ML18153A760

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Forwards one-time Relief Request from ASME Section XI Pressure Boundary Leakage Corrective Action & Flaw Evaluation Requirements to Permit Determination of Operability for Pump
ML18153A760
Person / Time
Site: Surry 
Issue date: 09/11/1995
From: Ohanlon J
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
95-470, NUDOCS 9509140006
Download: ML18153A760 (24)
v • d • e


Text

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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 September 11, 1995 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 1 ASME SECTION XI RELIEF REQUEST Serial No.

NL&P/ETS Docket No.

License No.95-470 R1 50-280 DPR-32 On September 9, 1995 evidence of minor leakage (less than two drops per minute) was detected on the Unit 1 'A' Residual Heat Removal (RHR) pump casing. Although available to perform its intended safety function, the 'A' RHR pump does not meet the ASME Code acceptance criteria due to through-wall leakage. An evaluation, which included a quantitative structural analysis, determined the pump to be fully capable of performing its intended safety function.

Therefore, pursuant to 10 CFR 50.55a (g)(5)(iv) a one-time relief is requested from ASME Section XI pressure boundary leakage corrective action and flaw evaluation requirements to permit a determination of operability for the pump. The relief request and the basis for this request is provided in Attachment 1. provides the results of the quantitative structural analysis assessment.

This request has been approved by the Surry Station Nuclear Safety and Operating Committee. If you have any questions or require additional information, please contact us.

Very truly yours,

~?~

James P. O'Hanlon Senior Vice President Nuclear Attachments

  • 1
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_t,'.i:J1.}r~U 9509140006 950911 PDR ADOCK 05000280

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cc:

U.. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.

  • Atl~nta, Georgia 30323 Mr. M. W. Branch NRG Senior Resident Inspector Surry Power Station

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Surry Power Station Unit 1 ASME Relief Request

I.

IDENTIFICATION OF COMPONENTS System:

Class:

Drawing:

Component:

Residual Heat Removal (RHR)

ASME Class 2 Surry Unit 1 - 11448-WMKS-RH-P-1A 1-RH-P-1A II.

IMPRACTICAL CODE REQUIREMENTS Since the 'A' RHR pump cannot be adequately isolated to assure an acceptable repair at the existing temperature and pressure, the plant must be depressurized to perform the repair. It is desired to perform this repair with the fuel off-loaded when the RHR system is not required to provide shutdown cooling. This condition would also permit double isolation of the RHR System.

However, to get the fuel off-loaded the RCS must be depressurized and RCS inventory initially reduced for removal of the reactor vessel head. At this point, the RCS loops are inoperable and only the RHR loops are available to meet the shutdown cooling requirements of TS 3.1.A.1.d and TS 3.10.A. 7.

The requirements of IWA-5250, Corrective Measures, and IWC-3600, Analytical Evaluation of Flaws, as applied to through-wall leakage are considered impractical for the specific flaw identified and the limited period of operation to depressurize and defuel (i.e., approximately ten days). The 9ode of reference is the 1989 Edition of ASME Section XI for Surry Unit 1.

Ill.

BASIS FOR RELIEF A through-wall leak has been identified on 1-RH-P-1 A. The pump is cast ASTM A351 Gr. CF-BA, 304 stainless steel. The leak has been quantified as less than two drops per minute. This leakage site is approximately 0.50 inch in diameter located approximately 2 to 3 inches from bottom dead center on the suction side of the pump casing.

The leakage site has a pitted, almost "spongy" appearance. Furthermore, the defect appears to have grown by a relatively slow corrosion mechanism. Visual examination of the leakage site revealed no linear indications in the area of the leak or surrounding material. The general area of the leak exhibited a rough appearance with some evidence of minor porosity or inclusions which would be original casting defects such as shrinkage, porosity, or sand inclusion. The defect does not display any linear indications as would be expected if it were stress related.

Given the apparent small size of the flaw and the slow leakage, the casting should retain a considerable portion of its original strength in the leakage area.

