NSD-NRC-97-5249, Provides Response to NRC Comment 4 Re AP600 SSAR Chapter 15 Accident Analysis,
| ML20216C317 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 08/29/1997 |
| From: | Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NSD-NRC-97-5249, NUDOCS 9709090021 | |
| Download: ML20216C317 (17) | |
Text
ww Westinghouse Energy Systems
$30p p,nnsyiyinia is23acass 3
Electric Corporation DCP/NRC0970 NSD-NRC-97-5249 Docket No.: 52-003 August 29,1997 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 A1TENTION: T.R. QUAY SUDJECT:
Response to NRC Comment 4 on SSAR Chapter 15 Accident Analyses
Reference:
1.
Letter from NRC to Westinghouse, " Comments on the AP600 Standard Safety Analysis Report (SSAR) Chapter 15 Accident Analyses", dated January 21,1997.
2.
Westinghouse Letter DCP/NRC0962," Responses to Comments on the AP600 Standard Safety Analysis Report (SSAR) Chapter 15 Accident Analyses," July 18, 1997.
Dear Mr. Quay:
This letter provides the response to Comment 4 of Reference 1. Responses to the other Reference I comments were provided in Reference 2. Comment 4 relates to the nonsafety related equipment credited for SSAR Chapter 15 accident mitigation. This includes the main feedwater pump trip, pressurizer heater block, main steam branch isolation valves, and turbine stop and control valves. To summarize the attached response, as requested by the NRC:
- 1. A summary table of nonsafety-related equipment credited for accident mitigation was added to Chapter 15 as Table 15.0.8 in Revision 13 of the SSAR.
- 2. This equipment meets Technical Specification inclusion Criterion 3 of 10 CFR 50.36 Item (c)(2)(ii)(C) and will be included in Revision 7 of the AP600 Technical Specifications. Refer
/
to the attached markups.
/
- 3. The valves which serve as backup valves to the MSIVs for steam flow isolation will be included in the in service testing (IST) program of SSAR Revision 17, Section 3.9.
.h0$
If you have any questions regarding this letter or the AP600 Technical Specifications, please contact i
Robin K. Nydes at (412) 374-4125.
&~Af"
- Brian A.McIntyre, Manager Advanced Plant Safety and Licensing jml 3 e c, 4
,'uLi y
,h Attachment 9709090021 970829 ~
PDR ADOCK 05200003 E
PDR m
~
DCIhNRC0970 NSD-NRC 97 5249 2-August 29,1997 cc:
N. J. Liparulo, Westinghouse (w/o Attachment)
W. C. IlufTman, NRC (w/ Attachment)
S. Sun, NRC (w/ Attachment)
G. lisii, NRC (w/ Attachment)
A. T. Chu, NRC (w/ Attachment) 3109A wpf w
d
Attachment to DCP/NRC0970 Response to NRC Comment 4 on AP600 SSAR Chapter 15 Accident Analyses Comment 4.
In several Chapter 15 analyses, nonsafety-related equipment was credited for accident mitigation. The equipment includes the main feedwater pump trip, turbine ston and control valves, pressurizer heater block, and main steam branch isolation valves. Westinghouse I.as summarized these systems in Table 2 2 of WCAP 14477 (The AP600 Adverse System Interactions Evaluation Report). A similar summary table should be included in Chapter 13.
The staff notes that items designated under item a.5 of Table 2-2 in WCAP-14477 appear to be used.
to mitigate the consequence of the Chapter 15 dc:ign basis analyses. 10 CFR 50.36 specifies the criteria for the systems that are required to establish technical specification limiting conditions for operation. Specifically, item c(2)(ii)C Criterion 3, states that "A structure, system, or component that
-is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to integrity of a fission product barrict." Westinghouse shouldjustify why these items should not be included in the AP600 technical specifications.
