ML15254A545

Response to Draft Request for Additional Information Regarding Proposed Relief Request Associated with the Common Emergency Service Water (ESW) System Piping

ML15254A545
Person / Time
Site:	Peach Bottom
Issue date:	09/11/2015
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MF6551, TAC MF6552
Download: ML15254A545 (9)

Text

200 Exelon Way Kennett Square. 'A 19348 Exelon Generation www.exeloncorp.com 10 CFR 50.55a September 11, 2015 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278

Subject:

Response to Draft Request for Additional Information Regarding Proposed Relief Request Associated with the Common Emergency Service Water (ESW) System Piping for Peach Bottom Atomic Power Station, Units 2 and 3

References:

1) Letter from D. P. Helker (Exelon Generation Company, LLC) to the U.S.

Nuclear Regulatory Commission, "Proposed Relief Request associated with the Common Emergency Service Water (ESW) System Piping,"

dated July 29, 2015

2) E-mail correspondence from R. Ennis (U.S. Nuclear Regulatory Commission) to S. J. Hanson (Exelon Generation Company, LLC),

"Peach Bottom Atomic Power Station - Request for Additional Information Regarding Proposed Relief Request 14R-56 Emergency Service Water Leak Repair Deferral (ML15223A515)," dated August 6, 2015

3) Letter from D. P. Helker (Exelon Generation Company, LLC) to the U.S.

Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding Proposed Relief Request associated with the Common Emergency Service Water (ESW) System Piping for Peach Bottom Atomic Power Station, Units 2 and 3," dated August 13, 2015.

4) E-mail correspondence from R. Ennis (U.S. Nuclear Regulatory Commission) to S. J. Hanson (Exelon Generation Company, LLC),

"Peach Bottom Atomic Power Station - Draft Request for Additional Information Regarding Proposed Relief Request 14R-56 Emergency Service Water Leak Repair Deferral (NRC TAC Nos. MF6551 and MF6552)," dated September 8, 2015

U.S. Nuclear Regulatory Commission Response to Request for Additional Information Concerning Relief Request 14R-56 September 11, 2015 Page2 By letter dated July 29, 2015, Exelon Generation Company, LLC (Exelon) submitted a Relief Request to the U.S. Nuclear Regulatory Commission (NRC) for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3 (Reference 1). Specifically, Exelon requested that the NRC authorize relief from Code Case N-513-3, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1" of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) and the condition placed on Code Case N-513-3 as listed in Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 17, dated August 2014.

In the Reference 2 e-mail correspondence, the U.S. NRC requested additional information.

Reference 3 provided Exelon's response.

In the Reference 4 e-mail correspondence, the U.S. NRC requested additional information.

Attached is our response.

There are no regulatory commitments in this response.

If you have any questions concerning this response, please contact Stephanie J. Hanson at 610-765-5143.

Respectfully, David P. Helker Manager, Licensing and Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Response to Draft Request for Additional Information Regarding Proposed Relief Request 14R-56 cc: USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, PBAPS USNRC Project Manager, PBAPS R. R. Janati, Pennsylvania Bureau of Radiation Protection S. T. Gray, State of Maryland

ATTACHMENT 1 Response to Draft Request for Additional Information Regarding Proposed Relief Request I4R-56

Response to Request for Additional Information Attachment 1 Relief Request Concerning I4R-56 Page 1 of 2 Docket Nos. 50-277 and 50-278 By letter dated July 29, 2015, as supplemented by letter dated August 13, 2015, Exelon Generation Company, LLC (Exelon) submitted a relief request to the U.S. Nuclear Regulatory Commission (NRC) for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3.

Specifically, Exelon requested that the NRC authorize relief from Code Case N-513-3, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1" of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) and the condition placed on Code Case N-513-3 as listed in Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 17, dated August 2014. Relief Request I4R-56 proposes an alternative that allows repair of leaking moderate energy Class 3 Emergency Service Water (ESW) piping during the Unit 2 refueling outage (scheduled to begin in October 2016) in lieu of the Unit 3 outage (scheduled to begin in September 2015).

The NRC staff has determined that additional information is needed to complete its review. The specific request for additional information (RAI) question, which was discussed in a conference call between the NRC staff and Exelon on September 9, 2015, is restated below along with Exelon's response.

Question 1:

Please discuss how the analysis supporting the proposed relief request is consistent with the requirements in Section 3.2(d) of Code Case N-513-3.

Response

The following response discusses how the analysis supporting proposed Relief Request I4R-56 is consistent with the requirements in Section 3.2(d) of ASME Section XI, Division 1 Code Case N-513-3. The text of 3.2(d) is provided below with discussion on how the requirements are satisfied:

1. Alternatively, if there is a through-wall opening along a portion of the thinned wall as illustrated in Fig. 5 the flaw may be evaluated as two independent planar through-wall flaws, one oriented in the axial direction and the other oriented in the circumferential direction.

This is also known as the planar characterization approach. This was initially performed by Exelon in support of the Relief Request by evaluating the discovered flaws against the fracture toughness requirements for the material and comparing the results to the allowable values for fracture toughness (KI).

