percent (MWD /MTU) % Thimble Available (Ref.)

Plant A Cyc 2 MAP 1 2,111 99.7 89.7 MAP 2 6,760 100.0 86.2 MAP 3 11,598 100.0 87.7 Plant A Cyc 3 MAP 1 304 100.0 98.3 MAP 2 10,322 100.0 100.O MAP 3 13,105 100.0 100.0 Plant B Cyc 1 MAP 1 2,950 90.5 98.3

. MAP 2 7,386 98.8 94.8 ,

MAP 3 10,924 98.8 91.4 Plant C Cyc 3 MAP 1 200 100.0 93.1 MAP 2. 5,050 100.0 87.9 Plant C Cyc 4 MAP 1 5,335 100.0 93.1 Plant D Cyc 3 MAP 1 500 100.0 100.0 MAP 2 5,200 97.0 96.6 MAPf3 0,806- 75.0 81.0'

. Plant D~Cyc 4 MAP 180 84.-0 96.6 l-MAP 2 3,715 100.0 93.1 l- 81.0

[- ' MAP 3 4,998 100.5 Plant E Cyc 1 f- ~ MAP 1 2,966 96.0 87.9 MAP 2 9,280 100.0 94.8 MAP 3 14,594 100.0 84.5

\

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l MCGUIRE UNIT 1 CYCLE 7 . AGE-13 lr

.i e

TABLE 2a j

SAMPLE STANDARD DEVIATION AND MEAN FOR INCORE MAPS WITH'50% OF THE THIMBLE AVAILABLE FOR FOUR LOOP REACTOR CORE PARAMETERS F, F, F,,

Plant Cycle MAP S, (%) X, (%) S (%)

3 X (%)

i S (%) 3 Xi (%)

~~

(a,c)

A 2~ 1--

A 2 2 A 2 3 A -3 1 A- 3 2 A 3 3 8 1 1

.B 1 2' B 1 3 C- 3 1 C 3 2 C 4 1 D 3 1 D 3- 2

-D 3 3 D 4 1.

-D. 4' 2 D 4 3

'E 1 1 E 1 2 E '1 ' -- 3 L- S como X scem i

md

TABLE 2b SAMPLE STANDARD DEVIATION AND MEAN FOR INCORE MAPS WITH 75% OF THE THIMBLE AVAILABLE FOR FOUP LOOP REACTOR CORE PARAMETERS F,* F, F,7 Plant Cycle MAP S (%)

3 X (%)

i S (%)

i X (%)

3 S (%)

i X, (%)

(a,c)

A 2 1 A 2 2 A 2 3 A 3 1 h 3 2 A 3 3 B 1 '1 B 1 2

-3 B 1 i C 3 l' C 3 2 C 4 1 D 3 1 D 3 .2 D 3 3 D 4 1 D '4 2 D- 4 3 E 1 1 E 1 2 E 1 3 S w.

l -

!~

h

Plant D Cycle 4 Map 3 S and X, b.. sed on 3 random deletions .

i All I

others based on 5 deletions.

l I

MCGUIRE UNIT 1 CYCLE 7 PAGE-15 I.-. . . _ . _ . _ . _.

. _ - . . . ..~ . . ~ - . _ .

TABLE 2c SAMPLE STANDARD DEVIATION AND MEAN FOR IN00RE MAPS WITH f0% THIMBLES AVAILABLE FOR FOUR LOOP REACTOR CORE PARAMETERS QUAD TILT + A.O.*

Plant Cycle MAP S,(%) X,(%) S,(%) X3 (%)

~

(a,c)

A 2 2 A 2 3 A 3 1 A 3 2 A 3 3 B 1 1 B 1 2 B 1 3 C 3 1 C 3 2 C 4 1 D 3 1 D 3 2 D 3 3 D -4 1 0 ~4. 2 D 4' 3 E 1 1 E 1. ?

E 1 3 S,. k.

+- Standard dedt tien for QUAD TILT about Atilt = (Ref. - Deleted) x 100%.

Standard deviation for A.O. about AA.O. = (Ref. - Deleted).

MCGUIRE UNIT 1 CYCLE 7 PAGE-16

, .... ]

1 TABLE 2d SAMPLE STANDAPD DEVIATION AND MEAN FOR INCCRE MAPS WITH 75% OF THE THIMBLE AVAILABLE FOR FOUR LOOP REACTOR CORE PARAMETERS QUAD TILT + A . ') .