The staff notes that WCAP-14477 states that components associated with item a.5 of Table 2-2 will be included in the in service testing (IST) program. However, the staff finds that the systems are not included in the program described in the SSAR 3.9.6. Westinghouse should providefurther discussion on this proposed action for the non-safety related systems and explain how it is addressed in the SSAR.
Response
SSAR Chanter 15. Accident Analvses A summary table of nonsafety-related equipment credited for accident mitigation was added to Chapter 15 as Table 15.0.8 in Revision 13 of the SSAR, dated May 30,1997. The changes presented in the attached markup of that table will be incorporated into Revison 16 of the SSAR. The following paragraph provides the basis for this change.
For the steamline break event, isolation of steam flow is assumed given a single failure of-an MSIV.
This is accomplished in LOFTRAN by " turning off" that steam flow, rather than by modeling particular valves. To equate this analysis assumption to plant operations and into the Technical Specifications, the valves downstream of the MSIVs which serve as backup valves for steam Cow isolation should be considered. These. include the turbine inlet stop or control valves (only one of each stop/ control valve pair is required), the turbine bypass valves, the main steam to auxiliary steam header valve, and the moisture separator reheat supply steam control valve. This is discussed in the -
attached Bases 3.7.2 markup.
SSAR Chapter 161. Technical Specifications i
l This equipment meets Technical Specification (Tech Spec) inclusion Criterion 3 of 10 CFR 50.36 Item (c)(2)(ii)(C), and the AP600 license meets the timing requirement of 10 CFR 50.36 Item (c)(2)(iii).
Therefore, the valves which serve as backup valves to the MSIVs for steam Cow isolation will be included in Revision 7 of the AP600 Tech Specs as shown in the attached markups of Section 3.7.2
(thisincludes the turbine stop or control, turbine bypass, main steam to auxiliary steam header, and mo,isture separator reheat supply steam control valves.)
The main steam branch isolation valves are included in Tech Spec 3.6.3, containment isolation valves (CIVs). The CIV actuation signals include those assumed in the safety analyses to actuate the main steam branch isolation valves in the event of a steamline break.
The main feedwater pump trip and pressurizer heaters trip actuation device testing is incorporated into the revision of Tech Spec 3.3.2 per DCP/NRC0987. (That markup reflects these changes as well as those resulting from a. lune 9.1997, meeting with the NRC I&C Branch.) The following definitions are used for the actuation logic test and the actuation device test.
't l-Actuation Logic Test An Actuation Logic Test shall be the application of various simulated or actual input combinations
' in conjunction with each possible interlock state and serification of th required logic output. The Actuation Logic Test shall be conducted such that it provides component overlap with the Actuation Device Test. These two types of tests demonstrate that the actuated device would have responded to-a simulated actuation signal.
Mtuation Device Test 4
An Actuation Device Test is a test of the actuated equipment. This test may consist of verification of actual operation but shall, at a minimum, consist of a continuity check of the associated action devices. The Actuation Device Test shall be conducted such that it provides component overlap 4
with the Actuation Logic Test. These two types of tests demonstrate that the actuated device would have responded to a simulated actuation signal. For actuated equipment included in the Inservice Test (IST) Program, the ISTs can be used as the Actuation Device Test.
4 SSAR Section 3 9.-In-Service Testing The main steam isolation valves are included in the IST (refer to SSAR Table 3.9-16 sheet 12).
The following valves will be included in SSAR Revision 16, Table 3.9-16 (This commitment is logged as Open item Tracking System item 5578.):
Turbine Stop (These are included in Table 2.2,4-3 of the Steam Generator System ITAAC) i Turbine Control Turbine Bypass to the Condenser Main Steam to the Auxiliary Steam lleader Moisture Separator Reheat Sapply Steam Control The SSAR Table 3.9-16 and 3.9-17 IST programs are applicable to valves and system level testing.
Testing at a component level is captured in Tech Spec Surveillances. As is done for safety related component actuation devices, the actuation devices for main feedwater pump trip and pressurizer heaters are being included in Tech Spec 3.3.2 Surveillances.
