ML20237E951
| ML20237E951 | |
| Person / Time | |
|---|---|
| Issue date: | 08/25/1998 |
| From: | Birmingham J NRC (Affiliation Not Assigned) |
| To: | Essig T NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9809010324 | |
| Download: ML20237E951 (12) | |
Text
- _ - _
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2005H001 yj August 25, 1998 MEMORANDUM TO: Thomas H. Essig, Acting Chief Generic Issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation FROM:
Joseph L. Birmingham, Project Manager Generic issues and Environmental g A Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation -
SUBJECT:
SUMMARY
OF AUGUST 11-13,1998, MEETING WITH THE BABCOCK
& WILCOX OWNERS GROUP TO DISCUSS CONCERNS FOR BORON DILUTION POST SMALL-BREAK LOSS-OF-COOLANT ACCIDENTS."
On August 11-13,1998, 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) in Lynchburg, Virginia, to discuss concems that the reactor might become critical after a small-break loss-of-coolant accident if a significant amount of reactor coolant, low in boron concentration, formed in the steam generators. Specific issues discussed were the risk significance of such an event, the status of the Owners Group's evaluation of the concem, and the schedule for continued actions to resolve the concem. During the three day meeting, the Owners Group reviewed with NRC the results of their evaluations to date, recent m9deling performed to determine expected boron concentrations in the reactor vessel and in the steam generators, and the expected boron concentration of the coolant that would pass through the reactor vessel upon a return to natural circulation. The Owners Group discussed in -
e detail the probable locations and quantities of deborated coolant that would form; the effect of operational history and wre loading characteristics; and the distribution of boron in the vessel, the vessel downcomer, the cold leg crossover piping, and in the steam generator tubing and plenum areas. The Owners Group also described the expected flow pattem during the retum to natural circulation and the boron mixing expected to occur during this process.
The Owners Group concluded that their calculations and modeling indicated that a boron L
~ dilution event would not cause an unacceptable return to criticality. However, the Owners l;
Group stated that additional effort was needed to complete the verification of their calculations and that further analysis of the conservatism used in their modeling was necessary.
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T. Essig
-2 August 25, 1998-NRC management participated in the exit meeting via telecon. During the exit meeting the staff made the following points:
1.
A realistic analysis approach is acceptable for assessment of safety significance. This includes use of realistic decay heat and two high pressure injection (HPI) systems. An
- analysis of conditions with one HPI available for various break locations should be
- developed to provide understanding and perspective of tho'se conditions.
2.
Probabilistic risk analysis aspects are important for risk significance and will be useful with respect to modeling acceptance.
3.
Reactor vessel vent valve behavior remains to be established, and may be critical to an acceptable solution.
4.
Fluid dynamic mcGling of pipes and steam generator tubes appears to be acceptable.
The remainder o; V.e modeling is not well developed.
5.
A substantial reactivity margin will be necessary to be acceptable in light of the fluid
)
dynamic modeling uncertainJes.
l 1
6.
Sensitivity studies and uncertainty estimates will be helpful in assessing safety significance and modeling assumption impacts.
The Chairman of the B&W Owners Group Steering Committee concluded the exit meeting by stating that the Owners Group was committed to resolving the concern fully and in a timely manner and that the B&WOG would provide a submittal by September 11,1998 describing the actions planned to complete that resolution and a schedule for implementing those actions. The submittal would include an assessment of the probability of the event, an explanation of the current analysis of the issue, an assessment of energy deposition based upon the current analysis, and an assessment of the margin to criticality demonstrated by the analysis. The submittal would also describe the status of each licensee's implementation of a recommendation by Framatome that reactor coolant pumps not be " bumped" or restarted if a significant amount of deborated water had collected in the steam generators. The Owners Group agreed to document this planned action in a letter to NRC the week of August 16.
A list of those attending the meeting is attached.
Attachment:
As stated cc w/att: See next page i
)
T. Essig
-2 August 25, 1998 NRC management participated in the exit. meeting via telecon. During the exit meeting the staff made the following points:
1.
