ML12090A155
| ML12090A155 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 03/29/2012 |
| From: | Helsel J Susquehanna |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| pla-3834 | |
| Download: ML12090A155 (9) | |
Text
Jeffrey M. Helsel PPLSusquehann~LLC Nuclear Plant Manager 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3510 Fax 570.542.1504 jmhelsel@pplweb.com U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop OP1-17 Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION RESPONSE TO EMAIL (DATED MARCH 27, 2012)
REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED AMENDMENT NUMBER 281 TO UNIT 2 OPERATING LICENSE NO. NPF-22 PLA-6834 Docket No. 50-388
References:
Proposed Amendment Number 281 to Unit 2 Operating License No. NPF-22 Temporary Change to Allow Implementation of Multiple Spurious Operations Modifications on SSES Unit 1 4160 v Buses: Technical Specifications 3.8. 7 and 3. 7.1 ",Dated March 8, 2012.
- 2. Email from B. Vaidya (USNRC) to PPL, Titled Susquehanna Unit 2, ME8152, Draft Request for Additional Information (RAJ) from Balance ofPlant Branch",
Dated March 16, 2012.
((Response to Email (Dated March 16, 2012) Request for Additional Information Proposed Amendment Number 281 to Unit 2 Operating License No. NPF-22 ",
Dated March 23, 2012.
- 4. Email from B. Vaidya (USNRC) to PPL, Titled ((Susquehanna Unit 2, ME8152, Additional Request for Additional Information (RAJ) from Balance ofPlant Branch",
Dated March 27, 2012.
The purpose of this letter is to respond to a Request for Additional Information (RAI)
(Reference 4) received from the NRC on March 27, 2012. The responses to the NRC questions are contained in the Attachment to this letter.
There are no regulatory commitments associated with the proposed changes.
PPL Susquehanna, LLC is providing the Commonwealth of Pennsylvania with a copy of this response to the RAI.
If you have any questions or require additional information, please contact Mr. Cornelius T. Coddington at (610) 774-4019.
Document Control Desk PLA-6834 Sincerely, q.11JnM1 /Jd~
J. M. Helsel
Attachment:
Response to Request for Additional Information, dated March 27, 2012 Copy: NRC Region I Mr. J. W. Andersen, NRR/EEEB/BC Mr. R. B. Elliot, NRR/STSB/BV Mr. P. W. Finney, NRC Sr. Resident Inspector Mr. D. M. Frumkin, NRR/AFPB Mr. D. G. Harrison, NRR/APLA/BC Mr. R. R. Janati, DEP/BRP Mr. A. R. Klein, NRR/AFPB/BC Mr. G. S. Matharu, NRR/EEEB Mr. B. K. Vaidya, NRC Project Manager Mr. K. V. Scales, NRR/EEEB Mr. G. M. Waig, NRR/STSB (Tech Specification Branch)
Mr. G. A. Wilson, NRR/DORL/LPL1-1/BC
Attachment to PLA-6834 PPL Susquehanna, LLC Response to Request for Additional Information, dated March 27,2012
Attachment to PLA-6834 Page 1 of6 NRC Question:
Background:
During the proposed extended Completion Time (CT) ofTS 3.7.1, the licensee will establish a return flow path for the inoperable RHRSW train by manually opening the RHRSW Spray Pond Return Bypass Valve. The licensee has stated that with this return flow path established, the affected RHRSW loop on Unit 2 will be functional.
The licensee has stated that the potential heat loads during the proposed one time extended CT will be less than design basis heat loads because a) Unit 1 will already be in Mode 4 or 5, and b) the extended CT will expire on May 31, 2012 before initial spray pond temperature and ambient conditions may reach limiting design conditions. Therefore, the licensee has justified extending the Completion Time (CT) for Conditions A.3 and B ofTS 3.7.1 by stating "Given this set of facts, it is expected that shutting down Unit 2 and continuing to cool Unit 1 through the open Spray Pond bypass valve, in the event that the operable loop ofRHRSW were to fail in a configuration similar to that described above, would be acceptable for a period approaching 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> with no additional actions on the part of the operators. In this 20-hour period, however, actions could be taken by the operators to access the RHRSW Spray Pond Valve Vault and to manually close the bypass valve and to manually open the spray array valves. Re-aligning the bypass and spray array valves would return the UHS to its design condition with spray cooling. These actions could be accomplished well within the available 20-hour time frame. Therefore, the safety consequences of this condition are not considered to be high."
