ML070160009

Relief Letter 2007-01-08

ML070160009
Person / Time
Site:	Duane Arnold
Issue date:	03/14/2007
From:	Raghavan L NRC/NRR/ADRO/DORL/LPLIII-1
To:	Vanmiddlesworth G Duane Arnold
Karl Feintuch, LPL3-1
References
TAC MD1844
Download: ML070160009 (8)

Text

March 14, 2007 Mr. Gary Van Middlesworth Vice President Duane Arnold Energy Center 3277 DAEC Road Palo, IA 52324-9785

SUBJECT:

SAFETY EVALUATION OF RELIEF REQUEST FOR THE DUANE ARNOLD ENERGY CENTER FOURTH 10-YEAR PUMP AND VALVE INSERVICE TESTING PROGRAM (TAC NO. MD1844)

Dear Mr. Van Middlesworth:

By letter dated May 8, 2006, as supplemented on November 3, 2006, FPL Energy Duane Arnold, LLC (FPL Energy) submitted a request for relief (designated as PR-03) from the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) requirements for the Duane Arnold Energy Center (DAEC).

The subject relief request is for the fourth 10-year inservice testing (IST) interval at DAEC, which began on February 1, 2006.

The U.S. Nuclear Regulatory Commission staff has completed its review of relief request PR-03 as documented in the enclosed Safety Evaluation (SE). Our SE concludes that the proposed alternative provides reasonable assurance of the operational readiness of the standby liquid control pumps. Therefore, the proposed alternative is authorized, pursuant to Section 50.55a(a)(3)(ii) of Title 10 of the Code of Federal Regulations for the remainder of the fourth 10-year IST interval, on the basis that compliance with the ASME OM Code requirements would result in hardship without a compensating increase in the level of quality and safety.

If you have any questions regarding this matter, please contact Mr. Karl Feintuch at (301) 415-3079.

Sincerely,

/RA/

L. Raghavan, Chief Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-331

Enclosure:

Safety Evaluation cc w/encl: See next page

ML070160009 OFFICE LPL3-1/PM LPL3-1/PM LPL3-1/LA CPTB/BC OGC LPL3-1/BC NAME KFeintuch REnnis THarris JMcHale TCampbell LRaghavan DATE 3/12/07 1/19/07 3/9/07 1/29/07 2/1/07 3/14/07 Duane Arnold Energy Center cc:

Mr. J. A. Stall Mr. M. Warner Senior Vice President, Nuclear and Vice President, Nuclear Operations Chief Nuclear Officer Support Florida Power & Light Company Florida Power & Light Company P. O. Box 14000 P. O. Box 14000 Juno Beach, FL 33408-0420 Juno Beach, FL 33408-0420 Mr. M. S. Ross Mr. D. A. Curtland Managing Attorney Plant Manager Florida Power & Light Company Duane Arnold Energy Center P. O. Box 14000 3277 DAEC Rd.

Juno Beach, FL 33408-0420 Palo, IA 52324-9785 Mr. R. E. Helfrich Mr. R. S. Kundalkar Senior Attorney Vice President, Nuclear Engineering Florida Power & Light Company Florida Power & Light Company P. O. Box 14000 P. O. Box 14000 Juno Beach, FL 33408-0420 Juno Beach, FL 33408-0420 Mr. W. E. Webster Daniel K. McGhee Vice President, Nuclear Operations Iowa Department of Public Health Florida Power & Light Company Bureau of Radiological Health P. O. Box 14000 321 East 12th Street Juno Beach, FL 33408-0420 Lucas State Office Building, 5th Floor Des Moines, IA 50319-0075 John Bjorseth Site Director Chairman, Linn County Duane Arnold Energy Center Board of Supervisors 3277 DAEC Road 930 1st Street SW Palo, IA 52324 Cedar Rapids, IA 52404 Steven R. Catron Manager, Regulatory Affairs Duane Arnold Energy Center 3277 DAEC Road Palo, IA 52324 U. S. Nuclear Regulatory Commission Resident Inspectors Office Rural Route #1 Palo, IA 52324 October 12, 2006 Regional Administrator, Region III U.S. Nuclear Regulatory Commission Suite 210 2443 Warrenville Road Lisle, IL 60532-4351

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO A RELIEF REQUEST FOR THE FOURTH 10-YEAR INTERVAL OF THE INSERVICE TESTING PROGRAM FPL ENERGY DUANE ARNOLD, LLC DUANE ARNOLD ENERGY CENTER DOCKET NO. 50-331

1.0 INTRODUCTION

By letter dated May 8, 2006, FPL Energy Duane Arnold, the licensee for Duane Arnold Energy Center (DAEC), requested relief from certain inservice testing (IST) requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for the Standby Liquid Control (SBLC) injection pumps.