Given the inherent toughness of the austenitic stainless steel material, the apparent lack of linearity of the defect, and the relatively low stress in any mode of loading including the OBA seismic event, fast propagation of the defect is highly unlikely. Growth of the defect by a stress corrosion cracking mechanism is not anticipated because of the low stresses and temperature and the generally excellent resistance of 304 stainless steel to stress crack corrosion in reactor coolant.

e The flaw does not affect the hydraulic performance of the pump and, therefore, does not affect the ability of the pump to perform the function for which it was designed. Based on this evaluation, the pump remains fully capable of

  • performing its intended function. Since the pump cannot be fully isolated under present conditions, the Code requirement to complete immediate repair or replacement is impractical and reduces the margin of safety.

Two repair options for the pump were considered. The first was to maintain the plant in the current condition, isolate the pump and repair the leak. This was determined to be impractical, since isolation of the pump is insufficient to assure an acceptable repair. This could result in the 'A' train of the RHR System becoming unavailable for plant cooldown which decreases the margin of safety.

The second option involved immediate depressurization of the RCS but postponement of the repair of the pump for approximately ten days until the fuel has been off-loaded from the reactor vessel. This will allow the 'A' train of the RHR System to be available for decay heat removal in the unlikely event that the 'B' train of the RHR System degrades before decay heat removal is no longer required (i.e., fuel off-load). In addition, the time required to perform an acceptable repair will be reduced since a more complete isolation is possible.

This should also result in a significant reduction in the radiological exposure.

A review of the probabilistic risk of the potential repair modes for the pump has been completed.

Assuming that, within ten days, the RCS is placed in a condition where the operation of the RHR pump is not required, no significant effect on any accident scenario was identified compared with the immediate repair of the pump. As noted above, an acceptable repair of the pump under the present conditions is not assured.

IV.

ALTERNATE REQUIREMENTS The pump will be repaired as soon as practicable after the unit can be placed in a condition where the RHR System is not necessary to meet the Technical Specification shutdown cooling requirements.

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Surry Power Station Unit 1 Structural Analysis Assessment of RHR Pump 1-RH-P-1A

Assessment e

Structural Integrity Assessment of with Flaw in RHR Pump 1-RH-P-1A Suction An analysis of a representative cross section of the residual heat removal pump (1-RH-P-1 A) was performed for verifying the ability of the pump to carry design basis loading with the identified flaw.

The loading conditions, material properties, pump body configuration and calculation showing limiting load analysis and un-reinforced opening calculations are included as Attachment A. Two different approaches were taken to verify the structural integrity of the pump body.

1)

Limit Load Analysis A limit load analysis was performed to determine the largest size crack the pump can sustain without a ductile rupture, when subjected to the design basis loading. The crack was postulate in the circumferential direction to get the worst effect. The crack size was determined from the analysis was 12.00 inches. The actual flaw identified in the component is not a crack or any linear indication. The inspected flaw in less than 0.50 inches in size. The actual flaw is significantly smaller than the largest size crack determined from the analysis.

2)

Largest Size Un-reinforced Opening in the Pump Body An analysis was performed to determine the largest size un-reinforced opening the pump body can sustain without tearing apart. The analysis shows that the pump body can easily sustain a design pressure of 600 psi with an un-reinforced opening of 4.0 inches. This is significantly larger than the identified 0.50 inch flaw on the pump body.

Conclusion Based on these two approaches it is concluded that the pump with the identified flaw will maintain full structural integrity when subject to design basis loading conditions.

ATTACHMENT A I

_j

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

LOADING CONDITION:

Loads at the degraded cross-section of the pump were taken from the stress analysis, CE-0880. The loads include thermal expansion, deadweight and design basis earthquake; these loads were combined by absolute sum:

- Axial Load, F F := 2873 lbs.

- Torsion, T T := 18985 ft-lbs.

- Bending Moment, MY MY:= 8340 ft-lbs.

- Bending Moment, MZ MZ := 21616 ft-lbs.

- Resultant Moment, MR MR := jMY2 + MZ2 + r ft-lbs.

