ML20154S382

Requests That Relief from ASME Boiler & Pressure Vessel Code,Section XI Re Boric Acid Transfer Pump Flow Measurement Be Reconsidered.Revised Justification Encl

ML20154S382
Person / Time
Site:	Sequoyah
Issue date:	10/03/1988
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TAC-R00479, TAC-R00480, TAC-R479, TAC-R480, NUDOCS 8810050057
Download: ML20154S382 (7)

Text

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TENNE @SEE VALLEY AUTHORITY CH ATT ANOOG A. TENNESSCE 37401 SN 1578 Lookout Place 00T 031988 U.S. Nuclear Regulatory Commission ATTh: Document Control Desk Washingten. D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT (SQN) - RELIEF REQUEST FROM AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) BOILER AND PRESSURE VESSEL CODE SECTION XI, REGARDING BORIC ACID TRANSFER PUNP (BATP) FLOW HEASUREMENT

References:

1. TVA letter to NRC dated November 4, 1982

2. NRC letter to TVA dated April 5,1985 "Safety Evaluation Report on Sequoyah Inservice Test Program for Fumps and Valves (IST)"

3. TVA letter to NRC dated August 16, 1985 By reference 1, TVA requested relief from the ASME code requirement to measure flow rate from SQN's BATPs during quarterly pump performance tests. The basis for relief was due to flow indication not being available for these pumps. NRC, by reference 2, transmitted their safety evaluation report (SER) for SQN's in-service test (IST) program.

Paragraph 2.3.2.4 of this SER contained a dental of TVA's relief request. Because modifications were considered necessary in order to meet the code requirement, interim reitef was granted for unit 2 untti the unit 2 cycle 3 refueling outage. Interim relief was granted for unit I until the 10-year update of the SQN unit 1 IST program.

TVA, by reference 3. stated that an alternate lineup was being examined for the BATPs, which would allow alignment through existing plant flow j instrumentation. TVA examined the alternate system configuration and  !

other types of flow instrumentation to determine a method of complying l with the SER determination. Under the existing system configuration and '

flow instrumentation constraints. TVA is unable to accurately measure t,.e I flow rate from these pumps. TVA requests that, in consideration of the revised justification presented in enclosure 1 the subject relief be ,

reconsidered. l l

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I An Equal Opporturnty Employer

t U.S. Nuclear Regulatory Commission 00T 031988 <

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Please direct questions concerning this issue to D. V. Goodin at  ;

2 (615) 870-7734.  :

Very truly yours, l

1 l TENNESSEEVALLEYAUTHORITJ k7peZp  ;

R. Gridley, Manager i Nuclear Licensing and Regulatory Affairs ,

J Enclosure .

! cc (Enclosure)* '

Ms. S. C. Black, Assistant Director i for Projects I TVA Projects Olvision j U.S. Nuclear Regulatory Commission  !

j One White Filnt, North  !

3 11555 Rockville Pike  !

Rockville, Marylend 20852 '

Mr. F. R. McCoy, Assistant Olrector for Inspection Programs  !

TVA Projects Olvision l U.S. Nuclear Regulatory Commission  ;

Region II  ;

, 101 Marietta Street, NW, Suite 2900  ;

i Atlanta, Georgia 30323  !

Sequoyah Resident Inspector I j Sequoyah Nuclear Plant j 2600 Igou Ferry Road I

, Soddy Daisy, Tennessee 37379 i

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j  !

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• ENCLOSURE 1 DESCRIPTION OF RELIEF REQUEST The SON pump and valve in-service test program is contalped in the SQN Final  ;

Safety Analysis Report (FSAR), section 6.8, appendix 6.8a. Table A of appendix 6.8a lists those pumps that are tested to meet the ASME Section XI

• requirements. Each code-required pump parameter is given at the top of i table A. Where conditions exist that preclude the measurement of a specific .

parameter, a note is provided to explain the basis for relief. Note 2 served j as the relief request for the BATPs when SQN's program was submitted to NRC in November 1982. N0te 2 reads as follows:

Flow rate is not required sinco this pump is tested in a fixed '

resistance pathway. Reitef is requested from the 1977 Edition -

through Summer 1978 Addenda for Unit 2 since flow indication is not available.