By letter dated November 3, 2006, the licensee provided additional information related to relief request PR-03.

2.0 REGULATORY EVALUATION

Title 10 of the Code of Federal Regulations (10 CFR) 50.55a, requires that IST of certain ASME Code Class 1, 2, and 3 pumps and valves be performed at 120-month (10-year) IST program intervals in accordance with the specified ASME Code and applicable addenda incorporated by reference in the regulations, except where alternatives have been authorized or relief has been requested by the licensee and granted by the Nuclear Regulatory Commission (NRC) pursuant to paragraphs (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a.

In accordance with 10 CFR 50.55a(f)(4)(ii), licensees are required to comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in the regulations 12 months prior to the start of each 120-month IST program interval. In accordance with 50.55a(f)(4)(iv), IST of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b),

subject to NRC approval. Portions of editions or addenda may be used provided that all related requirements of the respective editions and addenda are met.

In proposing alternatives or requesting relief, the licensee must demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance is impractical for the facility.

ENCLOSURE

Section 50.55a authorizes the NRC to approve alternatives and to grant relief from ASME Code requirements upon making necessary findings. NRC guidance contained in Generic Letter (GL) 89-04, Guidance on Developing Acceptable Inservice Testing Programs, provides alternatives to Code requirements which are acceptable. Further guidance is given in GL 89-04, Supplement 1, and NUREG-1482, Revision 1, Guidance for Inservice Testing at Nuclear Power Plants.

At DAEC, the code of record for the fourth 10-year interval is the 2001 Edition through 2003 Addenda of the ASME OM Code.

3.0 TECHNICAL EVALUATION

3.1 Pump Relief Request PR-03 3.1.1 Code Requirements The licensee requested relief from ISTB-3550 and ISTB-5300(a)(1) of the ASME OM Code.

Paragraph ISTB-3550 requires that when measuring flow rate, a rate or quantity meter shall be installed in the pump test circuit.

Paragraph ISTB-5300(a)(1) requires that for the Group A test and the comprehensive test, after pump conditions are as stable as the system permits, each pump shall be run at least 2 minutes. At the end of this time at least one measurement or determination of each of the quantities required by Table ISTB-3000-1 shall be made and recorded.

Relief was requested for the 1P230A and 1P230B SBLC pumps.

3.1.2 Licensees Basis for Requesting Relief In its letter dated May 8, 2006, the licensee stated:

Impracticality of Compliance The positive displacement SBLC pumps are designed to pump a constant flow rate regardless of system resistance. The SBLC system was not designed with a flow meter in the flow loop. The system was designed with a test tank, where the change in the level can be measured over time and a flow rate calculated. As part of the modifications made to the SBLC system for the ATWS Rule (10 CFR 50.62), DAEC installed instrumentation to measure flow. The ultrasonic flow meter that was installed, however, was not intended to meet the accuracy requirements of the ASME OM Code, and has not proven to be capable of meeting Code accuracy requirements. The accuracy performance of the flow meter is attributed to the lack of adequate straight length of pipe to establish fully developed flow.

In March, 2006, portable ultrasonic flow meters were installed on the common SBLC pump discharge piping to determine the practicality of using later-technology ultrasonic flow meters to measure flow per ASME OM Code requirements. The flow meter transducers were installed at three different locations on the discharge piping. A vendor

representative was on-site to facilitate proper installation and setup of the transducers and flow meters. Each location produced significantly different measured flow rates compared to the other locations and the test tank level method.

NUREG 1842, Revision 1 recognizes that plants may have difficulties with flow instrumentation. In Section 2.5.1, Justification for Relief, the NUREG states that compliance with the Code may be impractical because of design limitations. Imposition of the Code requirements would require significant system redesign and modifications.

For example, a flow meter does not meet the accuracy requirements of ISTB 3510

[4.7.1.] and Table ISTB 3500-1 [4.7.1-1] because the present system configuration does not have a straight section of pipe of sufficient length in which to measure flow accurately ... .

Burden Caused by Compliance Flow measurement cannot be achieved to the required accuracy using a flow meter.

