ML14077A091

BWROG-TP-13-008, Rev. 0, Containment Accident Pressure Committee (344) Task 2 - Equation for Pump Speed Correction (Cvic Pump), Attachment 9

ML14077A091
Person / Time
Site:	Peach Bottom, Browns Ferry, Boiling Water Reactor Owners Group
Issue date:	06/30/2013
From:	Kalra A BWR Owners Group, Sulzer Pumps (US)
To:	GE-Hitachi Nuclear Energy Americas, Office of Nuclear Reactor Regulation
Shared Package
ML14077A088	List: ML14077A090 ML14077A091 ML14077A092 ML14077A093 ML14077A095 ML14077A102
References
100072780, BWROG-14014 BWROG-TP-13-008, Rev. 0, E12.5.1940, Rev. 0
Download: ML14077A091 (8)

Text

BWROG-TP-13-008 Revision 0 June 2013 Containment Accident Pressure Committee (344)

Task 2 - Equation for Pump Speed Correction (CVIC Pump)

Authors: Ankur Kalra (Sulzer Pump)

Project Kenneth Welch (GEH)

Manager:

Committee John Freeman (Exelon)

Chair:

BWROG-TP-13-008 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-13-008 REV 0 Executive Summary This BWROG Technical Product provides a technical evaluation of the applicability of a standard equation to the Sulzer CVIC pump model used at the Browns Ferry, Peach Bottom, and other BWR stations. The equation correlates changes in pump speed to changes in pump NPSHR.

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 NPSHR as pump operating speed is changed.

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QUALITY LEVEL SULZER PUMPS (US) INC. DOCUMENT ASME CODE Direct DOC. NO: E12.5.1940 SECTION Indirect ORDER NO: 100072780 CLASS NO.

CODE EDITION TITLE: Task 2 - Equation for Pump Speed Correction (YEAR)

Sulzer Pumps (US) Inc. SEASON Browns Ferry & Peach Bottom - RHR Pumps YEAR CUSTOMER GE-HITACHI Nuclear Energy Americas LLC PROJECT Browns Ferry - Peach Bottom Power Station CUSTOMER P.O. NO. 437054820 CONTRACT 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 Risk Release Inspection Report # ________________

_For Manufacture at Sulzer Pumps (US) Inc. Other (specify)

_______________________

APPROVALS (SIGNATURE) Date Engineering 08/31/12 Quality Assurance CERTIFICATION (when applicable) Originating Advance Engineering This Document is certified to be in compliance Dept:

with THE APPLICABLE PURCHASE ORDER, SPECIFICATIONS, PROCEDURES, AND By:

ADDITIONAL REQUIREMENTS LISTED IN Ankur Kalra THE APPENDICES.

Title:

Hydraulic Design Engineer Date: 4/11/2012

__________________________________________

Professional Engineer APPLICABLE S.O. NUMBERS:

___________ _____________________________ 0 State Registration No.

Date _______________ 0 E12.5.1940 Rev.

DOCUMENT IDENTIFICATION

E12.5.1940 Task 2 - Pump Speed Correction BROWNS FERRY & PEACH BOTTOM -RHR PUMPS TABLE OF CONTENTS 1.0 PURPOSE ................................................................................................................................................................ 2

2.0 BACKGROUND

...................................................................................................................................................... 2 3.0 SCOPE ...................................................................................................................................................................... 3 4.0 ANALYSIS................................................................................................................................................................ 3 5.0 RESULTS AND CONCLUSION............................................................................................................................ 4 6.0 BIBLIOGRAPHY ..................................................................................................................................................... 4 1/4

E12.5.1940 Task 2 - Pump Speed Correction BROWNS FERRY & PEACH BOTTOM -RHR PUMPS 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 pumps installed in the Browns Ferry and Peach Bottom nuclear facilities. 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 a 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.

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E12.5.1940 Task 2 - Pump Speed Correction BROWNS FERRY & PEACH BOTTOM -RHR PUMPS 3.0 SCOPE The NPSHr prediction equation for pump speed correction from HI/ANSI 1.6 standard is:

2

§ n2

• NPSH 2 ¨¨ ¸¸ u NPSH 1 , ------- (1)

© n1 ¹ Where; NPSH1 = Net positive suction head at test speed; NPSH2 = Net positive suction head at specified speed; n1 = Test speed in rpm; n2 = 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 Browns Ferry/Peach Bottom 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 3/4

E12.5.1940 Task 2 - Pump Speed Correction BROWNS FERRY & PEACH BOTTOM -RHR PUMPS manufacturers. Johann Gulich's book; Centrifugal Pumps [2], uses test data from eight pump manufacturers for developing an equation for lower speed NPSHr prediction.

Gulich's Equation:

03

§ n2

• x

§ NPSH 3

• NPSH 2 ¨ ¸ u NPSH 1 , where x (exponent) = 2 u ¨¨ ¸ , ---- (2)

¸

© n1 ¹ © NPSH ref ¹ Where, NPSHref = 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 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, 2nd Edition.

[3]: Centrifugal Pumps Book, Stepanoff.

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