ML14259A305
| ML14259A305 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/28/2014 |
| From: | Farideh Saba Division of Operating Reactor Licensing |
| To: | Gerald Williams Tennessee Valley Authority |
| References | |
| Download: ML14259A305 (5) | |
Text
1 NRR-PMDAPEm Resource From:
Saba, Farideh Sent:
Thursday, August 28, 2014 3:24 PM To:
Williams, Gordon Robert (grwilliams1@tva.gov)
Cc:
Schrull, Edward Dustin (edschrull@tva.gov)
Subject:
Request for Additional Information for Browns Ferry AST Attachments:
MF3124-6_BFN1-3 ARCB RAIs - REVISE THE LEAKAGE RATE THROUGH MSIVS TS-485.docx
- Gordon, By letter dated November 22, 2013 (Agencywide Documents Access and Management System Package No.
ML14015A402), Tennessee Valley Authority (TVA, the licensee), submitted a license amendment request to adopt a change to the technical specifications to decrease the allowable leakage rate criteria for the Main Steam Isolation Valves. The U. S. Nuclear Regulatory Commission (NRC) staff has reviewed the information the licensee submitted and determined that additional information is required to complete the evaluation.
As we agreed on the phone, please provide TVAs response to the NRC staffs request for additional information by September 30, 2014.
- Thanks, Farideh E. Saba, P.E.
Senior Project Manager NRC/ADRO/NRR/DORL 301-415-1447 Mail Stop O-8G9A Farideh.Saba@NRC.GOV
Hearing Identifier:
NRR_PMDA Email Number:
1574 Mail Envelope Properties (Farideh.Saba@nrc.gov20140828152400)
Subject:
Request for Additional Information for Browns Ferry AST Sent Date:
8/28/2014 3:24:00 PM Received Date:
8/28/2014 3:24:00 PM From:
Saba, Farideh Created By:
Farideh.Saba@nrc.gov Recipients:
"Schrull, Edward Dustin (edschrull@tva.gov)" <edschrull@tva.gov>
Tracking Status: None "Williams, Gordon Robert (grwilliams1@tva.gov)" <grwilliams1@tva.gov>
Tracking Status: None Post Office:
Files Size Date & Time MESSAGE 871 8/28/2014 3:24:00 PM MF3124-6_BFN1-3 ARCB RAIs - REVISE THE LEAKAGE RATE THROUGH MSIVS TS-485.docx 33955 Options Priority:
Standard Return Notification:
No Reply Requested:
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Recipients Received:
1 REQUEST FOR ADDITIONAL INFORMATION BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2 AND 3 LICENSE AMENDMENT REQUEST TO CHANGE TECHNICAL SPECIFICATIONS TO REVISE MAIN STEAM ISOLATION VALVE LEAKAGE DOCKET NO. 50-259, 50-260 AND 50-296 By letter dated November 22, 2013, (Agencywide Documents Access and Management System (ADAMS) Package No. ML14015A402) Tennessee Valley Authority (TVA), (the licensee) submitted a license amendment request to adopt a change to the technical specifications to decrease the allowable leakage rate criteria for the Main Steam Isolation Valves (MSIVs). The U. S. Nuclear Regulatory Commission (NRC) staff has reviewed the information the licensee submitted and determined that the following additional information is required to complete the evaluation.
RAI-1
In the subject license amendment request, the licensee stated:
The primary ALT [Alternative Leakage Treatment] Pathway, from the outboard side of the MSIVs through orifice lines to the condenser, does not satisfy the sizing requirements of NEDC-31858P. Paragraph 6.1.1(2) of NEDC-31858P states that the ALT flow path, based on the radiological dose methodology, should be at least one square inch in internal cross sectional area due to the orificed bypass lines. The actual internal cross sectional area of the orificed bypass line around FCV-1-58 is 0.0276 square inches. However, the radiological dose analysis has been performed assuming the orificed pathway and demonstrated acceptable control room dose results and offsite dose results assuming the reduced MSIV leakage rates included in this LAR. The secondary ALT Pathway satisfies the sizing requirements of NEDC-31858 paragraph 6.1.1(2), but does not include orifices as describe in Section 5.3 of the NRC SER
[Safety Evaluation Report] for NEDC-31858P (Reference 6) [ADAMS Accession Number ML010640286].
