ML20133P968
| ML20133P968 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 10/29/1985 |
| From: | Tucker H DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8511010283 | |
| Download: ML20133P968 (12) | |
Text
e.
DUKE POWER GOMPANY P.O. BOK 33189 CHARLOTTE, N.C. 28242
' HAL B. TUCKER reuenous
=r=**'**"T (7% amn October 29, 1985
" = = ^ * - - "
Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Ms. E. G. Adensam, Chief Licensing Branch No. 4 Re: Catawba Nuclear Station Docket Nos. 50-413 and 50-414
Dear Mr. Denton:
By letter dated April 30, 1985,' Duke Power Company provided the results of an evaluation that was performed to provide additional justification for the additions to the generic Westinghouse Owners Group Emergency Response Guideline (Revision 1) ECA-1,2, "LOCA Outside Containment". These additions-are specified in the Catawba Nuclear Station Emergency Procedure Guidelines.
Additional justification was required in Section 13.5.2 of Supplement 4 of the Catawba Safety Evaluation Report.
In' subsequent phone conversations with the NRC staff on June 11, 1985 and October 23, 1985, the April 30, 1985 submittal was discussed. As a result of these discussions the NRC staff concerns were clarified and the additional justification required to close out this item was determined. The attachment to this letter includes the additional justification and demonstrates that the operational guidance in the current Catawba Emergency Operating Procedures with regard to LOCAs outside containment is appropriate.
Very truly yours, W.
Hal B. Tucker ROS: sib Attachment cc:
Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 8
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- Mr. Harald ' R. Denton, Dir ctor October 29, 1985 Page Two-t.
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.cc: Robert Guild, Esq.
P. O. Box 12097 Charleston, South Carolina 29412 Palmetto Alliance 2135 Devine Street Columbia, South Carolina 29205
.Mr. Jesse L. Riley.
Carolina Environmental Study Group 854 Henley Place Charlotte, North Carolina 28207 NRC Resident Inspector Catawba Nuclear Station T
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Justification.For Initiating Feed and Bleed For Mitigation of LOCAs Outside Containment In~the Catawba Emergency Procedure Guidelines
'I.
OVERVIEW OF THE LOCA OUTSIDE CONTAINMENT SCENARIO
~A LOCA outside containment presents a unique plant safety concern in that the RCS inventory lost out the break does not accumulate in the' containment sump..Therefore, as the ECCS pumps deplete the refueling water storage tank (RWST) an imminent. loss of ECCS : suction will. occur. The normal transfer to the sump recirculation mode for long term cooling is'not achievable.
The first mitigation action following the identification of a LOCA~
outside containment is to attempt to isolate the break.
In addtion,
- for very small unisolable breaks outside containment, it may be possible to maintain = the ECCS suction' inventory by making up to the RWST at a flowrate that matches the break flowrate.
Since the
' makeup flowrate-that is available is. limited, unisolable small breaks above a very small size will cause.RWST depletion. The generic
. mitigation strategy for these scenarios is to initiate a plant cooldown and to limit depletion of the RWST by minimizing ECCS and containment spray flowrates.
=II.
JUSTIFICATION OF'THE CURRENT CATAWBA EMERGENCY PROCEDURES During the development of the Catawba plant-specific Emergency Procedure Guidelines, the limited guidance in the generic ERGS for mitigating LOCAs outside containment was identified as an item of concern..Three. considerations resulted from the effort-to determine
.if any additional guidance'should be added to supplement the generic ERGS.
1.
It is desirable to establish sufficient sump inventory in the containment to enable recirculation
.after the RWST. depletes.
- 2. ~Depressurizing the RCS will reduce the leak rate outside containment.
3._
The ice condenser is a large source of borated water in containment if it can be melted, e.
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J NI 4
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-With:these considerations in mind the guidance in the. current Catawba
~ Emergency Operating Procedures was developed. These procedures (included as-Appendix A) specify the following guidance:
4 Y
IF a LOCA outside containment is identified 4
t
.THEN attempt to isolate it AND T-
- [b initiate makeup'to the RWST AND A
determine _if? feed-and-bleed cooling should be initiated
'The first two. responses are the same as the generic guidance in the ERGS.
