ML20059L139

Core Spray Crack Analysis for Peach Bottom Unit 3

ML20059L139
Person / Time
Site:	Peach Bottom
Issue date:	11/30/1993
From:	Booth R, Plaxton S, Torbeck J GENERAL ELECTRIC CO.
To:
Shared Package
ML20059L136	List: ML20059L139
References
GENE-637-040-11, GENE-637-040-1193-R0, GENE-637-40-11, GENE-637-40-1193-R, IEB-80-13, NUDOCS 9311160313
Download: ML20059L139 (23)

Text

_ _ _ _ _ -_ _ _ _

9 GENE-637-040-1193, Rev. O Class II DRF A00-05807 November 1993 j i

J i

CORE SPRAY CRACK ANALYSIS i FOR  !

PEACH BOTTOM UNIT 3 l i

i F

Prepared:

It.H.' Booth, Engineer l Plant Perfonnance Analysis Projects b

S.E. PlaxtE Engi6 '._

Structural Mechanics Projects  ;

Approved:

'. Torbeck, Project Manager Plant Performance Analysis Projects I

l I

l 9311160313 931105 gDR ADOCK 05000278 l"l l PDR jf __

j_

i i

1 GENE-637-040-1193, Rev. O J .

I

IMPORTANT NOTICE REGARDING  !

1 CONTENTS OF THIS REPORT l i

i  :

Please Read Carefully  :

i The only undertakmgs cf the General Electric Company (GE) respectmg infonnation in this j document are contamed in the contract between the Philadelphia Electric Company and GE, and ,

l nothing contamed in this document shall be construed as changmg the contract. 'Ibe use of this information by anyone other than the Philadelphia Electric Company , or for any purpose other than that for which it is intended under such contract is not authorized; and with respect to any j unauthorized use, GE make no representation or warranty, expressed or implied, and assumes no liability as to the completeness, accuracy, or usefulness of the information contamed in this i document, or that its use may not infnnge privately owned rights.  ;

t  ;

I

?

I 6

t i

i f 1

?

?  !

i s

i l

)

j  :

3 I

_ , . . _ _ _ . . - - _ , . I

GENE-637-040-1193, Rev. O TABLE OF CONTENTS P_ alt

1.0 INTRODUCTION

AND

SUMMARY

l-1 1.1 CRACK LEAKAGE ESTIMATE l-1 1.2 STRUCTURAL /WALYSIS 1-1 1.3 LOST PARTS ANALYSIS 1-2 1.4 EFFECT ON LOCA ANALYSIS 1-2

1.5 CONCLUSION

S 1-2 -

2.0 CRACK LEAKAGE ESTIMATE 2-1 2.1 ESTIMATE BASED ON PREVIOUS TESTS 2-1 2.2 ESTIMATE BASED ON ANALYTICAL METHODS 2-2

2.3 CONCLUSION

S 2-2  ;

3.0 CORE SPRAY PIPE STRUCTURAL INTEGRITY 3-1 3.1

SUMMARY

3-1 3.2 ALLOWABLE FLAW SIZE DETERMINATION 3-1 3.3 CRACK GROWTH ESTIMATE 3-3 3.4

SUMMARY

AND CONCLUSIONS 3-3 4.0 LOSTPARTS ANALYSIS 4-1

4.1 INTRODUCTION

4-1 4.2 LOOSE PIECE DESCRIPTION 4-1 4.3 SAFETY CONCERNS 4-1 4.4 EVALUATION 4-1 ,

4.4.1 General Description 4-1 i 4.4.2 Postulated Loose Pieces 4-2 4.4.2.1 Core Spray Pipe 4-2 4.4.2.2 Small Pieces 4-2

4.5 CONCLUSION

S 4-4 5.0 IMPACT ON ECCS ANALYSIS 5-1

6.0 REFERENCES

6-1

GENE-637-040-1193, Rev. O

1.0 INTRODUCTION

AND SUMhMRY I

During the current refueling and maintenance outage, the vessel in-senice inspection identified a crack indication (Figure 1-1) on the core spray line at Peach Bettom Unit 3 Atomic ,

Power Station. The indication was identified using an under water camera during the inspection in response to IE Bulletin 80-13 (Reference 1). The crack indication is located in the vertical section of the core spray line outside the shroud but inside the Reactor Pressure Vessel (RPV) where two sections of piping meet and are connected by two circumferential welded metal sleeves. He following additional information was provided by Philadelphia Electric Company (PECo):

a) He crack is approximately 3.0 inches in length along the outside diameter of the pipe based on visual measurements.

b) He cract. is approximately 0.25 inches below the upper most weld based on visual measurements.

c) No other cracks were found in the B loop of the core spray line.

