ML20036A250
| ML20036A250 | |
| Person / Time | |
|---|---|
| Site: | 05200002 |
| Issue date: | 04/30/1993 |
| From: | Mike Franovich Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9305110010 | |
| Download: ML20036A250 (76) | |
Text
N
' A dmc UNITED STATES Z
}
NUCLEAR REGULATORY COMMISSION g
WASHINGTON, D.C. 20555-0001 gv '/
April 30, 1993 Docket No.52-002 APPLICANT: ABB-Combustion Engineering, Inc. (ABB-CE)
PROJECT:
CE System 80+
SUBJECT:
PUBLIC MEETING OF APRIL 21, 1993, TO DISCUSS THE INTERSYSTEM LOCA (ISLOCA) ISSUE FROM THE CE SYSTEM 80+ DRAFT SAFETY EVALUATION REPORT (DSER)
On April 21, 1993, a public meeting was held at the U.S. Nuclear Regulatory Commission (NRC), Rockville, Maryland, between representatives of ABB-CE and NRC. provides a list of attendees. is the material presented by ABB-CE. contains material transmitted via facsimile to the NRC prior to the meeting. The purpose of the meeting was to discuss ABB-CE's evolving approach to resolve ISLOCA concerns as discussed in DSER Open Item 20.2-14 and Commission paper SECY-93-087, " Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water (ALWR)
Designs."
ABB-CE presented their mechanistic approach to resolve the ISLOCA issue.
Since the last meeting, ABB-CE has evaluated low-pressure systems capability on a case-by-case basis. Originally, ABB-CE proposed for the alternative ~
resolution issue that would credit pressure reduction from line resistance (e.g., check valves, filters, orifice plates) and relief valves as discussed in the February 22, 1993, meeting. ABB-CE would also credit operator action to terminate the ISLOCA. Since the February 22, 1993, meeting, ABB-CE has modified this approach to include " automatic" isolation of some low-pressure systems subject to ISLOCA conditions.
ABB-CE defined the scope of the ISLOCA evaluatio1 by identifying low-pressure systems that directly interface with the reactor coolant system (RCS):
(1) Shutdown Cooling System (SCS),
(2) Chemical & Volume Control System (CVCS) (letdown)
(3) Safety Injection System (SIS)
(4) Sampling System (SS)
In addition, ABB-CE postulated each potential ISLOCA pressurization pathway (case-by-case) and the affected subsystems for each of these ISLOCA scenarios.
There are a total of 10 pressurization pathways identified (see page 9 of ) for evaluation. Under this approach, ABB-CE would select the most limiting ISLOCA pressure transient for each system and subsystem under design evaluation.
060128 hh bh h0N s W WE E
\\
9305110010 930430 pi PDR ADOCK 05200002 PDR A
L 2
,?
i l
! April 30,1993 j
The main issue of the meeting centered on the proposed use (for some inter-faces) of automatic isolation features to prevent / terminate ISLOCA challenges i
from affecting portions of low-pressure systems that have not been upgraded to i
at least the ultimate rupture strength criteria. Specifically, ABB-CE -
proposed the addition of a new pressure indicator and controller.to automati-cally close the letdown line containment isolation valve (CIV). The CIV would close on high-pressure downstream of the letdown flow control valves, and the CIV would still receive its input for closure on a safety injection actuation i
signal (SIAS) and containment isolation actuation signal (CIAS). - Alarm i
indication for the new feature would also be provided in the main control room.
As a second line of defense, ABB-CE has provided a relief valve on the letdown line piping downstream of the CIV. This relief valve would discharge to the equipment drain tank (EDT) in the auxiliary building. The EDT is sized-to accommodate 30 minutes of discharge, and subsequent operator action would be required to terminate the event.
The staff considered ABB-CE's active design response as reasonable; however,
[
the " practicality" discussion was not fully developed. ABB-CE stated that it was impractical to design certain low-pressure portions of the CVCS because l
the changes would be an excessive requirement on standardized equipment.
Based on this discussion with the staff, ABB-CE should comprehensively address
-i the impracticality of upgrading this system. As indicated in the_ meeting,_
ABB-CE may discuss the. design aspects that reduce the likelihood of a system.
configuration that would challenge low-pressure letdown components -(auto closure / isolation, relief valves, etc.), cost aspects of upgrading systems /
-l components, and product availability, such as high-pressure hydrogen and l
nitrogen supply lines, gas treatment systems, and ion exchangers.
'i The staff was also concerned that CVCS reliability may be impacted by the added isolation feature. Also of ' concern was the potential for setpoint drift of the letdown relief valve and that early' lift prior to attaining the i
setpoint for the automatic isolation controller may complicate system response. Accordingly, ABB-CE indicated they would evaluate these concerns.
Additionally, the staff commented on the ABB-CE definition of an ISLOCA v
provided on page 3 of Enclosure 2.
In general, the definition appeared l
adequate; however, the staff noted that the scope of the definition may have to be altered to reflect the CVCS ISLOCA scenario. One of the CVCS ISLOCA challenges may result from the inadvertent closing of a charging pump suction line valve or stoppage of all charging pumps. Therefore,- ABB-CE's statement that the ISLOCA event is caused by leaking valves or inadvertent opening of l
valves would not capture the CVCS scenario mentioned, even'though ABB-CE has r
evaluated the scenarios in question.
The following commitments were made during'the meeting:
l (I) ABB-CE will fully develop the " practicality" argument for not designing
[
all low-pressure systems to higher-pressure capability as noted in the CVCS case.
t i
- April 30,1993
\\
(2) ABB-CE should document the rationale for limiting the scope of the ISLOCA evaluation to systems that only communicate through valves.
Speci-fically, ABB-CE must justify why heat exchanger tube failure should not be an ISLOCA consideration requiring shell side protection and designed to the ultimate rupture strength criteria. This should capture heat exchanger tubes that interface with the RCS such as a high-pressure seal cooler (HPSC), the CVCS letdown heat exchanger, the SCS heat exchanger, etc.
As discussed in the meeting, the justification for this issue may include the relief valve on CCW for HPSC load and the thermal reliefs on shell side of the letdown heat exchanger also in-containment.
For heat exchangers that are not continually in-service (especially Modes 1, 2, and 3) such as the SCS heat exchanger, ABB-CE should considered these operational aspects that limit such an event from occurring.
For the case of inadvertent SCS pressurization while at power, it is feasible to make a low-probability argument, but not exclusively, since the SCS heat exchanger tubes are rated for 900 psi.
(3) ABB-CE will justify (e.g., qualification, quantification) the bases for the structural integrity footnote on page 4 of Enclosure 2.
ABB-CE should provide the bases for determining that pump seal and valve bonnet leakage of the affected systems would be less than the system makeup capabilities.
(4) ABB-CE will promptly notify the staff if the option to design to the ultimate rupture strength (especially for stainless steel) is exercised.
(5) ABB-CE should modify the ISLOCA acceptance criteria (page 4 of Enclo-sure 2).
The staff noted that the first acceptance criteria should stipulate that a "high confidence" exists that a system experiencing ISLOCA conditions retains integrity throughout the event.
In addition, the staff noted that acceptance criteria number 3 should stipulate that potential offsite doses are within a "small fraction" (i.e.,10 percent) of the 10 CFR Part 100 guidelines consistent with the Chapter 15 dose definition in the Standard Review Plan (SRP), NUREG-0800.
(6) ABB-CE should address the system reliability effects of the proposed automatic closure feature for the CVCS and other systems where such a feature is proposed. ABB-CE will address potential overall CVCS relia-bility impact due to spurious closure, maintenance aspects, etc., for the added controller.
(7) ABB-CE will address setpoint drift for relief valves, especially for the CVCS relief to the equipment drain tank. ABB-CE should address impact /
feasibility of early lift of the relief valve prior to exceeding the pressure setpoint for containment isolation valve closure.
(8) A subsection of the ISLOCA report should reference the SSAR section addressing the responses and resolution to the Palo Verde high-pressure l
seal cooler (HPSC) tube rupture event as verbally indicated to l
2
' April 30,1993 S. Ritterbusch in February 1993. This was also a commitment made in the Februarv 22, 1993, ISLOCA meeting (see meeting summary).,
(9)
ISLOC's related alarms and instrumentation must be identified on the apprcpriate system Tier 1 (Design Description and ITAAC) figures. The alarrs to be shown are only those beyond the minimum inventory of alarms necessary to implement the EPGs as identified in CESSAR-DC Chapter 18 and the Control Panels Tier 1 information.
i (10)
For system design modifications that have resulted from ISLOCA resolu-tion, AEB-CE will evaluate the potential impact on the_ probabilistic risk assessment assumptionr results, and insights.
(11) ABB-CE will include configuration management aspects between the SCS and the containment spray system (CSS) in the pressurization pathway-discussion, especially if a SCS train is aligned to serve the CSS function.