4 I
l i
SSAR MARKUPS
HiU i!is 5
- 10. Steem and Power Conversion System O
l In addition, orientation of the turbine-generator is such that a high-energy missile would be I
directed at a 90 degree angle away from safety related structures, systems, or components.
1 Failure of turbine-generator equipment does not preclude safe shutdown of the reactor. The turbine-generator components and instrumentation associated with turbine generator overspeed I
protection are accessible under operating conditions.
10.2.2.1 Turbine Generator Desedption The turbine is a 1800-rpm, tandem-compound, four-flow, reheat unit with 47 inch last stage blades (TC4F 47 inch LRB). The high-pressure turbine element includes one double flow, high-pressure turbine.
The low-pressure turbine elements include two double-flow, I
low-pressure turbines and one external moisture separator / reheater (MSR) with one stage of I
reheating. He single direct-driven generator is gas cooled and rated at 880 MVA at 22 kV, 0.90 PF. Other related system components include a complete turbine-generator bearing lubrication oil system, a digital electrohydraulic (DEH) control system with supervisory instrumentation, a turbine steam sealing system (refer to subsection 10.4.3), overspeed protectise devices, turning gear, a generator hydrogen and seal oil system, a generator CO2 I
system, an exciter cooler, a rectifier section, an exciter, and a voltage regulator.
The turbine-generator foundation is a spring-mounted support system. A spring-mounted turbine-generator provides a low-tuned, turbine-pedestal foundation. The springs dynamically I
isolate the turbine-generator deck from the remainder of the structure.in the range of operating l
frequencies, thus allowing for an integrated structure below the turbine deck. The condenser I
is supported on springs and attached rigidly to the low-pressure turbine exhausts.
The foundation design consists of a reinforced concrete deck mounted on springs and supported on a structural steel frame that forms an integral part of the turbine building structural system. De lateral bracing under the turbine-generator deck also serves to brace the building frame. This " integrated" design reduces the bracing and number of columns required in the building. Additionally, the spring mounted design allows for dynamic uncoupling of the turbine generator foundation from the substructure. He spring mounted support system is much less site dependent than other turbine pedestal designs, since the soil structure is decoupled from turbine dynamic effects. The turbine-generator foundation consists of a concrete table top while the substructure consists of supporting beams and columns. The I
structure below the springs is designed independent of vibration considerations. He turbine-I generator foundation and equipment anchorage are designed to the same seismic design I
requirement as the turbine building. See subsection 3.7.2.8 for additional information on I
seismic design requirements. See subsection 10.4.1.2 for a description of the support of the I
condenser.
10.2 2.2 Turbine Generator Cycle Description Steam from each of two steam generators e e high-p i
u four stop valves and four governing control valves; op valve?gss: $ d on et'~
L xMy. Crosstics are provided upstream of the turbine stop valves to provide pressure equalization with one or more stop valves closed. After expanding through the Revision: 5 February 29,1996 10.2-2 3 W96tingh0088
- 15. Accidert Analyses I
l Table 15.0-8 I
i NONSAFETY RELATED SYSTEM AND I
EQUIPMENT USED FOR MITIGATION OF ACCIDENTS l
Event Nonsafety related System and Equipment i
15.1.5 Feedwater system malfunctions that result Main feedwater pump trip l
in an increase in feedwater flow (0 5)v h 3 ck.o T;. U.., my ~~p v cth e s i
15.1.4 Inadvertent opening of a steam generator
,;.. ;;. ve #
l relief or safety valve Main steam branch isolation valves i
15.1.5 Steam system piping failure bNfabbe! valves #
l Main steam branch isolation valves l
15.2.7 Loss of normal feedwater Pressurizer heater block l.
15.5.1 Inadvenent operation of the core makeup Pressurizer heater block i
tanks during power operation l
15.5.2 Chemical and volume control system Pressurizer heater block i
malfunction that increases reactor coolant I
inventory l
15.6.3 Steam generator tube rupture Pressurizer heater block i
fnslV bac1 T We nep
.d cc.. ; valves
- 9 "ain steam branch isolation valves I
M I
15.6.5 Small break LOCA Pressurizer heater block
+1hr iltlocb h twho (foo oc ankl valus,4W
.tvrbum byms3 o kes, od main.ske h auxhory skam ) vade valW, ad +hs ivoiske Pr*
reeat eam 59pty ccmbl valve.
