ML110670421
| ML110670421 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 03/02/2011 |
| From: | Swift P Constellation Energy Group, EDF Group, Ginna |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-08-001 | |
| Download: ML110670421 (6) | |
Text
Paul Swift Manager, Nuclear Engineering Services CENG a joint venture of 9Constellation e
O Enery
~
eDF R.E. Ginna Nuclear Power Plant, LLC 1503 Lake Road Ontario, New York 14519-9364 585-771-5208 585-771-3392 Fax Paul.Swift(.cenqllc. com March 2, 2011 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
SUBJECT:
Document Control Desk R.E. Ginna Nuclear Power Plant Docket No. 50-244 Response to Request for Additional Information Related to Generic Letter 2008-01 (a) Letter from Douglas Pickett (NRC) to John Carlin (CENG), dated January 18, 2011 (ADAMS Accession No. ML103610068), "Request for Additional Information Re: Generic Letter 2008 R.E. Ginna Nuclear Power Plant (TAC No. MD 7830)"
(b) Letter from John Carlin (CENG) to NRC, dated October 13, 2008 (ADAMS Accession No. ML082910042), "Nine-Month Response to NRC Generic Letter 2008-01, 'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems'"
REFERENCES:
On January 18, 2011, the NRC requested additional information (Reference (a)) regarding the October 13, 2008 response (Reference (b)) to Generic Letter 2008-01: "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems". Enclosed please find our response to this request.
If there are any questions or if additional information is required, please contact Mr. Thomas Harding at (585) 771-5219 or at Thomas. HardinqJr(ccenqllc.com Very truly yours, Paul M. Swift
Document Control Desk March 2, 2011 Page 2
Attachment:
R.E. Ginna Response to GL 08-01 Request for Additional Information CC:
W. M. Dean, NRC D.V. Pickett, NRC Resident Inspector, NRC (Ginna)
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Attachment R.E. Ginna Response to GL 08-01 Request for Additional Information
Attachnent R.E. Ginna Response to GL 08-01 Request for Additional Information This attachment contains the R.E. Ginna Nuclear Power Plant response to the Nuclear Regulatory Commission's Request for Additional Information (RAI).
Reference 1 was reviewed, which is generally consistent with the Nuclear Energy Institute guidance provided to the industry (Reference 2), to develop our responses to the RAIs.
- 1. The licensee states that there are no periodic venting requirements in the Ginna current licensing basis. How does the licensee determine that there are no operability concerns due to accumulated gas in piping?
Ginna ensures that there are no operability concerns for the Emergency Core Cooling System (ECCS) and Containment Spray (CS) systems due to accumulated gas in piping through monitoring that is required by the Gas Intrusion Management Program. The system monitoring includes periodic ultrasonic (UT) examinations, pressure trending, and required actions for accumulator fills.
Ginna performs ultrasonic examinations at potential gas intrusion pathways and select gas accumulation high points in ECCS and CS piping. UT examinations are performed at select locations for each RFO. Periodic UT examinations are also performed at select locations during online operation as governed by repetitive maintenance tasks. UT examinations are performed following refill of in-scope systems after maintenance and testing where required by the planning and work order review process.
The Gas Intrusion Management Program requires that all discovered gas is entered into the Corrective Action Process (CAP) and evaluated and dispositioned based on program criteria discussed in RAI #2 and RAI #3 below.
- 2. If the licensee does find a void,* what is done to evaluate, track and trend it?
Gas voids are compared against acceptance criteria. The acceptance criterion is included in the UT inspection procedures for periodic UT surveillances. The UT inspection procedures define operability screening decision points based on the acceptance criteria and measured void size. Discovered gas voids are entered into the CAP at Ginna for further evaluation by the Gas Intrusion Management Program Owner. The Program Owner evaluates discovered voids to determine the source of the intrusion, to determine if additional inspections are required, and to establish corrective actions. Reasonable efforts are made to remove discovered gas voids until no void remains. In cases where reasonable efforts have not completely removed a void but acceptance criteria are satisfied, the Program Owner may accept a void with no further immediate actions required. In these limited cases, the Program Owner accounts for the void and adjusts subsequent acceptance criteria accordingly. Void trending is accomplished by repeat UT inspections where necessary, and by the Program Owner tracking of voids. See the response to RAI #3 for discussion of gas void acceptance criteria.
