ML20038B405
| ML20038B405 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/01/1981 |
| From: | Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Clark R, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 908B, NUDOCS 8112080158 | |
| Download: ML20038B405 (10) | |
Text
-
VIROINIA ELucrunc Awn Powns CoxPANY HICitMOND, YIMOINIA 202G1 R.' H. Leass u no December 1, 1981 Vacs Penesnaar NCCLEAm Oramanons Mr. Harold R. Denton, Director Serial No. 908B Office of Nuclear Reactor Regulation PSE&C/jda/KSB 4
Attn:
Mr. Robert A. Clark, Chief Docket Nos. 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing U. S. Nuclear Regulatory Commission License Nos. NPF-4 Washington, D. C.
20555 NPF-7 December 1,1981 F
/ S, O
\\
Dear Mr. Denton:
//s 4r
/1' R GENERAL DESIGN CRITERIA 17 ANALYSIS g
9
'[ ;.
1 W
NORTH ANNA UNIT NOS.1 AND 2 g\\-
/c, 4?/
\\E In our recent letter to you dated August 21, 1981, Serial 'No. 90k,we committed to provide you with a complete GDC17 submittal by December l',N1981...
Due to unforseen problems, our analysis is not complete at this time.
Th'e' O purpose of this letter is to inform you of our current status and expected completion date.
The scope of our analysis is based on all the guidelines and requirements set forth in the NRC's August 8,1979 letter, entitled " Adequacy of Station Electrical Distribution System Voltages," the NRC's June 25, 1980 le t ter,
which included a " Request for Additional Information Regarding the Adequacy of Station Electric Distribution System Voltages," and our April 2,1981, telephone conference with your Mr. L. B. Engle and Mr. A. Uly of EC&G.
We are analyzing the electrical sys tem shown on Attachment I.
The Unit 1 generator breaker and the normal to emergency bus ties, Bus 1B to Bus lH and Bus 2B to lJ, are installed. The Unit 2 normal to emergency bus ties, Bus 2C to Eus 2H and Bus I A to Bus 2J, will be installed during the upcoming Unit 2 refueling outage (Spring,1982).
At the same time the normal to emergency bus ties are being installed, the administrative ties between buses lH and lJ and between buses 2H and 2J will be removed.
With the generator breaker in service, Unit 1 start-ups are accomplished with the Normal Station Service buses being fed from the Normal (Unit) Station Service trans formers (normal SST's) back-fed from the 500 kv switchyards, rather than from the Reserve Station Service transformers (RSST's).
For the majority of Unit 1 trips, Unit I will continue to have its Normal Station Service buses fed from its normal SST's.
This arrangement reduces the probability of combined loading from both Unit 1 and 2 normal and emergency buses on the RSST's.
'8112080158 811201 hDRADOCK 05000338 I 6 I PDR p9z
-jdm/0610/1
VIM 01MIA Etrernic AMo Powra CoxPANY TO The installation of the generator breaker on Unit I creates an additional independent source of offsite power from the transmission network to the onsite power distribution system, analogous to the Reserve Station Service system, which is not dependent on the mode of operation of the Unit 1 generator. In addition, the Unit 2 Normal Station Service system can be considered an additional independent source of offsite power from the transmission network to the onsite distribution system. This source, however, is dependent on the mode of operation of the Unit 2 generator.
The installation of the normal to emergency bus ties establishes an additional, physically independent source of offsite power to each emergency bus. Each emergency bus will now have two physically independent sources of offsite power in addition to its respective onsite source. All of the normal to emergency bus ties have a normally open breaker at each bus.
The bus ties will operate as follows:
On either degraded voltage or lots of voltage, an emergency bus will transfer from its normally connected RSST to the assigned Normal Station Service bus, provided that bus is available (voltage present) and electrically acceptable (no faults, etc.).
This transfer will be initiated and completed during the interval between the diesel generator start signal (degraded voltage, loss of voltage) and its designed closing time to the emergency bus.
If this transfer is not completed in this interval, the transfer will be aborted and the diesel generator will load to the emergency bus as designed.
To verify our computer model and to ensure the* our voltage analysis results are valid, we performed a voltage profile test, 1-ST-9, in which Unit 2 station service loads were transferred from the normal SST's to the RSST's, after which a charging pump was started on Bus 2J.
System voltages, RSST load tap changer (LTC) positions, and 4.16 KV (emergency and normal) and 480 volt (emergency) bus voltages and currents were recorded. The system voltages, RSST's LTC positions, and the bus current values were input into the computer model to calculate bus voltages. Attachments II and III are a tabulation of the recorded and calculated values after the transfer from normal SST to RSST and during the charging pump start, respectively. The largest error is 4.0%.
These results justify the use of our computer model in predicting voltages j
during worst case analysis.
l We have reviewed our electrical distribution system to determine its I
compliance with GDC-17 and whether or not any etents or conditions exist which could result in the simultaneous or consequential loss of both required circuits to the offsite network. The design of our offsite power supply is in full compliance with GDC-17. We have completed some minor modifications to comply with the requirement concerning the simultaneous or consequential loss of both offsite sources.
These modifications are indicated on Attachment IV.