F
.The recommendation to' determine if feed-and-bleed cooling should be initiated was based on all three of the considerations given-above'.
Additional explicit criteria are specified to assist the operator in determining if feed-and *aleed should be initiated:~
1.
Insufficient RWST makeup is avhflable and RWST depletion prior to reaching 200*F is imminent.
This means that some operap r action is necessary to. prevent ICC.
2.
Sump level is greater than 1.5+(feet.
s
.a This criterion requires the sump to already have sufficient level to enable nlignment.for recirculaiion.y This i$ plies that a' concurrent-LOCA inside containment-exists'.%
/
3.
The ECCS pumps have not been transferred to the sump -
recirculation mode. This confirms thdt RWST depletion is occurring.
4.
RWST level is between 20% and 50%. The upper limit of l
50% is required to ensure that th'e event has progressed--
sufficiently to allow break isolation actions to be taken and to estimate a -projected time to reach 200*F.
& The lower limit of 20% is a check that enough RWST water exists to make the. feed-and-bleed operation worth-while.
The significant benefits of initiating feed and bleed under the conditions
- -j of concern-are as follows:
i dtd l'fg.
- 1. _RCS pressure will decrease and cause the leak rate outside of containment to decrease.
2.
Mass and energy release into the containment will cause ice melt and increase the sump inventory availabic for recirculation.
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The.only potentially negative impact that has been identified with initiating feed a'nd bleed under these conditions is an accelerated depletion of the remaining RWST' inventory.
This is not a concern-E
- for the current Catawba procedures.since a sump' level greater than
- ~
.1.5 ft is required prior to initiating feed and bleed. With a pre-
- existing sump inventory the water relieved through the PORVs~i.s
-available'for recirculation. ' Therefore, although the RWST may deplete at a faster rate, the available ECCS suction inventory is only being
- redistributed and not depleted.
{.
- Based on the arguments presented.above, the use of feed-and-bleed to
. mitigate ~LOCAs outside containment as specified in the existing Catawba
' Emergency Procedure ' Guidelines is justified.
Significant benefits have
~ been identified and no negative' impacts exist due to the initiation
. criteria explicitly specified in the procedure.
1 FURTHER EVALUATION OF LOCAs OUTSIDE CONTAINMENT III.
30, 1985 letter,' analyses were performed to -
As discussed'in the April.
determine if broader utilization of feed-and-bleed for mitigation of LOCAs outside containment could' be justified. The results.of'these
. analyses indicated that for certian break sizes the initiation.of feed-and-bleed would have a negative impact. As stated above this negative impact would result from a faster depletion of the remaining FWST inventory. IThis situation is\\ easily. understood if it is recognized that for~a LOCA outside containment without a concurrent LOCA inside
- containment, the accumulation of the required 1.5 ft sump level will only result from the PORV relief and ice malt. This is a very sub-stantial percentage of the rsmaining RWST inventory and it is ' lost in terms of available ECCS suction inventory. No methodology to discriminate between those break sizes with acceptable results and those with unaccept-l able results could:be identified. :Therefore, the existing feed-and-bleed-initiation criteria'in the Catawba procedures were not modified as a.
~ result'of these analyses.
A different approach for mitigating LOCAs outside containment was discussed in the April 30, 1985 submittal. NRC review of this approach Eis not requested at this time.
It is recommended that if the NRC decides to further evaluate operator guidelines'for mitigation of LOCAs outside
- containment'as part of the NRC review of the generic ~ Emergency Response Guidelines, Revision 1, that the approach in the April 30, 1985 submittal
~ be raised'for discussion. Duke Power will follow any NRC/WOG interactions and then propose supplemental guidance based on the ice condenser contain-ment design'that wi11' enhance the generic guidelines. Until such enhance-F
- ments are justified, ' the existing Catawba procedures will be maintained.
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5-29-24 o a APPENDIX A (1 of 7)
Form 34913 (8 82)
CNS PAGE NO.
EP/1/A/5000/1C6 LOCA OUTSIDE CONTAINMENT 1
Retype #2 ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED 1.