It is important to note that the subject relief request was only applicable to unit 2, which is under the 1977/1978 Edition of the Section XI Code. This i edition requires measurement of pump flow rate, whereas the 1974 Edition (unit 1) does not, provided the pump is operated in a fixed resistance system. ,

NRC evaluated TVA's basis for relief in section 2.3.2.3 of the April 5,1985 SER. The staff's evaluations and conclusions are as follows:

Evaluation. Given the present system configurations, pump flow rate  !

cannot be measured in accordance with the requirements of Section XI  !

for these pumps. However, the licensee may not be able to adequately monitor the hydraulic characteristics of these pumps without measurement of pump flow rate. The current NRC staff position is that the licensee should measure both flow rate and differential pressure in accordance with the requirements of current edttions of i Section XI. The 1974 edition of Section XI is considered to be i incorrect in this regard and later editions properly require  !

measurement of both parameter:. Therefore, relief should not be  ;

granted from the Section XI requirement of measuring flow rate for ,

these pumps. Further, when Sequoyah unit 1 is due for Section XI update of its IST progrum*, the staff will require measurement of (

both flow rate and differential pressure at Unit 1. j i

Conclusion. The licensee must measure pump flow rate in accordance l with the requirements of Section XI for Sequoyah Unit 2. The ,

licensee should also consider future modifications to Unit I which I will become necessary when the IST for Unit 1 is upgraded *. The i licensee is required to make these modifications prior to startup at the end of the next refueling outage.**

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• The 10-year update fer the unit 1 IST program is currently projected for I 1993. l f

• • Unit 2 cycle 3 refueling outage, which is projected for January 1989. ]

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i for the balance of the period of the current fuel cycle, interim  ;

reitef is granted to test the pumps as proposed by the licensee. The '

pumps will be monitored on a op rterly basis for vibrations, amplitude, inlet pressure and differential pressure. Requ' ing the

, licensee to make these modifications for Unit 2 prior to tne next i refueling outage would impose unnecessary hardsnip on the licensee 1 without compensating increase in the level of safety. Taking into i account the inservice tests that will be performed as well as the relatively short operational time that the pumps have been in service '

to date, it is concluded that this interim relief will not endanger life or property or the comon defense and security of the public. l Following receipt of the staff's evaluation, TVA investigated three options l for measuring flow from the BATPs. These options included: (1) ultrasonics; I

(2) an alternate system alignment to allow the use of an existing ,

l plant-installed flow device (rotometer); and (3) a modification to install a l

flow orifice within the pump test circuit. The following evaluation discusses

the results of TVA's investigation into each of these options. ,

) (1) Ultrasontes j TVA evaluated the use of ultrasonics as a means of measuring flow from the j BATPs. The use of ultrasonics requires mounting a set of transducers to the

. outer pipe wall. The boric acid system at SQN is completely lined with two  :

1 layers of heat tracing cables surrounded by wrapped fiberglass insulation that l 1 ensure the temperature of the boric acid solution remains above this technical  ;

j specification (TS) limit of 145 degrees Fahrenheit (F). To facilitate the use

of ultrasonics woulc require removal of the insulation and heat tracing cables every quarter for testing one BATP (SON has two pumps per unit). This would place an unnecessary burden on the maintenance staff for frequent removal of the insulation and heat tracing. In addition, the plant would be required to i 3

enter a limiting condition of operation (LCO) if the temperature of the boric i acid solution drops below the TS limit. For these reasons, TVA considers the ,

use of ultrasonics to be impractical. Note that this conclusion was provided l j tr enclosure 2, section 2.3.2, of TVA's August 16, 1985 response. j (2) Rotometer 4

1 TVA investigated an alternate lineup for the boric acid pump test that would  !

align existing plant flow instrumentation. The only flow instrumentation

, within the boric acid system is a flow rotometer with an accuracy of

15 percent of full scale. This flowmeter is not designed to be removed frcm i 2

the system piping, and no means exist to calibrate the treter in place. This ,

constrairit precludes peelodic calibration to verify rotometer accuracy. '

Consequently, the rotometer has not demonstrated sufficient accuracy to  ;

j provide meaningful data for consistent trending to determine degradation in  ;

purrp performance. TVA thereby con-iders this option to be tropractical.  ;