4 MR =2.995*10 ft-lbs.

(359448 in-lbs)

DESIGN CONDITIONS:

- Pressure, P

- Temperature, T P := 600 T := 350 PUMP MATERIAL PROPERTIES

- SA351 CF8A STRESSES (at 200 degrees)

Basic Allowable Stress Yield Stress Ultimate Tensile Stress Flow Stress psi degrees Sh:= 17100 S

= 29800 y

Su:= 66000 a(= 0.5* (s Y + s u) a r=4.79*10 4

ATTACHMENT A ksi (15700 ksi @ 350 degrees) ksi ksi ksi

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

PUMP BODY CONFIGURATION:

Drawing showing detailed dimensions of the pump body was not available. The pertinent dimensions required for the analysis were obtained from the vendor by fax. The cross-section of the pump body varies from section-to-section. To perform a bounding evaluation circular cross-section of 14" and 19.063" were used in the analysis. An uniform pump thickness of 0.75" was used.

LIMIT LOAD ANALYSIS pump body thickness, t internal radius mean radius iteration factors half angle of the crack (radians)

for, the limit load is given by, t := 0.75 14 - 2*t Ri :=

2 14-t R

=--

m 2

L := 10, 10.25.. 12 M(L) := 2*cr rRm2*t*(2*cos(~(L)) - sin(0(L)))

inch/lbs M(L) := 2*cr rR m2*t*(2*cos(~(L)) - sin(0(L)))

inch/lbs The calculated factor of safety is, FS L := M(L)

( )

359448 ATTACHMENT A 3

x(L) := L + 0

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

  • SENSITIVITY ANALYSIS OF FS, Factor of Safety x(L)

FS(L)

IO 3.019 10.25 2.758 10.5 2.504 10.75 2.26 11 2.023 11.25 1.796 11.5 1.577 11.75 1.367 12 1.165 ATTACHMENT A 4

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

LOADING CONDITION:

Loads at the degraded cross-section of the pump were taken from the stress analysis, CE-0880. The loads include thermal expansion, deadweight and design basis earthquake; these loads were combined by absolute sum:

- Axial Load, F F := 2873 lbs.

- Torsion, T T := 18985 ft-lbs.

- Bending Moment, MY MY:= 8340 ft-lbs.

- Bending Moment, MZ MZ := 21616 ft-lbs.

- Resultant Moment, MR MR:= JMY2 +MZ2 + r ft-lbs.

4 MR = 2.995

  • 10 ft-lbs.

(359448 in-lbs)

DESIGN CONDITIONS:

- Pressure, P

- Temperature, T P := 600 T := 350 PUMP MATERIAL PROPERTIES

- SA 351 CF8A STRESSES (at 200 degrees)

Basic Allowable Stress Yield Stress Ultimate Tensile Stress Flow Stress psi degrees Sh:= 17100 Sy:= 29800 Su:= 66000 CJ r:= 0.5*(Sy+ Su)

CJ r=4.79*IO 4 ATTACHMENT A s

ksi (15700 ksi @ 350 degrees) ksi ksi ksi

e STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

PUMP BODY CONFIGURATION:

Drawing showing detailed dimensions of the pump body was not available. The pertinent dimensions required for the analysis were obtained from the vendor by fax. The cross-section of the pump body varies from section-to-section. To perform a bounding evaluation circular cross-section of 14" and 19.063" were used in the analysis. An uniform pump thickness of 0.75" was used.

LIMIT LOAD ANALYSIS pump body thickness, t t := 0.75 internal radius 19.063 t Ri :=

2 mean radius R

= 19.063 - t m

2 iteration factors L := 10,10.5.. 16.5 half angle of the crack (radians)

for, the limit load is given by, M(L) := 2-cr fRm2*t*(2*cos(j3(L)) - sin(8(L)))

inch/lbs M(L) := 2-cr fRm2*t*(2*cos(j3(L)) - sin(8(L)))

inch/lbs The calculated factor of safety is, FS(L) := M(L) 359448 ATTACHMENT A x(L) := L + 0

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

  • SENSITIVITY ANALYSIS OF FS, Factor of Safety x(L)

FS(L) 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 11.63 10.661 9.718 8.803 7.917 7.061 6.236 5.444 4.686 3.961 3.27 2.615 1.995 1.41 ATTACHMENT A

STRUCTURAL INTEGRITY EVALUATION OF RHR PUMP (1-RH-P-1A)

  • ANALYSIS OF UNREINFORCED OPENING:

Four different sizes of openings were analyzed with WALL THIN Computer Program. The results of the analysis show that the pump body has adequate thickness to provide reinforcing to the hole.

