ML110630413
| ML110630413 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/10/2011 |
| From: | Justin Poole Watts Bar Special Projects Branch |
| To: | Bhatnagar A Tennessee Valley Authority |
| Poole Justin/DORL/LPL3-1/ 301-415-2048 | |
| References | |
| TAC ME4620 | |
| Download: ML110630413 (4) | |
Text
March 10, 2011 Mr. Ashok S. Bhatnagar Senior Vice President Nuclear Generation Development and Construction Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
WATTS BAR NUCLEAR PLANT, UNIT 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING FINAL SAFETY ANALYSIS REPORT AMENDMENT RELATED TO SECTION 10.2.3 (TAC NO. ME4620)
Dear Mr. Bhatnagar:
By letter dated October 29, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103160411), the Tennessee Valley Authority (TVA) submitted Amendment 101 to the Final Safety Analysis Report (FSAR) for Watts Bar Nuclear Plant, Unit 2.
The U.S. Nuclear Regulatory Commission staff has reviewed the information provided by TVA in FSAR Amendment 101 and finds that additional information is needed to complete its review regarding FSAR Section 10.2.3, Turbine Rotor and Disk Integrity. The specific questions are in the enclosed request for additional information.
A response is required within 15 days of receipt of this letter.
If you should have any questions, please contact me at 301-415-2048.
Sincerely,
/RA/
Justin C. Poole, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-391
Enclosure:
Request for Additional Information cc w/encl: Distribution via Listserv
Mr. Ashok S. Bhatnagar Senior Vice President Nuclear Generation Development and Construction Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
WATTS BAR NUCLEAR PLANT, UNIT 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING FINAL SAFETY ANALYSIS REPORT AMENDMENT RELATED TO SECTION 10.2.3 (TAC NO. ME4620)
Dear Mr. Bhatnagar:
By letter dated October 29, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103160411), the Tennessee Valley Authority (TVA) submitted Amendment 101 to the Final Safety Analysis Report (FSAR) for Watts Bar Nuclear Plant, Unit 2.
The U.S. Nuclear Regulatory Commission staff has reviewed the information provided by TVA in FSAR Amendment 101 and finds that additional information is needed to complete its review regarding FSAR Section 10.2.3, Turbine Rotor and Disk Integrity. The specific questions are in the enclosed request for additional information.
A response is required within 15 days of receipt of this letter.
If you should have any questions, please contact me at 301-415-2048.
Sincerely,
/RA/
Justin C. Poole, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-391
Enclosure:
Request for Additional Information cc w/encl: Distribution via Listserv DISTRIBUTION:
RidsOgcRp Resource RidsRgn2MailCenter Resource PUBLIC RidsNrrDorlLpwb Resource RidsNrrDciCvib Resource LPWB Reading File RidsNrrLABClayton Resource RidsNrrPMWattsBar2 Resource RidsAcrsAcnw_MailCTR Resource RidsNrrDorlDpr SSheng, NRR ADAMS Accession No. ML110630413 OFFICE LPWB/PM LPWB/LA CVIB/BC OGC /NLO LPWB/BC NAME JPoole BClayton MMitchell DRoth SCampbell DATE 03/ 4 /11 03/ 4 /11 03/ 7 /11 03/ 9 /11 03/ 10 /11 OFFICIAL AGENCY RECORD
Enclosure REQUEST FOR ADDITIONAL INFROMATION WATTS BAR NUCLEAR PLANT, UNIT 2 FINAL SAFETY ANALYSIS REPORT AMENDMENT 101, SECTION 10.2.3 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-391
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Background===
Tennessee Valley Authority discussed the topic of turbine rotor integrity in Amendment 101 to the Watts Bar Nuclear Plant (WBN), Unit 2, Final Safety Analysis Report (FSAR),
Section 10.2.3, Turbine Rotor and Disk Integrity. The Nuclear Regulatory Commission (NRC) staff evaluated this section against the acceptance criteria specified in the Standard Review Plan (SRP) (NUREG-0800) Section 10.2.3, Turbine Disk Integrity, dated 1981 for low-pressure turbine disks. The acceptance criteria cover 5 areas: (1) materials selection, (2) fracture toughness, (3) preservice inspection, (4) turbine disk design, and (5) inservice inspection. On the basis of its review, the NRC staff finds that additional information is needed, as described below, to complete its review:
RAI-1
Regarding the second criterion (fracture toughness), SRP 10.2.3 requires the ratio of the fracture toughness (KIC) of the rotor material to the maximum tangential stress at speeds from normal to design overspeed be at least 2 square-root inch. Further, this criterion requires the KIC be obtained through one of the four methods specified in the SRP. However, Section 10.2.3.1 of Amendment 101 does not indicate how fracture toughness values for the rotor shaft and disks were obtained.
Confirm whether fracture toughness is obtained indirectly through a test data based KIC versus (T-FATT) curve, where T is the operating temperature and FATT is the 50-percent fracture appearance transition temperature. If the answer is affirmative, provide the KIC versus (T-FATT) curve applicable to the WBN Unit 2 turbine. If not, provide information regarding fracture toughness values for the rotor shaft and disks and how they are obtained.
RAI-2
Regarding the fourth criterion (turbine rotor design), SRP 10.2.3 requires two items: (1) the combined stresses of the low-pressure turbine rotor at design overspeed should not exceed 0.75 of the minimum specified yield strength of the material, and (2) the natural frequencies (critical speeds) of the turbine shaft assemblies should be controlled so as to cause no distress to the unit during operation. The CT-27467 report, which supports Section 3.5.1.3 of Amendment 101, contains the stress distribution of the rotor assembly at a speed exceeding the design overspeed. Section 10.2.3.1 of Amendment 101 contains yield strength ranges for the rotor and the disks. Therefore, Item 1 of this criterion is addressed. However, Amendment 101 does not address Item 2. Provide this supporting information.
RAI-3
Regarding the last criterion (inservice inspection), SRP 10.2.3 requires disassembly of the turbine at approximately 10-year intervals and complete inspection of all normally inaccessible parts, such as couplings, coupling bolts, turbine shafts, low-pressure turbine blades, low-pressure disks, and high-pressure rotors. Because Amendment 101 does not address this requirement, provide information regarding the planned inservice inspection of these components.