Ensure Possible Leak Paths isolated:
o Ensure Following Valves: CLOSED o ND:
o IND-2A, (ND Pump 1 A Suct Frm Loop B) o 1ND-1B (ND Pump 1A Suct Frm Loop B) c o 1ND-37A. 'ND Pump 1B Suct Frm Loop C) o IND-36B (ND Pump 1B Suct Frm Loop C) o IND-32A (ND Train 1A Hot Leg inj isol)
I o IND-65B (ND Train 1B Hot Leg inj isol) o 1ND-90 (ND Trn A Aux PZR Spray isol) o 1ND-91 (ND Trn B Aux PZR Spray isol)
NOTE PWR DISCON for 1NI-121 A,1NI-152B,1NI-183B must be in the " ENABLE" position before they can be operated.
o NI:
o 1NI-121 A (NI Pump 1 A To H-Legs B & C) l o 1NI-152B (NI Pump 18 To H-Legs A & D) o 1NI-183B (ND Hdr A &
B Hot Leg inj isol) l Page 1 of 5 l
(2 of 7)
Ecrm 3/915 (882)
CNS PAGE NO.
EP/1/A/5000/1C6 LOCA OUTSIDE CONTAINMENT 2
Retype #2 ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED NOTE PWR DISCON for 1Ni-1478 must be in the " ENABL" position before it can be operated.
2.
Ensure NI Pump Discharge Aligned to Miniflow Path in Preparation For Isolating NI Pump Cold Leg injection Header.
o Ensure Following Valves OPEN:
1NI-115A (Ni Pump 1 A o
Miniflow isol) o ~
1NI-144A (Ni Pump 1B Miniflow isol) o 1NI-147B (NI Miniflow Hdr To FWST isol) 3.
Attempt To identify AND isolate Possible Leak Paths.
a.
Place PWR DISCONs for following valves to "EN A B LE" o
1NI-173A (ND Hdr 1 A To Cold Legs C & D) o 1NI-178B (ND Hdr 1B To Cold Legs A & B) 1NI-162A (Ni to C-Legs o
inj Hdr isol) b.
CLOSE AND RE-OPEN following valves in the order listed.
Monitor NC pressure for increases during time each valve is closed.
1) 1NI-173A 2) 1NI-178B 3) 1NI-162A Page 2 of 5
(3 of 7)
Form 34913 (8-82)
CNS PAGE NO.
EP/1/A/5000/1C6 LOCA OUTSIDE CONTAINMENT 3
Retype #2 ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED NOTE The following valves are operated from the UHI Accumulator Hydraulic Service Panels (refer to OP/1/A/6200/10, UPPER HEAD INJECTION).
4) 1Ni-243A (UHI Accum isol) 5)
1NI-245A (UHI Accum isol) 4.
Ensure The PWR DISCON Switches For Following Valves In The "DISCON" Position:
o 1 NI-173A o
1 NI-178 B c
1NI-162A o
1 NI-147B.
5.
Verify Leak Path Identified AND isolated OR Under Control.
a.
Leak Path:
IDENTIFIED a.
Continue attempts to identify leak path.
b.
NC Pressure:
b.
IF_ leak CANNOT be isolated, THEN:
INCREASING o
initiate makeup to FWST referring to OP/1/A/6200/14, REFUELING WATER SYSTEM.
NOTE A feed and bleed of NC may decrease NC pressure and thus the Reactor Coolant leakage rate of inventory to outside contain-ment.
It may also result in melting of ice which will increase sump inventory.
c.
Verify Containment Sump c.
Consult plant engineering staff Level AND FWST are within to determine need for estab-ADEQUATE S/l INVENTORY lishing feed AND bleed of the NC region of Enclosure 1.
to increase containment sump inventory.
o IF feed and bleed of NC required, THEN refer to EP/1/A/5000/1E4, SGTR WITH CONTINUOUS NC SYSTEM LEAKAGE: SATURATED RECOVERY, Steps 44 thru 69.f Page 3 of 5
, - ~,, - -,,
(4 of 7)
Form 34913 (8-83) j CNS PAGE NO.
j EP/1/A/5000/1C6 LOCA OUTSIDE CONTAINMENT 4
Retype #2
\\
ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED d.