The pump body with a 4" diameter hole will sustain the applied pressure and will maintain full structural integrity. This size of hole is significantly larger than the 0.375" to 0.500" diameter flaw identified in the pump body.

ATTACHMENT A

Run CR)

Branch (B)

Do= 14.000 in do= 1.002 in Tn = 0.750 in Tn = 0.001 in Tm=

0.263 in Tm=

0.001 in Ta= 0.750 in Ta= 0.001 in WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Width Reinforcing Ring= 0.000 time Ta(R) Ta(B)

(yrs) (in)

(in) d1 d2 (in) (in) in L

C in)

BRANCH REINFORCEMENT AREA CHECK Component ID:1*RH-P-1A Line Number:

Reqd Reinforcement =

0.28 in2 A1 A2 (in2) (in2)

A4 A1+A2+A4 Req'd (in2) Total (in2)

Jo}o. ** :o.;zsg p;po.J ct/o.!'.l i;.?S. p:;q:o~

D.Jts >ornfl moo... **' ll/73 >ot28 9.0 0.750 0.001 1.00 1.25 0.003 0.73 0.00 0.00 0.73 0.28

Reference:

USAS B31.1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:01:12 AM q

Run CR)

Branch CB)

BRANCH REINFORCEMENT AREA CHECK Do= 14.DOO in do= 2.002 in Tn = 0.750 in Tn = 0.001 in Component ID: 1-RH-P-1A Tm=

0.263 in Tm=

0.001 in Ta= 0.750 in Ta= 0.001 in Line Number:.

WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Reqd Reinforcement 0.56 in2 Width Reinforcing Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

A1 A2 (yrs) (in)

Cin)

(in)

(in)

(in)

Cin2) (in2)

A4 A1+A2+A4 Req'd (in2) Total Cin2) ado

  • 9-:Z~o (hgoJ )2Wo f i}6Q o)oo~ /0)97 o)oq =::.6dio
  • 6)97? 6tsli.

9.0 0.750 0.001 2.00 2.00 0.003 0.97 0.00 0.00 0.97 0.56

Reference:

USAS B31.1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:02:04 AM to

Run (R)

Branch (8)

Do= 14.000 in do= 3.002 in Tn = 0.750 in Tn = 0.001 in Tm=

0.263 in Tm=

0.001 in Ta= 0. 750 in Ta= 0.001 in l,/Rate0.0000 in/yr 1,/Rate 0.0000 in/yr Te = 0.000 in alpha=

90 deg L,Jidth Reinforcing Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

(yrs) (in)

(in) (in)

(in)

C in)

BRANCH REINFORCEMENT AREA CHECK Component 1D:1-RH-P-1A Line Number:

Reqd Reinforcement 0.84 in2 A1 A2 (in2) (in2)

A4 A1+A2+A4 Req*d (in2) Total (in2)

O)OJ 0/7$9 oHitiJ 3}pp *** )~#)Q.. PMP.t / hA~ P{QQ :p;o:o ****

'1i4'.t'{ ():;84 9.0 0.750 0.001 3.00 3.00 0.003 L46 0.00 0.00 1.46 0.84

Reference:

USAS 831.1.0 - 1967 "Power Piping" Section 104.3 1,/ALLTHIN Version 1.2 09/12/95 12:02:21 AM

e Run (R)

Branch (B)

BRANCH REINFORCEMENT AREA CHECK Do= 14.000 in do= 4.002 in Tn = 0. 750 in Tn = 0.001 in Component 1D:1-RH-P-1A Tm= 0.263 in Tm=

0.001 in Ta= o. 750 in Ta= 0.001 in Line Number:

WRate0.0000 in/yr WRate O.DOOO in/yr Te= 0.000 in alpha=

90 deg Reqd Reinforcement =

1.13 in2 Width Reinforcing Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

A1 A2 A4 A1+A2+A4 Req'd (yrs) C in)

< in) < in)

C in>

C in)

C in2> C in2)

Cin2)

Total C in2)

. mo ** ()its.¢: P~Qq} \\MP9

@QQ @CIQ~ JA\\9.?