GE Nuclear Energy has performed an evaluation to address the safety significance of the crack. He technical basis to support the continued structural integrity of the core spray line through the next fuel cycle for all normal and injection conditions is provided. A discussion of the possible consequences of potential loose pieces from a cracked pipe is also presented. Firally, the consequences of a postulated Loss-of-Coolant Accident (LOCA) with a crack in the core spray piping are discussed.

t 1.1 CRACK LEAKAGE ESTIhMTE l

i A bounding estunate of the leakage through the crack is presented in Section 2. The j results indicate that for this crack configuration including the postulated crack growth, the total ,

I leakage flow is conservatively estimated to be 7 gpm.

l.2 STRUCTURAL ANALYSIS The structural analysis, presented in Section 3, concludes that the integrity of the core spray piping will be maintained for all conditions of operation including a LOCA over the next operating cycle. The crack is estimated to grow no more than 1.4 inches during this 24 month cycle to a total length of 4.4" (80* circumferential) which is much less than the maumum allowable crack size of 270* (15.0 inches) which will assure core spray line integrity.

l

)

1-1 1

GENE-637-040-1193, Rev. 0 1.3 LOST PART ANALYSIS Because continued core spray line structural integnty was demonstrated, lost parts (loose pieces) are not expected. Nevertheless, a lost parts analysis has been performed and is presented in i Section 4. It is concluded that the probability of unacceptable flow blockage of a fuel assembly or unacceptable control rod interference due to lost parts is negligible. The potential for corrosion or other chemical reactions with reactor materials does not exist because the piping material is designed for in-vessel use. Therefore, it is concluded that there is no safety concern posed by any postulated loose parts.

1.4 EFFECT ON LOCA ANALYSIS i

Section 5 presents the results of the LOCA evaluation. The evaluat'on shows that the l difference between the core spray flow rate used in current LOCA analyses and the Technical l i

Specification requirement for core spray flow is large compared to the small amount of leakage estimated through the crack. Therefore, it is concluded that there will be no impact on LOCA analyses due to the crack in the core spray line.  ;

i

1.5 CONCLUSION

S ,

f A detailed evaluation of the Peach Bottom Unit 3 core spray crack has been performed.

This evaluation included structural, lost parts and LOCA analyses to determine the impact on plant operation with the crack in the core spray piping. Based on the analysis, it is concluded that Peach >

Bottom Unit 3 can safely operate in this condition during the next fuel cycle, and that no operational changes or restrictions are required during that period.

l l

l l

l l

l-2

J IENE-637-040-II93, Rev. 0

)

1 1

l CORE SPRAY l LINE CRACK

, l i WELD -+ ' \

l -

DOWNCOMER

}- 3" 4 ANNULUS g

1 l

SLEEVE

)

! l I

I I

i I

l

, l l

SLEEVE I I

e TO SHROUD l

I 1

I N

l l l

\

l 4

I

' FIGURE l-1: CORE SPRAY LINE CRACK LOCATION I

' l-3

(.-.-. .-. . . - . . . _ -

I GENE-637-040-1193, Rev. O j l -

J 2.0 CRACK LEAKAGE ESTIMATE 2

There are no direct measurements ofleakage from the crack during the operation of the l core spray system. However, from previous analyses and tests performed for the cracks observed in BWRs, it is possible to establish an upper bound leakage for the crack identified at the Peach l Bottom Unit 3 Plant.

2.1 ESTIMATE BASED ON PREVIOUS TESTS .

The signincance of previous c:::k occurrences at BWRs has been assessed by both visual inspections and air-bubble tests. Based upon these inspections and tests, the upper bound leakage for any core spray line crack was estimated to be less than half the leakage through the 1/4 inch vent hole present in the T-box. (He vent hole is part of the original piping design and is included to allow the release of any non-condensable which could collect in the core spray piping).