Plant Cycle MAP- S,(%) X,(%) S,(%) X (%)

i (a,c)

A 2 1 A 2 2 ,

A 2 3 A 3 1 A 3 2 A 3 3 B 1 1 B- 1. 2

-B 1 3-C S 1 C 3 2 C 4 1

D 3 1 D 3 2 0 3 3 D 4l 1 D 4 2-D 4 3 E 1- 1 E- 1 2 E 1 3 S,,,,, k.

+ Standard deviation for-QUAD TILT about Atilt = (Ref. - Deleted) x 100% .

E* Standard deviation for A.O. about AA.O. = (Ref. - Deleted). t 1

i4CCUIRE UNIT 1 CYCLE 7 PAGE-17

TABLE 3a

, COMPARISON OF: DROPPED. ROD AND THIMBLE DELETION INCOPE MAPS F, F,- F,,

Thimble Meas. ;Loca- F,- Meas. 'Loca- F, Meas. Eleva-Run

' tion % Diff.* tion % Diff.* F,, tion F,'Diff.*

Burnup. F, F,-

(a, c) .

200 IND/MTU 0

.50A-

.50B

.50C-

.50D

.50E 3: 200 MWD /.TIU 0 c$ .75A N .75B A .75c g .75D R .75E e

w a

E5 N

% Diff. = Ref. - Deleted x 100%

y

.Rei.

E5

?

g - --

,. . . - . .-- . ~ . . . . . ~ . . - . . - . . . - _ ~ . _ . ~

TABLE 3b COMPARISON OF DROPPED ROD AND THIMBLE DELETION INCORE MJJS Thimble Quad Meas.

Burnup Run Tilt Atilt + A.O. AA.O.*=

(a,c) 200 MWD /MTU 0

.50A

.50B

.50C

.500

.50E 200 MWD /MTU 0 t .751 l .75B

.]SC I-

.l5D 75E l

l I: + Atilt =~(Ref. - Deleted).x 100%

! ** 4AO = (Ref. - Deleted) i I~

t l-i

~

MCGUIRE UNIT 1 CYCLE 7 PAGE-19

TABLE 4 TEST PROBLEM

SUMMARY

Min. i Thim. Left in Method 1 or Simulati0ns Analytic Solution i Thimbles Left in Method 1 Method 2 Method 2a 01 is Method 2 % Cases % Cases Probability %

(a,c)

Analytic Solution for Method 1 is not available, l

l t

I l

l l-1 MCGUIRE UNIT 1 CYCLE 7 PAGE-20 I

-. . - . - .. - - . . . . - . . . . . . ~ . . - . . .-. . _ . -.. .

t-TABLE 5 4-LOOP CORE SUV#ARY 3000 CASE THIMBLE DELETION SIMULATIC:;

29 THIMBLES DELETED Minimum'No, of Number of Percent of Cumulative Thimbles Left Cases Cases Percentage (a,c) t 1

h MCGUIRE UNIT 1 CYCLE 7 FAGE-21

i R P N M- L K J H G F E D C B A 1- e ,

i 1

2 e e o f

3 e o e -e 4 e- e. e 5 e e

e 6 e o e e .

7 e e e e B e e e e e e

.e o

9 e e e e e e e .-

- 10 ,

11; *

e

e 1

* * -i 12

- 13. ,

14 * ,

. 15' '

I i 0'

Movable Detector (58)-

Figure 1. Movable Detector Locations for Four Loop Plants MCGUIRE UNIT 1 CYCLE 7 PAGE-22

r

, - 1 l

t (a,c)

!=

i'

[:

i A

-1 t

3

- Figure 2. Thimble Deletion Uncertainty C0mponent Versus Percentage-of Thimbles Available MCGUIRE UNIT.1 CYCLE 7 ,PAGE ,

Analytic Solution: ol-Q3 45 Thimbles Initial 60 Thimbles Ir.itial Total 30 Thimbles Remaining Ol.

15 Thimbles Initial l

l l

Computer Simulation:

No Thimbles on Axis Q1 Q2 60 Thimbles Initial Total 15 15 30 Thimbles Remaining Q4 Q3 15 15 a

CA No Thimbles on Diagonal 15 60 Thimbles Initial Total 30 Thimbles Remaining QD 15 15 CB ~)

s 15 QC i

l Figure 3. Test Problem Description l

MCGUIRE UNIT 1 CYCLE 7 PAGE-24 L

-o .. , _

l l l Ri P N M' L K J G 'F E D C B A 1

1. .- i . .II. a I

1 2 . . p t

i

-3 4 . . .