O Revision: 13 May 30,1997 15.0-34
[ W85tlfigh0US8
3.7 PLANT SYSTEMS 3.7.2 Main Steam Isolation valves (MSIvs)
LCO 3.7.2 The minimum combination of valves required for steam flow isolation Twe-MsWs shall be OPERABLE.
I APPLICABILITY:
MODE 1, I
Mo0ES 2, 3,le: d.and 4 except when steam flow is isolated. both MsIV: cre c ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.
One MSIV inoperable A.1 Restore MsW valve to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in MODE 1.
OPERABLE status.
ovd b One or more of the 0550Clokd YUMC Cydrol V 2kVC turbine stop valves l
turbine bypass valves, main steam to auxiliary : team header valve, ne moisture separator reheat supply steam control valve inoperable in MODE 1.
B.
TWo MSIVs inoperable B.1 Be in MODE 2.
6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> in MODE 1.
l QB One MSIV inoperable OM ig and one or more of the turbine stop 0550Cidkd brl$yv cffnhoj vak c valvess r_our turoine bypass valves main steamtoauxiliary steam header valve, or moisture separator reheat supply steam control valve inoperable in MODE 1.
D8 Required Action and associated Completion Time of Condition A not met.
_ _AP600 _
3.7-1 DRAFT
Main steam Isolation valves (MsIvs) 3.7.2 l
1 CONDITION REQUIRED ACTION COMPLETION TIME
........... NOTE-----------
separate condition entry is allowed for each MSIv.
C.
One or two MSIvs C.1 Glose-M&lv Isolate 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> i
inoperable in MODE 2, associated steam flow l
3, or 4.
path.
QB AND Once per 7 days One or more of the C.2 verify MsIV flow path turbine stop valve,
remains closed, four turbine bypass valves, main steam to and 60550ciakd hchot Cm hl vokVt' auxiliary steam s
header valve, or moisture separator reheat supply steam control valve inoperable in MODE 2, 3, or 4.
c.
nvc MSIV: incper-aMe c.1 cic:e "sIV.
1--houe 4r. "00E5 2, 3, er '.
eHE 0.2 verify "sIV: cre cle cdr Once per 7 days D.
Required Action and 0.1 Be in MODE 3.
6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated completion Time of Condition C AND l
sown-4> not met.
I D.2 Be in MODE 4 with RCs 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> cooling provided by the RNs.
AP600 3.7-2 DRAFrf rim C:Wes 10-062297
Main Stetm Isolation valves (MSIvs) 3.7.2 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY l
NOTE------------------
only required to be performed prior to entry into MODE 2.
l verify MSIV closure time s 5 seconds on In ac'cordance an actual or simulated actuation signal, with the Inservice Testing Program SR 3.7.2.2
NOTE------------------
only required to be performed prior to entry into MODE 2.
brbink ccdol; t
verify turbine stoplsturbine bypass, In accordance main steam to auxil ary steam header, with the and moisture separator reheat supply Inservice steam control valves' closure time s 10 Testing Program seconds on an actual or simulated actuation signal.
( h AP
~ ~ _ _600 3.7-3 DRAFlr
Main Steam Isolation valves (MSIvs)
B 3.7.2 B 3.7 PLANT SYSTEMS B 3.7.2 Main Steam Isolation valves (MSIVs)
BASES BACKGROUND Each main steamline has one safety related MSIV to isolate steam flow from the secondary side of the steam generators following a high energy line break.