Finally, it should be noted that ABB-CE has modified some low-pressure systems in view of the ISLOCA pressurization pathway (s) analysis with supporting justification.
For example, ABB-CE has eliminated an interface between the SCS and the CVCS. This interface was used for RCS purification during shutdown operations. ABB-CE has provided an alternate means for achieving this purification function. ABB-CE has also upgraded the CSS portion outside containment to 900 psig, and the SIS suction piping outside containment.is now I
also rated for 900 psig.
The next working meeting will be scheduled for the mid to late May 1993, time frame following ABB-CE's submittal in response to this meeting.
7,
,l A
Michael
. Franovich, Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of Nuclear Reactor Regulation
Enclosures:
As stated cc w/ enclosures:
See next page
.i
% April 30,1993 l
S. Ritterbusch in February 1993. This was also a commitment made in the February 22, 1993, ISLOCA meeting (see meeting summary).
(9)
ISLOCA related alarms and instrumentation must be. identified on the appropriate system Tier 1 (Design Description and ITAAC) figures. The i
alarms to be shown are only those beyond the minimum inventory of alarms i
necessary to implement the EPGs as identified in CESSAR-DC Chapter 18 and the Control Panels Tier 1 information.
(10) For system design modifications that have resulted from'ISLOCA resolu-tion, ABB-CE will evaluate the potential impact on the probabilistic risk assessment assumptions, results, and insights.
(11) ABB-CE will include configuration management aspects between the SCS and the containment spray system (CSS) in the pressurization pathway discussion, especially if a SCS train is aligned to serve the CSS:
function.
Finally, it should be noted that ABB-CE has modified some low-pressure _ systems' in view of the ISLOCA pressurization pathway (s) analysis with supporting justification.
For example, ABB-CE has eliminated an interface between the SCS and the CVCS. This interface was used for RCS purification during shutdown operations.
ABB-CE has provided an alternate means for achieving 1
this purification function. ABB-CE has also upgraded the CSS portion outside containment to 900 psig, and the SIS suction piping outside containment is now also rated for 900 psig.
The next working meeting will be scheduled for the mid to late May 1993, time frame following ABB-CE's submigal ingesgon*8 b )this meeting.
{
to e
Michael X. Franovich, Project' Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal-Office of Nuclear Reactor Regulation
Enclosures:
As stated cc w/ enclosures:
See next page DISTRIBUTION w/ enclosures:
Docket File PDST R/F DCrutchfield PShea PDR MFranovich RPerch, 8H7 TWambach SMagruder TEssig DISTRIBUTION w/o enclosures:
TMurley/FMiraglia RBorchardt JMoore, 15B18 EJordan, MNBB3701 MMalloy RJones, 8E23 MRubin, 8E23 SSun, 8E23 HBrammer, 7H15 GGrant, 17G21 DTerao, 7H15 JHuang, 7H15 ACRS (11)
- SEE PREVIOUS CONCURRENCE OFC:
- LA:PDST:ADAR SC:SRXB BSSA PM:PD 1ADAR SC:PDST:ADAJ NAME: PShea MRubipal3)
MXFpi yich:tz TEssig '(\\\\'Li DATE: 04/27/93 04/br/9 04/3; 93 04/30/93' OFFICIAL RECORD COPY:
DOCUMENT NAME: MSUM0421.MXF
)
ABB-Combustion Engineering, Inc.
Docket No.52-002 cc:
.Mr. C. B. Brinkman, Acting Director Nuclear Systems Licensing
.e ABB-Combustion Engineering, Inc.
1000 Prospect Hill-Road Windsor, Connecticut 06095-0500 Mr. C. B. Brinkman, Manager Washington Nuclear Operations ABB-Combustion Engineering, Inc.
12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Mr. Stan Ritterbusch Nuclear Systems Licensing ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Post Office Box 500 Windsor, Connecticut 06095-0500 Mr. Sterling Franks e
5 U. S. Department of Energy NE-42 Washington, D.C.
20585 Mr. Steve Goldberg Budget Examiner 725 17th Street, N.W.
Washington, D.C.
20503 Mr. Raymond Ng 1776 Eye Street, N.W.
Suite 300 Washington, D.C.
20006 Joseph R. Egan, Esquire Shaw, Pittman, Potts & Trowbridge 2300 N Street, N.W.
Washington, D.C.
20037-1128 Mr. Regis A. Matzie, Vice President Nuclear Systems Development ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Post Office Box 500 Windsor, Connecticut 06095-0500
ABB-CE SYSTEM 80+
ISLOCA Meeting April 21,1993 -
Rockville, Maryland 7
NAME ORGANIZATION R. Jones NRR/DSSA/SRXB -
M. Rubin NRC/DSSA/SRXB M. Franovich NRR/PDST S. B. Sun NRC/NRR/SRXB H. Brammer NRC/DE J. Huang NRC/DE M. Cross ABB-CE J. Longo ABB-CE M. Voledzko ABB-CE 4
l l
l
)
SYSTEM 80+ ISLOCA hGiEBlh o SUMMARIZE WORK PERFORMED TO-DATE.
o REVIEW RESULTS AND OBSERVATIONS MADE TO-DATE.
l o REVIEW SPECIFIC EXAMPLES OF ISLOCA DESIGN RESPONSES...
SHUTDOWN COOLING SYSTEM (SCS)
'l LETDOWN SYSTEM SAMPLING SYSTEM (88)
CONTAINMENT SPRAY SYSTEM (CBS) i SAFETY INJECTION SYSTEM (SIS) o DISCUSS RESULTS AND FUTURE WORK.
7 7
4 h
r i
t I
h
'i
+
-i
'l i-i Page 1
SYSTEM 80+ ISLOCA f
SUMMARY
OF WORK PERFORMED-TO-DATE o DEFINED'ISLOCA (FOR PURPOSES OF DEVELOPING DESIGN-RESPONSES).
o IDENTIFIED ISLOCA JOCEPTANCE CRITERIA.
o IDENTIFIED COMPLIANCE METHODS SATISFYING THE ISLOCA ACCEPTANCE CRITERIA.
o JUSTIFIED THE COMPLIANCE METHODS.
o DESCRIBED THE ISLOCA EVALUATION PROCESS.
i o PRESENTED PRELIMINARY RESULTS AND OBSERVATIONS OF THE ANALYSIS.
i o PRESENTED TWO EIAMPLES OF ISLOCA DESIGN RESPONSES.
LETDOWN SYSTEM SHUTDOWN COOLING SYSTEM I
i f
i Page 2
SYSTEM 80+ ISLOCA ISLOCA DEFINITION I
AN INTER-SYSTEM LOCA (ISLOCA) IS AN EVENT-IN WHICR A BREAK OCCURS IN A SYSTEM DIRECTLY OR INDIRECTLY CONNECTED TO THE REACTOR COOLANT SYSTEM (RCS) CAUSING A LOSS OF THE PRIMARY COOLANT OUTSIDE OF CONTAINMENT.
THE EVENT IS CAUSED BY LEAKING VALVES OR INADVERTENT OPENING OF-VALVES.
i l
t r
i V
I b
8 t
i i
r t
t i
Page 3
3,
- *[ -
- j 11 SYSTEM 80+ ISLOCA l
i ISLOCA ACCEPTANCE CRITERIA i
SYSTEMS SUSCEPTIBLE TO AN ISLOCA SHALL BE' DESIGNED SO
{
THAT ALL OF THE FOLLOWING CONDITIONS ARE' SATISFIED l
WITHOUT ANY OPERATOR ACTION....
t
- . }
r
...THE SYSTEM RETAINS ITS STRUCTURAL INTEGRITY
- THROUGHOUT THE EVENT,
...ANY LEAKAGE CAUSED BY THE EVENT'IS LIMITED TO MAKEUP SYSTEM CAPABILITIES; AND i
...OFFSITE DOSES ARE LIMITED TO VALUES SPECIFIED IN 10 CFR 100.
PRESERVATION OF STRUCTURAL INTEGRITY IS DEFINED TO IMPLY I
THE PREVENTION OF SYSTEM BOUNDARY RUPTURE EXCEPT FOR SUCH.
l AREAS'AS PUMP. SEALS AND VALVE PACKINGS TO THE EXTENT THAT SUCH LEAKAGE (COLLECTIVELY) DOES NOT EXCEED SYSTEM MAKEUP-CAPABILITIES.
h~
i i
i
.i r
.i k
r I
,f Page-4
-l I
I-i
i j
l I
u
. i i
SYSTEM 80+ ISLOCA COMPLIANCE METHODS l
o PASSIVE DESIGN RESPONSE...
r
... INHERENT PHYSICAL ATTRIBUTES WHICH WILL PREVENT i
FAILURE OF SYSTEM INTEGRITY (E.G.,
INCREASING SYSTEM DESIGN PRESSURE),
j
...DOES.NOT REQUIRE OPERATOR ACTION TO SATISFY ISLOCA ACCEPTANCE CRITERIA,
... REQUIRES OPERATOR ACTION TO TERMINATE THE EVENT, f
...DOES NOT PREVENT AN ISLOCA OR LIMIT.IT'S COOPE.
i o ACTIVE DESIGN RESPONSE...
