ML19284A608

Provides Comments on Preliminary Final Rept on Model Testing of Containment Sump Recirculation Intakes, Prepared by Canada Hydraulic Labs.Includes Reactor Safety Distribution List for Consultant Repts

ML19284A608
Person / Time
Site:	Farley
Issue date:	12/18/1978
From:	Macagno E, Nakato T IOWA, UNIV. OF, IOWA CITY, IA
To:	Watts J Office of Nuclear Reactor Regulation
References
CON-NRC-03-78-130, CON-NRC-3-78-130 NUDOCS 7903150101
Download: ML19284A608 (6)

Text

Comments on INTERIM REPORT Accession No.'7@3/5d/d/

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Contract Program or Project

Title:

Comments on preliminary " Final Report on Model Tes, ting of Containment Sump Recirculation Intakes for Joseph M. Farley" Subject of this Document: Contract letter containing consultants' comments relative to containment sump recirculation tests performed for Farley Units 1 and 2 (Docket Nos. 50-348 & 50=364)

Type of Document: Contract Letter Author (s): Macagno, E. 0. , and Nakato, T. , University of Iowa, Institute of Hydraulic Research Date of Document: December 18, 1978 Responsible NRC Individual and NRC Office or Division: J. J. Watt, NRR/ DSS This document was prepared primarily for preliminary or internal use. It has not received full review and approval.

Since there may be substantive changes, this document should not be considered final.

NRC Research and Technica Assistance Report NRC Contract Number: NRC-03-078-130 7903359 ,gj f( A

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REACTOR SAFETY DISTRIBUTION LIST FOR CONSULTANT REPORTS Review of Western Canada Hydraulic Laboratories' " Final Report on Model Testing of Containment Sump Recirculation Intakes for Joseph M. Farley Nuclear Plant - Units No. I and 2" December 18. 197R (Subject of Letter) (Date of Letter)

University of Iowa, Institute of Hydraulic Research James J. Watt (Name of Consultant) .

(PRINTyourname)

Indicate No. of Copies C *NRC Pn D General Electric, ATTN:

21 ACRS Westinghouse, ATTN:

1 RS Branch File Combustion Engineering, ATTN:

1 TA, EDO Babcock & Wilcox, ATTN:

Appropriate SS:RS Engineers Exxon, ATTN:

(Please PRINT Names) Gulf Ur.ited, ATTN:

I G. Kelly 1 Farley Local PDR IMPORTANT - Reviewer must read and indicate Review for Proprietary Information NRC Bethesda Technical Library This report contains Proprietary info.

Appropriate PM/0R/SS&EA: Engineers (Please PRINT Names)

X Report does not contain proprietary info 1

%D/ / -f?Qf QY l ? 7, 3 itials & date BC initi'als '& 'da'te I R. Mattson, DSS 1 Director, DPM ADDITIONAL INFORMATION:

SS Asst. Directors 1 Director, 00R .

Director, SS&EA Director, SD Naval Reactors NTIS (Nat'l Tech. Info. Serv.)

Director, ISE ANC, ATTN:

PNL, ATTN: _

BNL, ATTU:

ANL, ATTN:

BMI, ATTN:

HNL, ATTN:

DISTRIBUTION COMP.

Director, RES date & initials NRC Researc1 and Iechn.ica

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e Jniversity of Iowa - ~

j gg City. Iowa. 52242

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'P'- M E~ -9 JUUUU tute of Hydraulic Research ryggg kphone: (319) 353-4693 18 December 1978 semammaum ,,

Mr. James Watt U.S. Nuclear Regulatory Cm: mission Washington D.C. 20555 Re: Contract No. NRC-03-078-130 -

Dear Mr. Watt:

We have completed our review of " Final Report on Model Testing of Containment Sump Recirculation Intakes for Joseph M. Farley Nuclear Plant - Units No. 1 and 2", prepared by Western Canada Hydraulic'Labora-tories (WCHL). Although this report is marked " PRELIMINARY", we feel that .

we crm formulate our opinions on Farley Nuclear Plant No. 2 (FARLEY 2) since we have visited the plant with you, and.during ourf. visit to~NCHL, observed a series of demonstrations of the type of laboratory tests involved.

We would like, however, to postpone making final recommendations until a copy of the FINAL REPORT, which is not subject to any restrictive classi-fication, is obtained.

We believe, that it is unfortunate that delays have developed f in this project, and that our opinions, which were in advanced Gate of definition in May 1978, must be formulated in December 1978, and that tney cannot yet be accompanied by our recommendations. But it appears that formulating the opinions at this moment is a contribution we can make to the ne VJ of NRC in relation to uar contractural relationship.

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OPINION _1 The model studies for FARLEY l and 2 were carried out at a geometric scale of 1:1. Since temperatures could not be reproduced in the model in the ratio 1:1 (the maximum temperature in the prototype is 212*F; in the model only 180*F could be obtained), exact dynamic and kine- '

matic similitude were not attained. Of course, departures from exact similitude were small compared with the ones that would have resulted at other geometric scales (see Table 1 of REPORT). In the model studies, censervatism was generally practiced by testing for larger flow rates and for water levels lower than the normal ones. Also, the expected circula-tion was increased in the model to establish a margin of safety. Although the report does not include photographs of flow-visualization tests, video-tapes were provided by NCHL ccntaining such visualirations, and during the visit to NCHL a number of flows were observed. All this has led us to the opinion that the choice of geometric scale of 1:1 plus the flow distoruons is justified, and should provide more reliable information -

than tests with geometric scales smaller than unity, or combinations of other scales and distortions.