A realistic analysis approach is acceptable for assessment of safety significance. This includes use of realistic decay heat and two high pressure injection (HPI) systems. An analysis of conditions with one HPl available for various break locations should be developed to provide understanding and perspective of those conditions.
2.
Probabilistic risk analysis aspects are important for risk significance and will be useful with respect to modeling acceptance.
{
3.
. Reactor vessel vent valve behavior remains to be established, and may be critical to an acceptable solution.
4.
Fluid dynamic modeling of pipes and steam generator tubes appears to be acceptable.
The remainder of the modeling is not well developed.
5.
A substantial reactivity margin will be necessary to be acceptable in light of the fluid i
dynamic modeling uncertainties.
)
l I
6.
Sensitivity studies and uncertainty estimates will be helpful in assessing safety significance and modeling assumption impacts.
The Chairman of.the B&W Owners Group Steering Committee concluded the exit meeting by stating that the Owners Group was committed to resolving the concem fully and in a timely manner and that the B&WOG would provide a submittal by September 11,1998 describing the actions planned to complete that resolution and a schedule for implementing those actions. The
-submittal would include an assessment of the probability of the event, an explanation of the l
current analysis of the issue, an assessment of energy deposition based upon the current l
analysis, and an assessment of the margin to criticality demonstrated by the analysis. The submittal would also describe the status of each licensee's implementation of a recommendation l
by Framatome that reactor coolant pumps not be " bumped" or restarted if a significant amount l
of deborated water had collected in the steam generators. The Owners Group agreed to document this planned action in a letter to NRC the week of August 16.
A list of those attending the meeting is attached.
Attachment:
As stated cc w/att: See next page -
DOCUMENT NAME:g:\\jlb\\boronmtg
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hgk OFFICE PGEB SC:P NAME JBirmingham:sw = FAdNew#I ic DATE 8/W98 '
8/24/98 m.__._______._.___
DISTRIBUTION: Mtg. Summrry w/B&WOG Dited Auaust 25. 1998 HARD COPY Central File.
PUBLIC PGEB r/f OGC ACRS TAttard LLyon JBirmingham EMAll SCollins FMiraglia BSheron BBoger GHolahan SNewberry
.TCollins EWeiss JRoe DMatthews TEssig FAkstulewicz i
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_-__.-._.._-_-_L__.-._-._--
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Attendees for B&WOG Meeting with NRC t
August 11-13,1998 NAME ORGANIZATION
{
- Bill Foster
- B&W Owners Group Steering Committee Chairman
{
John M. Link B&W Owners Group Analysis Committee Chairman 1
Eric Henshaw Duke Energy Steve Hopper Toledo Edison l
Ted Lang Toledo Edison Paul Fleming Florida Power Corporation Dick Deveney Florida Power Corporation Ken Wilson Florida Power Corporation J. J Cudlin Framatome Technologies, Inc. (Framatome)
Joe Kelly
Gim Gloudemaus Framatome Brent Brooks Framatome
)
Gordon Wissinger Framatome
)
Mike Schoppman**
Framatome Scott Newberry" Deputy Director DSSA, NRC j
Tim Collins" NRC j
Warren Lyon NRC
{
Tony Attard NRC Joseph Birmingham NRC Attended exit meeting on August 13,1998
{
- Attended exit meeting via telecon l
I 1
l
' Attachment l
l' t______1_____._____
\\
cc:
Mr. Randy Hutchinson, Chairman Mr. John Link, Chairman B&WOG Executive Committee B&WOG Analysis Committee Entergy Operations Inc.
Framatome Technologies, Inc.
P.O. Box 1439 PO Box 10935 1448 S.R. 333 Lynchburg,VA 24506 Russellville, AK 72801-0967 Mr. W. W. Foster, Chairman Mr. J. J. Kelly, Mgr B&WOG Steering Committee B&WOG Licensing Operations Duke Power Company Framatome Technologies, Inc.