The first modification concerned the 34.5kv tie breaker between the two 34.5kv buses which supply the redundant offsite power supplies. This tie breaker would normally be open and would be automatically closed upon the loss of supply power to either 34.5kv bus.
However, to eliminate any possibility of simultaneous loss of both offsite sources due to tie breaker failure, we have incorporated operating procedures to leave both 34.5kv disconnects open (one disconnect is installed one each side of the brerker). The automatic close feature is removed and manual closing is required.
jdm/0610/2
Vraotx1A EtzcTaic Axp Powsm Courm to The second modification involved the switchyard service transformers.
Each of these 1500KVA transformers can supply the entire switchyard load. The primaries of these transformers are connected to each 34.5kv bus and the secondaries are routed in a common cable through manual throwover switches.
The purpose of the throwover switches is to allow the loads to be transferred to either_ transformer.- In order to eliminate the possibility of simultaneous loss of both offsite sources, switches have been installed in the secondary leads of both transformers and all the secondary leads of one of the transformers have been removed from the common. trough and installed in conduit. The new switches are operated such that only one transformer source will be available at the throwover switch at any time.
We have completed our steady state equipment overload analysis and equipment rating determination (with the exception of motor operated valves as discussed later in this letter). These results are currently being reviewed.
The current and voltage analyses are being conducted in accordance with our interpretation of item 2 of the " Guidelines for Voltage Drop Calculations" which was attached to our letter to you dated August 8,1979. The interpretation is as follows:
In the analyses of voltage conditions available from the Reserve Station Service System, we are assuming that the worst case would be for Unit 2 to have all of its loads on the reserve, while Unit I has only its SI activated safety loads and intake structure loads on the reserve. We are able to rake this assumption on the basis that Unit 1 now has a generator breaker which provides the capability of tripping the unit without transferring loads to the reserve system.
We feel that the " accident" or the " anticipated transient in the unit being analyzed" discussc J in item 2 of the above reference, does not include the occurrences that would cause Unit 1 to transfer loads to reserve at the same time that Unit 2 is fully loaded from the reserves.
Our analysis includes conditions with the emergency buses fed from the 1) i reserve station service system, which is the normal mode of operation, 2) j normal station service system, and 3) combinations of the two alignments.
I j
Presently, our voltage analysis is incomplete. Our major problem has been ensuring that the motor operated valves (MOV's) which receive either a Safety Injection (SI) or a Containment Depressurization Actuation (CDA) signals have sufficient voltage to start and complete the valve movement. Initial investigations by our consultant indicated that the MOV's were rated for starting and running to a minimum of 90% of their rated voltage. Further investigation has shown that our consultant has a record of verbal indication from the MOV manufacturer that a majority of the MOV's in question are rated at 80% voltage for starting. We have contracted with the MOV LMnufacturer to verify starting voltage ratings on all MOV's required to operate for an SI or CDA. The majority of voltage analysis which we have completed to date have been directed at supplying the MOV's with 90% voltage for starting in a time frame which ensures they will accelerate prior to the operation of their overload relays. Consequently, we cannot make a complete GDC-17 submittal at this time. We realize this does not meet the December 1,1981 submittal date to which we previously conaitted. However, it is necessary to determine a correct MOV rating prior to concluding our ana!ysis.
jdm/0610/3 g
.c VInotx1A ELECTRIC AMD POWER COMPANY TO i
We are presently continuing our analysis on the basis that the MOV's will be rated for.80% voltage starting. This is in a parallel path with the MOV vendor evaluation, which we are expediting.
Assuming a timely response from the MOV vendor, our final submittal,
]
including equipment ratings, assumptions, results, and identification of any required modifications, will be made by February 28, 1982.
4 Please contact us if you require further information prior to our final submittal.
%O
(-
R. H. Leasburg At ta chments
- cc: Mr. J. P. O' Re illy, Director Office of Inspection and Enforcement Region II i
i 4
i i
i jdm/0610/4 L
hg t'8 l
y
~
L_
n N
q ).
\\
u!
gtS4 ga.tQ.y i t t o 2
y S
- g8 5 g e d' ly.
1 Mg d
.i ' t t
t i.
yGU 4ga l
m.
5p a.~y g
3 r
u p
s
~
7wA s
o7D0a 0
0t n
t Np.
S qvpOase C p lJ,n sa D
Rt.
4 gt.te s u6 gt Gti 4
2 l
M n
9 tG 1
d g
2 O
D A
j O
e
. N 9 D 2
i u
m h
OC t
J g
2 D
0 5
O t
l LH Q
d F
i p
9 g
g C
i i
S i
U
_d I
N 0
n
\\
9 T
E OfA
/
6 Tw n
r M
S H
C CAT i
T 0
D B
\\
A 9
9 OYA Tw W
/
_.~
E S
B t
0 D
N
_9 OYA 6
Tw U
/
D S
A 1
I S
R n
Q g
Q C
I C
N n
i i;
g G
0 0
e g
e ed I
h l
B ts i
n G
D i
y h
g g
u a
A s
p s
u 7
x p
S U
,nt M
, i A,
n atn R.
yCu g
3 c
D D
0t 1aA W
e S
Page.1 of 2
~
ATTACHMENT II.
