ML19259D176
| ML19259D176 | |
| Person / Time | |
|---|---|
| Site: | Crystal River, Rancho Seco  |
| Issue date: | 05/16/1979 |
| From: | Bennett J, Vosbrugh R SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML19259D175 | List: |
| References | |
| TASK-2.K.2.10, TASK-TM 86-1102525, 86-1102525-00, TAC-45188, NUDOCS 7910160478 | |
| Download: ML19259D176 (28) | |
Text
.
L t
ANTICIPATORY TRIP FUNCTIONS FOR 177 FA PLANTS 86-1102525-00 Document Identification
/
GIr/?7 Prepared by M
I D
Reviewed by
- 23 Approved by r,
i6 /
/i Il60 329
'7 91016 0 + 76
86-1I02;23-00 1
4 INDEX i
1 1
1.0 INTRODUCTION
2.0 ASSESSMENT
OF POSSIBLE ANTICIPATORY TRIPS j
3.0 FUNCTIONAL ANALYSIS
4.0 CONCLUSION
S AND
SUMMARY
APPENDIX A: LOSS OF ONE FEEDPUMP ANALYSIS APPOGIX B:
SAFETY EVALUATION PROGRAM FOR ANTICIPATORY TRIPS ii60 330 1
1 y-.
n
86-1102525-00 1.0 INTROD'JCTION For the pucposes of this report, an anticipatory trip is defined ac a trip function that would sense the start of a lose of OTSG heat sink and actuate much earlier than presently installed reactor trip signals. Possible anticipatory trip signals indicative of changes in OTSG heat resoval are:
turbine trip, loss of main feedwater, low steam generator level, and low pressurizer level.
This report evaluates the effectiveness of anticipatory trips compared to the cristing high RC pressure trip for a LOTW. Qualitative and quantitative arguments are presented which support elimination of the level trips in the pressurizer and steam generators from final design considerations of anticipatory trips.
Functional response is presented in terms of a parametric study of time to trip. Thus, irrespective of the plant specific trip signals and actuation time, the hardware design can proceed with greater flexibility.
That is, by presenting system parameters, such as pressurizer fill time, as a function of tLse to trip.then if one plant's turbine trip signal occurs 2.1 secs af ter initiation of the event and another plant'e trip signal occurs at 2.5 secs, this study will still be applicable to both.
Some of the results presented in this report have already been sub-mitted to the NRC in Reference 1, the balance of the information will be submitted by May 21, 1979. The analyses are performed wit'a the revised setpoints, i.e., high RC pressure trip at 2300 psig and PORV setpoint at 2450 psig.
It is shown that anticipatory trips provide additional margin between the peak RC pressure af ter the reactor trip and the PORV setpoint, but provide little additional margin in the longer term re-pressurization to the PORV setpoint with continued delay,.of auxiliary feedwater initiation.
.e
86-1102525-00
2.0 ASSESSMENT
OF POSSIBLE ANTICIPATORY TRIPS In accordance with Directive 79-05B, an evaluation for design basis for anticipatory trips on turbine trip, loss of main feedwater, and low steam gener-ator level has been completed. One of the trip functions investigated was deter-mined not to be anticipatory as discussed below:
Low steam generator level has not been recommended as an anticipatory trip function.
Figure 2-1 shows the OTSG start-up level from site data and the CADDS calculated 0TSG mass inventory as functions of time following the TMI-2 event. The time of reactor trip on high RC pressure is noted on the figure and clearly demonstrates that a steam generator level trip would not have been anticipatory for a level setpoint that would not interfere with normal opera-tions and maneuvers. The initial rapid fall in OTSG level occurs as the turbine stop valves close, mementarily stopping steam flow out of the generators.
The mass inventory increases during this period due to the loss of flow friction AA.
By the time the reactor trip occurs, at 8 seconds, steam flow is re-established through the bypass system, flow friction Aa re-establishes the level and both mass and measured level start to decrease uniformly. An OTSG 1evel trip set to trip on the initial drop shown in Figure 2-1 would need to be set restrictively high for normal plant manetivec: 6nd/or lower power levels.