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I F .

I 7 e e l . .

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y . e..-- m. - e- .- -- - s. .-- s .4- -s . --- --

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cil- :.. . q' . -.

7 j

l *- *

- 12 '

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'A 13 -

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14. .-

l 1

1s :iy1 y 111 l-P' l1 E

-* Movable Detector (58)

Figure 4. Horizcatt; Vertical Quadrants Movable Detector Thimble. Number Scheme f

MCGUIRE' UNIT 1 CYCLE 7 iPAGE-25

t

, A R P N M L K J H G F E D C B A

\ /

/

1

\\ e e

/

f

\ /

2 N . . e /

\ /

s 3 \ s e e o j

f e N /

4 e

N e /

\

/

s 5 \ ~

g N /

6 *

A e / e N /

7

k ,/

0

D8 . . . .

[,'A . . . . B

' 'n .

9 e f .

- s

/

10 * /

N

j N j N 11

p , A

s

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t 12

/ * *

\ s N

13 ,/g' *

N N

/ s 14 / * * * * \

/ \

\

15 f g

/ \

O' C

Movable Detector (58)

Figure 5. Diagonal Quadrants Movable Detector Thimble Number Scheme MCGUIRE UN7T 1 CYCLE 7 PAGE-26

i APPENDIX A THIMBLE DELETION UNCEFTAINTY COMPObENTS 95% PROBABILITY AND 95% Coh.*IDENCE (5,,,+KS,,,)

NORMAL (TYPICAL' FLUX MAPS Eu (a , c)

T. D. Uncert. Component (50%)

7. D. Uncert.. Component (75%)

F, T. D. Uncert. Component (50%)

T. D. Uncert. Component (75%)

l I ny T. D. Uncert Component-(50%)

i=

T. D.:Uncert. Component (75%)

i I

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l-l- MCIA' IRE UNIT 1 CYCLE 7 PAGE-27 i

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? w- , .;:i;s ' .%

r c.,c .-t i fcN g :g m[* < ,

L WO i !

, . AlPENDIX B- .

37 %o, NJ g?# '

.1 m

/N 3 ;: . THIMBLE DELETION UNCERTAINTY COMPONENTS ,

e -j L '(_

- i

- IW j ; , ;. 4 954- PROBABILITY AND 954 CONFIDENCO (Xg + KS;.,)

n s .

1 PEEUDO-DROPPED ROD FLUX MAPS i

-Fa' a:

(a, c)

T. D. Uncert.' Component (50%)-

- i

,.== _ y.

s

~'

T. D. Uncert. Component -(75%)

i

[ ,;g . s ,

w;, , .

m

no , , , r Q ,

lFf

, .l

y. '

?:

< ,!Tl D 'Uncert . -Componen,;- (50%)

-["

i a..:. .T. : D. .-.Unce rt . - Component (75%).

i

Q F r

.g LH

g %

, , ' T.';.D'.) Uncert . , Cotuponent - (50%);

ni ,

+ 'I '

i ._ m T : t D. -Uncert.LCemponent' (75%) _

'. s

$ ,4.E.

~ :, I-t gis ,'-

is .

i J-14 4

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ll MOGUIRE UNIT 1 CYCLE 7-- PAGE-28 !

f 5 e y .e_ m r vr = + = ~ + - --- rr-- er -er-* - - -

7-4 l I

APPENDIX C TWO-SIDED 95% CONFIDENCE LIMITS v:' MEAN A7ILT AND MEAN AA.O

, e.o . i t.,, s ,,, , / hN (approximate t by z) tilt or tilt or A.O. A.O.

QUADPJdIT TILT:

(a , c) 1 AXIAL OFFSET:

(a , c)

MCGUIRE UNIT 1 CYCLE 7 PAGE-29

r i

PROPOSED TECHNICAL _ SPECIFICATION and COLR MODIFICATIONS INSERT A When the number of available movable detector thimbles is less than 75% of the total, the 5% measurement uncertainty shall be increased to

[5% + (3-T/14. 5) (2 % ) ] where T is the number of available thinbles.

INSERT B When the nur ser of available movable detector thimbles is less than 75% of the total, the 4% measurement uncertainty shall be increased linearly by 1%

as specified by the COLR.

