ML20036B513
| ML20036B513 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 05/19/1993 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9305250177 | |
| Download: ML20036B513 (11) | |
Text
Y o
j l
GE Nuclear Energy
, t.,
,;~...e
! ' :vi [,4 i. 3
_ q: r i
May 19,1993 Docket No. STN 52-001 Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of the Nuclear Reactor Regulation
Subject:
Submittal Supporting Accelerated ABWR Review Schedule - Revised LCO 3.7.5
Dear Chet:
Enclosed is a SSAR markup of the revised LCO 3.7.5, Main Turbine Bypass System.
Please provide a copy of this transmittal to George Thomas.
Sincerely.
Jack Fox Advanced Reactor Programs ec: Norman Fletcher (DOE)
Cal Tang (GE)
L'1001y Ji9. bra
v 1
3.7.$#
3.7 PLANT SYSTEMS S
3.7.1 Main Turbine Bypass System
~
5 LCO 3.7.E The Main Turoine Bypass System shall be OPERABLE.
0R_
LCO 3.2.2, " MINIMUM CRITICAL POWER RATIO (MCPR)," limits for T
an inoperable Main Turbine Bypass System, as specified in the COLR are made applicable.
'/O APPLICABILITY:
THERMAL POWER e 21h RTP.
ACTIONS CONDITION RE0VIRED ACTION COMPLETION TIME A.
Requirements of the A.I Satisfy the 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> LCO not met or Main requirements cf the Turbine Bypass System LCO or restore Main inoperable. @
Turbine Bypass System toOPERABLEstatus.b B.
Recuired Action and B.1 Reduce THERMAL POWER 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> y
associated Completion to < X% RTP.
N Time not met.
40
,{
N b
nY t
.t SURVEILLANCE REQUIREMENTS
]
SURVEILLANCE FREQUENCY
'T A
I
/
s SR 3.7.(.1 Veri iy te-cycTE~of each main 31 days turbin ass va i
f f er form byfess V2/ve ofen hy (continued)
L
-le s t f o ayy yo xo%alely / o l4 f o s> Y to n f r each -t%rbdre bSWR$STS b
.7-16 0, 07/::/92
,g g j,g,
\\
i I
l Main Turbine Bypass System l
- 3. 7. 5 5
SURVEILLANCE REQUIREMENTS (continued)
SURVEILLANCE FREQUENCY i
SR 3.7.i 2 Perfom a system functional test.
18 onths/
3 Verify the TURBINE BYPASS SYSTEM RESPONSE l18 onths TIME is within limits.
l g gruCL/ ^)G p.)fe AVAl.
i 1
l I
I i
i i
i l
1 S BWRN STS 3.7-17
-;e,.
O, ;;/: /2 i
Main Turbine Bypass System B 3.7.5E i
BASES i
ACTIONS-S.d 11 0
, 40 (continued)
If the Main Turbine Bypas ystem cannot be restored to OPERABLE status r the CPR limits for an inoperable Main Turbine Bypass System are not applied, THERMAL POWER must be reduced to <
% RTP. As discussed in the Applicability section, operation at <
% RTP results in sufficient margin to the required limits, and the Main Turbine Bypass System is not required to protect fuel integrity during the feedwater controller failure, maximum demand event. The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Completion Time is reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.
S g'
SURVEILLANCE SR 3.7.5.1
-lo//.5Nkhjy$/,.a/e/[
REQUIREMENTS Cycling each main turbine bypass valve thr0 ugh sne cowiete ges,-[2ycle of ful' travel demonstrates that the valves are l
mechanically OPERABLE and will function when required. The 31 day Frequency is based on engineering jud;;;nt, i;
<ensistent with the procedttrel-centrels gevarning v:'"a geratinn 2nd ;n30ce5 cecrect valv; p;sitions.
Ther:fc:c,-
Negnen;y j 3 ggui:pggjJle irum a s el'aebility 's [In
),
^
st
-the C. relig bs'/,*-lj 4 n a /
so SR 3.7.B.2 l
The Main Turbine E,ypass System is required to actuate automatically to perfonn its design function. This SR demonstrates that, with the required system initiation si nalsp:;e valves will actuate to their required position.
T 1S, ntir Frequency is based on the need to perform ffEpu E4/4 this Surveillance under the conditions that apply during a s
/MA*M#
unit outage and because of the potential for an unplanned d
transient if the Surveillance were performed with the reactor at power. Operating experience has shown the M187":3 nth-Frequency, which is based on the refueling cycle, is acceptable from a reliability standpoint.
(continued)
PBWR76 STS B 3.7-29 Rev.