!:t
...THE APPLICATION OF SPECIFIC EQUIPMENT AND i
INSTRUMENTATION TO PREVENT OR MITIGATE THE CONSEQUENCES OF AN ISLOCA,
...DOES NOT REQUIRE OPERATOR ACTION TO TERMINATE AN-f l
ISLOCA EVENT.
i f
s 1
i f
.i
?
Page'5 i
I SYSTEM 80+ ISLOCA i
EXAMPLES OF COMPLIANCE JUSTIFICATION USING PASSIVE RESPONSE
... LOCATING THE SYSTEM OR
...ISLOCA's CAN ONLY OCCUR SUBSYSTEM COMPLETELY IN WHEN A BREAK EXISTS IN A CONTAINMENT, SYSTEM OUTSIDE CONTAINMENT,
... DESIGNING THE SYSTEM OR
...ISLOCA's CAN ONLY OCCUR IN SUBSYSTEM TO RCS NORMAL SYSTEMS HAVING A LOWER DESIGN OPERATING PRESSURE, PRESSURE THAN RCS NORMAL OPERATING PRESSURE,
... DESIGNING THE SYSTEM OR
...ISLOCA ACCEPTANCE CRITERIA SUBSYSTEM TO AT LEAST 40% OF SATISFY THE APPROACH IN NRC RCS NORMAL OPERATING PRESSURE, DOCKET 52-001,
... DESIGNING THE SYSTEM OR
...ISLOCA's CANNOT OCCUR IN SUBSYSTEM SO THAT THE ULTIMATE SYSTEMS OF SUFFICIENT ULTIMATE STRENGTH OF THE SYSTEM EXCEEDS
- STRENGTH, THE STRESS PRODUCED BY RCS NORMAL OPERATING PRESSURE,
... PHYSICALLY SEPARATING THE
...ISLOCA's CAN ONLY OCCUR IF SYSTEM OR SUBSYSTEM FROM THE A SYSTEM IS PHYSICALLY RCS DURING CONDITIONS WHEN THE CONNECTED TO THE RCS.
RCS PRESSURE EXCEEDS THE (LOWER PRESSURE) SYSTEM'S DESIGN PRESSURE.
i Page 6 i
e e
i
.i l
SYSTEM 80+ ISLOCA EXAMPLES OF COMPLIANCE JUSTIFICATION i
USING l
ACTIVE RESPONSE f
... ISOLATION OF A
...ISLOCA's CAN ONLY PROCEED' l
PRESSURIZATION PATHWAY IN A IF AN OPEN PATHWAY EXISTS SYSTEM OR SUBSYSTEM'AT THE BETWEEN THE PRESSURE' SOURCE-r INTERFACE BETWEEN THE LOWER AND THE (LOWER. PRESSURE)
PRESSURE SYSTEM OR SUBSYSTEM SYSTEM OR SUBSYSTEM, j
AND ITS PRESSURIZATION SOURCE,
(
.I
... PRESSURE RELIEF TO LIMIT f,
THE PRESSURIZATION TO WITHIN
...ISLOCA's CANNOT OCCUR IF THE DESIGN CAPABILITIES OF THE THE PRESSURIZATION OF t"HE SYSTEM OR SUBSYSTEM.
(LOWER PRESDURE) SYSTEM OR SUBSYSTEM DOES NOT EXCEED ITS DESIGN PRESSURE.
[
1 f
I f
f b
l r
+
t I
r Page 7 i
[
1 I
t i
I SYSTEM 80+ ISLOCA ISLOCA~ EVALUATION PROCESS l
o THE RCS P&ID WAS REVIEWED TO IDENTIFY ALL SYSTEMS OR-SUBSYSTEMS THAT INTERFACE WITH THE RCS.
j l
o ALL POSSIBLE ISLOCA EVENTS WERE IDENTIFIED AND ARRANGED INTO CLASSES FOR THE PURPOSE OF ORGANIZING THE EVALUATION l
PROCESS AND TO ENSURE THAT NO EVENT WAS OVERLOOKED.
-f o
EACH CLASS OF ISLOCA EVENTS IS CHARACTERIZED BY A SET OF.
PRESSURIZATION PATHWAYS FROM A COMMCN INITIATING SYSTEM DIRECTLY CONNECTED TO-THE RCS.
o PRESSURIZATION PATHWAYS REPRESENT ALL THE OPLN FLOW PATHS l
TO INTERCONNECTING SYSTEMS BY WHICH THE RCS CAN j
PRESSURIZE INTERFACING SYSTEMS ASSUMING THE INTERFACING VALVES ARE POSTULATED TO BE OPEN.
THE ISLOCA CLASSES ARE ILLUSTRATED IN FIGURES 1-10.
o PRESSURIZATION PATHWAYS ARE EXAMINED TO IDENTIFY ANY l
PATTERN WHICH MAY SUGGEST A HIERARCHY OF DESIGN l
RESPONSES.
A HIERARCHICAL PATTERN WOULD BE NOTIVATED BY THE DESIRE TO SATISFY THE ISLOCA ACCEPTANCE CRITERIA WITH A DESIGN RESPONSE COMMENSURATE WITH PERCEIVED BENEFIT AND l
COST.
o EACH INTERFACE IN THE PRESSURIZATION PATHWAYS ARE f
EVALUATED TO IDENTIFY THE TYPE AND LOCATION OF DESIGN i
RESPONSE.
i i
4 I
1 5
Page s' j
I a
k
~.
f i
1 i
I SYSTEM 80+ ISLOCA PRELIMINARY OBSERVATIONS-OF ISLOCA EVALUATION o
ONLY FOUR SYSTEMS OR SUBSYSTEMS ARE DIRECTLY CONNECTED TO THE RCS FOR ANY ISLOCA EVENT...
I
+
.. 8HUTDOWN COOLING SYSTEM (SCS),
... SAFETY INJECTION SYSTEM (SIS),
... CHEMICAL & VOLUME CONTROL SYSTEM (CVCS),
'l
... SAMPLE SYSTEM (88).
o TEN CLASSES OF ISLOCA EVENTS HAVE BEEN IDENTIFIED.
THESE i
ARE PRESSURIZATION BY...
j
...SCS SUPPLY LINE,
...SCS RETURN LINE,
.. 818 DELIVERY LINE,
... LETDOWN LINE,
... CHARGING LINE, j
... SEAL INJECTION,.
...RCP CONTROLLED BLEEDOFF,
.. 88-HOT LEG,
...SS
. PRESSURIZER SURGE LINE,.
t
.. 88-PRESSURIZER STEAM SPACE.
o CONTAINMENT SPRAY SYSTEM (CBS) IS NEVER DIRECTLY i
CONNECTED TO.THE RCS.
~!
o THE APPLICATION OF A PASSIVE DESIGN RESPONSE HIGHLIN THE '
PRESSURI2ATION PATHWAY HIERARCHY DOES NOT PROTECT INTER-CONNECTING SYSTEMS LOWER IN THE HIERARCHY.
THAT IS, APPLICATION OF A PASSIVE DESIGN RESPONSE DOES NOT t
TERMINATE OR LIMIT THE SCOPE OF THE EVENT.
THE INTER -
CONNECTING SYSTEMS.STILL REQUIRE A DESIGN RESPONSE OF THEIR OWN.
1 o
THE APPLICATION OF AN ACTIVE DESIGN RESPONSE HIGH IN THE PRESSURIZATION PATHWAY HEIRARCHY CAN TERMINATE THE EVENT l
WITHOUT HAVING TO APPLY ADDITIONAL DESIGN RESPONSES TO I
INTER-CONNCECTING SYSTEMS LOWER IN THE HIERARCHY.
l J
1 P..,
i h
i
FIGURE 1
- 3 PATHWAY
PRESSURIZATION BY SHUTDOWN COOLING SYSTEM SUPPLY UNE C
SYSTEM DIRECTLY SHUTD0WN INTERFACNG u m RCS COOLING SYSTEM
/
/
/
SYSTEMS
$S[RFA c CVCS ATM SS CSS SIS PCPS NTH RCS REFUEUNG POOL SS
\\
NCI" REMOVED
\\
C S'
2 95 ATM CVCS CVCS y
'^
'PMWS ATM SWMS
\\
k
FIGURE 2 PATHWAY:
PRESSURIZATION BY SHUTDOWN COOLING SYSTEM RETURf LINE SYSTEM DIRECTLY SHU TDOWN
'QRFA COOLING N
pC SYSTEM NN SYSTEMS
$T[RFADNc
- CVCS ATM SS CSS SIS PCPS WITH RCS REFUEUNG POOL SS SYS EMS MCE REMOVED c S CVCS SIS ATM SS
- FROM RCS H
2
. SIS ATM CVCS CYCS AIR SUPPLY 33 3
3 ATM P
ATM
.SWMS
-e iv
- =
+-,r-e*
-~
e w
e.
w e
.-vt' e
4
- u-
=
--4 m -r
-w-
FIGURE 3 PATHWAY:
PRESSURIZATION BY SAFETY INJECTION DELIVERY LINE SYSEM DIRECTLY INTERFAONG w m Rc5 SAFETY INJECTION SYSTEM
/
SYSTEMS INDIRECTLY INERFAONG WiiH RCS ATMOS SCS CVCS CSS SS
/
SYSTEMS PCPS.