. Oconee Nuclear Station P.O. Box 10935 PO Box 1439 Lynchburg, VA 24506-0935 Seneca, SC 29679 l
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1 UNITED STATES
.l j
NUCLEAR REGULATORY COMMISSION e
WASHINGTON, D.C. 20066-0001
%g*
August 25, 1998 MEMORANDUM TO: Thomas H. Essig, Acting Chief I
Generic issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation i
i FROM:
Joseph L. Birmingham, Project Manager j
Generic issues and Environmental A
l Projects Branch l
Division of Reactor Program Management Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF AUGUST 11-13,1998, MEETING WITH THE BABCOCK
& WILCOX OWNERS GROUP TO DISCUSS CONCERNS FOR BORON DILUTION POST SMALL-BREAK LOSS-OF-COOLANT ACCIDENTS."
On August 11-13,1998, 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) in Lynchburg, Virginia, to discuss concerns that the reactor might i
become critical after a small-break loss-of-coolant accident if a significant amount of reactor
{
coolant, low in boron concentration, formed in the steam generators. Specific issues discussed were the risk significance of such an event, the status of the Owners Group's evaluation of the l
concem, and the schedule for continued actions to resolve the concem. During the three day
{
meeting, the Owners Group reviewed with NRC the results of their evaluations to date, recent l
modeling performed to determine expected boron concentrations in the reactor vessel and in the steam generators, and the expected boron concentration of the coolant that would pass through the reactor vessel upon a return to natural circulation. The Owners Group discussed in detail the probable locations and quantities of deborated coolant that would form; the effect of operational history and core loading characteristics; and the distribution of boron in the vessel,
)
the vessel downcomer, the cold leg crossover piping, and in the steam generator tubing and plenum areas. The Owners Group also described the expected flow pattern during the retum to natural circulation and the boron mixing expected to occur during this process.
l The Owners Group concluded that their calculations and modeling indicated that a boron l
dilution event would not cause an unacceptable retum to criticality. However, the Owners Group stated that additional effod was needed to complete the verification of their calculations and that further analysis of the conservatism used in their modeling was necessary.
l
T. Essig 2
August 25, 1998 NRC management participated in the exit meeting via telecon. During the exit meeting the staff made the following points:
l l
1.
A realistic analysis approach is acceptable for assessment of safety significance. This
)
includes use of realistic decay heat and two high pressure injection (HPI) systems. An j
analysis of conditions with one HP: available for various break locations should be developed to provide understanding and perspective of those conditions.
)
l I
2.
Probabilistic risk analysis aspects are important for risk significance and will be useful l
with respect to modeling acceptance.
l 3.
Reactor vessel vent valve behavior remains to be established, and may be critical to an acceptable solution.
l 4.
Fluid dynamic modeling of pipes and steam generator tubes appears to be acce0 table.
l The remainder of the modeling is not well developed.
I 5.
A substantial reactivity margin will be necessary to be acceptable in light of the iluid dynamic modeling uncertainties.
6.
Sensitivity studies and uncertainty estimates will be helpful in assessing safety l
significance and modeling assumption impacts.
The Chairman of the B&W Owners Group Steering Committee concluded the exit meeting by stating that the Owners Group was committed to resolving the concem fully and in a timely manner and that the B&WOG would provide a submittal by September 11,1998 describing the actions planned to complete that resolution and a schedule for implementing those actions. The submittal would include an assessment of the probability of the event, an explanation of the current analysis of the issue, an assessment of energy deposition based upon the current analysis, and an assessment of the margin to criticality demonstrated by the analysis. The submittal would also describe the status of each licensee's implementation of a recommendation by Framatome that reactor coolant pumps not be " bumped" or restarted if a significant amount of deborated water had collected in the steam generators. The Owners Group agreed to document this planned action in a letter to NRC the week of August 16.
l A list of those attending the meeting is attached.
Attachment:
As stated cc w/att: See next page l
l l
l
I l*
l T. Essig
-2 August 25, 1998 i
NRC management participated in the exit meeting via telecon. During the exit meeting the staff l
made the following points:
i 1.