C, 09/20/92 i
l
i a
1 Main Turbine Bypass Systea B 3.7.
BASES 6
ggpus L.ws SURVEILLANCE SR 3.7.%.3 jgrggva L REQUIREMENTS ti (continued)
This SR ensures that the TURBINE BYPASS SYSTEM RESPONSE TIME is in compliance with the assumptions f the appropriate j
safety analysis. The response time li its are specified in
{ unit specific documentation]. The9 f8 S r.th Frequency is k
based on the need to perform this Surveillance under the j
conditions that apply during a unit outage and because of the potential for an unplanned transient if the Surveillance 1
were performed with the reactor at power. Operating experience has shown the7 0TCenth Frequency, which is i
based on the refualing cycle, is acceptable from a reliability standpointn ga J (
~ 26/~WEl-/^1G
, s als o ha s ed upon + 4 c A4. 3.
il yel,'ab,'/,% a.,k4>'s <-Y
/MERt/A 4--
psuz 3
'g
/
REFERENCES 2 /SAR, Section3 7.7.1.$ [
/SAR, Scctier gg Ch. apt e r Ib, i
- 3. (
)
i i
4 BBWRN STS B 3.7-30 Re/.
O, 0;/2S/92-
1 i
ABWR Main Turbine Bypass Valve Failure Rate The ABWR has three main turbine bypass valves (BPVs) with the capacity to dump 33% of reactor steam directly to the main condenser.
In event of a turbine trip at modest power, less than 33%, the BPVs will open quickly to dump steam before a reactor scram can occur because of high j
reactor pressure.
If a turbine trip occurs at high power, even fast action of the bypass valves will not avoid reactor scram. However, the proper BPV function will limit the pressure rise in the reactor.
The hydraulic fluid l
loop showing the fast acting solenoid valve (FASV) and its connection-to i
the BPV is shown in Figure 1.
The FASV it. the key to fast opening of BPVs.
The number of safety related demands on the bypass valves and the FASV will depend on the number of turbine trips for which operability of the BPVs is assumed.
That analysis included only one transient in which it was assumed that the BPVs would function properly.
The transient is i
described in SSAR Section 15.1.2, Feedwater Controller Failure -- Maximum Demand; and the estimated frequency is less than once in 10,000 years.
However, the event is analyzed as a moderate frequency event (once in 20 years), which overestimates its importance by a factor of 500.
Bypass valves of current BWRs in the U.S. are tested monthly in a test that includes slow stroking for 90% of valve travel followed by rapid stroke for the final 10% of travel.
This monthly test frequency has no technical basis and was established on the basis of other turbine valve 4
testing.
Because of the lit power capability of a single bypass valve in the ABWR plant, it is desirable to test the full stroke and fast travel of bypass valves only during plant shutdown, approximately every two years, to minimize disturbance to the electrical grid and to minimize potential challenges to the plant safety systems. At shutdown the total valve stroke time can be measured.
The valves can be stroked slowly during plant operation over partial travel (such as 10%) to assure that they are not bound and will open on demand.
Such a test will have little impact on operation.
The circuit to cause fast opening of the BPV is attached as Figure 2.
i The fault tolerant, _ solid state digital controller components are checked frequently by the self-check circuits.
They are also combined in 2-out-of-3 logic so there will be a very low probability of failures of l
the controller that lead to inadvertent opening of the fast acting l
solenoid valves (FASVs). Because of the high reliability of this circuit, l
the main contributor to failure of the FASV to perform its desired l
function will be the FASV itself.
The referenced IEEE Standard gives failure rates for much nuclear i
plant equipment, including solenoid valves. The "all modes" failure rate for solenoid valves is 1.32E-6/h, but this is primarily for " catastrophic" (spurious open or spurious close) failures, 0.95E-6/h.
The failure rate l
for " degraded" performance is 0.37E-6/h.
A demand failure rate of
[
1.08E-6/d is also given in IEEE 500-1984.
. r
i j
The demand failure rate for solenoid valves is very low, and demand failure rates are generally not time dependent. Therefore, it will be
. assumed to be independent of test frequency.
It is pessimistic to assume that the time dependent failure rate is dominant, in which case the failure rate will be proportional to the test interval.
For such a pessimistic. approach, the average failure probability during a time
.j j
interval T is given as t
f
)\\ - 2( T/2 0.37E-6 x T/2 s
O.185E-6 x T (hours) - 1.35E-4 x T (months) l Test 'aterval T (months) -
1 3
6 12 24 i
Failure Probability
- 1.35E-4 4E-4 8.1E-4 1.6E-3 3.2E-3 Valve failures / year
- 2.0E-5 6.lE-5 1.2E-4 2.4E-4 4.9E-4 During FWC Maximum Demand Failure l
The valve failures per year are based on three valves in the plant j
and on the assumed 0.05 safety related turbine trips per year.
To i
summarize the table, at a current test frequency of monthly for the FASV, less than one bypass valve failure in 50,000 years would be expected during failure of the feedwater controller resulting in maximum FW demand.
i (This failure could result in reactor overpressure, if bypass capability with the other valves were lower than power level.)
If the test frequency were once per six months, one failure per 16,000 years could be expected.
A 24-month interval between tests would result in the expectation of one failure per 2,000 years.
i The determination of test frequency for turbine bypass valve testing abould be based on the acceptable frequency of valve. failure during the trancient caused by FWC failure and leading to maximum flow demand.