10CFR 50.36, "Technical Specifications," paragraph (c) (2) (ii) (C) Criterion 3 requires a technical specification limiting condition for operation to be established for a "structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident (emphasis added) or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier." Therefore, the NRC staff concludes that TS
- 3. 7.1 LCO established the limiting condition for operation for the RHRSW to mitigate a design basis accident including loss of coolant accident (LOCA).
Furthermore, FSAR Section 9 .2. 7.3 .1 states, "The maximum heat load to the spray pond will occur with a LOCA/F arced Shutdown combination, as opposed to a two unit forced shutdown."
Attachment to PLA-6834 Page 2 of6 Issue:
As stated above in Background, the licensee has justified the proposed extended CT by stating that the configuration is adequate for Unit 2 shutdown, but did not address the heat loads for LOCA for which the TS was established as required by 10CFR50.36. The FSAR also provides justification for considering LOCA heat loads in this scenario.
Request:
a) Restate your technical analysis for justification of the proposed extended CT by considering LOCA heat loads on the RHRS W system and ultimate heat sink (UHS). The justification should include any new assumptions and new design inputs made compared to the design basis LOCA analysis. Clearly explain inputs and assumption and compensatory measures that add conservatism to your analysis.
b) Surveillance Requirements (SR) 3. 7 .1.3 through 3. 7 .1. 7 are required every 31-92 days. Ifthe last Surveillance Requirements have not been performed for times approaching the SR limits, what will the licensee do to ensure that when entering Condition A and B of TS 3. 7.1 that the assumed operable loop/train of RHRSW system is actually operable?
PPL Response to NRC Question Part a:
Prior to the beginning and after completing work on the Unit 1- 4.16kV ESS Buses, both loops ofRHRSW on Unit 2 will be operable. Power to the RHRSW Loop 'A' and 'B' Spray Pond Return Valves, which are powered from Unit 1, will be available and power to the Unit 2 RHRSW Pumps, which are powered from the Unit 2- 4.16kV Buses, will be available.
While work is being performed on the Unit 1 - 4.16 kV ESS Bus 1A20 1 or 1A202, the operability ofRHRSW on Unit 2 will be affected. When 1A201 is out of service, the RHRSW return to the 'A' Loop Spray Pond Valves will not have power. Similarly, when 1A202 is out of service, the RHRSW return to the 'B' Loop Spray Pond Valves will not have power.
Without power, the ability of the Operator to operate these valves remotely is removed. The normal alignment for the RHRSW return to the Spray Pond Valves on either loop is as follows: (1) the Large and Small Spray Array Valves are normally closed and (2) the Bypass Valve is normally open.
Attachment to PLA-6834 Page 3 of6 During the extended completion time, the RHRSW Spray Pond Return Bypass Valve, HVO 1222A or B, on the out of service loop will be electrically de-powered in the open position. The RHRSW Spray Array valves on the out of service loop will remain in their normally closed position.
With the out of service RHRSW Loop configured with the bypass valve open and deenergized, a return flow path is established. With this return flow path established, the affected RHRSW Loop on Unit 2 will be functional. Since only one loop at a time will be affected by the Unit 1 - 4.16kV breaker work, this alignment provides Unit 2 with one functional RHRSW loop and one operable RHRSW loop. This condition is described in table format below:
Busln Limiting Unit2 Unit2 Affected Condition Operable RHRSW RHRSW Comments for RHRSW Functional Loop Operation Loop Loop (LCO) 1A201 Loop A LoopB Loop A Flow through
[Case 1] Bypass only on Loop A, until operator action is taken.
1A202 LoopB Loop A LoopB Flow through
[Case 2] Bypass only on Loop B, until operator action is taken.
With the RHRSW Spray Pond Return Bypass Valve, HV01222A orB, electrically disabled in their open positions, all flow through the affected loop will go directly to the Spray Pond. With process fluid flowing through the bypass valve, spray co~ ling to the returning process fluid is not available. This will result in a more rapid heat up of the Spray Pond. Under Design Basis LOCA/LOOP Conditions, Spray Pond temperatures exceeding the design Spray Pond temperature for supporting cooling of both units can occur unless the manual return line bypass valve is closed within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The conditions driving the elevated Spray Pond temperatures in the design basis analysis are as follows:
Attachment to PLA-6834 Page 4 of6
- The use of conservative reactor decay heat values.