Subsequent to the initial evaluation, per NRC request, Exelon has performed additional evaluations consistent with the original methodology in accordance with the attached spreadsheet (Enclosure 1) where the axial flaw length (Laxial) and circumferential flaw lengths (Lcirc) are compared to the calculated allowable flaw sizes.

2. The minimum wall thickness tmin, shall be determined by eq. (4).

This was determined to be 0.0635 inch for design pressure of 150 psig and 0.0246 inch for the maximum operating pressure of 58 psig.

Response to Request for Additional Information Attachment 1 Relief Request Concerning I4R-56 Page 2 of 2 Docket Nos. 50-277 and 50-278

3. The allowable through-wall lengths in the axial and circumferential directions shall be determined by varying tadj shown in Fig. 5 from tnom to tmin.

A value of tadj = 0.328 was chosen for the subsequent evaluation. This is 87.5%

of the nominal wall thickness and is, therefore, between tnom and tmin as required.

4. The allowable through-wall flaw lengths based on tadj shall be greater than or equal to the corresponding Laxial and Lcirc (see Fig. 5) as determined from CC N-513-3 paragraphs 3.1(a) and 3.1(b) or 3.1(c), as appropriate.

The calculated allowable flaw lengths in the axial and circumferential directions are determined in accordance with 3.1(c) (Enclosure 1). This was the same methodology used in the initial analysis attached to Relief Request I4R-56. Laxial and Lcirc may be conservatively taken to be 4.5 inches from the UT inspections.

This approach takes no credit for any of the material less than tadj (i.e., the structural evaluation assumes a through-wall hole with a diameter of 4.5 inches).

The calculated allowable flaw lengths determined by the additional evaluations and using the maximum operating pressure, as allowed by the Code Case, are 8 inches in the axial direction and 13.5 inches in the circumferential direction.

Therefore, the allowable through-wall flaw lengths based on tadj are significantly greater than Laxial and Lcirc. In addition, the anticipated wear over the temporary acceptance period is not likely to challenge the structural integrity of the piping given the large margin between the conservatively characterized through-wall flaw and the allowable through-wall flaw.

5. The remaining ligament average thickness, tc,avg, over the degraded area bounded by Laxial and Lcirc shall satisfy eq. (9).

This requirement was first added to N-513-3 and is also known as the pressure blowout check. It is intended to provide margin against rapid failure of the remaining ligament to prevent personnel injury. Again taking Laxial and Lcirc as 4.5 inches, the required average wall thickness using the maximum operating pressure is 0.1 inch. Note that this calculation results in a larger thickness than the minimum required wall thickness calculated previously. However, based on the UT inspections, the average remaining wall thickness exceeds tc,avg.

Therefore, the requirement of Equation 9 is satisfied. Additionally, based on the corrosion rate of 0.012 inch/year as stated in Relief Request I4R-56, the remaining average wall thickness is also not anticipated to fall below the required tc,avg during the temporary acceptance period.

Response to Request for Additional Information Enclosure 1 Concerning Relief Request 14R-56 Page 1 of 4 Docket Nos. 50-277 and 50-278 Planar Flaw Evaluation in ferritic ninine IA W Code Case N-513-3 PBAPS ESW Min Wall "B" ESW {IR 2494904-03}

I Definitions:

I Flaw depth (lnom . tmin) - Information Only a= 0.047 in I

Pipe wall thickness (lnom) t= 0.375 in I

Maximum assumed circumferential flaw length (dadi): l= 13.500 in I

Pipe outside diameter: D= 12.75 in I

Mean pipe radius: R = D-t R= 6.21 in 2

I I= 7t[D -(D-2t)4 J 4

Piping bending moment of inertia: I= 247.06 in"4 64 I

Flaw half-angle per Figure I, N-513: 0 = 2*R 8= 1.087 rad I

Unit definition for kips: I kip= 1000 lbf I

Unit definition for psi: I ksi = 1000 psi I

Pinine Loads <Moments Increased bv 25% for Uncertainties):

I Maximum operating pressure: OP= 58.00 psi I

POP =7t(~ -t) *OP 2

Maximum operating pressure axial force: Pop= 6662.82 lbs I

Axial load on pipe for Normal/Upset condition forces : Pnu= 957 .00 lbs I

Axial load on pipe for Emergency/Faulted condition forces: Pnf= 1109.00 lbs I

Total axial load on pipe, including pressure from piping analysis for normal/upset condition forces: Pn = Pop+Pnu Pn= 7619.82 lbs I

Total axial load on pipe, including pressure from piping analysis for emergency/faulted condition forces: Pr= Pop+Pnr Pf= 7771.82 lbs I

Applied bending moment on the pipe from piping analysis Mn= 2206.25 ft-lbf for normal/upset condition (SRSS(MA, MB, MC) for WTOl+SEISOB)