TWCE REMOVED SCS CVCS FROM RCS CVCS ATMOS SCS CSS (EDT)
SS ATMOS ATMOS
%++--e.*
.=,y-w
-,,-r
-,+.--<4 y<+
w
...r-,y n-a
,4-w--
=m--*-
1e--
,-c.-
,g-*.w-<
,-<=
n-
FIGURE 4 PAmWAY:
PRESSURIZATION BY LETDOWN UNE SYSEM DIRECTLY INTERFACING LETDOWN wim RCS.
LINE f
ATM SS SCS H
- BORM SYSitus RECOVERY INDIRECTLY i TERFA NG
- SEAL N
INJECTION 2
- MAKEUP GWMS gggg SYSTEus TwtCE REMOVED SCS CSS FROM RCS ATM 33 CSS 33 LWMS 53 SS SWMS SCS ATM
.w-.
+. -
.i%%
x,y..
r.,
FIGURE 5 PATHWAY:
PRESSURIZATION BY CHARGING LINE SYSTEM DIRECTLY
'%RQ NG CHARGING w
LINE ATM SS SCS H
- DORON 3UE RECOVERY 2
gg gE Y
INTERFACING
- SEAL N
WiTH RCS INJECTION 2
- MAKEUP GWMS SWMS SYSTEMS SFP TWCE REMOVED SCS CSS FROM RCS
^*
SS' CSS g3 LWMS SIS SS SCS ATM
. ~..
FIGURE 6 PATHWAY:
PRESSURIZATION BY SEAL INJECTION SYSTEM DIRECTLY
'y3%R SEAL INJECTION NG
,sgpggy BORON-PURIFICATION ATM TE INTERFAC!No RECOVERY W1TH RCS SYSTEMS PURiflCATION B 0 A
TwtCE REMOVED MAKEUP ATM FROM RCS CCWS SS SCS SWMS' CWMS LWMS SWMS GWMS N
2 SS
.N 2 i+r
%,w--
v-
?-er s-v e r e
,e w
--e--aw -- s w
-+-o.-
i-ee-e 7
r e +w e
-,e-e na e-b s wi
FIGURE 7 PATHWAY:
PRESSURIZATION BY RCP CONTROLLED BLEEDOFF SYSTEM DIRECTLY RCP IN TERFACINc CONTROLLED WITH RCS BLEED 0FF
,svSTEny BORON PURIFICATION ATM g gg INTERFACINc RECOVERY WITH RCS SYSTEMS PURIRCATION BORON VERY TWTCE REMOVED -
MAKEUP FROM RCS ATM CCWS' SS SWMS C S LWMS SWMS:
GWMS H
2 SS y
2
FIGURE 8-PATHWAY:
PRESSURIZATION BY SAMPLING - HOT LEG SYSTEM DIRECTLY HOT LEG IERFA '"
SAMPLING pCS
\\
/
s m ig9g$y SCS ATtAOS rugcAgoN MLWMS SIS CSS INTERFACING 9
W1TH RCS SYSTEMS CSS BORON RECOVERY ATWO SS TWICE REMOVED -
FROM RCS WAKEUP ss ATuo CYCS AND SCS ATWO CWWS CYCS SwuS H
2 N.
2 m
.m..
,.-,.-,,,m.
.,m g.,.
y
,m-
b FIGURE 9 PATHWAY:
PRESSURIZATION BY SAMPLING - PRESSURIZER SURGE LINE SYsitM DIRECTLY PRESSURIZER
'IhRA SURGE LINE gc "
SAMPLING
/
IND RE Y
SCS ATMOS PURtRCAMON MLWMS SIS CSS INTERFACING OW WITH RCS SYSTEMS CSS BORON RECOW.RY ANO Ss TWICE REMOVED FROM RCS~
MAKEUP SS ATM0 cycs ATM0 ses -
Am0 cws l.
sws ess cves H
2 N
2 I
,.m.
.,,,,m,
..J..
m,
+
FIGURE 10
.. PATHWAY:
PRESSURIZATION BY SAMPLING - PRESSURIZER STEAM SPACE SYSTEM n:RECTLY PRESSURIZER
'$RFA STEAM SPACE pC SAMPLING S
iND R Y
SCS ATMOS PUgCA ON MLWMS SIS CSS 9
INTERFACING WITH RCS -
SYSTEMS -
CSS BORON RECOVERY ATWO SIS TWICE REMOVED FROM RCS
-uAgtup i
3,3 ATWO CVCS ATWO SCS ATWO CwWS CVCS SWMS H
2 N
2 l
l P
l i
,.s..
,.m..-
J.
4 SYSTEM 80+ ISLOCA r
SPECIFIC EXAMPLES OF DESIGN RESPONSES 2
P P
L i
6 5
Page 11 t'
k
ISLOCA RESPONSE FOR THE SHUTDOWN COOLING SYSTEf! (SCS)
DESIGN CHANGE DESCRIPTION JUSTIFICATION Change No.
1...
...The entire system has been The 900 psig design pressure designed to a pressure of 900 meets the 40% of RCS normal psig.
In addition, as a operating pressure criterion.
result of this evaluation, the design pressure of the IRWST return line between the containment isolation valves and the containment penetration has also been increased to 900 psig.
Change No.
2...
This inter-connection has been evaluated to be unnecessary in
...The purified water return view of the ISLOCA challenge.
line from the CVCS (used As an alternative, the during shutdown cooling) has charging pumps can be used to been deleted.
return purified water to the RCS during shutdown cooling.
Change No.
3...
...Two new contianment This new configuration deletes i
penetrations have been added the interface with the SCS to provide a path for the thereby eliminating the ISLOCA make-up system to adjust the pressurization pathway.
boron concentration in the IRWST.
This configuration also eliminates-the interface between the SCS and the Pool Cooling and Purification System (PCPS).
(
t i
6 t-6.
ISLOCA RESPONSE FOR THE SHUTDOWN COOLING SYSTEM t
i I
t O
M
' HOT LEC RY 8
l SCS HX v
=
c
~Xi i
sc6-2485 900 e PUMP
,.,I
,,5..
9
,7 1_
- m3 900 9
IRWfT Q %)
RETURN LlHE 7 u
o I
_ i IRWST A
100 900 pl3t)E OUT31DE DE3m WANE ft coNTAweest DESCM PRES 3URE HAS BEEN WW:REASED 10 900 PSG l
I l
l I
..,;.1
..._1..,
s' NN 2
RE
( UETB E
T RS O
N AD mHE A
T g
W TSf ACl WSE N
D C
DE 0,
S EH E
1TF
,.S D
RO ll P
UT M
P U
X P
H m'
o-t-
^
SC S
^
P M
i
.v U
P S
C I,
S D[
3i x
3 f
T" N
EM' A
3i U^
P" I'
=
I-E""
F Q
A
~
A
. 0 E E 0
NT 02 S
0 Y
_~2 i.
RS l'
l O
- e. 0 '
g FG 0
_'5 f
8 SU 4
2 N O OO PC SEN RW 00 O
9 AD
~
CT hm,
'5MO e
l OU 7
wr LH S
8 IS 4
E 2
D I
S T
T U
N E
O M
I
!f e
l i,.
ge N
.A T
E N
h IS C
D O
E D
IN r
X A
H M
NW C
O EL
- r X
D O
I EH i
T I
1E.
e fi H
s I
1 0
Nv A
V R
J
w
~
a e
C W
a C UK 4
TN AA BT s
M e
i u
c E0AU EP DnM AuP m"
.b v
3, e
w bsAST E
A o)RK
~
NEON M
+
oCTA E ms i
I ITY
=
S 4
/
e y$
ROG s
M FN m
I E L At c
S O o
T s N N O E
u M
C O
M O
'l ill:;e
t
!,OI.!e ll, A
P T
S t
N o
O EN w
s C
RW m
w O
O U L
H S
-r I S u
e.
TS T
e PU T
I
+
5W U1R
+
R TEKE NAH m
EMMT
-r
$ MROD 3
[
m E
T D AO I
ETFSV w
N SO e
N OS R
CN&P A
4 OIC 0 DTAN EA E
T N ARME TEB C ET M
DNSS C EEYA D DPSH 3
=
~
l ll1iill
4-A ISLOCA RESPONSE FOR THE
- HOT LEG SHUTDOWN C00UNG SYSTEM R4
( gijy; Mar y )
r,.