The vent hole is a 1/4 inch hole present in the T-box. The leakage rate through the vent hole is estunated assuming incompressible Bernoulli flow through the hole:

Q = CA)2gp /p where, C = flow coefficient (assumed to be 0.6 for an abrupt contraction)

A = area p = mass density of fluid AP = pressure difference across the pipe / vent ne flow rate through the vent hole was determined using a bounding pressure of 150 psid across the core spray line. This corresponds to the maxunum differential pressure expected during the rated core spray flow conditions. Utilizing the equation above, the estimated leakage rate through the vent hole during a LOCA was determined to be less than 14 gpm. Therefore, during the core spray injection phase of a LOCA, the total leakage through the crack is expected to be less than 7 gpm (one-half of the vent hole leakage).

2-1

GENE-637-040-1193, Rev. 0 2.2 ESTIMATE BASED ON ANALYTICAL METHODS I

In order to estimate the maximum leakage expected through the crack, the configuration l for a 180 through-wall crack was used. He 180* crack length is very conservative compared to I 1

the maximum crack size of 4.4" (80 ) predicted in Section 3.3. A linear clastic fracture mechanics ]

(LEFM) analysis using the applied loads described in Section 3.2 and the 180* through-wall crack l

configuration was performed to predict the t. rack opening. Using the calculated crack opening, the  !

leakage was estunated to be less than 6 gpm. i l

2.3 CONCLUSION

S Based on information from the Peach Bottom Unit 3 inspection, it is consenatively predicted that the crack in the core spray line will grow to 4.4 inches in length (80*) during the i next operating cycle. An analytical estimate of the leakage with a 180 crack was 6 gpm.

However, utilizing the test results from previous crack occurences, the maxunum leakage from the core spray line crack is conservatively estimated to be 7 gpm which is one half of the vent hole leakage. l i

l f

i i

P I

l i

1 1

2-2 i

- + - - m-- - -,.,

,_l

1

( .

i l

GENE-637-040-1193, Rev. O j l

3.0 CORE SPRAY PIPE STRUCTURAL INTEGRITY l

l I

The structural integrity aspects of the core spray piping have been resiewed to assess the i I

impact the crack could have on the structural integrity of the piping. Structural analyses were  ;

i performed to determine the potential sources of stress in the piping and the likelihood of crack 1

propagation. Although there is currently not enough information to definitively detemune the mode of cracking, it is expected that the crack is due to an Intergranular Stress Corrosion Crackmg 1

(IGSCC) mechanism. He results of these assessments are discussed below.

3.1

SUMMARY

l All identified stresses expected during normal reactor operation and LOCA were found to be small. Based upon a review of these stresses, it is concluded that the structural integrity of the piping with the crack will be maintained during core spray injection. The stresses considered include those due to seismic loading, pressure, weight and core spray flow induced loads.

Although the normal operating loads by themselves do not result in stresses which are sufficient to cause IGSCC initiation, the addition of the weld residual stresses coupled with local cold work could result in exceedmg the initiation threshold. Once initiated, the normal operating load stresses and the residual stresses could cause subsequent growth of the induced cracks.

3.2 ALLOWABLE FLAW SIZE DETERMINATION An evaluation was performed to determine the maximum allowable circumferential through-wall flaw size in the core spray pipe. This analysis provides an assessment of the safety margin in the pipe due to primary loads such as deadweight, pressure, core spray flow and seismic.

A finite element model of the core spray pipe was developed to obtain the stresses due to deadweight and seismic load on the pipe at the location ofinterest using the ANSYS computer code (Reference 4). A sketch of the finite element model is shown in Figure 3-1. The following boundary conditions were applied to the model:

Nodes I,31,35,80: completely fixed Nodes 25,56 fixed in vessel radial direction to account for bolted vessel clamps.

3-1 I

1 GENE-637-040-1193, Rev. 0 Loads due to the weight of the pipe (including captured water in the pipe) were applied to l

the model along with vertical and horizontal seismic loads. The largest resulting stresses in the i

region of the crack (nodes 6-8) were used from the finite elemer.t model results.

He resulting stresses were then combined with the stresses due to pressure and core spray i flow loads in order to get the total stresses acting on the pipe. Stresses due to downcomer flow impingement are compressive in the crack area and conservatively neglected. Based on presious l

experience, stresses due to water hammer and thermal mismatch loads were considered insignificant and neglected in this analysis. He resulting total stresses are shown in Table 3.1.