According to the above paragraph, the proposed change does not satisfy the sizing requirements of NEDC-31858P. Provide the following additional details describing the ALT drain path and the basis for the functional reliability of the ALT pathways during a design basis accident as described in Title 10 of the Code of Federal Regulations, Section 50.67.
- a. Justify why the bypass line around FCV-1-58 is assumed to not plug for the duration of the accident.
- b. Provide information regarding the bypass line around the FCV-1-58 valve including the:
dimensions of the bypass line, the orifice in this line and the valve flow pathway (in the most closed position allowed during operations) minimum flow length of the flow through the orifice and the valve flow pathway
2 range of flow velocities that could occur, assumed gas viscosity of the accident leakage through the orifice, time dependent distributions of density, mass and diameter of the aerosols in the accident leakage.
Please justify any assumptions made regarding the information provided.
- c. Provide the same information requested in RAI-1b for any other orifices or valves in the primary or secondary ALT pathways with less than one square inch cross sectional area.
RAI-2
Identify and justify all changes from the current licensing basis (See Issue 1 of NRC Regulatory Issue Summary 2006-04, Experience with Implementation of Alternative Source Terms (ADAMS Accession No. ML053460347) for more details).
RAI-3
Page E1-8 of the submittal states that valve FCV-1-57 will have its power removed to ensure it remains open.
- a. Is the power to be permanently removed? If not, please explain when the power is to be removed.
RAI-4
RAI-4 was deleted by the NRC staff.
RAI-5
Regulatory Guide (RG) 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," dated July 2000 (ADAMS Accession No. ML003716792), Appendix A, Regulatory Position 6.3 states:
Reduction of the amount of released radioactivity by deposition and plateout on steam system piping upstream of the outboard MSIVs may be credited, but the amount of reduction in concentration allowed will be evaluated on an individual case basis.
The new analysis performed by the licensee credits deposition and plateout on steam system piping. The analysis modifies the results of a report entitled Accident Evaluation Report (AEB) 98-03, Assessment of Radiological Consequences for the Perry Pilot Plant Application Using the Revised (NUREG-1465) Source Term (ADAMS Accession No. ML011230531), to account for the change in aerosol distribution that occurs in multiple control volumes in series.
Follow-up studies performed by the NRC, since the AEB 98-03 study, investigated the effect of the changing aerosol distribution over space and time and indicate that the removal coefficients for aerosol deposition may be less than those used by the licensee (see Analysis of Main Steam Isolation Valve Leakage in Design Basis Accidents Using MELCOR 1.8.6 and RADTRAD, Sandia Letter Report, SAND2008-6601, dated October 2008 (ADAMS Accession No. ML083180196)). Therefore, the NRC staff needs the following additional justification why the inputs and assumptions selected by the licensee appropriately account for the deposition of aerosols in the main steam line.
3
- a. Provide a justification for the inputs and assumptions used in the AEB 98-03 report for Browns Ferry.
- b. Larger (i.e., heavier) particles deposit more in the upstream volume, and therefore, the distribution of the aerosol that leaks to the subsequent volume is smaller (i.e., lighter) particles. This particle behavior leads to the conclusion that the choice of an effective settling velocity in any volume should account for the distribution of particle sizes in that volume. Justify why the average settling velocity of the condenser is higher than the B2 volume up stream of the condenser.
- c. As described on page E10 of Attachment 6 of the license amendment request, the proposed removal coefficient of two steam line volumes in series are the same (the Volume B1 and Volume B2 removal coefficient are both 8.93 hr-1). This is different than the current removal coefficient model provided in Attachment 6, page 19. For the current model the removal coefficient of a downstream volume is smaller than the upstream volume (the Volume B1 removal coefficient is 8.93 hr-1 and the Volume B2 removal coefficient is 2.26 hr-1).
An NRC review of the licensees calculation indicates that using the methodology provided by the licensee that the removal coefficient for volume B2 is overestimated on page E10. In addition the overall removal efficiency for particles in this pathway is very high (i.e. 99.997% as stated on page E13).
Provide a justification for the modification of the AEB 98-03 report to account for the change in distribution that occurs in multiple control volumes in series and justify why this methodology is conservative. Alternately, rather than providing this justification, you may provide the NRC staff an analysis of the consequences of the MSIV leakage pathway using the methodology developed in the SAND2008-6601 letter report.