Qu SCS HX y
N V
>M W
4 e
SCS Pt) M P
=
l l
l l'
RECENERATIVE r-HX-
~~
2485 00
.mA, p
r, LETDCWN MX e
$iS =
- h Ir l 1 ix H ver l 1
248s 200
% Eaumur.
ORArN TANK
'A~$
=
3 cHnRGmG a
. iN90E l00TSDE Pt]M P CONTANWENT DESGN CHANGE (2 CHARCWC PUMP 3 WLL RETURN PURIRED WATDt -
TO THE RCS DURING SHUTDOWN
--yw.
r4-
%c-~.. -,
a4,r wa p.*g e-w-
r,
- .s w,--
y
-e-..,.
ew 3,
3-
.+*w*e-<
-%-w w
a
-..,n t-w-r
.n.
,e..-w
i ISLOCA RESPONSE FOR THE LETDOWN LINE DESIGN CHANGE DESCRIPTION JUSTIFICATION A new pressure indicator and The letdown line is divided controller has been added to into high and low pressure i
automatically close the sections.
System integrity is letdown line containment preserved in the high pressure isolation valve on high section because the portion of pressure downstream of the the Letdown System pressurized letdown flow control valves.
by the ISLOCA is designed to 2485 psig.
The portion of the Letdown System downstream of the letdown flow control valves (low pressure section) is not pressurized by this event.
In-addition, a relief valve limits pressure to within design capabilities of downstream equipment.
Limiting the ISLOCA within the high pressure letdown section limits the concern of all the downstream interfacing systems.
These systems are typically of low pressure design and any change to the design would be an excessive requirement on standardized equipment.
I I
i l
e
.4 ISLOCA RESPONSE FOR TIIE LETDOWN IJNE INTERFACE REGDI HEAT EXCANNER RCS
.i m
COLD LEC LETDOWN j
HEAT EXCMMER
+
t LETDOWN ORW1ES X.
. INS 0E CONTAINtfENT CUT 30E CONTAMMENT -
DESKN 04AME PRESSURE INDICATOR AND C(MIROURt
- t HAS BEDI ADDED.
'"""i
,__-- PtC
-5ArtE HK II
' 5 p
_ TO 1
~
t_J
' vcr
. C(MTAIMbe6T e
!I-. ENT -
IslaAit(pg '
'8
- ygg LETDOWN FLOW CONTROL VALVES e
DRAM TANK-4 w..y9 Q
.t y
9edg+4-34-mp--->-yp.a9 y
=>g,m
,g-yyag+-y 9g p.s*qe-g y
-3
+-+g-RM werh W e m
g 5 9
.-gg'q-.s-p
.v'.gmma.:
Sty q..g g g
my e g _y s-g+
em
-y
,y.g ig wqee-g..peyp ye. sy-Q 4
q'pg4 y
r-g.a.-
ISLOCA RESPONSE FOR THE SAFETY INJECTION SYSTEM (SIS)
DESIGN CHANGE DESCRIPTION JUSTIFICATION Change No.
1...
...The design pressure of the The number of systems SIS pump suction piping up to interfacing with the SIS which the containment penetration will also be pressurized by has been increased to 900 the ISLOCA event is minimal; psig.
Change No.
2...
...The design pressure of the Most of the SIS is already piping between containment designed to a high pressure (a isolation valve and pressure exceeding 40% of-containment penetration in the normal RCS operating pressure; IRWST return lines has been increased to 900 psig.
The SIS is not open to the RCS during normal operation.
y I
__---__._-.,,--_a.-----
M E
E B
NI C
S9 AF H
L h
u 0
E E0 M9 E M N
M 3O f
3T M
t o
geD G rE r
S T
m mA aE C
m sW E ts E
D ep J
[
~
N I
7 G
/
E E
N L
I L
To I
H E
V M
D II f
T Ers R Y O S F
N E
S 0 1
r N
r c
Oc osT PE tN uE SJ oM lI lle
- \\ !Ii t
B'.
ll' EN M
RI ATN tO Y
A v.
eC C
T m
s O
t L
f S A v.
T5 I S ruR ub' c
ToH I
v.
D EB c 3s Ae v
H A
F o
L.
Eo W
ps E usn w" E si In o
PEsa m mE u Mm s
c E
o Dm L.
ISLOCA RESPONSE FOR THE SAMPLING SYSTEM DESIGN CHANGE DESCRIPTION JUSTIFICATION A pressure relief valve has Flow control valves upstream been added just upstream of of the pressure relief valve flow indicator F-550 with will cause a pressure drop to relief flow directed to the take place when the relief EDT.
valve passes flow that is equivalent to normal operation; The amount of flow rate passing through the relief will be within makeup system capabilities and will be small enough to allow sufficient time for operator action to terminate the event; Action is required to limit the pressure in the SS to prevent the process radiation monitor from exceeding its design pressure (this equipment is not currently i
available to withstand pressures exceeding 250 psig);
Action is required to protect the VCT from exceeding its design pressure and to prevent undermining the design response applied to the Letdown System; Action is required to limit the pressures in the SS to prevent personnel injury and excessive airborne contamination in the event a sample line is inadvertently opened during the ISLOCA i
event.
l i
l
+
h -
4 -
I ISLOCA RESPONSE FOR TIIE SAMPLING SYSTEM 1
p
) y --
SLH E UNE A
M gy-Hor us 3-e 5 AMPLE HEAT EXO4ANCDt lll rl l
k b
-- ver v
i l
m3 =
L:.
l l
CONTAINMENT l'
I-t-
i..
i-.
l --
ta.!Mf.y tg y e-sw.ar e yr--+m--
"a44 9**
-pg et.
r+Sw g tg rr--CP Tymusa.
g--Ovg gegm.9 aym y V.g-
- -*Aymno w-e+e9.. gun-i-e w
y sp59-1'-m-g w.smpm9 y
ya#
-,-wp
'ee gg=e'my ae yg.,4 9g p--
y gyw,a y.sw.w-ge,-+,ev dis.r-m---
- ine=w,a wm-e u.w
.s emm,a-.mw uw-
6
.h
' SAMPLING SYSTEM INDIRECT INTERFACES WITH RCS M EIT TMFI To lif. GT HOT LIG 3 g
V TO 3CS U
- WCT PUMP b
\\
[
l O
4-24es soo l
X X
W N--
=
'l 1
m3 1
~
soo - 2o3o 23.
r l
l
-j'
- W ses i
=i i
=
l
.l (OPD6 TO ATWO5PHERE) i smPtr som i
i l'
e w
~
NM WW CONTAMMENT -
l l
L
..,;, ~..
m.
....m..
.r.
c.
ISLOCA RESPONSE FOR THE CONTAINMENT SPRAY SYSTEM (CSS)
DESIGN CHANGE DESCRIPTION JUSTIFICATION Change No.
1...
...All sections of the CSS The 900 psig meets the 40%.of-located outside containment normal RCS operating pressure have been designed to 900 criterion.
psig.
Change No.
2...
..The alternate fill Two flowpaths are provided connection for the Refueling which can be used to fill the Pool has been located off the Refueling Pool.
One is IRWST return line from the through the reactor vessel and CSS.
In addition, a spool-the other through a direct piece has been inserted in connection at the Refueling this Refueling Pool fill line.
Pool from the CSS.
This second connection is considered the alternate, or backup, flowpath.
As a result, removing the spool-piece in this flow path during normal operation is considered acceptable.since it will not-interfere'with establishing the primary pool filling flowpath.
O e
L 4
9 s
a u
fA.
a 3
.g 4
'l s
fg-uf i
. 5 ll,s Ed "a
i,,
x
=
=Mk
~
1
?
. g 4
5:M
=
8e
[
e-n AC N
j' e
Cxx e
eg&
cn o
m a=
,f g,E m
S E~~
@K g
g3 E-ls s l i
E c....s l8 s
~
i.I 1
@g
,y e
\\
e gNg g
@KL a Eg.
g
.e EE gg C =)
I 12 j
L
)
l SYSTEM 80+ ISLOCA i
AGENDA l
o SUMMARIZE WORK PERFORMED To-DATE.-
o REVIEW RESULTS AND OBSERVATIONS MADE TO-DATE.
o REVIEW SPECIFIC. EXAMPLES OF ISLOCA DESIGN RESPONSES...
SHUTDOWN COOLING SYSTEM (SC8)
LETDOWN SYSTEM
-I SAMPLING SYSTEM (88)
CONTAINMENT SPRAY SYSTEM (CBS)
SAFETY' INJECTION SYSTEM (SIS) e i
o DISCUSS RESULTS AND FUTURE WORK.
l l
l
-i I
I 3
b 1
?
i l
l--
a r
j I
i Page.'.