Further level information (in terms of mass inventory) is given in the figures for the analysis in Section 3.0.
The results for those cases also indicate that the steam generator low level trip function would not be sufficiently fast to be considered anticipatory.
Anticipatory trips for loss of feedwater and turbine trip can be designed to trip the reactor in a more expedient manner than the high RC pressure trip for some overheating transients. An anticipatory trip will provide more margin to PROV setpoint during the initial overpressurization resulting from loss of feed-water and/or turbine trip. These trips will provide slightly more time to PROV setpoint and pressurizer fill for delayed auxiliary feedwater. initiation conditions.
1160
$32
86-1102525-00 Figure 2-1 LOFW (TMI-2 EVENT) 2.0 160 TRIP DN HIGH RC 1.6 p
PRESSURE O
m 120 g
=
5 E
.=
5 1.2
- jg
{
\\
/
=
y
,e
\\
80 g
a
=
\\
o
.8 y,
M N
40 E g
\\
.4
~
\\
N
_~
g 0
I f
0 20 40 60 80 Time, seconds
' TOTAL S/G MASS, CADOS
- START-UP LEVEL, TMI-2 SITE MTA 1160 333 7
ou A4v o u-vu 3.0 FUNCT!ONAL ANALYSIS A series of LOFW evaluations was performed at 100% full power (2772 MWt) with a reactor crip assumed on an anticipatory signal. With the new high RC pressure setpoint of 2300 psig, a reactor trip would be =2perted at about 8 seconds after the LOFW. The anticipatory trip study considered reactor trips with 0.4 sec,2.5 sec, and 5 sec delays from time zero. These studies also in-cluded sensitivities to AFW failure and reactor coolant pump coastdown.
The anticipatory trip study modeled a generic 177 FA plant, and is con-sidered applicable to raised or lowered loop designs. A feedwater coastdown similar to that estimated to have occurred at the March 28th IMI-2 event was used to generate separate heat demands for each CADDS analysis. The beat demands will chcnge as the reactor trip time is delayed, because the additional haat input will boil off the fixed steam generator inventory at dif ferent rates.
For the cases whee AFW flow was modeled,1000 gpm was assumed, starting at 40 seconds. With proper steam generator level and pressure control, the system parameters will begin to stabilize at 195-290 seconds, depending on trip delay time and RCP operation; see Table 3-1 and Figure 3-12.
The PORV will not be actuated, nor would the pressurizer fill or empty.
1160 D,4 With the assumption of no AFW, the PORV will be actuated aoout three minutet into the event, as a result of system swell; the pressurizer fills as 10-12 minutes (see Table 3-1).
A delay of reactor trip of 2-3 seconds is seen to reduce PORV time to actuate by about one minute, and pressurizer fill by about 2 minutes For PORV setpoints other than 2450 psig, the times will vary and can be determined from Figures 3-3, 3-4, 3-8, and 3-10.
In each of these cases, the mass addition and cooling effect of expected make-up system operation is not modeled. One make-up pump running will add about 10 inches per minute to pressurizer level, and N1/2% heat demand.
It should be noted that the May 7 report used a heat demand which reproduced the THI-2 LOFW event; it has been reported by the operator that two make-up pumps were running from 13 see into the event, creating a higher heat demand than 7
s
86-1102525-00 the anticipatory trip studies of the report ar.sume.
This is shown in Figure 3-12.
The steam generator heat demands, reactor power, RC system p' essure, pressurizer level, and RC inlet / outlet temperatures are given in Figures 3-1 through 3-5 for the trip at time zero case and Figures 3-7 through 3-11 for the trip on high RC pressure (t=8 secs) case. The effects of delayed auxiliary feedwater initiation are also shown on the high RC pressure trip curvesc l6033f)
O e
a
86-1102525-00 TABLE 3-1 LON EVENT (LOW at T=0. nee)
TIME OF REACTOR REACTOR AUXILIARY PORV PRESSURIZER S/G Lvl CONTROL TRIP (" DELAY")
COOLANT PUMPS FEEDWATER OPERATES FULL (400")
(P
=1025 psig) stm 0.4 Run at 40 see 195 see 2.5 Run at 40 see 225 sec 5.0 Run at 40 see 275 sec 0.4 Run None 235 sec 790 see 2.5 Run None.