MSIV closure terminates l
flow from the unaffected (intact) steam generator.
One MSIV is located in each main steam line outside containment. The MSIvs are downstream from the main steam safety valves (MSSys).
Downstream from the MSIVs main steam enters the high pressure turbine throuch fou,r stop valves and four governing control valves. Closing the MSIVs isolates each steam generator from the other and 1solates the turbine bypass system, and other 4 _ili_r, steam supplies from the steam generator.
The MSIvs.in steam to auxiliary steam header-valve, andturbine stop and contro valves, ma moisture separator reheat supply steam control valve close l
on a main steam isolation signal generated by either low or high negative steam pressure rate. steam line pressure, high containment pressu i
The MSIvs fail close on loss of control air or actuation signal from either of two 1E power divisions.
Each MSIV has an MSIv bypass valve. Although these bypass valves are normally closed, they receive the same emergency closure signal as do their associated MSIVs. The MSIVs may also be actuated manually.
A description of the MSIvs is found in the SSAR,bine bypass Section 10.3 (Ref. 1).
Descriptions for the tur valves, main steam to auxiliar steam header valve, and moisture separator reheat supp y(steam control valve are found in the SSAR, Section 10.
Ref. 6).
APPLICABLE The design basis of the MSIvs is established by the SAFETY ANALYSES containment analysis for the large steam line break (SLB) inside containment, discussed in the SSAR Section 6.2 Itisalsoaffectedbytheaccldentanaly(Ref.3).
(Ref. 2).
sis of the SLB events presented in the SSAR Section 15.1 The design precludes the blowdown of,more than one steam generator, assuming a single active component failure (e.g.,
the failure of one MSIV to close on demand).
Design basis events of concern for containment analysis are SLB inside containment with the failure of the associated MSIV to close or a main feedline break with the associated failure of a feedline isolation or control valve to close.
At lower powers, the steam generator inventory and temperature are at their maximum, maximizing the analyzed mass and energy release to the containment. Due to (continued)
_ _AP600 B 3.7-4 DRAFT
Main steam Isolation valves (MsIvs)
B 3.7.2 BASES (continued)
APPLICABLE-reverse flow and failure of the MsIV to close, the additional mass and energy in the steam headers down SAFETY ANALYSES contribute to the total release. stream (continued) from the other MsIV,d cluster control assembly assumed stuck With the most reactive ro in the fully withdrawn position, there is an increased possibility that the core will become critical and return to power. The core is ultimately shut down by the boric acid injection delivered by the core Makeup Tanks (cMTs).
The accident analysis compares several different sLB events against different acceptance criteria. The large SLB outside containment upstream of the MsIV is limiting for offsite dose,has a very low probability.although a break in this short section of mai steam header The large SLB inside containment at hot zero power is the limiting case for a post trip return to power.
The analysis includes consideration of scenarios with offsite power available,ble, and with a loss of offsite power. With offsite power availa the reactor coolant pumps continue to circulate coolant for a longer period through the steam generators, maximizing the Reactor Coolant system cooldown.
The reactor protection system includes a safety related signal that initiates the coastdown of the reactor coolant pumps early in the large SLB transient. Therefore, there is very little difference in the predicted departure from nucleate boiling ratio between cases with and without offsite power.
significant single failures considered include failure of an MSIV to close.
The non-safety related turbine stop or control valves, in combination with the turbine bypass, main steam to auxiliary steam header, and moisture separator reheat supply steam control valves, are assumed as-a backup to isolate the steam flow path given a single failure of an MSIV. whHelhe safety analyses do not differentiate between the availability of the turbine stop valve or its series control valve g i mosius rivvi mt4t@c :::;;;gity whtd h,j,C.
,in vi o om o m vu
- 7. o.