- The use of conservative meteorology.
- The use of conservative initial Spray Pond temperatures, i.e., Technical Specification Maximum Temperature.
The use of conservative values for these parameters is required in the design and licensing basis for SSES. Calculations performed using still conservative, but more "best estimate" values for each of these parameters have determined that additional time is available for the operator to perform a manual action to prevent Spray Pond temperatures from exceeding the peak Spray Pond temperature. The assumptions used in the "best estimate" analysis are as follows:
- Both Units are operating at 100% power.
- LOCA/LOOP conditions require shutdown of both Units due to a LOCAILOOP on one Unit and the other Unit being shutdown by the LOOP.
- The bypass valve on one loop is assumed to fail open. The large and small spray array valves on this loop are closed. Within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, operator actions will be performed to realign this loop to prevent further bypass of the spray arrays.
- The large spray array valve on the other loop is open and spraying. The bypass and small spray array valves on this loop are closed and remain closed.
- "Best Estimate" meteorology is used, e.g., the 30 worst consecutive days measured at the site synthesized into a single day and repeated for the full 30 day duration is used.
- "Best Estimate" decay heat is used, e.g., the 2 sigma conservatism of the decay heat input is removed.
- "Best Estimate" initial Spray Pond temperature is used, e.g., 80° F +
0.5° F, for instrument tolerance. The 80° F initial Spray Pond temperature is based on the highest monthly average pond temperature.
For this "best estimate" analysis, with one loop's bypass valve open for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and the large spray array valve open on the opposite loop, the peak Spray Pond temperatures are still approximately 4 degrees F below the peak Spray Pond temperature required to safely shut down both units under LOCA/LOOP conditions.
Attachment to PLA-6834 Page 5 of6 There are also some additional conservatisms that apply to the configuration described for either Case 1 or Case 2 described in the table above that will exist during the extended completion time. They are as follows:
- The initial Spray Pond temperature, in the "best estimate" case discussed above, was around 80° F. The Spray Pond temperatures for the duration of this temporary change would not be expected to be anywhere near this level since the work is being performed in April when the daytime temperatures average less than 80 degrees F.
- Additionally, for either Case 1 or Case 2 described in the table above, Unit 1will be in cold shutdown, Mode 4 or 5.
- The meteorology during the time frame when the extended completion time applies would not be expected to be anywhere near the temperatures assumed in the "best estimate' meteorology.
Based on the analysis described above for the Spray Pond, it is expected that should a LOCA/LOOP condition occur on Unit 2 with Unit 1 already in cold shutdown, the time required for performing an operator action to isolate the loop ofRHRSW with the open bypass valve would be substantially longer.
It is estimated that Spray Pond temperature would remain below the peak allowable limit even if no additional operator actions were taken for a period approaching 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. Since closing of the manual bypass valve can be accomplished in as little as 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, significant margin exists.
Therefore, the safety consequences associated with extending the LCO completion time for the 4.16kV Bus work are not considered to be high.
PPL Response to NRC Question Part b:
PPL has reviewed the completion dates for the referenced Surveillance Requirements and determined that the completed surveillances provide confidence that the RHRSW Loops will be operable when needed during the Unit 1 4.16 kV ESS Bus outages. The following is a summary of the completion dates for each surveillance:
SR 3.7.1.3 (valve alignment check every 31 days) -last performed on 02/29/2012 and will be performed prior to the bus outages.
SR 3.7.1.4 (spray array bypass valves every 92 days) -last performed 03/24/2012.
SR 3.7.1.5 (large spray array valves every 92 days) -last performed 03/24/2012.
Attachment to PLA-6834 Page 6 of6 SR 3.7.1.6 (small spray array valves every 92 days) -last performed 03/24/2012.
SR 3.7.1.7 (spray array bypass manual valves every 92 days) -last performed 02/23/2012 for Loop A and 02/27/2012 for Loop B.
Having just completed the surveillances provides confidence that the RHRSW loops are operable. In addition, the operable RHRSW loop's equipment will be protected. Thus, this will assure that the required loop will remain operable.