If-one turbine trip cauring reactor overpressure in 2,000 years is j
acceptable, a 24-mouth test interval can be justified.
Consideration was given to the probability 'that accumulator failure vould preclude rapid BPV action when needed. The accumulators are precharged with nitrogen to 900 psig with the_ hydraulic system pump off.
When the pump operates, system pressure climbs to'1600 psig. This; i
pressure is maintained by the operating pump, and.a standby pump will l'
automatically start if system pressure drops to a preset value, indicating failure of the operating pump.
If the accumulator leaks nitrogen,-without-being detected, and subsequently the operating pump fails and the standby pump fails to start, or starts and fails to run, the plant would be.
j vulnerable to the FWC ' maximum demand event, with its assumed 0.05/ year probability.
fa
~!
- 1
I 4
2 The probabilities of the above sequence are as follows:
I 0.30 l
Accumulator leaks in 2 years:
1.7E-5/h x 8760 x 2 h
- Operating pump fails to run 3 months (assume that pump switches
-l to standby after 3 months):
1.63E-2 7.4E-6/h x 8760 h/4
- Standby pump fails to start or starts & fails to run for one month (failed pump could be repaired in one month):
6.7E-3 (1.3 + 5.4) E-3 1.3E-3 + 7.4E-6 x 8760 / 12 i
Demand for BPV operation, F6'C maximum demand:
0.05/ year
- Total event probability:
0.30 x 1.63E-2 x 6-.7E-3 x 0.05 - 1.6E-6/ year The probability of this sequence of events is so low, even when the-frequency is overestimated by a factor of 500, it need not be event considered.
It will have no impact on the frequency of BPV testing.
i e
f I
Reference:
IEEE Std. 500-1984, "IEEE Guide to the Collection and Presentation of Electrical, Electronic, and Sensing Component Reliability Data for Nuclear Power Generating Stations", Dec
-I 13, 1983 t
e i
I e
?
'?
i
-g 1
9
4 9
\\ %
gn I
/
i 8
/
uta. ' t fl ai t'
t I" vt n',,
i t
at l
sit ta e0a Sf l
r5v
~
g e
~
W poo L
l or ts t
t a
n t
pe g
C o
tv l
a g
e d
yb a t
i v
a l
P Ji n
S u
la l
q F
7 o
9
.t
.a c
w g
. t i
I, 0t Ig Pa l
e u
c a
e s
r re 0
d at Q
t a
y at ta l
t t f
$s 4
f l
0 l
ta e
4M
=t t
e v
t g
l t
t t
a e
v V
D l
r
_C t
a l6 s
te h n:a l
s st a
l.
W ta a
P C
iv 5
s T
t p
S c
t SP y
i 9 0N t
1 s
4 R0 B
e fl O 0 t
3 l
F 9 1
e 5
e t
9 la 50 r
1 op 81 n
o
(
P9 9
1 t 4
i h G l
b tR a
U8 e
r 1
WN D
t C u
C9 T
Ct SP a
1 e
r s
i u
t t
IIgg n
e g
t e
h i
1 C
F 1
s t
t 99t l
P4a t
(
a 4
s f
4 4
6 t i at 8
e 8
1Gn h
h u
a i
t t G#g go 8
0 >
ot t
t O
t t
T) tts 9
- in P e e
la ts t ';
t t
l.ge 1 tM
- tt t C
.tsv e
- 4. S 1 ih t o i
st 1
et t
tv t
$, t e S. F
- 8. F s tt t
l,tS PC t.ts s
P nti
- 1. e
- 1. e e tF
$t v
w, PgO
$a a
aa 0em 0st 9n 0gt 0et 1 g 4y p 6vi re 1 mO 1 as 9t
(
Il lll lllIl;!J lI!ll
9 O
y O
e 9
9 a"
a h
^
W W
Z Z
7.
7 z
3 g
4
~
a s'
g7 O
O O
E*
-3 ME e
M a5 hf An
%M Mn C
Cy
<g
, w U
y 3V
~
r cc dh Ok s.
Eu
~
7 Vr*
r:
-X J<
W gM w
F A
v W
6 g
- 4 1r If y 1r m
u.
v 4
u.O U
WO w2 W
$D 7"
Ou g
3 M,3 55 E
IkgOk 3*
eO gz
~ + -
S hO I
M 5
C e
A SC H >^
+
n a
~
V p
"r e
^
D
- [
n
<w
-y
.* v.
y.
H N
M M
k if
-n c
h n
e
?
,..v x
/
e e.
r-
.a 9
m'
~.
+
Ds E
C E
y 5
K
~
4 t~
-'h
/
l bL A
y
,x u<
W D
2 E
O MO E
Z ex k
Z I
ke d
O C%
bk2 Y>
w" Z
hlEEN
~
w c it w
- w 5" D?z h*
)
w e w n;;;
b j,-
Zy7yM 2 # E W"M
+jL uYx
- S NNNh$
w Cd)
O
(
l 39 e,
nu Mw w
$ O.
y $e..., y
+e$
0 wa
- uaw hOAE