SWnce -4+-4s the turbine stop valves,@along with the turb,y this Lco
.._.m.,.,.
are required b to be OPERABLE. These valves, me, bypass, main steam to auxiliar)i steam header, and moisture separator reheat supply steam ntrol valves are considered as alternate downstream valves.
or N5 M M Q N N ol The MSIvs serve a safety related function and remain open Ya!V6 during, power operation. These valves operate under the following situations:
a.
High energy line break inside containment.
In order to maximize the mass and energy release into containment, the analysis assumes that the MsIV in the affected steam generator remains open.
For this accident scenario, steam is discharged into containment from both steam generators until the unaffected loop MsIV closes. After MSIV closure, steam is discharged into containment only from the affected steam generator and from the residual steam in the main steam header downstream of the closed MSIV in the unaffected loop. Closure of the MSIV isolates the break from the unaffected steam generator.
(continued)
AP600 B 3.7-5 DRAFT rkn cMpwmNhmsarto m_____._.___
Main steam Isolation valves (MsIvs) 8 3.7.2 BASES APPLICABLE b.
A break outside of containment, and upstream or SAFETY ANALYSES downstream from the MSIvs. is not a containment (continued) pressurization concern. The uncontrolled blo'idown of more than one steam generator must be prevented to limit the potential for uncontrolled RCS Cooldown and positive reactivity addition.
Closure of the MSIvs or alternate downstream valves isolates the break, and limits the blowdown to a single steam generator, c.
Following a steam generator tube rupture, closure of the MsIvs isolates the ruptured steam generator from Jm i..t;,,;;;c. ;: e :::r to minimize radiological
- releases, d.
The MsIvs are also utilized during other events such as a feedwater line break; however, these events are less limiting so far as MSIV OPERABILITY is concerned.
The MSIvs and the alternate downstream valves satisfy Criterion 3 of the NRC Policy Statement. Tht:0 ;lisi..at; de-tr;;; iolyca ois in:lud_d da t e
^"A^^
' :h-ic;l h
Speci'i;;ti:n: d;; t^ th; 10 CFR 50.30 C(2)iii icaui rcrtnt,
appl i siui c lic;n:^' 4e'"?d 2fter
^"0"'t 15, 1305 tv 7
LCO This LCO requires that one MSIV in each of the two steam lines be OPERABLE. The MSIvs are considered OPERABLE when their isolation times are within limits, and they close on an isolation actuation signal.
g 4 s a socia h
This LCO requires that four turbine stop valveso four turbine bypass valves, one main steam to auxiliary steam header isolation valve, and one moisture separator reheat supply steam control valve be OPERABLE. A valve is considered operable when its isolation time is within the safety analysis isolation time limit of 10 seconds and it closes on an MsIV actuation signal. The turbine bypass valves and main % to auxiliary header isolation valve are alternativb y considerec OPERABLE when closed and administratively main ined clos with automatic actuation blocked as appropriate.
5%rn This LCO provides assurance that the MsIvs will perform their design safety function to mitigate the consequences of accidents that could result in offsite exposures comparable to the 10 CFR 100 limits or the NRC staff approved licensing basis.
This LCO provides assurance that the design and performance of the alternate downstream valves are compatible with the accident conditions for which they are called upon to function (Ref. 5).
(continued)
_AP600 B 3.7-6 DRAFT j
Main steam Isolation valves (MsIvs)
B 3.7.2 BASES (Of 0 %CCJa W brbit4 C4M Wei APPLICABILITY The MSIvs, turbine stop) valves, turbine bypass valves, (continued) main steam to auxiliary steam header isolation valve, and moisture separator reheat supply steam control valve must be OPERABLE in MOJE 1 and MODES 2, 3, and 4, except when steam flow is isolated I' : d when there is significant mass and energy in the RCs and steam generators. Therefore, these valves MHvs must be OPERABLE or closed.
When these MHvs valves are closed they are already performing their safety related required function.