TABLE 3.1 RESULTING PRIMARY STRESSES IN CORE SPRAY LINE l

Membrane Stress, Pm 859 psi Bending Stress, Pb 336 psi The stresses of Table 3.1 were utilized to determine the acceptable through-wall flaw size based on the net section collapse formulation of Reference 5. He acceptable flaw size was determined by requinng a suitable design margm on the critical flaw conditions. The critical flaw size was determined by using limit load concepts. It was assumed that the pipe with a circumferential crack was at the point ofincipient failure when the net section at the crack developed a plastic hinge. Plastic flow was assumed to occur at a critical stress level, ef, called the l flow stress of the material. For ASME Code analysis, o rwas conservatively taken as equivalent to f 3Sm. This resulted in considerable simpli6 cation of the analysis.

I Consider a circumferential crack oflength, I = 2Ra, and constramt depth, d, located as ,

shown in Figure 3-2. In order to determine the point at which collapse occurs, it is necessary to apply the equations of equilibrium assuming that the cracked section behaves like a hinge. For this condition, the assumed stress state at the cracked section is as shown in Figure 3-2 where the maximum stress is the flow stress of tl e material, ro . Equilibrium oflongitudinal forces and i moments about the axis gives the followrg equations: l 1

1 l

3-2 l l

l

l l

l GENE-637-040-1193. Rev. O I l

(For neutral axis located such that a + p < x) l l p = [(x - ad/t)-(Pm/a r)x]/2 l

l

! Pb= (2a/x)(2 sin p -d/t sin a)  ;

l r

where, t = pipe thickness, inches.

a = crack half-angle as shown in Figure 3-2.

i p = angle that defines the location of the neutral axis.

Using the stresses of Table 3.1 and a d/t ratio of 1.0 (through-wall flaw), the allow 2ble through-wall crack for which failure by collapse might occur is 270' i

l 3.3 CRACK GROWTH ESTIMATE l

In order to estimate the crack growth during the next 24 month operating cycle, a conservative IGSCC crack growth rate at moderate conductivity for 304 stainless steel is assumed (4x10-5 in/ hour) and crack growth from both ends of the crack is considered. He assumed IGSCC .

crack growth rate used in this analysis is conservative compared to the rate predicted by the NRC curve (Reference 6). Using the NRC curve, the assumed crack growth rate of 4x10-5 in/ houris predicted at a stress intensity factor, K, of 25 ksi(in)la. Since the subject crack is assumed to be through wall (thus, the weld residual stress induced K is expected to be very low) and the applied stresses are low, the K values are expected to be less than 25 ksi (in)lU for realistic crack geometries. Based on the crack growth rate of 4x10-5 in/ hour it is estimated that the current crack size will grow approximately 1.4 inches during the next 24 month cycle to 4.4 inches in total length (less than 80* of the pipe circumference).

3.4

SUMMARY

AND CONCLUSIONS Re potential sources of stress in the piping resulting from normal operation and operation during postulated Loss of Coolant Accidents were reviewed. An assessment nas made to determine the critical flaw size of the core spray pipe by treating stresses associated with the design loadings as primary stresses and performing a net section collapse evaluation. The results of this evaluation confirm that a through-wall crack of up to 270 around the circumference would not cause pipe failure. This length is much greater than the maximum estunated crack length at the end of the next fuel cycle (predicted to be 4.4 inches, 80 circumferential). Herefore, it is 3-3

GENE-637-040-1193, Rev. 0 l I i

concluded that the structural integrity of the piping with a crack will be maintained for all i anticipated conditions including those of a hypothetical LCP.A far the next operating cycle.

)

L I

i i

I f

, r P

I F

t E

1 t

i 3-4 i

l 1

ANSYS 4.4A1 .

NOV 3 1993 15:01:39 POSTI ELEMENTS TYPE NUM TDIS h V 1 r 2V -1 DIST-134.486 f YF -67.783 x ZF --51.38

\ ANGZ--60

3s n 2 !E m

Y

( '

31 $

~

i 25 x g

k80 O l

l v7 1

h i FIGURE 3-I

PEACil BOTTOM 3 CORE SPRAY LINE ANALYSIS

- _ _ _ _ . . _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ . - - - - . . _ - - - v i.v<---r - = ,.. -- -.-.- .-,...-m __-_v.--w,,._wv - .>-w _-,-__.______________m___

Hominal Stress in the Uncracked Section of Pipe Crack Length = 2Ra Pm+Pb

-> + Flow Stress, a , g->

I 4- . , - .

, d 4-l, ,

s 4 .

g\ l s ./ 4_. ( i

\l#

f t > 4- 4 I

' '8

$ ' R P.l 4- , .s a E

f

^

N I l ..w ) \ n y . . ,

____________ J p a '

., _ i E

~ '

Neutral  ! .

