ML20154A790
| ML20154A790 | |
| Person / Time | |
|---|---|
| Issue date: | 09/29/1998 |
| From: | Birmingham J NRC (Affiliation Not Assigned) |
| To: | Essig T NRC (Affiliation Not Assigned) |
| References | |
| PROJECT-693 NUDOCS 9810050002 | |
| Download: ML20154A790 (5) | |
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l l l* @r t UNITED STATES j '
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[ NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001 t
September 29, 1998
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! MEMORANDUM TO: Thomas H. Essig, Acting Chief l Generic issues and Environmental Projects Branch !
Division of Reactor Program Management I Office of Nuclear Reactor Regulation I i
FROM: Joseph L. Birmingham, Project Manager Generic issues and Environ ntal l Projects Branch P4.
Division of Reactor Program Management l Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF SEPTEMBER 24,1998, MEETING WITH THE BABCOCK & WILCOX OWNERS GROUP ON BORON DILUTION On September 24,1998, members of the U.S. Nuclear Regulatory Commission (NRC) met with representatives of the Babcock and Wilcox Owners Group (B&WOG) and Framatome Technologies, Inc. (FTI) to discuss information obtained from tests and experiments performed at a test facility at the University of Maryland, College Park (UMCP). The test facility is scaled to 1/500 in volume and 1/4 in elevation. The aspect ratio of the various components are chosen so that a proper balance of the hydrostatic head and of the flow resistances is maintained.
Also, the test facility has eight reactor vessel vent valves similar to the ones in B&W reactor vessels. The test facility is used to examine small-break loss-of-coolant accidents (SB-LOCA) and has examined the effect of a SB-LOCA occurring in the cold leg. The results of these tests have been reported in numerous industry publications. ,
The B&WOG has been examining the consequences of a SB-LOCA occurring in the cold leg because of concerns that, after certain size breaks in the cold leg, reactor coolant, low in boron I f
concentration, may form in the steam generators and, upon retum to natural circulation, cause /j the reactor to become critical. The B&WOG has been evaluating this break using computer codes and calculations and has not run experiments. The experiments at the UMCP facility are ()
considered to be potentially applicable to the B&WOG reactor because the design is similar. V 3
However, the parameters of the experiments at the test facility must be carefully evaluated to determine the applicability to B&W reactors.
A significant phenoma seen during experiments at the UMCP facility was a pattern of rising and falling levels in the steam generator and in the hot leg as the system began to return to natural circulation. System pressure rose and fell at the same time indicating that steam condensation is the likely driving force. This oscillatory period is called the Interruption Resumption Mode (IRM) by the test conductors. Because the steam generator and hot leg levels rise and fall I
during IRM, it is likely that considerable mixing takes place in the steam generator at this time.
i 9810050002 980929 Ly'. .4 s
T. Essig September 29, 1998 Another phenomena discussed during the meeting was the tailing of fluid as a return to natural circulation was simulated. That is, as a homogeneous fluid in a pipe began to move, a portion of the fluid lags behind the main body of fluid and forms a tapering tail. This mechanism would cause condensate in the steam generator to mix with borated coolant as the system returned to natural circulation. Depending on the volume of condensate, this action could provide l significant mixing before the diluted coolant entered the reactor core.
The Owners Group representatives indicated that they were interested in the test results and l would look at them to determine the applicability to the boron dilution concern. However, B&WOG intends to continue their current efforts to model a return to natural circulation in the B&W reactor.
A list of those attending the meeting is attached.
Project No. 693 cc: Mr. John Link, Chairman B&WOG Analysis Committee Framatome Technologies, Inc.
P.O. Box 10935 Lynchburg, VA 24506-0935 Mr. Bert Dunn, Adv. Engineer Framatome Technologies, Inc.
P.O. Box 10935 Lynchburg, VA 24506-0935 i
I
, T. Essig -2 September 29, 1998 i
Another phenomena discussed during the meeting was the tailing of fluid as a return to natural circulation was simulated. That is, as a homogeneous fluid in a pipe began to move, a portion of the fluid lags behind the main body of fluid and forms a tapering tail. This mechanism would cause condensate in the steam generator to mix with borated coolant as the system returned to j natural circulation. Depending on the volume of condensate, this action could provide l significant mixing before the diluted coolant entered the reactor core.
The Owners Group representatives indicated that they were interested in the test results and would look at them to determine the applicability to the boron dilution concern. However, B&WOG intends to continue their current efforts to model a return to natural circulation in the l B&W reactor.
A list of these attending the meeting is attached.
Project No. 693 cc: Mr. John Link, Chairman B&WOG Analysis Committee Framatome Technologies, Iric.
P.O. Box 10935 Lynchburg, VA 24506-0935 Mr. Bert Dunn, Adv. Engineer Framatome Technologies, Inc.
P.O. Box 10935 Lynchburg, VA 24506-0935 DOCUMENT NAME: G:\JLB\BORONMT .h24t OFFICE PGEB:DRPM /)/ / PGEB:k NAME JBirmingham:sw FAke cz DATE 1/ R(/98 @/}k98 OFFICIAL RECORD COPY
Summary: BWOG Analysis Committee Mtg. With NRC September 24,1998 l
Hard Cooy iPfoject FiW PUBLIC PGEB r/f OGC ACRS l J.Birminaham l
E-Mai! !
l S. Collins /F. Miraglia l R. Zimmerman l B. Sheron
! G. Holahan B. Boger J. Roe D. Matthews T. Essig i F. Akstulewicz ;
J. Birmingham W. Lyon ,
T. Attard 1 A; Levin i E. Weiss M. DiMarzo D. Bessette l
l l i
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l Attendees for B&WOG Meeting with NRC September 24,1998 j
NAME ORGANIZATION John M. Link B&W Owners Group Analysis Committee Chairman Bert Dunn Framatome Technologies, Inc.
Warren Lyon NRC\NRR Reactor Systems Branch Tony Attard NRC\NRR Reactor Systems Branch Alan Levin NRC\NRR Reactor Systems Branch Eric Weiss NRC\NRR Reactor Systems Branch Norm Lauben NRC\RES Reactor and Plant Systems Branch Marino DiMarzo NRC\RES Reactor and Plant Systems Branch David Bessette NRC\RES Reactor and Plant Systems Branch Joseph Birmingham NRC\NRR Project Manager I
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