In addition, the SBLC test tank is not large enough to provide two minutes of flow prior to recording flow data. As discussed in NUREG 1482, Revision 1, Section 5.5.2, requiring installation of a flow meter to measure the flow rate, and to guarantee the test tank size, such that the pump flow rate will stabilize in 2 minutes before recording data, would be a burden because of the design and installation changes that would have to be made to the existing system.

3.1.3 Licensees Proposed Alternative Testing In its letter dated May 8, 2006, the licensee stated:

Flow rate for the SBLC pumps will be determined by measuring the change in test tank level over time. The pump will be started with suction from the test tank and will discharge to storage barrels. The test tank level will be approximately the same at the beginning of each test to ensure repeatability. After at least two minutes of pump operation and a change of tank level of at least 20 inches, the time and level are recorded and the pump stopped. The change in level over the measured time will be converted to flow rate by the following formula:

Q (GPM) = L (inch) / t (second)

Where: Q is flow rate is a constant which reflects tank dimensions and unit conversions L is the measured change in level in the tank in time t Pump discharge pressure will match system pressure up to the shutoff head of the positive displacement pump. Because of the characteristics of a positive displacement pump, there should be virtually no change in pump discharge flow rate as a result of the rising level in the temporary storage barrels. Therefore, increasing level will not have an impact on test results. By having approximately the same level in the tank at the beginning of each test, repeatable results can be achieved.

Per NUREG 1482, Revision 1, Section 5.5.2, Use of Tank Level to Calculate Flow Rate for Positive Displacement Pumps, when flow meters are not installed in the flow loop of a system with a positive displacement pump, it is impractical to

directly measure flow rate for the pump. The staff has determined that, if the licensee uses the tank level to calculate the flow rate as described in Subsection ISTB 3550 [4.7.5], the implementing procedure must include the calculation method and any test conditions needed to achieve the required accuracy. ... If the meter does not directly indicate the flow rate, the record of the test shall identify the method used to reduce the flow data. The test tank level will be measured in accordance with the accuracy requirement of OM Code Table ISTB-3500-1. The calculation method and test conditions required to achieve this accuracy are documented in the implementing procedures.

3.1.4 Evaluation The ASME OM Code requires that pump flow rate be measured in order to determine the extent of any pump degradation. A 2-minute run time is required by the ASME OM Code in order to achieve stable pump performance parameters before data are recorded during the test.

The positive displacement SBLC pumps utilized at DAEC are designed to pump a constant flow rate regardless of system resistance. The SBLC system was not initially designed with flow meter instrumentation in the flow loop, and uses a test tank to determine flow rate by measuring the change in tank level over a period of time. As part of the modifications made to the SBLC system to meet 10 CFR 50.62 requirements, DAEC installed an ultrasonic flow meter to measure SBLC flow. However, the ultrasonic flow meter was not intended to meet the accuracy requirements of the ASME OM Code, and has not proven to be capable of meeting OM Code accuracy requirements due to the lack of an adequate straight length of pipe which is necessary to establish fully developed flow.

In March 2006, DAEC installed portable ultrasonic flow meters to determine the practicality of using later technology instrumentation to measure flow per ASME OM Code requirements. The portable ultrasonic flow meters failed to produce consistent results using tank level to calculate flow rate (the remaining practical alternative). However, the test tank is not large enough to provide 2 minutes of flow prior to recording flow data. Requiring DAEC to install a larger test tank to facilitate pump testing would be a burden because of the design, fabrication, and installation changes that would have to be made.

As an alternative to the ASME OM Code requirements, the licensee is proposing to measure the flow rate by determining the change in source tank level over a period of time and calculating an average flow rate from the tank. The change in flow resistance due to the rising level of temporary storage barrels, will be small in comparison with the pump discharge pressure, thereby having no significant effect on the test results. Provided the tank level at the beginning of each test is approximately the same, repeatable results can be achieved. This method is consistent with the NRC Staffs recommendation in NUREG-1482, Revision 1, and therefore provides reasonable assurance of the pumps operational readiness when the test tank level is measured in accordance with the accuracy requirements of Table ISTB-3500-1.

Implementing procedures must include the calculation method and any test conditions required to achieve this accuracy.

4.0 CONCLUSION

The NRC staff concludes that the proposed alternative provides reasonable assurance of the operational readiness of the SBLC pumps. Therefore, the proposed alternative is authorized, pursuant to 10 CFR 50.55a(a)(3)(ii) for the remainder of the fourth 10-year IST interval, on the basis that compliance with the ASME OM code requirements would result in hardship without a compensating increase in the level of quality and safety.

Principal Contributor: Y. Wong Date: March 14, 2007