Axis I s' Pm-> +

• o Stress Distribution in Pm - Applied Membrane Stress in Uncracked Section the Crocked Section at the Point of Collapse Pb = Applied Bending Stress in Uncrocked Section FIGURE 3-2:

STRESS DISTRIBUTION IN A CRACKED PIPE AT Tile POINT OF COLLAPSE

]

4 GENE-637-040-1193, Rev. O l

i 1 4.0 LOST PARTS ANALYSIS ,

4.1 INTRODUCTION

Based on the structural analysis given in Section 3, it is expected that the Peach Bottom i Unit 3 Atomic Power Station core spray pipe will not break and consequently, will not result in l I

loose pieces in the reactor. However, an evaluation of the possible consequences of a potential loose piece is presented in this section.  ;

i 4.2 LOOSE PIECE DESCRIPTION i

i

~

i Since a piece has not been lost, it cannot be uniquely described. Two different types of loose pieces are postulated:  :

1) a section of core spray pipe, and;

2) a small piece of the core spray pipe. i 4.3 SAFETY CONCERNS l The following safety concerns are addressed in this analysis. [

1) Potential for corrosion nr other chemical reaction with reactor materials.

2) Poten:ial for fuel bundle flow blockage and subsequent fuel damage.

3) Potential for interference with control rod operation.  !

l

4.4 EVALUATION The above safety concerns for the postulated loose pieces are addressed in this section.

The effect of these concerns on safe reactor operation is also addressed.

4.4.1 General Description Since the core spray pipe with the crack is in the anr ular region of the reactor pressure vessel, a potential loose piece generated from the core spray pipe will most likely sink into the downcomer region.

For a loose part to reach, and potentially block the inlet of a fuel assembly, it would have to be carried into the lower plenum. To accomplish tids, it would have to be carried q the 4-1

GENE-637-040-1193, Retr. 0 9

recirculation flow through the jet pump nozzle into the lower plenum, then make a 180 turn and be j carned upward to the fuel assembly inlet orifices.

For a piece of the core spray pipe to reach a control rod it must first migrate to the lower plenum, pass through the fuel inlet orifice, and traverse the fuel bundle. Then, it must either fall through the restrictive passage between two fuel channels, or fall through an opening between the peripheral bundles and the core shroud. Both of these potuntial paths are unlikely.

The core spray pipe is fabricated from Type-304 grade stainless steel and all parts of the  ;

core spray pipe are designed for in-reactor senice. Consequently, there is no postulated loose part that will cause any corrosion or other chemical reaction with any reactor material.

4.4.2 Postulated Loose Pieces 4.4.2.1 Core Spray Pipe The core spray pipe is 6 inch Schedule 40 pipe. In order to generate a loose piece of pipe, ,

a minimum of two through-wall cmcks would have to propagate 360' around the pipe. Due to the slow propagation rate of potential cracks, and based on previous experience with cracks in core spray spargers, it is judged that a piece of the piping will not break off and become loose.

If a pipe segment were postulated to break off, it would sink into the downcomer region.

Since it cannot fit through the jet pump, it cannot enter the lower plenum, and therefore will not cause any flow blockage at the fuel inlet orifice or cause any interference with control rod operations.

4.4.2.2 Small Pieces in order to generate smal! pieces of the core spray pipe, both longitudinal and l circumferential through-wall cracking must occur. Small pieces, if assumed to be generated, could sink and be carried into the downcomer annulus. Larger pieces would most likely come to rest on thejet pump support plate since it is unlikely they would achieve the correct orientation required to fall through thejct pump openings. Small pieces could also come to rest on thejet pump support plate, however, some may pass through thejet pump and enter the lower plenum. Some of the small pieces could also be entrained into the recirculation line and enter the lower plenum after l passing the recirculation pump. Thus, pieces entering the lower plenum are expected to be small 4-2

i GENE-637-040-1193, Rev. O and would probably be driven by the jet pump flow to the bottom of the reactor pressure vessel where they would be expected to remam i

Smaller pieces could be carried by the flow up to the fuel inlet ori5ces. The orifice sizes in l

the Peach Bottom Unit 3 Plant vary from approximately 1.24 to 2.21 inches in diameter (Figure 4-l 1). It is extremely unlikely that a piece from postulated pipe cracks could block the inlet orifice and cause substantial flow blockage since only small pieces could enter the lower plenum and be lifted to the inlet orifice. These pieces would most likely pass through the inlet orifices and be trapped at the lower tie plate grid and cause some bundle flow blockage. However, the flow blockage is expected to be much less than that required to initiate cridcal boiling transition in the bundle.

