RNP-RA/14-0028, Response to NRC Request for Additional Information Re Pressurized Water Reactor Internals Program Plan for Aging Management of Reactor Internals

Response to NRC Request for Additional Information Re Pressurized Water Reactor Internals Program Plan for Aging Management of Reactor Internals

ML14056A193
Person / Time
Site:	Robinson
Issue date:	02/19/2014
From:	William Gideon Duke Energy Progress
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RNP-RA/14-0028, TAC ME9633
Download: ML14056A193 (5)

Text

William. R. Gideon H. B. Robinson Steam Electric Plant Unit 2

~DUKE Site Vice President ENERGY.

S Duke Energy Progress 3581 West Entrance Roaa Hartsville, SC 29550 0:8438571701 F: 843 857 1319 Randy.Gideon@duke.energy.con, 10 CFR 54.21 Serial: RNP-RA/14-0028 FEB 1 9 2014 ATTN: Document Control Desk United States Nuclear Regulatory Commission Washington, DC 20555-0001 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261/RENEWED LICENSE NO. DPR-23 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE PRESSURIZED WATER REACTOR INTERNALS PROGRAM PLAN FOR AGING MANAGEMENT OF REACTOR INTERNALS (TAC NO. ME9633)

Ladies and Gentlemen:

By letter dated January 08, 2014, the NRC requested that Duke Energy Progress, Inc., respond to a request for additional information (RAI) regarding the Aging Management Program for the Reactor Vessel Internals at Robinson Nuclear Power Plant. The Duke Energy Progress response to this RAI (RAI-5(b)-I)(NRC Accession No. ML14016A279) is provided in the enclosure to this letter.

There are no regulatory commitments made in this submittal. If you have any questions regarding this submittal, please contact Mr. R. Hightower at (843) 857-1329.

I declare under penalty of perjury that the foregoing is true and correct.

Executed On: if ('i1' William. R. Gideon Site Vice President

United States Nuclear Regulatory Commission Serial: RNP-RA/14-0028 Page 2 of 2 WRG/am

Enclosure:

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE PRESSURIZED WATER REACTOR INTERNALS PROGRAM PLAN FOR AGING MANAGEMENT OF REACTOR INTERNALS Summary of the Evaluation of H.B. Robinson Unit 2, Lower Internals Assembly, Lower Support Columns - Ferrite Content and Casting Method cc: Mr. V. M. McCree, NRC, Region II Mr. Siva P. Lingam, NRC Project Manager, NRR NRC Resident Inspector, HBRSEP Unit No. 2

United States Nuclear Regulatory Commission Enclosure to Serial: RNP-RA/14-0028 Page 1 of 3 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE PRESSURIZED WATER REACTOR INTERNALS PROGRAM PLAN FOR AGING MANAGEMENT OF REACTOR INTERNALS (TAC NO. ME9633) DOCKET NO. 50-261 Summary of the Evaluation of H.B. Robinson Unit 2, Lower Internals Assembly, Lower Support Columns - Ferrite Content and Casting Method

Background

The H.B. Robinson Unit 2 [Robinson Nuclear Plant (RNP)] PWR Reactor Vessel Internals (RVI)

Aging Management Program Plan (AMP) (Reference 1) was developed in accordance with the requirements and expectation contained in MRP-227-A (Reference 2). Included in Reference 1 is the RNP compliance demonstration with the Reference 2, U.S. Nuclear Regulatory Commission (NRC) applicant/licensee action item 7 (A/LAI 7). Specifically, Reference .1,Table 6-2, includes an entry for the RNP cast austenitic stainless steel (CASS) lower support columns which are low 0.5 percent maximum molybdenum content, were static cast, have ferrite content less than or equal to 20 percent, and thus, based on the NRC criteria (Reference 3, Table 2), are not susceptible to thermal embrittlement (TE). The U.S. Nuclear Regulatory Commission (NRC) staff issued requests for additional information (RAIs) as part of its review of the AMP for the reactor internals at RNP (Reference 4). RNP's response to the RAIs included a response to RAI-5 (Reference 5). The NRC subsequently issued RAI-5(b)-1.

RAI-5(b)-1 (Action Item 7 of the NRC staff's SE for MRP-227-A):

"Forthe CASS lower support columns at RNP Unit 2, provide the ferrite contentfor each lower support column using CMTRs. Provide the casting method for the columnn (static or centrifugal), if known.

Response

The RNP lower internals assembly - lower support column bodies were cast from ASTM A296, Grade CF8 material. The certified material test reports (CMTRs) in the Westinghouse fabrication records show that eleven different heats of material were used to produce all 68 CASS lower support columns for use in the fabrication of the RNP lower internals assembly.