A realistic analysis approach is acceptable for assessment of safety significance. This i
includes use of realistic decay heat and two high pressure injection (HPI) systems. An analysis of conditions with one HPI available for various break locations should be developed to provide understanding and perspective of those conditions.
i l
2.
Probabilistic risk analysis aspects are important for risk significance and will be useful i'
- with respect to modeling acceptance.
l 3.
Reactor vessel vent valve behavior remains to be established, and may be critical to an acceptable solution.
- 4. '
Fluid dynamic modelir g of pipes and steam generator tubes appears to be acceptable.
The remainder of the modeling is not well developed.
5.
A substantial reactivity margin will be necessary to be acceptable in light of the fluid dynamic modeling uncertainties.
6.
. Sensitivity studies and uncertainty estimates will be helpful in assessing safety l
significance and modeling assumption impacts.
The Chairman of the B&W Owners Group Steering Committee concluded the exit meeting by stating that the Owners Group was committed to resolving the concem fully and in a timely manner and that the B&WOG would provide a submittal by September 11,1998 describing the I
actions planned to complete that resolution and a schedule for implementing those actions. The submittal would include an assessment of the probability of the event, an explanation of the current analysis of the issue, an assessment of energy deposition based upon the current i
analysis, and an assessment of the margin to criticality demonstrated by the analysis. The submittal would also describe the status of each licensee's implementation of a recommendation by Framatome that reactor coolant pumps not be " bumped" or restarted if a significant amount q
[
of deborated water had collected in the steam generators. The Owners Group agreed to j
document this planned action in a letter to NRO the week of August 16.
A list of those attending the meeting is attached.
Attachment:
- As stated cc w/att: See next page l
.l DOCUMENT NAME:g:\\jlb\\boronmtg
)
I hgk OFFICE PGEB SC:P 3
NAME' JBirmingham:sw FAksvv.
)
lewicz DATE 8/W98 8/24/98 i
4 i
DISTRIBUTION: Mtg. Summary w/B&WOG Dated Auaust 25. 1998 HARD COPY l
Central File PUBLIC4 l
PGEB r#
LLyon JBirmingham EMAIL SCollins FMiraglia l
BSheron BBoger GHolahan SNewberry TCollins -
EWeiss JRoe DMatthews TEssig FAkstulewicz
\\
t Attendees for B&WOG Meeting with NRC August 11-13,1998 NAME ORGANIZATION Bill Foster
- B&W Owners Group Steering Committee Chairman John M. Link B&W Owners Group Analysis Committee Chairman Eric Henshaw Duke Energy Steve Hopper Toledo Edison Ted Lang Toledo Edison Paul Fleming Florida Power Corporation
[:
Dick Deveney Florida Power Corporation Ken Wilson Florida Power Corporation J. J Cudlin Framatome Technologies, Inc. (Framatome)
Joe Kelly
. John Klingenfus Framatome Nira Shah Framatome l
Gim Gloudemaus Framatome Brent Brooks Framatome Gordon Wissinger Framatome Mike Schoppman" Framatome Scott Newberry" Deputy Director DSSA, NRC
[.
Tim Collins" NRC l
Warren Lyon NRC l
Tony Attard NRC l
l Joseph Birmingham NRC 1
- Attended exit meeting on August 13,1998
" Attended exit meeting via telecon.
l l
l i
I L
Attachment
0 cc:
Mr. Randy Hutchinson, Chairman Mr. John Link, Chairman B&WOG Executive Committee B&WOG Analysis Committee Entergy Operations Inc.
Framatomo Technologies, Inc.
P.O. Box 1439 PO Box 10935 1448 S.R. 333 Lynchburg,VA 24506 Russellville, AK 72801-0967 Mr. W. W. Foster, Chairman Mr. J. J. Kelly, Mgr B&WOG Steering Committee B&WOG Licensing Operations Duke Power Company Framatome Technologies, Inc.
Oconee Nuclear Station P.O. Box 10935 PO Box 1439 Lynchburg, VA 24506-0935 Seneca, SC 29679 i
l
~
-.