Multiple pieces migrating to the same bundle may result in critical flow blor,kage, but the probability for such an occurrence is extremely low.

It is also very unlikely that a small piece could lift and migrate from the lower plenum through the fuel bundle and fall into the control rod guide tube. In order to do this, the piece would have to be so small that it could pass through all the bundle spaccrs and out through the top of the bundle. Such a small piece would not present any potential for control rod interference.

Figure 4-2 shows a typical unit cell of four fuel assemblies and one control rod. He control rod moves in the gap between the fuel channels. Here is a small possibility that a piece small enough to fit in the gap between the channel wall and control blade could sink and pass through the cavity between the control blade and the fuel support casting and migrate into the control rod guide tube. Should this happen the piece will most likely come to rest on the top of the velocity limiter where it is expected to remain and move only with the movement of the velocity limiter as the control rod is inserted or withdrawn. If the piece is small enough to pass between the velocity limiter and the guide tube wall it will most likely sink and come to rest at the bottom of the guide tube. Rus, any potential small piece which migrates to the control rod guide tube is not expected to pose any concem for potential interference with control rod operation.

4-3

1

. l l

! GENE-637-040-1193, Rev. O i l

i l

4.5 CONCLUSION

S l The core spray pipe at Peach Bottom Unit 3 is expected to remam intact; therefore, it is  ;

.n highly unlikely that pieces of the core spray pipe will break off. Even ifpieces are gs.sted, the l above evaluation shows that the potential for unacceptable flow blockage or other damage to the j i

fuel assemblies is negligible. It is also concluded that the probability for unacceptable corrosion or (

other chemical reaction due to loose pieces is zero since the pipe material is designed for in-vessel  !

t i

use. The potential for unacceptable control rod interference is negligibly small. 'Therefore, it is concluded that there is no safety concern posed by any postulated loose parts.  ;

1 1

4 b

t

[

f

.i i

i i

! i i

l l

l l

l r

l 4-4 l

GENE-637-040-1293. Rev. O j j . -. _

p W  !

i' i ___

\ f

), _-

J V ,

• i l

=

9 J

{0hhdi) _-

~

i t j MODERATOR OPEND4G FOR CONTROL ROD BLADE ,

FLOW PATH

] ,

5 4k -

4k

(

) .

! IN CORE GUIDE

's j

i TUBE t

/g;.:< - .

i

[ ,

i I

l 3

/ .

{ { ,,J s CORE PLATE  :

) ,

(5 i

Cl se 0  ;

d!

CONTROL ROD l GUIDETUBE g

j -

lW l 1

INLET ORIFICE i

I FIGURE 4-1: ORIFICED FUEL SUPPORT 4-5

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

i GENE-637-040-1193, Rev. O t

I i -

l .

\

s .. .

m_

m FUEL N 2 5 3 ASSEMBLIES / '

,s 4

& CONTROL r E

• ROD MODULE '4 16 56  !

1. TOP FUEL GUIDE i

2. CHANNEL FASTENER ~' ~

' '3

3. UPPER TE PLATE '

i 4. EXPANSION SPRING

l

! 5. LOCKING TAB

l

6. CHANNEL 9 l l l 7. COffrROL ROD

' / l

8. FUEL ROD .

l 9. SPACER l 10. CORE PLATE ASSEMBLY -

l 11.LOWERTE PLATE

12. FUEL SUPPORT PIECE -

13. FUEL PELLETS .  ;

l

14. END PLUG -

! 15. CHANNEL SPACER

! 16. PLENUM SPRING t 1

10 11 l

. 12 -

1 l

l FIGURE 4-2: FUEL ASSEMBLIES AND CONTROL ROD MODULE 4-6 l

l GENE-637-040-1193, Rev. 0 ,

I 5.0 IMPACT ON ECCS ANALYSIS His section describes the effect the core spray line crack will have on ECCS performance.