Page 1 of 3
Attachment R.E. Ginna Response to GL 08-01 Request for Additional Information
- 3. Please describe the basis for the void acceptance criteria used at Ginna. Note that Reference 5 contains void acceptance criteria that the NRC will accept without/further justification.
Ginna uses standard industry methods to define acceptance criteria for pump suction void fractions, Net Positive Suction Head (NPSH) changes (for steady state gas intrusion),
delay of delivery, non-condensable gases injected to the core, and water hammer analyses. This includes the use of Reference 7 for pump suction void fraction criteria and NPSH, Reference 8 to assess non-condensable gasses delivered to the Reactor Coolant System (RCS), and delay of delivery is assessed in accordance with Reference 7 guidance on degraded pump performance and Ginna's cun'ent Accident Analyses.
The criteria in Table 1 of Reference 7 for pump suction void fractions are similar to the Table included in Section 1.4.1 of Reference 5. The difference between the Staff's criteria discussion in Reference 5 and Ginna's ingestion limit criteria is that Ginna does not specifically determine the instantaneous void fraction to ensure it is less than 1.7 times the average void fraction limit from Table 1 of Reference 7. This maximum instantaneous void fraction limit is equivalent to the maximum expected instantaneous void fraction if the average void fraction is based on the criteria in Reference 7. The instantaneous limit ensures that slug flow is not developed. Ginna recognizes that slug flow is unacceptable, and uses standard industry methods to preclude slug flow. For example, Ginna has used the 0.5 second interval criteria contained within Reference 4 to ensure slug flow was precluded. In addition, the "Simplified Equation" approach discussed in Reference 7 is a method currently used by Ginna to ensure that slug flow is
- not introduced into the pump suctions.
- 4. Training was not identified in the GL but is considered to be a necessary part of applying procedures and other activities when addressing the issues identified in the GL. Briefly discuss training.
The Operations and Engineering training programs include initial and continuing training on GL 2008-01 concerns and related industry operating experience.
Courses include gas intrusion mechanisms, concerns with gas in liquid filled systems, and an overview of what is evaluated to determine acceptable gas volumes. Engineering training also includes design modifications that are currently used in the industry to mitigate gas accumulation.
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Attachment R.E. Ginna Response to GL 08-01 Request for Additional Information REFERENCES
- 1. Ruland, William H., "Preliminary Assessment of Responses to Generic Letter 2008-0 1,
'Managing Gas Accumulation in emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems,' and Future NRC Staff Review Plans," NRC letter to James H. Riley, Nuclear Energy Institute, ML091390637, May 28, 2009.
- 2. Riley, James H., "Generic Letter (GL) 2008-01, 'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Contain Spray Systems' Evaluation and 3 Month Response Template," Letter to Administrative Points of Contact from Director, Engineering, Nuclear Generation Division, Nuclear Energy Institute, Enclosure 2, "Generic Letter 2008-01 Response Guidance," March 20, 2008.
- 3. Case, Michael J., "NRC Generic Letter 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems,"
Letter from Director, Division of Policy and Rulemaking, Office of Nuclear Regulation, NRC, ML072910759, January 11, 2008.
- 4. Lyon, Warren C., U.S. Nuclear Regulatory Commission, "Revision 2 to NRC Staff Criteria for Gas Movement in Suction Lines and Pump Response to Gas,"
ML090900136, March 26, 2009.
"Guidance To NRC/NRR/DSS/SRXB Reviewers for Writing TI Suggestions for the
, Region Inspections," ML103400347, December 6, 2010.
- 6. Carlin, John, "Nine-Month Response to NRC Generic Letter 2008-01,"Managing Gas Accumulation in Emergency Core Cooling Decay Heat Removal, and Containment Spray Systems,"" Letter to Document Control Desk, NRC, from Site Vice President, Constellation Energy Nuclear Group, ML082910042, October 13, 2008
- 7. NEI document NEI-09-10, Revision 1, "Guidelines for Effective Prevention and Management of System Gas Accumulation," ML110240126, December 2010
- 8. PWR Owner's Group - LTR-LIS-08-627, "PWROG Position Paper on Non-condensable Gas Voids in ECCS Piping; Qualitative Engineering Judgment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events, Task 3 of PA-SEE-450," ML090980303, April 2, 2009 Page 3 of 3