INSERT C When the number of available movable detector thinbles is less than 75% of the total the 4% measurement uncertainty shall be increased to

[4% + (3-T/14.5) (1%)1 where T is the number of availaole thimbles.

-INSERT D a)

F ,"' = 1.49 for % of available thimbles 275%

F,'" =

[(0.0149/14.5)7 + 1.4453) for % of available thimbles 250% and <75%

where T is the number of available thimbles, i

MCGUIRE UNIT 1 CYCLE 7 PAGE-30

(;.

n

.i

?

ATTAClIMENT 3 .

Analysis- of Significant llar.ards Consideration

.e r

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1 i

i I

Q Analysis of Significant !!azards Consideration:

As required by 10CFR 50.91, this analysis is provided concerning whether the proposed amendments involve significant hazards considerations, as defined by 10CFR 50.92.- Standards for determination that a proposed amendment involves no significant hazards considerations are if operation ~of the facility in accordance with the proposed amendment would not: 1) involve a significant increase in the probability or consequences of an accident previously evaluatodi or 2) create the possibility of a new or different kind of accident from any accident previously evaluated; or 3) involve a significant reduction in a margin of safety.

The proposed amendments are a change for McGuire Unit 1 Cycle 7 to reduce from 75% to 50% the number of available moveabic incore detector thimbles required for the Moveable Incore Detection System to be operable, thus allowing continued operation of Unit I should a current problem with sticking detector thimbles become worse. !

The proposed amendments would not involve an increase in the probability of an accident previously evaluated. The Moveable Incore Detection -

System is used only to provide confirmatory information on the neutron flux distribution and is not required for the day-to-day safe operation of the core. Its information is not considered in the accident analyses. The system is not a process variable that is an initial condition in FSAR Chapter 15 analyses.- The only previously evaluated accident the system could be involved in is breaching of the detector thimbles (due to wear by the detectors for example) which would be enveloped by the small break loss of coolant accident (LOCA) analysis.

As the proposed changes do not involve any changes to the system's equipment and no equipment is operated in a new or more deleterious L manner, there is no increase in the probability of such an accident.

l- The proposed' amendments would not involve an increase in the consequences of an accident previously evaluated. The-Moveable Incore Detection System is not used for accident mitigation (the system is not used in the primary success path for mitigation of a Design Basis Accident). The system is a control system not required for safety. The ability of the Reactor _ Protection System or Engineered Safety Features System instrumentation to mitigate the consequences of an accident have l not been impaired._ The small break LOCA analysis (and thus its consequences) continues to bound potential breaching of the system's detector thimbles. Therefore, the change does not involve an increase in the probability or consequences of an accident previously evaluated.

The proposed amendments would not create the possibility of a new or different kind of accident from any accident previously evaluated as they only. affect the minimum complement of equipment necessary for operability of the Moveable Incore Detection System. As discussed above, no new equipment is introduced and no equipment is operated in a

--new manner. Thus the changes could create no new or different accident causal mechanisms. Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated since it does not modify plant operation or 1-components.

J

f l The proposed amendments would not involve a significant reduction in a margin of safety. The reduction in the minimum complement of equipment necessary for operability of the Moveable Incore Detection System could only impact the monitoring / calibration functions of the system.

Reduction of the number of available moveable incore detector thimbios to the 507.-level does not significantly degrade the ability of the Moveable Incore Detection System to measure core power distributions.

. Core peaking factor measurement uncertainties will be incrcased, but will be compensated for by conservative measurement uncerta'nty adjustments in the Te ;tnical Specifications to ensure tL -tinent core design parameters are maintained. Sufficient additional penalty is added to the power distribution measurements such that this change does not impact the safety margins which currently exist. Also, available detector thimble reduction has negligible impact on the quadrant tilt and core average axial power shape measurement. Sufficient detector

-thimbles will be available to ensure that no quadrant will be unmonitored. Based on these factors, the margin of safety is not reduced as the core will continue to be adequately monitored.

In addition, similar changes for other plants in the past (as well as for McGuire Unit 1 Cycle 6) have been determined not to involvo Significant Hanards Considerations. ,

Based upon the preceding analysis, Duke Power Company concludes that the z proposed amendments do not involve a Significant Hazards Consideration..

l

-

ML20065T187

Text

Conclusions:

SUMMARY

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