180 sec 685 see 5.0 Run None 140 sec 575 see 0.4 Coastdown at 40 see 255 0.4 Coastdown None 190 sec 700 see LOW EVENT - TIME =0 see REAC'IOR TRIP AT 2300 PSIG TIME OF TRIP RCP AW PORV PRESS. FULL S/G LEVEL CON _T.
8.0 Run at 40 see 260 sec 8.0 Run None 175 sec 620 see 1160 536 l_
bY b
Y' Figure 3-1 lleat Demand Model for Reactor Trip at Time Zero Studies I
I I
i 1.0 p
0.8 0
e y-g 0.6 2
E L'
5 0.4 -
0.2 i
~
C sn
'*4 I
I I
I b
N o
100 200 300 400 500 600 Time, s D
blI M 'M JA44teMti&$..-
%d5
.. ~ -.. -.
Figure 3-2 Reactor Trip at T=0, No AFW I
I 100 4
4 80 o
as W
e 50 3
C1 C1 M
O W
40 1
e e
9
~
20 E.
~
i H
H C
o N
v.
N (W
D e
v, k
CD I
I i
100 200 300 400 500 600 Time, e r*
86-1102525-00 E
n-a-
o y
i I
I I
I oo m
W oo
~
w>
E<
t O
M 2:
O o
E o
H g
uo w
o.
+
9 h
M w
r, C
a u
o as I
=
c>
s:
[
{
D m'
=
M 8e o
o N
eu o
4 eo H
Ese w
o
. ~
o p
- ~
W*
I
',hh.
l t
f f
I f
W e
o o
e, o
a 9
o o
e o
e o
o m
o o
.o-m m
m m
g elsd 'ajnssajd malsAs.38 W
r 1160 339 V
V*
Figure 3-4 Reactor Trip at T=0, No AFW
^
l i
i I
8 8
400
,c_
- P o.
~
T
~
300 e
.~_
a
- een, v
=
- 200, i
s
.~
100 E
i os
.I w
~
a O
N
(~
s t
I
't I
100 200 300 400 500 600 Y
^
o o
O Time, s
Figure 3-5 Reactor Trip at T=0. No AFW 3
I i
1 660
~
' f 640 B
m 620 5
60G
.5 580 OUTLET c
s 560 t
/
\\
/
a y-L INLET
~
~
520 E
g O
C o
500 i
f I
1 u
100 200 300 400 500 600
[
O Time, s
~ h.
l $
E.
~
b' Figure 3-6 Steam Generator Heat Demand Vs Time Following Loss of Main Feedwater From Rated Power a
1.C 40 S AFI DELAY E
E
.8
.6 E
AFW,,
AFE LEVEL
'4 M
INITIATION
[ CONTROL t
.2 0
120 S AFI DELAY 10 y
2
.8 e
4
~
INITIATION CONTROL
)
/
M
.2
~
0.0 E
1.0 g
INFINITE AFI DELAY ch 4
8 g
,L C
.6 E;
v ri n
e-1:
.4 M
^
Y' u,
N to
.2
~
o 0'0 L 100 200 300 400 500 600 Time,'s
86-1102525-00 e
L, I
s s
a r
I i
I i
1 8
i.
ca M U
=a o
x-om e
u O e0 m-mu O =
a-u oo -
ac
- e-a o
3 :n o,r O
- u.
=
t 2m L-o
=
W E5 e.O
-u F
s=>
o b_
m o
>u n
O k 4.e P.
