ML12300A219

Attachment 9: BWROG-TP-12-011, Revision 0, Task 2 - Equation for Pump Speed Correction (Cvds Pump)

ML12300A219
Person / Time
Site:	Monticello, Boiling Water Reactor Owners Group
Issue date:	08/31/2012
From:	Kalra A Sulzer Pumps (US), BWR Owners Group
To:	Office of Nuclear Reactor Regulation
Shared Package
ML123000308	List: ML12300A219 ML12300A220 ML12300A221 ML12300A222 ML12300A224
References
BWROG-12051 BWROG-TP-12-011, Rev 0
Download: ML12300A219 (8)

Text

Containment Accident Pressure Committee Task 2 - Equation for Pump Speed Correction (CVDS Pump)

Author: Ankur Kalra (Sulzer Pump) Project Manager: Kenneth Welch (GEH) Committee Chairman: John Freeman (Exelon) BWROG-TP-12-011 Revision 0 August 20 12 BWROG-TP-12-011 REV 0 INFORMATION NOTICE Recipients of this document have no authority or rights to release these products to anyone or organization outside their utility.

The recipient shall not publish or otherwise disclose this document or the information therein to others without the prior written consent of the BWROG, and shall return the document at the request of BWROG. These products can, however, be shared with contractors performing related work directly for the participating utility, conditional upon appropriate proprietary agreements being in place with the contractor protecting these BWROG products. With regard to any unauthorized use, the BWROG participating Utility Members make no warranty, either express or implied, as to the accuracy, completeness, or usefulness of this guideline or the information, and assumes no liability with respect to its use. BWROG Utility Members CENG - Nine Mile Point Chubu Electric Power Company DTE - Fermi Chugoku Electric Power Company Energy Northwest

- Columbia Comisión Federal de Electricidad Entergy - FitzPatrick Hokuriku Electric Power Company Entergy - Pilgrim Iberdrola Generacion, S.A. Entergy - River Bend/Grand Gulf Japan Atomic Power Company Entergy - Vermont Yankee J-Power (Electric Power Development Co.) Exelon (Clinton) Kernkraftwerk Leibstadt Exelon (D/QC/L) South Texas Project Exelon (Oyster Creek) Taiwan Power Company Exelon (PB/Limerick) Tohoku Electric Power Company FirstEnergy

- Perry Tokyo Electric Power Company NPPD - Cooper NextEra - Duane Arnold PPL - Susquehanna PSEG - Hope Creek Progress Energy

- Brunswick SNC - Hatch TVA - Browns Ferry Xcel - Monticello

BWROG-TP-12-011 REV 0 2Executive Summary This BWROG Technical Product provides a technical evaluation of the applicability of a standard equation to the Sulzer CVDS pump model used at the Monticello station and other BWR stations. The equation correlates changes in pump speed to changes in pump NPSH R.Implementation Recommendations This product is intended for use to address (in part) issues raised in the NRC Guidance Document for the Use of Containment Accident Pressure in Reactor Safety Analysis (ADAMS Accession No. ML102110167).Implementation will be part of the BWROG guidelines on the use of Containment Accident Pressure credit for ECCS pump NPSH analyses. Benefits to Site This product provides a technical response to the NRC concerns raised in the reference above regarding the potential for changes in NPSH R as pump operating speed is changed.

QUALITY LEVEL SULZER PUMPS (US) INC. DOCUMENT ASME CODE SECTION Direct DOC. NO: E12.5.1910 Indirect ORDER NO:

100072780 CLASS NO.CODE EDITION (YEAR)TITLE:Task 2 - Equation for Pump Speed Correction Sulzer Pumps (US) Inc.

SEASON YEARMonticello - RHR & CS Pumps CUSTOMERGE-HITACHI Nuclear Energy Americas LLC PROJECT Monticello Nuclear Power Station, Monticello, MN CUSTOMER P.O. NO.

437054820CONTRACT NUMBER SPECIFICATION NO.

ITEM / TAG NUMBER CUSTOMER APPROVAL NUMBER: CUSTOMER APPROVAL REQUIREMENT Yes No Information Only SPACE FOR CUSTOMER APPROVAL STAMP CERTIFIED AS A VALID SULZER PUMPS (US) INC. DOCUMENT (when applicable/available) For Outside Vendor For Manufacture at Sulzer Pumps (US) Inc. Risk Release Inspection Report # ________________ Other (specify)

_______________________ APPROVALS(SIGNATURE)Date Engineering 03/12/12QualityAssurance CERTIFICATION (when applicable)

Originating Advance Engineering This Document is certified to be in compliance Dept: with THE APPLICABLE PURCHASE ORDER, By: SPECIFICATIONS, PROCEDURES, AND ADDITIONAL REQUIREMENTS LISTED IN Ankur KalraTHE APPENDICES. Title: Hydraulic Design Engineer Date: 11/7/2011__________________________________________Professional Engineer APPLICABLE S.O. NUMBERS:

___________ _____________________________

0State Registration No.

Date _______________

E12.5.1910 0 Rev.DOCUMENT IDENTIFICATION Task 2 - Pump Speed Correction E12.5.1910 MONTICELLO -RHR & CS PUMPS 1/4 TABLE OF CONTENTS 1.0PURPOSE ..............................................................................................................................

.................................. 22.0BACKGROUND ..............................................................................................................................

........................ 23.0SCOPE ..............................................................................................................................

........................................ 34.0ANALYSIS ..............................................................................................................................