I Aoolied bending moment on the pipe from piping analysis Mf= 4328.02 ft-lbf for emergency/faulted condition (SRSS(MA, MB, MC) for WTO I +SEISSS)

I Pipe thermal expansion stress from piping analysis: Pe= 0.000 ksi I

I Adjusted thickness per CC N-513-3, § 3.2(d) tadi = 0.328 in I

Response to Request for Additional Information Enclosure 1 Concerning Relief Request 14R-56 Page 2 of 4 Docket Nos. 50-277 and 50-278 Circumferential Flaw Evaluation Usinl! N-513 Pioinl! Material Prooerties Ref. ASME B31.1):

Young's Modulus: E= 27850 ksi Poisson's Ratio: µ= 0.30 E'= (FJ(I-µ2) E'= 30604.40 ksi Material Prooerties for Flaws oer H-4000:

2 From ASME XI C-8322 J1c = 45 in*lbf/in 5

Allowable Fracture Toughness, Kie: K1c = 37.l 11 ksi*in°*

05 Kie= (CJ1c

• E') I (1000 lbf/k.ip))

• N-513 Annendix I Circumferential Flaw eouations:

Accurate between 5 and 20. Conservative over 20. R/t= 18.936 Acceptable 3

Am= -2.02917 + I.67763*(R/t) - 0.07987*(Rlt/ + O.OOJ 76*(R/t)

Am= 13.05 2 3 Bm = 7.09987 - 4.42394*(R/t) + 0.21036*(R/t) - 0.00463*(R/t)

Bm= -32.68 2

Cm= 7.79661 + 5.16676*(R/t) - 0.24577*(R/t) + 0.00541 *(R/t)3 Cm= 54.24 5 25 Fm= 1.0 + Am*(0ht{ + Bm*(0ht) ' + Cm*(0hr) 3*5 Fm= 2.68 2 3 Ab= -3.26543 + I.52784*(R/t) - 0.072698*(R/t) + 0.0016011 *(R/t)

Ab= 10.47 Bb = l 1.36322 - 3.91412*(R/t) + 0.18619*(R/t/- 0.004099*(R!t}3 Bb= -23.82 2 3 Cb= -3.18609 + 3.84763*(R/t)- O.l8304*(R/t) + 0.00403*(R/t)

Cb= 31.40 5 25 Fb = 1.0 + Ab*(0ht/ + Bb*(0ht) + Cb*(0hr)3- 5 Fb= 2.22

Response to Request for Additional Information Enclosure 1 Concerning Relief Request 14R-56 Page 3 of 4 Docket Nos. 50-277 and 50-278 Annlied Stress Intensitv Factor KI for Circumferential Flaw:

N-513 Appendix I requires that the flaw depth in the C-7300 stress intensity equations be changed to the flaw half-length, c:

Maximum assumed circumferential flaw length: l= 13.500 in Flaw half-length, c = 1/2: c= 6.75 in Note: Units are converted automatically.

NormaVUnset Condition <ref. C-4311):

Kim=( 2.1*Pn }(Jr*c)0.5 *Fm Kim= 19.804 ksi-in° 5

2*Jl'*R*t K lb = ( 2.3

• Mni Jl'*R *t

+~ . J( Ji. c )o.s . Fb K1b= 15.646 ksi-in°*

5 Kr= Krm+Krb Kr= 35.450 ksi-in°.s Therefore, Kr< Klc: Acceptable Emer2encv/Faulted Condition <ref. C-4311 ):

K Im

= ( 1.8 P1 *Jl'*c 2 . :Jl'

• R . t J( ) *Fm Krm= 13.466 ksi-in° 5

K lb = ( 1.6 M 2 1

+ Pe ) . (Jr . c )°' . Fb Krb= 21.351 ksi-in°*

5 Jr* R *t 5

K1= K1m+K1b Kr= 34.817 ksi-in° Therefore, K1< Klc: Acceptable

Response to Request for Additional Information Enclosure 1 Concerning Relief Request 14R-56 Page 4 of 4 Docket Nos. 50-277 and 50-278 Axial Throu!!h-walll Flaw Evaluation Usin!! N-513 Stress Intensitv Factor KI for an axial flaw subiect to the boundin!! condition <ref. C-4311):

Axial flaw length: l= 8.000 in Flaw half-length, c = 1/2: c= 4 in Maximum operating pressure: OP= 58 psi Safety Factor for normal/upset conditions from C-2622: SF= 2.7 N-513 Appendix I assigned flaw shape parameter for a through-wall flaw: Q= 1.00

/... = c/(R *t) 0*5 /...= 2.802 Therefore, O<'A.<5: Acceptable Note: Units are converted automatically 2 3 4 F = 1.0 + 0.072449*/... + 0.64856*/... - 0.2327*/... + 0.038154*/... - 0.0023487*/...5 F= 3.122 K

I

= SF. OP. R t

(r 7t.

Q c .F Ki=

Therefore, K1 < Kie:

32.823 Acceptable kSI-In

.. 0.5 END OF ASME CODE CASE N-513-3 EVALUATION