3 h O U
- a. a
~ 2 5
=m U G O W C3 e he o
m M
w w
z m
e-o -
,r z.-
n w <
n m
I aut
-4 m
o
=.0 M N W P
w - o a
v,
= i.
o o
z w
o o u.
m Q.
Mr 4 ao m
w m w r u.
m o -
6 "'"
I m
z w w
= :s u.
o a =
n.
m i
I s..
o
,o o
a o
e a
w o
o o
g patcJ 5 'Jamod le101 Ii60 343 r'
o T
4 f
I e
86-1102525-00 m
yd N
P3 2
1 i
\\
gi i
a e
Q
\\
I W
5 s
C5a
\\
M I:f a =
g
=
e
==
A
=
E==
\\
.=
3 p O. C
\\
g 5c2 4
lt ts-bu k =*
5-2 7s
'a i
= !:' *
\\
e
<
1 8,
. m' 2
\\
mm n3
- 13 a
@"E
\\
g!
l
\\
i it l
s
=
a s
es i
I l
/
g I
S
! ?,
- 2 na
,/
8
..n k
uli
.J u
4
=
m
~
nM
(
g a
V C
e4 1
i i
@3'
=
=
=
=
=
~
~
~
~
g@
. iso unssue masses a w
1160 344 w
.1 5
y N
i
Figure 3-9 Pressurizer Pressure Vs Time Following Loss of Main Feedwater From Rated Power
]'
2600 2400 -
5.
KEY c,
a,-
_. _ 40 S. AFW INITIATION DELAY y
120 S. AFW INITIATION DELAY
{
2200 INFINITE AFW INITIATION DELAY
\\
g 5
\\
3
\\
y
/,,,,,,. -'#,,
2000 _
s
=
N.\\
s 1800 -
O E
w.
,n.,
s 1600 1
I I
I I
g
~
100 200 300 400 500 600 u
Time, s 2
D D
D D _T' _M TLT1 O.... n n ' n n r T rT m
m
M b
bbbb II;;d l
[
Figure 3-10 Pressurizer Level Vs Time Following Loss of Hain Feedwatec From Rated Power i
i i
6 I
KEY 40 S. AFW INITIATION DELAY 120 S. AFW INITIATION DELAY 00 3._
INFINITE AFW INITIATION DELAY
~
s f
300 2
U
-2 5
m u
200 t
- 'em 100 s
w
- .=-- -
=
b C
8 w
^
~
a t
I i
1 I
e o
100 200 300 400 500 600 8
g Time, s
Figure 3-11 Core Inlet and Outlet Temperature Vs Time Following Loss of Main Feedwater From Rated Power
~
i i
i i
i KEf 40 S. AFW INITIATION DELAY 120 S. AFW INITIATION DELAY INFINITE AFW INITIATION DELAY 660 u
640 1
B 5
620 E
d 600 00TLET 7
=
\\
d 580 560
'r 3
-- vm_wsw INLET 540
-~
520 g
A ch I
I 500 100 200 300 400 50'0 600 0
^
A w
Time, s o
0 O
C D
D D
C C
C C
C C. Q Q
( ;'
[~"
17C 7
71
,'] a a
a m
cm ca sua l,
m
86-1102525-00 Figure 3-12 LOSS OF FEE 0 WATER AT T = 0 SEC NO AUXILIAtlY FEEDWATER b
=~
l i
i i
i 800 PRESSURIZER FILLS (RCP RUlittlNG) 700 RCP C0ASTOOWN AL '
600 o
il e-b 500 4 Q FLOW AS REPORTED IN REFERENCE I.
E 3
m 400 300
~
PORY OPERATES (RCP RUNNING) 200 E3 RCP COAST 00XN 100 1
I f
I I
I a__
F 0.4 1.0
?.0 3.0 4.0 5.0 B.0 Time 29 reactor trip (" delay") - seconds 1160 348 zz
86-1102525-00 4.0 CONCLUCIONS AND
SUMMARY
A spectrum c f delay times, representing an'.icipatory trips, has been i
analyzed for the loss of feedwater transient. The spectrum included trips at time zero, with a 0.4 second instrument del.:y, up to high RC pressure trip at time 8.0 seconds. Since a high RC pressure trip occurs very soon af ter a loss of teat sink (overpressurizaticn) transient from 100% FP, only turbine trip and direct loss of feedwater detection trips would be considered Anticipatory.
