ML20207G061
| ML20207G061 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/17/1986 |
| From: | Sieber J DUQUESNE LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-86-003, IEB-86-3, NUDOCS 8701060308 | |
| Download: ML20207G061 (7) | |
Text
.
/
t-
$VL
'Af Telephone '4? 2) 3516000 Nuclear Group P.O. Box 4 December 17, 1986 Shippingport, PA 15077-0004 r
U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Attn:
Dr. Thomas E. Murley, Regional Administrator Region 1 631 Park Avenue King of Prussia, PA 19406
Reference:
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66
/
IE Bulletin 86-03 Gentlemen:
By letter dated November 14,
- 1986, we provided you with the results of our review which addressed the concerns of I.E. Bulletin No.
86-03, Potential Failure of Multiple ECCS Pumps Due to Single Failure of Air-Operated Valve in Minimum Flow Recirculation Line.
We also indicated that we were continuing our review with respect to single-failure vulnerability during other accident scenarios' assuming i
various plant configurations and requested a 30-day extension for i
providing a
follow-up report to close out this action.
The purpose l
of this letter is to provide you with our follow-up report.
The attached figure shows the ECCS flowpaths and~ components pertinent to this report.
The BVPS-1 ECCS is comprised of both low l
head and high head safety injection systems.
The minimum flow recirculation lines for both the lowhead cafety injection (LHSI) and the highhead safety injection (HHSI) pumps contain motor-operated valves (MOVs) in series to ensure isolation of these lines.
The normal system arrangement for these valves is open and they cre designed to fail in the "as is position".
t The LHSI pumps recirculate water to the refueling water storage tank (RWST) during the initial LOCA injection modo of operation with RCS pressure above the LHSI shutoff head.
Upon switchever to the recirculation mode, the LHSI pumps will be aligned to take suction on the containment sump and discharge to the cold legs of the reactor coolant system (RCS).
During the switchover, the MOVs in the minimum flow recirculation lines also receive an automatic signal to close.
This action protects the RWST from possibly becoming contaminated by the recirculated water from the containment sump.
A simultaneous signal is sont to open valves realigning the HHSI pumps suction to the discharge of the LHSI pumps.
This ensures a continuous LHSI pump i
discharge flow path even if the reactor coolant pressure is still relatively high (i.e., a SBLOCA).
Because of this alignment to the gj{$$h$o334 87010 PDR PDR I
t 0
[I l
J
N:nvar Valley Powsr Station, Unit No. 1 Dock 3t No. 50-334, Licensa No. DPR-66 Page 2 suction of the HHSI
- pumps, the LHSI pumps are provided with an alternate discharge flow path and we
- believe, therefore, are adequately protected from operating in a deadheaded condition.
The HHSI pumps take suction on the RWST on an SI signal and discharge to the RCS during the injection mode of operation.
Since the HHSI pumps also function as the RCS charging pumps during normal power operation, their normal suction and discharge flowpaths are isolated upon SI actuation.
The MOVs in the minimum flow recirculation lines of the HHSI pumps do not receive a SI signal but require manual closure after SI actuation and prior to reaching the reactor coolant pump trip setpoint.
The SI initiated automatic closure signal was removed from the HHSI minimum flow recirculation valves and the Emergency Operating Procedures instructions for their manual closure and opening were provided as a result of our review and evaluation as required by I.E.
Bulletin No.
80-18,
" Maintenance of Adequate Minimum Flow Thru Centrifugal Charging Pumps Following Secondary Side High Energy Line Rupture".
Additional details of our response to Bulletin No. 80-18 can be found in our submittal dated September 24, 1980.
This configuration was also found desirable during solid water pressurizer operation in the shutdown modes in mitigation of overpressure events.
The resultant modifications to equipment and procedures were also determined necessary to insure the availability of adequate minimum flow under all FSAR accident transient analyses.
In particular, secondary high energy line breaks were considered since it is this type of break which could cause either a RCS cooldown or heatup depending on its
- size, location and the plant operating conditions at the time of the break.
Since the BVPS-1 HHSI pumps are designed to pump against heads normally encountered during power operation, the issue of deadheading these pumps or operating them under inadequate minimum flow becomes one of considering relatively high RCS pressures concurrent with SI actuation and isolation of the HHSI minimum flow.
Since the valves in the minimum flow lines are normally open, the isolation of these lines would only occur if RCS pressure decreased sufficiently to require manual closure of the valves prior to an RCS l
repressurization.
- Morcover, for this repressurization to cause inadequate minimum flow conditions, the RCS pressure must increase to the pressurizer safety valve setpoint (i.e., no credit taken for the pressurizer power operated relief valves or pressurizer spray valves in terminating the pressure increase).
We have reviewed the BVPS-1 UFSAR Chapter 14 Accident Analyses relevant to the concerns of Bulletin No. 86-03 and those above.