The element weight percentages from the CMTRs for the RNP CASS lower support columns are input into Hull's formula (per the guidance of References 3 and 6) to calculate the delta ferrite content of the CASS material. The RNP lower support columns CMTRs do not list the weight percentage for nitrogen; thus, per the guidance of Reference 6, nitrogen is assumed to be 0.04 percent. The CMTRs do not list the weight percentage for molybdenum. ASTM A296, Grade CF8 did not have a requirement for percent molybdenum and that specification was withdrawn in 1977 and replaced by ASTM A743. ASTM A743, Grade CF8 chemical requirements are identical to those of ASTM A296, and also do not list a requirement for percent molybdenum. ASTM A351 is another casting specification that is typically used in the fabrication of RVI. ASTM A35 1, Grade CF8 chemical requirements are also identical to those of ASTM A296, Grade CF8 and the current ASTM A351-13, Grade CF8 chemical requirements do specify a maximum of 0.5 percent molybdenum; thus, this maximum value is input into Hull's formula. Using the maximum 0.5 percent molybdenum in Hull's formula results in higher calculated ferrite content and conservatively increases the possibility of susceptibility to TE.

The calculated ferrite contents are listed in Table 1. The maximum ferrite content is 18.4 percent, the minimum is 7.1 percent, and the mean ferrite content is 11.2 percent.

United States Nuclear Regulatory Commission Enclosure to Serial: RNP-RA/14-0028 Page 2 of 3 The lower support columns are assumed to have been static cast. The historical fabrication records do not definitively show the casting method - static or centrifugal. It is conservative to assume static cast because static cast has a lower ferrite content acceptance criteria limit than centrifugal cast to show TE susceptibility (Reference 3, Table 2). The shape of the lower support column also leads to the reasonable assumption of static cast.

The RNP lower support columns are of low molybdenum CF8 material, are assumed static cast, and have maximum fenite content 18.4 percent which is less than the 20 percent screening level.

Documentation supporting this information is retained in Westinghouse proprietary Class 2 calculation, CN-RIDA-12-42 (Reference 7), and available for review under standard quality assurance protocols at an appropriate Westinghouse location, upon request. Therefore, consistent with the NRC criteria of Reference 3, it is concluded that the RNP lower internals assembly, CASS lower support columns are not susceptible to TE.

Table 1 Robinson Nuclear Plant Lower Internals Assembly - Lower Support Columns Heat and Ferrite Content Calculated Ferrite Content (2)

Quantity of CASS Casting Supplier Heat Number Columns Method (1)

(Percent)

L602 1 Static 7.1 L697 7 Static 8.3 L705 5 Static 15.1 L707 3 Static 17.7 L716 6 Static 14.0 L720 7 Static 11.4 L722 6 Static 8.3 L735 20 Static 9.7 L736 9 Static 10.6 L741 3 Static 18.4 L745 1 Static 10.1 Notes:

1. Material specification and CMTRs are silent on casting method, castings are assumed to have been static cast.

2. Ferrite content calculated based on guidance for application of Hull's formula (References 3 and 6).

United States Nuclear Regulatory Commission Enclosure to Serial: RNP-RA/14-0028 Page 3 of 3 References

1. Westinghouse Report, WCAP-17077-NP, Revision 1, "PWR Vessel Internals Program Plan for Aging Management of Reactor Internals at Robinson Nuclear Plant," August 2012.

2. MaterialsReliability Program:PressurizedWater ReactorInternals Inspection and Evaluation Guidelines (MRP-227-A). EPRI, Palo Alto, CA: 2011. 1022863.

3. U.S. Nuclear Regulatory Commission Letter, "License Renewal Issue No. 98-0030, Thernal Aging Embrittlement of CastAustenitic Stainless Steel Components," May 19, 2000. (NRC ADAMS Accession No. ML003717179).

4. U.S. Nuclear Regulatory Commission Letter "H.B. Robinson Steam Electric Plant, UnitNo. 2 -

Request for Additional Information Related to the Pressurized Water Reactors Internals Program Plan for Aging Management of Reactor Internals (TAC No. ME9633)," March 27, 2013. (NRC Accession No. ML13079A293).

5. Duke Energy Letter, RNP-RA/13-0053, "Response to NRC Request for Additional Information Related to the Pressurized Water Reactors Internals Program Plan for Aging Management of Reactor Internals (TAC No. ME9633)," May 23, 2013. (NRC ADAMS Accession No. ML13156A144).

6. U.S. Nuclear Regulatory Commission NUREG/CR-4513, Rev. 1, "Estimation of Fracture Toughness of Cast Stainless Steels During Thermal Aging in LWR Systems," August 1994.

(Available NRC ADAMS Accession No. ML052360554).

7. Westinghouse Calculation Note, CN-RIDA-12-42, Rev. 1, "H.B. Robinson Reactor Internals MRP-227-A Aging Management Program Plan Update Licensee Action Item 7, Evaluation of CASS,"

January 28, 2014. (Westinghouse Proprietary Class 2).