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3 (3) Flow Orifice TVA evaluated the installation of a flow orifice within the pump test circuit. Experience has shown that this type of flow measuring device would be difficult, if not impossible, to maintain in an accurate condition. The high concentration of boric acid requires the flow orifice to be thoroughly flushed after each use to preclude solidification of boron on the orifics plates and instrument sense lines. Flushing the boric acid from the system would require a modification to install a heat-traced collection tank to allow storage of the boric acid during the flushing process. Frequent flushing of the boric acid system would create additional operational burdens for maintaining a borated water source. SQN TSs 3.1.2.5 and 3.1.2.6 require that minimum volume, concentration, and temperature of the boric acid storage system bei maintained while in modes 1 through 6. Based on the above evaluation, TVA concludes that the installation of a flow ortftce, for the purpose of measuring BATP flow, is impractical and would result in undue hardship.

In light of TVA's examination of the three options above, TVA requests that the subject relief be reconsidered by the NRC staff. Attachment A of this enclosure provides TVA's revised basis regarding the request for relief and the proposed alternate testing.

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ATTACHMENT A I. BATPs A. Code Requirements Article IWP-3100 of Section XI of the ASME Code l requires that, for Section XI pump tests, the pump '

flow rate be measured.

S. Relief Request TVA requests relief from the requirements of IMP-3110 to measure the flow rate during testing of the SQN BATPs. TVA proposes to test the BATPs in a constant resistance flow path and to measure ,

the other hydraulle and vibration parameters to '

detect pump degradation.

C. Basis for Relief The current plant configuration contains only one flow measuring instrument in the boric acid system. This flow device is a flow rotometer with an accuracy of 25 to 110 percent of f Jll scale.

This flow meter is not designed to be removed from the system piping, and no means exist to calibrate the meter in place. Therefore, the existing flow l meter does not provide meaningful data of ,

sufficient accuracy with which to detect degradation in pump performance.

The use of external flow measurement has been l Investigated. The boric acid system is required to be heat traced to prevent the solidification of boron in the piping. The two layers of heat tracing cables and the insulation covering  ;

preclude the use of external flow measuring  ;

devices such as ultrasonics.  ;

Because of the high concentration of boric acid in this system, a modification of the system to install a new flow measurement device would not provide the accuracy needed to detect pump I degradation. TVA experience with the '

solidification of boron in instrument sensing i lines and the plating of boro'1 on the inner walls I of the piping indicates that any flow measuring orifice or flow rotometer would be difficult, if not impossible, to maintain in an accurate condttion.

D. Alternate Testing TVA proposes to perform the pump testing by l recirculating to the boric acid tank through the i normal recirculation flow path with all valves in the fully open position to provide a constant system resistance. By maintaining the system resistance constant, any degradation in the pump's performance will produce a corresponding change in both delivered flow and developed head. Based on the pump manufacturer's head versus capacity curve, any significant performance degradation would be detectable by a measured drop in the pump de/ eloped head. The pump suction and discharge  ;

pressures will be measured using test gauges, which have greater sensitivity than regular plant instruments. The pump bearing vibration readings will be recorded, which will also provide  ;

indication of pump degradation, j E. Conclusion The BATPs (two per unit - A traln/B train) are required by TSs to be capable of delivering l 10 gallons per minute (gal / min) to the reactor coolant system by the charging pumps. This requirement is provided for reactivity control to ensure that :hutdown margin is maintained within the required TS limits. Each BATP is a dual-speed i pump (fast speed / slow speed) that, by design, will  !

deliver 37.5 gal / min on slow speed and 75 gal / min  !

on fast speed. Normally these pumps operate at slow speed to recirculate the boric acid between the boric acid tanks and boron injection tank.

These pumps will automatically swltch to fa:t speed for automatic makeup to the volume control tank or the operator can manually switch them to  ;

fast speed from the control room, if desired. The design flow rates at either speed provide a large l margin ovF the 10 gal / min TS required flow rate. I Any significant change in pump performance that i would reduce this flow rate margin would be  !

detectable through changes in pump differential t pressure and/or bearing vibration measurements. '

For these reasons, TVA finds the code requirement i to be impractical and the proposed alternate test  ;

method acceptable. In conclusion, a plant modification to install a flow instrument that is t compatible with the boron heat tracing system, if one exists, would result in an undue hardship .

without a commensurate increase in the level of  !

qual 1ty or safety. l l

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