@QQ o.rno J)9!i t@J 9.0 0.750 0.001 4.00 4.00 0.003 1.95 0.00 0.00 1.95 1.13

Reference:

USAS 831. 1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:02:39 AM

Run (R)

Branch (8)

BRANCH REINFORCEMENT AREA CHECK Do= 19.063 in do= 1.002 in Tn = 0.750 in Tn = 0.001 in Component ID:1-RH-P-1A Tm=

0.358 in Tm=

D.001 in Ta= o. 750 in Ta= 0.001 in Line Number: xx WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Reqd Reinforcement=

0.38 in2 Width Reinforcing Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

A1 A2 A4 A1+A2+A4 Req'd (yrs) (in)

(in) (in) (in)

(in)

(in2) (in2)

(in2) Total (in2) odl/ $??'$9. t1,tiQ1 ?J#lQ J\\?S !PPP.t ** ti\\$9 >oyoo P#>O: tJ>l$~

  • Willi 9.0 0.750 0.001 1.00 1.25 0.003 0.59 0.00 0.00 0.59 0.38

Reference:

USAS 831.1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:12:25 AM 13

Run CR)

Branch CB)

Do= 19.D63 in do= 2.002 in Tn = 0.750 in Tn = 0.001 in Tm=

0.358 in Tm=

0.001 in Ta= 0. 750 in Ta= 0.001 in WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Width Reinforcing Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

(yrs) (in)

Cin)

Cin)

Cin)

C in) e BRANCH REINFORCEMENT AREA CHECK Component ID: 1-RH-P-1A Line Number: xx Reqd Reinforcement =

0.77 in2 A1 A2 Cin2) (in2)

A4 A1+A2+A4 Req'd (in2) Total (in2) rogo ** Pfrs.P: o\\pot 2}oti

~Jog. iM()Q3 ** otra osoo tJ)po r o?r& ota 9.0 D.750 D.001 2.00 2.00 0.003 D.78 O.DD 0.00 0.78 D.77

Reference:

USAS B31.1.D - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:12:05 AM 14

Run CR)

Branch CB)

Do= 19.063 in do= 3.002 in Tn = 0. 750 in Tn = 0.001 in Tm= 0.358 in Tm=

0.001 in Ta= 0.750 in Ta= 0.001 in WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Width Reinforcing Ring= 0.000 in time Ta(R) Ta(B)

(yrs) (in)

(in) d1 d2 (in) (in)

L c in)

BRANCH REINFORCEMENT AREA CHECK Component 1D:1-RH-P-1A Line Number:

Reqd Reinforcement=

1.15 in2 A1 A2 C in2) C in2)

A4 A1+A2+A4 Req'd Cin2)

Total Cin2)

\\Pitt I J:f/t$Q.\\ :.t~{Q.qt /{$JOO.! t)\\~}QQ \\\\Q#QQ.$.il \\ tJ)jij</19\\P.tt i?\\?P.\\Q_Q*............

)W:15.

1.15 9.0 0.750 0.001 3.00 3.00 0.003 1.18 0.00 0.00 1.18

Reference:

USAS B31.1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:06:21 AM 15

Run CR)

Branch CB)

BRANCH REINFORCEMENT AREA CHECK Do= 19.063 in do= 4.002 in Tn = 0.750 in Tn = 0.001 in Component I0:1-RH-P-1A Tm= 0.358 in Tm= 0.001 in Ta= 0.750 in Ta= 0.001 in Line Number:

WRate0.0000 in/yr WRate 0.0000 in/yr Te= 0.000 in alpha=

90 deg Reqd Reinforcement 1.53 i n2 Width Reinforcing-Ring= 0.000 in time Ta(R) Ta(B) d1 d2 L

A1 A2 A4 A1+A2+A4 Req'd (yrs) (in)

(in) (in) (in)

(in)

Cin2) Cin2)

Cin2)

Total (in2) 9.PP

  • Jh:7$9. PIPPA M9.P #M)P9. @oQl f1N$.1 : Q#@ *PiPli
U$.1/

9.0 0.750 0.001 4.00.,4.00 0.003 1.57 0.00 0.00 1.57 1.53

Reference:

USAS 831.1.0 - 1967 "Power Piping" Section 104.3 WALLTHIN Version 1.2 09/12/95 12:05:16 AM

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