A loss-of-coolant accident (LOCA) analysis was recently performed for Peach Bottom 2/3 using SAFER /GESTR-LOCA (Ref. 2). The analysis incorporated values for some emergency core cooling system (ECCS) performance parameters that are more consersative than the current i Technical Specifications and expected equipment performance. Rese calculations were performed in accordance with the NRC requirements and demoristramd conformance with ECCS acceptance criteria of 10CFR50.46 in which the Appendix K Peak Clad Tempe.ature (PCT) must be less than 2200 F.

'Ik core spray (CS) flow rate assumed for each loop in the above referenced Peach Bottom 2/3 SAFER /GESTR-LOCA evaluations was 5000 gpm at a RPV pressure of 105 psig (Ref. 2). This value reflects the CS flow rate which is assumed to actually inject inside the core l shroud, and is 1250 gpm less than the Technical Specification of 6250 gpm per core spray system at 105 psig.

l From Section 2 a leakage flow rate of 7 gpm through the core spray line crack was estunated. As stated above, there is a 1250 gpm margin assumed in the core spray flow rate for I the SAFER /GESTR-LOCA analysis (Ref. 2). This margm of 1250 gpm is much greater than the total estunated leakage flow of 7 gpm from a crack in the CS line. Hus, the SAFER /GESTR-LOCA analysis for both the nominal and Appendix K assumptions as documented in Reference 2 covers, with significant margin, the estimated leak through the CS line crack.

l Following is a summary of the SAFER /GESTR-LOCA analysis of Reference 2. For the Peach Bottom plant only two single failure candidates are potentially limiting for ECCS performance following a LOCA. These are associated with the limiting break which is a ,

I recirculation suction pipe break (Ref. 2). Rese limiting cases are: l A. Battery Failure. This postulated failure leaves I core spray (LPCS) + 3 Low Pressure Coolant Injection (LPCI) + the Automatic Depressurization System (ADS) operable; B. LPCI Injection Valve Failure. This postulated failure leaves 2 LPCS + 2 LPCI +

High Pressure Coolant Injection (HPCI) + the ADS operable.

5-1 l

GENE-637 040-1193, Rev. 0 i

Since the HPCI (High Pressure Coolant Injection) is steam turbine pum. 4 it is not a t significant contributor to mitigating medium to large breaks which depressurize the reactor vessel rapidly. Also, since the function of the ADS is to depressurize the reactor as a backup to the l

HPCI, it contributes little toward mitigatmg medium and large break LOCAs. Therefore, failure j mndide~ A and B result in a @h on only the low pressure ECCS. j f

'Ihe Reference 2 nommal LOCA analysis showed that for large breaks the Design Basis  !

Accident (DBA) suction line break with battery failure was the limiting transient with a PCT of 1024* F. For small breaks a 0.08 ft2discharge break with battery failure was limiting with a PCT j of 1051* F. The limiting Appendix K case occurs for the DBA recirculation suction line break ,

with battery failure. LOCA analysis results show a PCT of 1682* F for this break. ' Ibis value is well below the 2200* F Appendix K limit.  ;

i I

t i

l l

I i

1 l

l l

l ,

i 5-2 ,

I

. 1 GENE-637-040-1193, Rev. 0

6.0 REFERENCES

i

1. USNRC IE Bulletin No. 80-13, Cracking in Core Spray Sparger, May 12,1980 l

2. Bott, C.P. and D.C. Serell, Peach Bottom Atomic Power Station Units 2 and 3 l l SAFER /GESTR-LOCA Loss-of-Coolant Accident Analysis. GENE NEDC-32163P, l January 1993.

l l 3. Core Sorav Scarcer Crack Analysis at Peach Bottom Atomic Power Station l Umt 2, GENE NEDO-22139, May 1982.

l

4. DeSalvo, G.J., Ph.D. and Swanson, J.A., Ph.D., ANSYS Encineerine Anah sis System User's Manual. Revision 4.1. Swanson Analysis Systems, Inc., Houston, PA, March 1, 1983.

5. Rangannth. S. and Mehta, H.S., " Engineering Methods for the Assessment of Ductile Fracture Margin in Nuclear Power Plant Piping," Elastic-Plastic Fractum: Second Symposium, Volume II - Fracture Resistance Curves and Engineering Applications, ASTM STP 303, C.F. Shih and J.P. Gudas, Eds., American Society for Testing and Materials,1983, pp. II-309 330.

6. Hazelton, W.S. and W.H. Koo, Technical Reoort on Material Selection and Proecssing Guidelines for BWR Coolant Pressure Boundarv Pininc. Figure 2, NUREG-0313, Rev. 2, January 1988.

l 6-1