'Mr. James Watt 18 December 1978 Page 2 OPINION 2 ,

The model study for FARLEY 2 did not include an investigation of the far field. From an examination of flows recorded on video tapes for FARLEY 1, it appears that the flow in the case of FARLEY l was quite free from any important vortex formation. In the model for FARLEY 1, the detailed geometry in the neighborhood of the sumps was reproduced rather faithfully, down to any structural elements larger than two inches in dia-meter. From an examination of the drawings for the two plants (FARLEY -

1 and 2) it is apparent that the far field lay-out for FARLEY 2 is simpler than that of FARLEY l (the elevator shaft was removed and Intakes 2 and 3 were separated in Unit 2), and one should expect a less disturbed flow in this case. More important, however, is the fact that velocities in the far field are lower in FARLEY 2 than in FARLEY 1. In our opinion, this makes acceptable the claim of WCHL that there was no need to repeat a study of the far field for FARLEY 2, because no dangerous vortices formed .

in the 1:1-scale model of FARLEY 1. It should be clear, however, that -

without this parallel between FARLEY l and FARLEY 2, a study without due consideration of the far field flow would be unacceptable. The model re-sults for FARLEY l also influenced the approach and methodology used in FARLEY 2 in regard to determining the boundaries for the model. Once the need for outer and inner grating cages was recognized for FARLEY 1, it appears logical to proceed on a similar basis for FARLEY 2. The selection f of a single,14-in. diameter intake in the test program also appears to be justified due to the fact that the 14-in. .tntakes take inrger flows (5,900 gpm) than the 10-in. intakes (3,050 gg:1) , and the tests of Unit 1 demonstrated that the 14-in. intakes can produce slightly higher intake loss coefficients than the 10-in. intakes.

OPINION 3 The model for FARLEY l demonstrated that a flow with few upstream disturbances could develop serious circulations and vortices inside the outer cage if the different possibilities of blockage were tested.

It appeared that the outer cage would take care of those circulations ap-proaching the cage from the outside, but obviously would become ineffective in suppressing inside circulations originating in the flow after the fluid had passed the grating. It is our opinion that in the specific case of FARLEY 2, the boundaries of the model were properly determined because blockage of the outer cage outweighed by far the possible effects of generated vortices in the far field.

OPINION 4 Testing of vortex suppressors by subjecting them to a genera-lized flow field should be done with extreme care. Although it is .

true that any cascade of plates or foils will induce a change in direction of an oncoming flow (as was initially shown both theoretically and analyti-cally by Betz, and after him by others), one should not assume the change

. Mr. James Watt 18 December 1978 Page 3 of direction to be entirely in the direction of the guiding plates, unless a certain espect ratio is exceeded. Such an aspect ratio is still an unknown function of the different parameters involved, especially for gratings of different types. Tests are therefore absolutely necessary at the present time for any new vortex suppressor in a new situation. Tests at a scale of 1:1, and with incruased discharges and circulations, surely provide conservative conclusions about the performance of gratings to be used in vortex-suppressing devices, both frem the points of view of determining

'their head-loss coefficients, and of estimating their effectiveness in suppressing or abating circulation. Therefore, our opinion is that the vortex suppressors were properly tested.

OPINION 5 The outer grating-screen cage and the inner grating cage

, tested for EARLEY 2 appen to be very effective in suppressing air entrain-ing vortices. However, internal vortices were seen to develop (either in video tape or in the laboratory) when smooth walls were present. In the laboratory tests, the internal vortices became visible because they picked up dirt from the walls, and also because vapor, gas, or other tracers made them evident. When grating was placed over the vortex smooth wall over which the vortex had attached itself, the vortex was obviously abated, if not destroyed. This can be explained in terms of the Bodewadt boundary #

layer which feeds organized near-wall vorticity into the core of the cir-culation maintained by the incoming flow. When the grating is applied, the boundary layer is disrupted, and the vortex may break down because turbulent lumps of fluid may now be fed into the core. Whatever the actual

. mechanism may be, the fact is that lining smooth walls with grating surely tabates the vortex formation, as demonstrated by some of the tests in WCHL.

The model tests conducted at a scale of 1:1, to investigate the effectiveness a f the outer and inner grating cages in suppressing vortices, appear to indicate that no air-entraining vortices would form in the prototype. How-ever, internal vortices may form in the space between the two cages. From the results of the tests, as reported in the " Preliminary" Final Report, it appears that such internal vortices would not produce serious distur-bances. In our opinion, however, it is necessary to require additional measures which would tend to eliminate those internal vortices. This could be accomplished by lining any smooth walls existing in the space between the cages with the same kind of grating used in the cages. A short clearance between wall and lining is acceptable, in our opinion.

OPINION 6 The reported values of the head losses observed in the model study are lower than those predicted by WCHL. Since the model was al. a geometric scale of 1:1 and was run with increased discharges, there appears '

to be incontrovertible experimental proof that the losses will in fact be less than those estimated analytically by WCHL.

• ~' kr. James Watt 10 December 1978 Page 4 If there is any question, or clarification that you wish..

we remain ready to expand on any of the opiniens, and to provide details of our reasoning and our calculations to verify data contained in the NCHL report on the model study.

. Sincerely yours, Enzo O. Macagno Professor and Research Engineer Tatsuaki Nakato Research Scientist EOM/TNakn

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