I l-
A__BB_
\\\\owa
(\\\\r.+
TELECOP7 from A33 Combus; ion 3ngineering Nue:. ear Sys; ems-
?:.uic.
Sys; ems 3ngineering Far-x-swoui 9:Lso O
O Date: t'-/ 3 - F3 Time:
Reference:
To: My Phone: Jo/ -Sat'-//ftf Company:
g From: M b.o Phone: Bo39Pf-Parr Our Telecapy Number is: (203) 285 - 3267 This page with 46 pages to follow, s2r x Mai(~ yd -y '* ( 24 Prst i
I
Mike Fronovitich The attached summarizes our work on the ISLOCA issue up to this time.
It provides the information that we agreed to supply you during our 4-2-93 telephone conversation. We have completed the development of the pressurization pathways and identification of all systems involved in the ISLOCA evaluation.
The acceptance criteria has been refined and the ways of complying with the acceptance criteria re-evaluated. We have included two examples, which represent the implementation process for this evaluation. These examples provide summary results of the evaluation involving two pressurization pathways, and they provide a discussion of design changes needed to satisfy the ISLOCA criteria.
After you have had a opportunity to review this information, we should schedule a meeting to discuss the issue in more detail.
M. T. Cross MTC: dig 4
1 e
{
{
- p k
SYSTEM 80+ ISLOCA RESPONSE
{
I
't
[
ISLOCA DEFINITIQH i
.}
An inter-system LOCA (ISLOCA) is an event in which a break occurs in a system directly or indirectly connected to the reactor coolant system (RCS) causing a loss of the primary. coolant outside. of containment.
The event is caused by leaking valves or inadvertent opening of valves.
I i
IBLOCA ACCEPTANCE CRITERIA Systems susceptible to an ISLOCA shall be designed so that all of-h the following conditions are satisfied without any operator action...
(a) the system retains its structural integrity throughout I
the event; l
(b) any leakage caused by the event is limited to makeup system capabilities; and-(c) offside doses are limited to values specified in 10 CPR f
100.
i COMPLIANCE WITH THE ISLOCA ACCEPTANCE-CRITERIA Compliance with the ISLOCA Acceptance Criteria can be accomplished -
using passive or active design features.
i i
Passive design features are inherent physical attributes which vill f
prevent failure of system integrity'when the system is pressurized i
to normal' RCS pressure.
Passive design features do not require any
{
action by equipment or. operators to satisfy the ISLOCA Acceptance Criteria.
In this context, preservation of system integrity means to prevent leakages (especially non-isolable leakages) or limit i
leakages to makeup system capabilities, i
Examples of passive design features are...
(1) locating the system or subsystem completely within containment; f
F Page 1
+
8 i
'l
SYSTEM 80+ ISLOCA RESpONBE i
(2) designing the system or subsystem to RCS normal operating pressure; i
(3) designing the system or subsystem to at least 40% of the RCS normal operating pressure; i
(4) designing the system or subsystem so that the ultimate strength of the material comprising the system exceeds the stress produced in the material by pressure equal to normal RCS operating pressure; and (5) physically separating the system or subsystem from the RCS during conditions when the RCS pressure exceeds its design pressure.
.t Active design features are design responses to ISLOCA events consisting of specific equipment and instrumentation which perform actions to prevent or mitigate the consequences of an ISLOCA.
Active design responses that will be considered will not require operator action to prevent or mitigate the event, but will eventually require operator action to perform remedial. action, inspection of equipment following the event and returning the plant to normal operation.
Active design features are intended to be applied to systems for-which it is either not practical to apply passive design features or for which the benefit is perceived to be better than passive design features.
Examples of active design features are...
(1) the isolation of a
system.or subsystem in the pressurization pathway at the interface between the lower r
pressure system or subsystem and its pressurization source; and (2) pressure relief to limit the pressurization to within the design capabilities of the system.
r i.
Page 2
~
.q.
-- i SYSTEM 80+ ISLOCA RESPONSE t
JUSTIFICATION OF COMPLIANCE METHODB-The use of passive and active design features to address the ISIDCA 1
issue is motivated by the desire to apply an sppropriate ' degree of-design response that is commensurate with the perceived benefit of-
/,
the response and its cost.
i The passive design responses mentioned above are justified, where
'l practical, because...
(1)
ISLOCA's can only occur when a break exists in a system:
outside containment;
+
i (2)
ISLOCA's can only occur in systems having a. lower design pressure than RCS normal operating pressure; t
(3)
ISLOCA Acceptance Criteria are considered satisfied by.
]
the NRC.for systems'having a-' design pressure 40% of RCS.
j operating pressure based on the approach takenz in NRC Docket 52-001; 4
j!
(4)
ISLOCA's cannot occur. in systems' ' having an ultimate' strength exceeding the maximum stresses produced by-i pressure equal to RCS-normal operating pressure; and '
a (5)
ISLOCA's can. only. occur if a system isi physically.
connected, directly or indirectly, to the RCS.i The active. design features. mentioned above are justified, where applicable,ibecause...
(1) -an ISLOCA event can only proceed ' if ' an ' open pathway exists between the pressure source (RCS) and the system
- i or subsystem; and 1
(2) an ISIDCA cannot occur if the ? pressurization does not i
exceed the system's design pressure.
-t i
E j
l I
f
'L Page.3 i
i
'f
SYSTEM 80+ ISIDCA RESPONSE
~
ISLOCA EVALUATION PROCESS The evaluation of ISLOCA events and the subsequent determination of appropriate design responses is characterized by the following
+
steps...
(1)
The RCS P&ID was reviewed to identify all systems or subsystems that interface with the RCS.
Only systems or subsystems that were located outside containment and were i
designed for 1sss than RCS operating pressure were noted to reduce the number of systems for evaluation.
- Then, these systems were evaluated to dstermine pressurization pathways from the RCS.
These pathways represent all the possible ways of pressurizing low pressure systems connected to the RCB.
(2)
These pressurization pathways were further evaluated to determine the impact of systems or subsystems interfacing with the initiating pressurization pathway. A summary of these pressurization pathways is illustrated in Figures 1-10.
The figures show a pyramid structure beginning at the top with a system or subsystem that is directly connected with the RCS.
A. given pyramid represents a class of potential ISLOCA events characterized by a finite set of pressurization pathways which identify.the various systems that can potentially be pressurized if the interfacing valves were postulated to be open during normal operation.
(3)
The pressurization pathways are analyzed to identify any-pattern which may suggest a hierarchy of design responses to prevent or mitigate the ISLOCA event.
Any hierarchical pattern would be motivated by the desire to satisfy the IsloCA Acceptance Criteria with a design response commensurate with perceived benefit and cost.
1 (4)
Each interface in the pressurization pathways are analyzed to identify the type and location of design response to satisfy the ISLOCA Acceptance Criteria.
l 1
Page 4
4 SYSTEM 80+ ISLOCA RESPONSE PRELIMINARY RESULTS OF PRESSURIZATION-PATHWAY ANALYSIS As a result of the process illustrated in Figures 1-10, the following observations have been made.
(1)
The following systems or subsystems are directly connected to the RCS for one or more ISLOCA events (i.e.,
for one or more pressurization pathways)...
Safety Injection System (SIS),
Shutdown Cooling System (SCS),
Chemical & Volume Control System (CVCS),
Sampling System (SS).
As a result, all ISLOCA events (pressurization pathways) begin with these systems.
(2)
There have been ten classes of pressurization pathways identified.
They are...
Pressurization by Shutdown Cooling Supply Line Pressurization by Shutdown Cooling Return Line Pressurization by Safety Injection Delivery Line Pressurization by Letdown Line Pressurization by Charging Line Pressurization by Seal Injection Pressurization by RCP Controlled Bleedoff Pressurization by Sampling-Hot Leg Pressurization by Sampling-Pressurizer Surgo Line Pressurization by Sampling-Pressurizer Steam Space.
(3)
The Containment Spray System (CSS) is never directly connected to the RCS for all ISLOCA events identified.
(4)
A given system can occupy several levels in the interface hierarchy for any ISLOCA event.
(5)
The design response applied to a system should be commensurate with the highest interface level (i.e.,the highest position in the pyramid) a system may have for any ISLOCA event.
The rationale being that there is a correspondence between a
system's position in the hierarchy and the scope of the event (the number of interfacing systems affected), which is one measure of consequence of the event.
Page 5 1
SYSTEM B0+ ISLOCA RESPONSE (6)
The application of passive design responses to a system high in the pyramid will not protect connecting systems lower in the pyramid. These lower systems will still require a design response of their own. For example, for ISLOCA's where the SCS is directly connected to the RCS, designing the SCS to 40% of RCS normal operating pressure does not address protection of the various systems that interface with the SCS against ISLOCA's.
However, the application of active design responses to a system high in the pyramid can protect connecting systems lower in the pyramid.