Go to EP/1/A/5000/1C, HIGH ENERGY LINE BREAK INSIDE CONTAINMENT, f
Step 1.
-EN D-l 9
Page 4 of 5
(5 of 7)
Form 349Y3 }8 82}
CNS LOCA OUTSIDE CONTAINMENT EP/1/A/5000/1C6 S/l SUCTION INVENTORY 5
ENCLOSURE 1 Retype #2 00 00 ADEQUATE $/t INVENTORY M
WITH NS PUMPS ON g
i ",EEBEMk..
NEWSSESS.
mammeggpf,,
20 INAOEQUATEINVENTORY mrammmEBMBh,
" N%%RMMMMMM@>>n O
.50 SA t.5 2D 25 30 3.5 40 4.5 54 5.5 4.0 6.5 CONTAINMENT $ UMP LEVEL (PT) 100 M
to ADEQUATE S/t INVENT 0mv D
waTN NS PUMPS OFF g
50
?
VAV/4V/Ab~
S$7AMMA
" awsammb s
20 INADEQUATEINVENTORY 773
.. fk Y b-VA%V74@%WFA F A%V>
A x 0
.50 1A 1.5 20 2.5 30 35 40 45 50 55 60 65 CONTAINMENT SUMP LEVEL (FTl i
l Page 5 of 5 l
e
. Form 34913 (8-82)
(6 of 7)
PAGE NO.'
CNS SGTR WITH CONTINUOUS NC SYSTU
- EAKAGE:
EP/1/A/5000/1E4 SATURATED RECOVERY 19 Retype #1 ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED
- 44. Check Containment Status:
CAUTION After the NS pumps have been stopped, either the NS pump suction must be realigned to containment sump or NS Resets must be reset, to restart pumps.
a.
Containment pressure a.
Verify both NS pumps
<15 psig.
running AND go to Step 45.
, b.
Containment pressure b.
Ensure only one NS pump
< 10 PSIG.
running AND go to Step 45.
NOTE NS pumps are stopped to conserve FWST water, making more water available for core cooling.
c.
Stop both NS pumps.
45.
Check Containment Sump Level:
a.
Sump level < 1.5 ft.
a.
Go to Step 46.
NOTE Auto swap is defeated to prevent cavitation of ND or NS Pump (s) if allowed to swap to the Containment Sump.
b.
Depress " Defeat":
o C-Leg Recirc FWST to Cont Sump Swap Train A o
C-Leg Recirc FWST to Cont Sump Swap Train B c.
Verify enable lights dark.
- 46. Evaluate FWST Depletion:
a.
Determine need to makeup to FWST, based on Si flow (if
.any) AND time to reach <200 F.
Page 19 of 30
a em 34913 (8-82)
(7 of 7)
- GTR WITH CONTINUOUS NC SYSTEM LEAKAGE:
PAGE NO.
EP/1/A/5000/1E4 SATURATED RECOVERY 20 Retype #1 ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED b.
Initiate makeup to FWST, b.
IF sufficient makeup flow as required.
to the FWST CANNOT be achieved, THEN consult TSC to determine need to go to Step 47 to establish feed AND bleed on NC System to increase containment sump inventory.
The following criteria must be met to establish feed AND bleed.
o Sump level > 1.5 ft.
o NV and Ni pumps on FW o
NS pumps off o
FWST level: 20% - 50%
/
- 47. DO NOT Proceed Unless Directed By Step 46.b
" RESPONSE NOT OBTAINED".
NOTE Steps 48-67 initiate feed AND bleed cooling through the PZR PORV's in order to minimize FWST depletion out of the containment, AND to increase the containment sump level to allow cold leg recirculation.
- 48. Ensure All NC Pumps Stopped.
- 49. Check S/l Flow:
o At least 2 of the 4 NI o
Restore at least 2 Ni and NV pumps running.
and/or NV pumps.
- 50. Establish Path From NC System To Containment By:
o Opening 1 PZR PORV.
o Opening Reactor Vessel Head Vent.
- 51. Check NC System Pressure:
o NC pressure:
Stable o
Open an additional PZR PORV.
O_R decreasing.
,,.c Page 20 of 30
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