In MODE 5 or 6 the steam generators do not contain much energy because,their temperature is below the boiling point of water; therefore the MSIvs and alternate downstream valves are not regulred for isolation of potential high energy secondary system pipe breaks in these MODES.
h tb f,h
_a
- )CTIONs M
h [
....mw With one MSIV, or any number of the turbine sto turbine
, bypass, main steam to auxiliary steam header is iation, or moisture separator reheat supply steam control valves inoperable in MODE 1, action must be taken I
to restore OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, some repairs to the MHV valves can be made with the plant hot.
The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion Time is reasonable considering the low probability of an accident occurring during this time period that would require a closure of the mIVs these valves.
With a single MSIV or the backup isolation valves inoperable, the safety function isolation of the steam flow path, is provided by the remainlgn OPERABLE valves,1 single but can not accommodate a unavailable previd:d : 2ddition:
failure i: not 2:::::d. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion Time is reasonable considering the low probability of an accident during this time period that would require a closure of the steam flow path. The assumptions and criteria of the accident analyses are preserved by the ability to automatically isolate the steam flow path.
In addition the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion Time is greater than that normally allowed for containment isolation valves because the MsIvs are valves that isolate a closed system penetrating containment. These valves differ from other I.
containment isolation valves in that the closed system provides an addition '
er: positive means for containment isolation.
M l
with two MSIVs inoperable in MODE 1 or if the MSIV can not i
be restored to OPERABLE status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> in accordance with
- Required Action A.1, the unit must be placed in a MODE I
in which the LCO does not apply. To achieve this status, the unit must be placed in MODE 2 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and condition C er-e would be entered. The com reasonable, based on operating experience, pletion Times are to reach MODE 2 and to close the MSIVs in an orderly manner and without challenging unit systems.
GdVW()
AP600 B 3.7-7 DRAFT fitti CMpwmS2W4fv t$
Main Steam Isolation valves (MSIvs)
B 3.7.2 BASES ACTIONS C.1 and C.2 (continued) conditiqn C is modified by a Note indicating that a separate condid il entry is allowed for each MSIV.
Since He MSIvs are required to be OPERABLE in MODES 2, 3, and 4, the inoperable MSIVs may either be restored to OPERABLE status or closed. When closed, the MSIvs are already in the position required by the assumptions in the safety analysis.
l The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> completion Time is consistent with that allowed in condition A, and conservative considering the reduced energy in the steam generators in MODE 2, 3, and 4.
For inoperable MSIVs that cannot be restored to OPERABLE status within the specified completion Time but were closed, these inoperable valves must be verified to be continually closed on a periodic basis. This is necessary to ensure that the assumptions in the safety analyses remain valid.
The 7 day completion Time is based on engineering judgment, and is considered reasonable in view of MSIV status indications available in the control room and other l
administrative controls which ensure that these valves will continue to be closed.
c.1 and era Sin 0 the "0!v: are re and 1, the incperabic " quired t0 bc OPCPaSLE in MOOES 2, 3, SIV: ::y either be re:tered te OPEPASLE :tatus e lc;cd.
When closed, the "SIVs we I
already in the pc:itien required b-j the assumption; in-the safety analysi.
With both " :v: :ncperable and o hour cc=plet4cn Time i: necessary ince the valve pen, a 1 can-net funesien :: ::ered in the : fety analy: :.
rcr incperabic "SIV: that nnet be restored-to OPERABLE statu rithin the specified ccepletien 'ime but are cle:cd, the incper ble "0!v must be verified en a periodic basic t-e bc cle:cd. 'hi: i: necc:: ry te en:ure that the assumptions in the :sfety analy;b :cd en engineering judgey cceplet4en i: rc=:in valid. The 7 da T4:e 1: rea:cn:ble, indication:
i
- cat, n ci er, cf the "SIV ; tate av 44 ble in the contrcl reem and other ad=inistrative centrols, te ensure th:t-these valve cre in the cle:cd pcsition.
(continued) hk)AP600 B 3.7-8 DFUAFT m-.