For all trips considered, including high RC pressure, the PORV is not actuated when normal system operations occur The pressure rise in the primary side is less for the anticipatory trips providing additional margin to PORV lift.
If auxiliary feedwater is significantly delayed, then an anticipatory trip will, at best, provide about 1 minute additional time to PORV lift and about 3 minutes additional time to filling of the pressurizer. These results can be seen in Table 4-1 which shows 'the sequence of events for a LOW transient with trip cn high RC pressure (2300 psig) and trip at time zero.
~
1160
$49 i
2.3 e
86-1102525-00 Y
TA4LE 4-1.
LOFW-SEOUENCE OF EVENTS COMPARISON 40-s 120-s TRIP AT ZERO, EVENT AFW DELAY NO AFW NO AFW Loss of feedwater initiated 0
0 0
0 (trip occurs)
(0.4 delay)
High-pressure trap (2300 psig) 8 8
8 a
l PORV opens (2450 psig) a a
175 235 Peak RCS pressure 10 10 175 235 Pressurizer full a
a 620 790
- Does not occur for these cases 1160 350 i
2.54 v
86-1102525-00 t
REFERENCE:
1
- 1) B&W Report to the NRC, May 7, 1979, " Evaluation of Transient Behavior and Small Reactor Coolant S stem Breaks in the 177 f
Fuel Assembly Plant".
1160 351 O
l
~.'
(
t 86-1102525-00 APPENDIX A LOSS OF ONE FEEDWATER PUMP' i
A special s. alysis was performed at the 1;&W Owner's Group request.
This analysis considered the loss of one main feedwater pump with the plant operating at 100% FP, RC pumps running, no power runback or auxiliary feedwater initiation and a RC high pressure trip setpoint at 2300 psig. The base partmeters for this study are the same as those used in the " realistic" analysis presented in Section 4.2 of the May 7, 1979, B&W Report for 177 FA plants.
The objectives of this study were two-fold:
- 2) Determine if the OTSG level would be a viable anticipatory trip, i.e., how rapidly does the steam generator inventory decrease in relation to the time a high RC pressure trip would occur.
RC system pressure and pressurizer level as functions of time are shown in Figures A-2 and A-3, respectively. Reactor trip occurs on high pressure (2300 psig) in 15.8 seconds af ter the loss of one main feeavater pump. Figure A-4 shows the steam generator mass as a function of time and only 30% of the mass is boiled off by the time the reactor trip occurs. This
~
is insufficient inventory decrease to cause a level trip in an anticipatory mode. Figure A-2 shows that no PORV actuation results fron this transient.
l l
4 86-1102525-00 Figure A 1 FEE 0 WATER C0AST00XN TO 50%
I i
l i
100 90 80 TO m
[
60 E
50 40 30 e
20 10 b
0 I
I I
0 20 40 60 80 100 Time, seconds i
e
86-1102525-00 Figure A-2
. FEE 0 WATER COAST 00WN TO 50%
2400 l
I i
i I
2.100 E
a a
5=
U cm 2200 w
2100 2040 I
O 5
10 15 20 25 Time, seconds i160 354 I.
,a
86-1102525-00 i'
i f
Figure A-3 i
FEEDWATER C0AST00NN TO 50%
f 240 I.
I i
i l
230 5E
=
2
- ~
j 220 a.
210 1160.555 200 0
5 10 15 20 25 Time, seconds i
'~
86-1102525-00 Figure A-4 LOSS OF ONE FEEDPUMP-RAMP TO 50". IN 10 SEC TOTAL S/G MASS, CADDS i
i i
i 1.0 n
.8 5
2 y
.6
.4 i
i i
i 0
5 10 15 20 25 Time, seconds 1160 356 e
c
%