NORTH' ANNA r.
CASE 1-ST-9-A CONDITION: 0.5 seconds after load transfer; before motor start
% ERROR (V V )
R C RECORDED VALUES COMPUTER CALC VALUES BUS --
- ----AMPERES - --
VOLTS-VOLT 5-
-(
VR.)
100%
1H 228 4060 4043 0.4%
1J 264 4095 4064,.
' O. W.
I 1G 1200 4078 NC
+
2H 312 4025 4032
-0.2%
2J 132 4130 4043 2.1%
(POWER FACTOR =
.91) 2G 1120 4113 NC 2A 1200 3885 4039
.-4.0%
_(POWER FACTOR =
.89) 2B 1640 3850' 3994
-3. '/%
2000 3938 3977
-1.5%
4 2C
'3239/39
F Page 2 of 2
% ERROR RECORDED VALUES COMPUTER CALC VALUES (V V )
R C BUS
- -- -- AMPERES
- VOLTS
-VOLTS
(
VR - )
100%
480 VOLT 2J 64 468 464.8 0.6%
I 480 VOLT 2H 122 Nh0 467.2
-1.6%
34.5KV BUS 4 NR 36119 NC 500 KV AR 522 NC
= Amperes at 4KV NR = Not read NC = Not calculated
'?39/40
i 00 1
8 5
1 3
1 2
1 3
0 1
R)
)
O C RV R
?
0 0
3 0
R -
V s
E g V
%(
(
S E
UL A
V C
A 9
4 2
9 9
4 5
L C S 9
6 C
3 9
C 3
9 8
T 8
0 N
0 8
N 0
9 8
R L 3
4 4
3 4
3 3
E O J
T V 2
U P
s M
u O
b C
no p
mup g
I n
I i
I A
B g
N N
9 a
0 0
8 5
5 0
5 0
5 T
N r
A h
S 9
6 7
2 2
6 2
9 5
T c
T 9
0 0
0 0
0 0
9 9
H H
S L
3 4
4 4
4 4
4 3
3 E
M C
T t
O A
R 1
r V
T O
a T
N E
t S
s A
A S
C E
r U
e L
)
)
f A
7 9
6 8
s V
na D
r E
=
t D
=
R d
O R
R a
C O
O o
E T
T l
R C
C A
A r
F F
e t
R R
f S
E E
R 8
4 0
2 1W 0
0W 0
6 a
,E d
E 2
6 0
1 0O 2
0O 0
5 n
P 2
2 2
3 7P 1
2P 6
8
(
1 1(
1 1
1 o
M c
A es 0
1 1
N O
0 I
8 T
4 I
3 D
O U
H J
G H
J G
A 8
C
/
N S
C B
I I
1 2
2 2
2 2
2 W
2
~f i
o 2
e g
0 a
0 P
1 5
5 R}
)
O C HY R
2 2
H ~
V E RV
%(
(
SE LLAV C
L 4
2 AC S 8
7 C
C T
4 6
N N
R L 4
4 E O T
V UPM O
d C
e ta luc lac to N
0 6
9 2
=
S 6
5 1
2 T
4 4
1 5
C L
6 N
O 3
V SEULAV 0ED V
R K
O 4 d C
a E
t e R
ar st eo rN S
e E
p=
R 4
4 6
2 R
R m
n 1
N N
AW iA 4
J H
2 2
SU 2
T T
B
/0 L
L O
O V
V 8
V V
K K
43 5
0
/
S 0
0 U
8 8
4 0
W B
4 4
3 5
<:: w n,sec s.s 7"o s >st:.;e r.:w.'?
.: ra rio a.> n sic y sv.w< rd AdwA
. : :- a r,8yAap go, ATTACHMENT IV Se **; / Bas ]
N
~
f_ 3tS.e-/ 1;.: -
4 oP.fd DJS a - M f G ~~Z o s1 BOTH J c.
T35 sde LLJ.)
Loll
.fflB fTT' I
l l
l l l 8
,,as, u I/ l/
s e..:rp oise,,.iec, u. a-w s.s 7; w a:-
,r - - - - - { - - - -
csw l
l g
l
)
,qdD ros.::
Y""*
i es rm mee-
<=/ dig 3 /~A'em C/842' l
,1 i
r neouas to.ran r.c
,7 q r
ErC6/- Ccap uj -r-l-_/
i I
I I
I I
I I
r_a,-
I l
9 o'
o C
O~
!.O MO O
ai q
e l
l I
a l
I l
e__
s I
i I
rn ~oe s-,ra a.r 9
c:
o q
MC 3
C OH l
l e
e c
c:
I L_ _..
_t I
L_______
r.
& Dircoww-swirms :
t s s oem rso rs,wos ur.c cos rscrs YO ES C / hie MD s& L t.
e PE/J CA:.
.44l CL c.5~J-4 s97 Q fa*D-
~
Nore:
/J. C. = A/02 MALL Y ope 79 0/48 => 2fo)zo vc?i.7 pi572/B0 T/st! PMEL i~oR SWITCH)'ARD LOADS
,,,