.................................. 35.0RESULTS AND CONCLUSION

............................................................................................................................ 46.0BIBLIOGRAPHY ..............................................................................................................................

....................... 4 Task 2 - Pump Speed Correction E12.5.1910 MONTICELLO -RHR & CS PUMPS 2/4 1.0 PURPOSE To evaluate the use of the equation provided in standard HI/ANSI 1.6 2000 [1] for predicting NPSHr at different pump speeds. More specifically, this analysis is being performed for RHR

and CS pumps installed in the Monticello nuclear facility. These pumps, when tested at the

Sulzer Pumps factory, were operated at a fixed speed using electrical induction motors. Test

motors have a slip factor that is dependent upon motor design (efficiency and motor power

ratings) and applied load. In the nuclear facility, operation at less than full-rated motor power

or with high-efficiency motor tends to reduce motor slip, which can cause the pump to operate

at slightly higher speeds in the field compared to factory test speed. In addition, an increase in

the frequency of the motor power source may result in pumps running at higher speeds than

the tested pump thus increasing the required NPSH.

2.0 BACKGROUND The physical process of cavitation (boiling) involves a phase change. In the context of a centrifugal pump inlet the energy, or latent heat of evaporation, required to facilitate the phase

change associated with cavitation must be supplied by the liquid surrounding the cavitation

vapor bubbles. This heat transfer process from the supporting fluid to the vapor gives rise to

important physical characteristics of the cavitation process in pumps, one of which includes

temporal component. That is, it takes some finite amount of time for the heat transfer

associated with the formation of cavitation bubble to take place. The implication of this in the

context of a pump inlet is that the longer the residence time of the flowing fluid in the low

pressure zone at the blade leading edges, the greater the bubble formation. And conversely, the shorter the residence time of the fluid in the low pressure zone the less bubble formation

there will be. This explains why the exponent 2 (square law as discussed in section 3 below)

overpredicts the NPSHr when scaling up in speed and why it underpredicts the NPSHr when

scaling down in speed.

Task 2 - Pump Speed Correction E12.5.1910 MONTICELLO -RHR & CS PUMPS 3/4 3.0 SCOPE The NPSHr prediction equation for pump speed correction from HI/ANSI 1.6 standard is:

1 2 1 2 2 NPSH n n NPSH, ------- (1)

Where;NPSH 1= Net positive suction head at test speed; NPSH 2= Net positive suction head at specified speed; n 1= Test speed in rpm; n 2= Operating speed in rpm; The above equation (1) provides a square law relationship between the pump speed and

NPSHr. This relationship is evaluated for speed changes encountered in the field. The range of assessment will be limited to

[[ ]] of the nominal pump speed, which should bound all speed variations that could be encountered in the field. Moreover, alternative NPSHr speed correction methods are compared to equation (1) for predicting NPSHr speed dependence.

These sources also provide physical reasoning for using equations derived from empirical data

when predicting NPSHr at speeds lower than the test speed.

4.0 ANALYSIS Equation (1), has been endorsed in several centrifugal pump books and papers on cavitation

and has been termed as a conservative approach to NPSHr speed correction when adjusting

for higher speeds because it tends to overestimate NPSHr. As an example of the application of equation (1) for increased pump speed, consider that at

[[ ]], test curves for the Monticello RHR pumps show an NPSHr of

[[ ]] at a test speed of

[[ ]]. A [[ ]] increase in pump nominal speed equals

[[ ]]. In equation (1) we substitute this speed and obtain an NPSHr of

[[ ]]. This is

[[ ]] higher than the test NPSHr.

For predicting NPSHr at speeds below the test speed, equation (1) tends to underestimate NPSHr. This can lead to pumps experiencing degraded performance due to cavitation if the

NPSHa provided by the plant is insufficient due to an optimistic prediction of the pump NPSHr

at a reduced speed. For estimating NPSHr under certain conditions (e.g. speed reduction)

HI/ANSI 1.6 standard allows the use of empirical data obtained by respective pump

manufacturers. Johann Gulich's book; Centrifugal Pumps [2], uses test data from eight pump Task 2 - Pump Speed Correction E12.5.1910 MONTICELLO -RHR & CS PUMPS 4/4 manufacturers for developing an equation for lower speedNPSHr prediction.

Gulich's Equation:

1 2 1 2 NPSH n n NPSH x , where x (exponent) =

3.0 3 2 ref NPSH NPSH , ---- (2)

Where, NPSH ref= 20 m. If we use Gulich's equation (2) above, that is based on empirical data, to predict the NPSHr at

[[° ° ° ° ° ° ° °

° ° ° ]] we would obtain x =

° ° ° ° ° ° ° and new NPSHr as

[[° ° ° ° ° ° ° ° ° ° ° °

° ° ° ]] less than the[[° ° ° ° ° ° °

° ° ° ]] predicted by equation (1). This illustrates that the use of exponent 2 (square law approach) is a conservative approach when correcting NPSHr for higher operating speeds.5.0 RESULTS AND CONCLUSION For speed variations of

° ° ° ° ° ° ° of the test speed, the HI/ANSI 1.6 2000 square law equation is suitable for determining changes in NPSHr for speed increases for the RHR and CS pumps. For speed decreases, an empirical correlation such as that prescribed by Gulich is

recommended.

6.0 BIBLIOGRAPHY

[1]: ANSI/HI 1.6, 2000, American National Standard for Centrifugal Pump Tests

[2]: Centrifugal Pumps, Johann Gulich, 2 nd Edition.

[3]: Centrifugal Pumps Book, Stepanoff.