For example, for an ISLOCA event having a pressurization pathway beginning at the letdown line interface with the RCS, isolation of letdown flow will terminate the event and protect downstream portions of the CVCS as well as the various interconnecting systems (such as Spent Fuel Pool and the waste management systems) for a particular class of ISLOCA events.
Such "down-stream offects" which are characteristic of some design responses should be considered in selecting an appropriate design response.
I Page 6
m l
SYSTEM 80+ ISLOCA RESPONSE i
i AN EXAMPLE OF THE APPLICATION OF A__ PASSIVE DESIGN RESPONBE l
(Shutdown Cooling System) t As an example of the application of a passive design response consider the Shutdown Cooling System (SCS) shown in Figure 11. For the class of ISLOCA's for which the SCS is directly connected to the RCS (see Figures 1 and 2) the primary interface through which
{
ISLOCA events can begin is either the SCS suction line or the SCS r
return line; that is, all ISIDCA's in this class are postulated to occur because of the opening of either all the suction line or all i
the return line isolation and check valves.
After evaluation of the current design, certain design changes were.
l identified to be required to satisfy the ISLOCA Acceptance Criteria.
Figure 11 shows the design response for the SCS.
The entire SCS is designed to a pressure of 900 psig, which is 40% of the RCS normal operating pressure. Sections of the SCS between the l
IRWST return flow isolation valves (SI-300, SI-301) and the containment penetration, which previously were not designed to 900 psig, have been upgraded to this pressure.
The pressurization pathways characterizing an ISLOCA event are
. defined to terminate at system boundary locations which interface l
with the environment (labeled as ATM for atmosphere in Figures 1-l 10).
These interfaces will be' designed to maintain integrity against the pressures equal to normal RCS operating pressure without rupture.
It is not considered practical to respond to ISLOCA events by postulating that these interfacing valves are open since there are no design responses which can satisfy the ISLOCA Acceptance Criteria for such an event.
Accordingly, all vent, drain and sample connections in the SCS are closed with at least one block valve.
These valves will be designed to withstand the upstream pressures characterizing this event without rupture.
Discharge from thermal relief valves will be collected in either the Equipment Drain Tank (EDT) or the Reactor Drain Tank (RDT).
For the purpose of this evaluation the discharges to the RDT will not be considered because the tank and piping are located inside containment.
The EDT is located within the Auxiliary Buidling.
The EDT is designed for 50 psig and is provided with overpressure t
protection by a relief valve that discharges to the Auxiliary _
Building sump.
The EDT has sufficient capacity to collect in i
excess of 30 minutes of thermal relief valve discharge before pressurizing the EDT above the design pressure.
The RCS makeup capacity of the CVCS is sufficient to match the fluid loss from the t
Page 7 I
l
SYSTEM 80+ ISLOCA RESPONSE thermal relief valves, thereby maintaining RCS inventory.
This design response satisfies the ISIDCA Acceptance Criteria because it preserves SCS integrity, controls leakage and prevents off-site doses.
However, this design response does not terminate the event and, consequently, systems interfacing with the SCS (i.e., systems lower in the hierarchy shown in Figures 1 and 2) will also be pressurized, assuming that all interfacing valves are postulated to be open.
As an example, consider the flow path DEF in Figure 12.
This path will cause pressurization to continue to the CVCS letdown line just downstream of the regenerative heat exchanger. However, since this portion of the CVCS (flow path FGH) is desigr.ed to full RCS operating pressure the ISLOCA Acceptance Criteria is satisfied.
The design response beginning with point H in Figure 12 is discussed below in connection with the an example of the application of an active design response.
As another example, consider the flow path ABC in Figure 12, which is used to return purified water from the CVCS to the SCS pump suction.
This path will cause the pressurization to continue to the CVCS just downstream of the ion exchangers.
After reviewing the need for having this interconnection between the SCS and'the CVCS and identifying an alternative flow path to perform this function, flow path ABC will be eliminated thereby deleting this physical connection between the systems and removing this ISLOCA challenge to the CVCS.
Page 8 l
1
SYSTEM 80+ ISLOCA RESPONSE l
1 AN EXAMPLE OF THE APPLICATION OF AN ACTIVE DESIGN RESPONSE (Purification Letdown System )
As an example of the application of an active design response consider the Purification Letdown System, a part of the chemical &
Volume Control System (CVCS), shown in Figure 13.
For the class of ISLoCA's for which the Purification Letdown System is directly connected to the RCS (see Figure 4) the primary interface through which the ISLOCA event can begin is the letdown line valves.
Figure 4 shows the various pathways ISIOCA's in this class can take and the systems it will affect assuming all downstream interfacing valves are opened.
After evaluation of the current design certain design changes were identified to be necessary to satisfy ISLOCA Acceptance Criteria.
Figure 13 shows the design response for this class of ISLOCA's.
The containment isolation valve located in the letdown line (downstream of the letdown valves and upstream of the letdown flow control valves) will receive a new signal (in addition to the CIAS) to response to a pressure signal originating from a pressure sensor located downstream of the letdown flow control valves.
When high pressure is sensed a signal is generated to closo this valve and discontinue letdown flow.
This automatic action terminates the ISLOCA by preventing any further pressure communication downstream from this valve.
Operator action is not required to terminate the event, but with letdown isolated remedial action by tho' operator will eventually be required.
This design response satisfies the ISLOCA Acceptance Criteria for the following reasons.
(1)
System integrity is preserved because the portion of the Purification Letdown System pressurized by the ISLOCA is designed to full RCS operating pressure. In addition, the valve will be designed to close, and remain closed, against tho differential pressure characterizing the event.
(2)
The portion of the Purification Letdown System downstream of the letdown flow control valves, and all other downstream interfacing systems, are not pressurized by this event and, therefore, do not have there integrity challenged.
(3)
No coolant leakage or increased off-site doses occur l
Page 9 l
..m, i
j
-i
' h SYSTEM 80+ ISLOCA RESPONSE resulting from this event.
.[
4 The justification in applying this; design response is-based on considering the following observations.
, )
(1)
In evaluating passive design responsas'_for this. event, the design of the CVCS ~ (and,- necessarily, all systems
'j that interface with the CVCS downstream: of the letdown flow control valves) to full RCS operating pressure has been considered._ This design feature _is not considered practical because the increased cost-to the.CVCS, and:
systems interfacing with the CVCS, is not perceived to be
)
- j commansurate.
with the benefit
.of the' response,.
j particularly when compared with active design responses.
}
i (2)
Increasing the design pressure..of the low pressure portion of the CVCS does not terminate,- mitig, ate or even control the scope of the event.
It;merely allows the CVCs (and-downstream. systems). to tolerate. the i event without compromising. integrity.. Such a design 1 response may, at-first, appear to be beneficial simply because no operator. action is required, to. mitigate - the event.
However, there are many other low pressure systems, which interface with the CVCS, that can also be'. exposed to RCS'
-pressure.
Thus, these' additional systems must also be designed:to a higher preissure to mitigate' the ' effects of.
this event.
It is our. opinion that-increasing the_ cost' of all~these low pressure systems _is impractical.
There i
must~ be ' some design - provision _ which terminates : the, involvement of such an extraordinary number of low l
pressure systems.
(3)- The-active design response shown.~in ' Figure 4 also satisfies the ISIDCA Acceptance Criteria'-but,
'in addition, accomplishes the following....
- I (a).
it automatically terminates the' event without any..
operator action; (b) it limits the scope of the event by~ terminating the event at-a location which prevents the rest of the CVCS and' its interfacing systems from-being pressurized;-
i s
Page 10 l
e i
t
/
m -
h l
e i
SYSTEM 80+ ISLOCA RESPONSE (c) it can be implemented at a significantly lower f
cost.
(d) it avoids the need to design and procure special 3
equipment to withstand the high pressures characteristic of this event, some of which may not i
be considered "available technology".
)
Based on these observations, the active design response shown in Figure 4 is considered to be the preferred approach for this class of ISLOCA's.
t II I
I i
a i
t 5
i i
I t
Page 11 1
i
-~
SYSTEM 80+ ISIDCA RESPONSE SUMFJLRY Upon concluding the example evaluations several design changes were identified to be necessary to meet the ISIDCA Acceptance Criteria.
(1)
For the pressurization pathway beginning with the SCS, sections of the SCS not previously designed to 900 psig will be increased to this value, t
(2)
For the pressurization pathway beginning with the SCS and cor,municating to'the CVCS, a flow path interconnecting the SCS with the CVCS will be eliminated and replaced i
with an alternative flow path which eliminates this ISLOCA challenge to the CVCS.