I
Main steam Isolation valves (MSIvs)
B 3.7.2 BASES ACTIONS D.1 and D.2 (continued)
If the MSIvs cannot be restored to OPERABLE status or closed within the associated completion Times of condition C-ee-9, the unit must oe placed in MODE 4 with normal residual heat removal system in service where the probability and consequences of an i
event are minimized. To achieve this status, the plant must be I
placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and in MODE 4 with normal residual heat removal system in service within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The allowed completion Times are reasonable,tions from full power based on operating experience,in an orderly manner and without challenging plant to reach the required unit condi conditions systems.
SURVEILLANCE SR 3.7.2.1 REQUIREMENTS The MsIV closure time is assumed in the accident and containment analyses. This surveillance is normally performed upon returning the plant to operation following a refueling outage. The MsIvs should not be full stroke tested at power, since the resulting plant transient is significant ;xx;n..a ef 0.: m'v: chnr; 1
when the plant is i
A partial valve stroke I
giriirnal p(approximately 10%generat ng power.
) is performed during plant operation and has ee-erturbation on plant operations but ensures the freedom of valve movement. The MSIVs surveillance tests are performed in accordance with the Inservice Testing Program.
The Freguency is in accordance with the Inserv' ice Testing Program.
The minimum surveillance Frequency to demonstrate valve closure time is based on the refueling cycle. The Frequency was concluded to be acceptable from a reliability standpoint.
This surveillance is modified by a Note that allows entry into and operation in MODES 3 and 4 prior to performing the SR.
This test is conducted in MODE 3 with the plant at operating temperature and pressure, in accordance with the Inservice Testing Program. This allows a delay of testing until MODE 3, in order to establish conditions consistent with those under which the test criterion was generated.
SR 3.7.2.1 Because the MsIV closure time is assumed for steam f. low isolation in the accident and containment analyses, the alternate downstream valves must meet the MSIV closure time. This surveillance is normally performed upon returning the plant to operation following a refueling outage. The alternate downstream valves should not be full stroke tested at power,f Omsince the resulting plant transient is significant cax;:n c
.J.s; chxx when the plant is generating power. A partial valve stroke (approximately 10%) is performed during plant operation and has cet perturbation on plant operations but ensures the freedom of valvebovement. The surveillance tests for the turbine stop valves, turbine bypass valves, main steam to auxiliar steam h de isolation valve, and moisture separator reheat supp y steam ont ol valve are performed in accordance with t e Inser ce esting Program.
nWd (continued)
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_AP _600 8 3.7-9 DRAFT
Main Steam Isolation valves (MSIvs B 3.7.
BASES SURVEILLANCE I REQUIREMENTS I
f~"'-*
SR 3.7.2.2 (continued)
The Frequency is in accordance with the Inservice Testing Program.
The minimum surveillance Frequency to demonstrate valve closure time is based on the refuelin c tobeacceptablefromareliabilfcle.
The Frequency was Concluded ty standpoint.
This Surveillance is modified by a Note that allows entry into and operation in MODES 3 and 4 prior to performing the SR.
This test is conducted in MODE 3 with the plant at operating temperature and in accordance with the Inservice Testing Program. This pressure, delay of testing until MODE 3, hi h allows a in order to establish conditions consistent with those under w c the test criterion was generated.
REFERENCES 1.
APC90 SSAR, Section 10.3, " Main Steam System."
l 2.
AP600 SSAR, Section 6.2.1, " Containment Functional Design."
3.
AP600 SSAR, Section 15.1, " Increase in Heat Removal by
~
Secondary System."
4.
AP600 SSAR, Section 10.2, " Turbine Generator."
5.
NUREG-[138. Issue 1. " Staff Discussion of Fifteen Technical Issues Listed in Attachment to November 3, 1976 Memorandum from Director NRR to NRR Staff."
6.
AP600 SSAR, Section 10.4.,,"Other Features of Steam and Power Conversion Systems.
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