(3)
For the pressurization pathway beginning with the Letdown Line, a new pressure instrument will be added to provide a signal to automatically close the containment isolation valve in the letdown line in response to a high pressure in the CVCS to terminate the ISLOCA event.
f k
h I
Page 12
FIGURE 1 PATHWAY:
PRESSURIZATION BY SHUTDOWN COOLING SYSTEM SUPPLY UNE SYSTEM DRECTLY SHUTDOWN FA NG 1,N COOLING p
SYSTEM SYSTEMS gDggNc CVCS ATM SS CSS SIS PCPS wim RCS -
RETUEUNG POOL SS Twt OVED CYCS SIS ATM SS FROM RCS N
2 SS ATM CVCS CVCS AIR SUPPLY gg 2
Am Sg 33 py3 PMWS AN py3
+t
--w
-=
w
---w-w
-..n,_.-.-
a, FIGURE 2
>;a
- PATHWAY:
PRESSURIZAT10N BY ' SHUTDOWN. C00UNG SYSTEM RETURN UNE
- SYSTEM DRECR.Y SHUTDOWN MERFAONG.
WTH RCS COOLING SYSTEM -
SYSTEMS '
INDRECn.Y mtRFADNc CVCS ATM SS CSS SIS PCPS MTH RCS REFUEUNG POOL SS SYSTDeS CSS my gm CY4tS CYCS SIS ATM SS
^ FROM RCS
- H 2
SS ATM
' CYCS
'CYCS AIR SUPPLY
ATM -
SS SS PCPS PWWS l
' SWMS ATW l.
I l'
r I'
I l-i 5.,.
~,..1,.
,,.,.2.,,,--..-.-.
. - - -.. ~
~
- =::
- s.,
-l'
_-W
.. i t-d-
FIGURE 3
+
PATHWAY:
PRESSURIZA110N BY SAFETY lNJECTION DEUVERY LINE 5
SYSTEM DRECTLY WTERrAaNG WTH RCS SAFETY INJECTION.
SYSTEM I
- sYSM:WS:
INORECTLY INTERFAONG ~
ATMOS SCS CVCS CSS SS um ncs SYSTEMS -
'PCPS TWIT REWOWD SCS MS
- FROW RCS-CYCS A7WOS SCS.
CSS.
ND
! CSS --
ss cves Atuos..
' Ains0S :.
~g' i
l-e I
a 1
m-
.e ?
'<vv**
=.m ww wr W vwe, *,+ww=-
w,<e,+
-v4e ~ e -t-w - w - e i v o-w-
-.nw
- w-e te-ern M
,*'w,e-=
-s*v v.
c m-v -m
- i..--%e--
,+3.<ve-.re-e ye eev
-*-4-we-wsy-e,",-
3 +, w-w ',
c+ = reyw w a -,- v ev evwwe.w
.4-w >v m #--wege -w
,,v
,i e v w, r--
FIGURE 4 PATHWAY:
PRESSURIZATION BY LITDOWN UNE SYSTEM DRECTLY rotwAONc LE1DOWN w m acs
~.
UNE 1
ATM SS SCS H
_m SYSTEMS RECOVERY 2
MDRECM wtEFAQNC '
,g
=N w m acs.
NECTKM 2
- MAKEUP gg3 SWMS SYSTEMS TMCE REMOVED SCS CSS ATM FROM RCS E
GS 33 LWS g
33 SWMS SCS ATM
.. ~,.., -,, _.. - - -,,.,.,,.. _... -
...a...a
.?
.4 FIGURE 5 PAmWAY:
PRESSURIZATION BY CHARGNG UNE T
. system DIRECR.Y -
INTERFAONC CHARGING w m acs UNE 3
i ATM SS SCS H
- aman
- sysuus-REN 2
- IM REC U N
INTMFAONG
- SEM. -
- w m RCS INECTKN 2
CWM3 SWMS TWE RDdOVED -
. Am -
- FROW RCS -
. 33 CSS
. 3:3 1.DNS
-SS S5 SWS SCS ATW e
...m.
.ev
-mw
,-v.m.-
~m, v-v -
t -=w e
v
- v re w -+'
.v,,-3w.<~
w.
,-w w w
.,,,+rr,-<
e v vw
- wtw,
- vrww i w
sw,re-*s,-.wm-+w-'ww,,-,,
.w e r-w..,,i
-~wn.,
en r.
w w-,
ww
FIGURE 6 PATHWAY:
PRESSURIZATION BY SEAL INJECTION t
SYSTEM DRECTLY
- INTERFACING SEAL INJECTION NTH.RCS sn
_ m,My
' RECOVERY ORON PURIFICATION ATM munrAcnc -
WTH acs i'
' BORON RECOWRY
$y3gyS.
PUR!f1 CATION gp TWCE RDADVED MAKEUP ATM FROM RCS CCWS SS SCS
-SWWS gm3
~ LWS~
SWS -
s
- CWS -
H 2
SS N 2 l
'm-,--my-9r -
yg.*www y-
,--g-ge yg q-
-we,-wbetwyv--+m-tww,--5e er -
4-w-er-awy4 w-,i+avte v
-r'e--r+eTe e-
- =='r**7
-w w
wN 1
T==
e+-3 w
1V w a t e ire
+y a
mswy w,-
e-~-gar y
-.-yr--eg--,,, < -
,,w y,
6 FIGURE -7
\\
PATHWAY:
PRESSURIZATION BY RCP CONTROLLED BLEED 0FF SYSTEW OIRECR.Y RCP INTERFADNo.
CONTROLLED WTH RCS
. 8LEEDOFF sgpc BORON-PURIFICATION ATM Trus y in
SMS
'a CWS
~N 2
' 55 -
.N 2' 1
e.
.a.
M
.... r m.
.. __... - _., _. ~....
-_.._...a.,_
FIGURE 8 PATHWAY:
PRESSURIZATION BY SAMPUNG - HOT LEG sYsitu otaccTLY HOT LEG
.. E^$"G SAMPLING sa$y SCS ATMOS PUmnCADON MLWMS SIS CSS i
INTERFACING WTH RCS SYSTEMS CSS BWtDN 14ECCMRY ATWO 5t5 TWCE REMOWD MApalp
~
5es A1MO CYCS A1MO SCS l
ATWO CWS cygg sws I
-H l
2 N
2 i
r t-l-
L m--
-,-~.. -. -
~,.......~-4 r
.-. m--.
'^y FIGURE.9 PATHWAY:
PRESSURIZATION BY SAMPUNG - PRESSURIZER SURE UNE SYSTDJ DIRECU PRESSURIZER SAONG SURGE UNE SAMPLING
$gC SCS AIMOS 7 4mm MLWMS SIS.
. CSS TEM Y
--INTERFAONG VfiTH RCS.
L-SYSTEMS
SS i
TWlE REMOVED WAKEUP FROM RCS ss Amo cycs A1W0 SCS A7WO N'
- H FF g.
N, 2:
4
.a.a.-.
-.,a
.,.s-.-..~
r,,~.
s-,n-,...-
+mn..,--w-,.ss---
e.
wn m,,
s e
,a.
nn.r
-, se - v an
,,,n,ew,.r.,
e,w e,
-4
,w,wn,-w.>+-
,em a
..v,-
+
v
..wr n ew - +
.. t
- e-
'+
FIGURE 10.
=
PATHWAY:
PRESSURIZATION' BY SAMPUNG - PRESSURIZER STEAM SPACE G
t SYSTEM DIRECTLY PRESSURIZER
E%^c7 STEAM SPACE SAMPLING hhREdY SCS ATMOS Pugn um MLWMS SIS CSS INTERFAONG,
- NTH RCS~
' SYSTEMS '
- ANO 95
. TNT REWOVED MANDP FROW RCS '
SCS AND CWWS StMS
. g
' N 2
N-
,2:
. /
c.
_ y _
,m,.
by.-g g 49 'WW 4e F1
$-9T-w
-g ea4+'g..
W-3
%--mi*
-p y s'
"4 sh y 9YqN W if a*w-g-b tt gW*g 11 T' q T4$y$
y M
T"Y'4-*
w F
?9P$W
- r
?
D
++-P tu 4m W
F hW
+w+
4 rya 4
w-+-9-5y -t 4 y
,rys.
-we,e m_6.,inm q, e,c-
,,my, Q g,A__.w,_.
g
if N
o aa
=m
@i y
i
'9 M :!
_l li 1
e s................
JL
% :~ g ~
~
9 E :
~~I E
T C
E
.5l I
}
I i
/.
//
/
N
~
ZA//
A
}n
/
e l[
3 R
9-
,/-
/
g
/
4 O
4(w u
t l /
n
!I l
k
/
_L Ws,
/
8
/
(f:
t
/
1ll
/
)
8
@W cWe-y l9
,/
ll
/5
}
ll a:a 3::e a:e
~
1l-8 l
is ii e
E:
5 m__
nm lr s
eK 1
g
(
1
4 i-a
[* 9 W
EN 4 5 t
x x
n c
~
g-L_
jid
=
W e,
L--
Es N v aa n g,!
as ee 5 9 =s e
dX i
i 8lls E 28 gi "9
5!
9
?
=8 l
c o
5 la.
1 i
- n)a l
W l
g i5 1I w
98
-