We have determined, for the secondary side high energy line break accident which assumes the worst case single failure and RCS heatup, that the RCS pressure remains above the value for which the Emergency Operating Procedures (EOPs) require that the minimum flow valves for the HHSI be closed.
Therefore, a major rupture of a main feedwater i
'anysr Vallcy Powsr Station, Unit No. 1 B
Dock 3t No. 50-334, Licensa No. DPR-66 Page 3 pipe does not require closure of these valves prior to RCS pressurization to the pressurizer safety valves setpoint.
This precludes operating at a
deadhead condition for the HHSI pumps for the UFSAR feedline break analysis.
The initial depressurization following the initial pressure increase, shown in the UFSAR for this
- accident, is to a minimum value slightly higher than 2300 psig in the pressurizer.
The EOPs require the miniflow valves to be open when the RCS pressure is greater than 2000 psig.
We have also reviewed the UFSAR secondary side high energy line break for' which there is an RCS cooldown and SI actuation.
We have determined that the RCS depressurization would require the HHSI minimum flow valves to be closed.
However, the RCS repressurization transient as shown in the UFSAR is less severe than the one above for the feedline break and does not indicate that it will be necessary to immediately reopen the valves in order to preclude deadheading the HHSI pumps.
- Finally, we have determined that there is-no potential for deadheading the HHSI pumps or operating them under inadequate minimum flow conditions for either the UFSAR small or large break LOCAs for which there is a
valid SI actuation.
These accidents indicate RCS pressures remaining low enough to assure continuous HHSI flow and break flow'would assure that minimum flow requirements were met.
During the review required by Bulletin 86-03, we examined conditions beyond those for the BVPS-1 Chapter 14, UFSAR accidents for which the potential of deadheading the ECCS HHSI pumps might exist.
We postulated the occurrence of accident conditions for which the RCS pressure would initially decrease below 2000 psig and then, due to an RCS heatup, would cause repressurization of the RCS to the pressurizer safety valve setpoint of 2485 psig.
This accident is postulated to be a
secondary side high energy line break which combines the effects of an RCS cooldown with a
subsequent RCS heatup.
The net effect, relative to the concerns of Bulletin 86-03, would be to assume manual closure of the minimum flow valves, an assumption that they cannot be reopened, and the RCS repressurizing to the shut-off head of the HHSI pumps.
This hypothesized scenario results in the HHSI pumps experiencing operation under deadheaded conditions.
In crder to address this postulated condition, we are evaluating the following backup instructions for inclusioncin the BVPS-1 EOPs should 'the operator discover that the miniflow valves cannot be opened from the control room when required.
The' operator should attempt local manual operation of the MOVs if it can be performed safely.
(It is noted that this and the following action would be explicit although we believe 'the operators would by virtue of their training currently attempt such, actions.)
~
Besvar Vclley Powar Station, Unit No. 1 Dockot No. 50-334, Licensa No. DPR-66 Page 4 Use the reactor vessel head venting system to open a discharge flowpath'through the PCs for the HHSI pumps.
Attempt to restore operability to the pressurizer power operated relief valves and their associated block valves.
We will be presenting the above EOP action to the WOG for their evaluation in accordance with requirements of our Precedures Generation Package which dictates that revisions of this type be i
controlled in this manner.
In the
- meantime, we are providing instructions to our operating shifts of the above concerns and the l
proposed measures to recognize and mitigate the concerns.
Based on the information submitted herein, we believe that the concerns of Bulletin 86-03 have been adequately addressed and BV-1 is
.not succeptable to the scenario as described in the bulletin..This conclusion was documented in our letter dated November 14, 1986.
Furthermore, our review of UFSAR accident scenarios indicates that the potential for deadheading the HHSI pumps is not anticipated due
.to the expected RCS pressure response during the transients.
- Lastly, the hypothesized scenario does not consider the actual plant response because it does not take credit for:
pressurizer PORV's pressurizer sprays high pressurizer pressure reactor trip safety injection, charging and letdown availability of offsite power two phase flow from the line break imme.ato auxiliary feedwater flow upon loss of the main feed pumps.
steam generator low level coincident with feed flow mis-match reactor trip We believe that the realistic approach to the hypothesized accident would result in the plant responding in such a manner that i
the potential for deadheading these pumps is not considered a likely event.
Operator response to the transient following the EOPs would result in SI flow reduction sequences as appropriate and protect the l
HHSI pumps.
The evaluation as described above in providing back-up instructions to the operators is considered another step in a
defense-in-depth approach to protecting these pumps.
If you have any questions on this submittal, please contact either myself or members of my staff.
Very truly yours,
.4A.J.
J. D. Sieber Vice President Nuclear Operations w--,
,..,--,,.,._,,,..,,,-,,,,,,.,,,,,,r.,_,,,_
~, _ -, - -
-,v.,
._,,-,a-,.,w.---
'Bacvar Valley Powar Stction, Unit No. 1 Docket No. 50-334, Licnnse No. DPR-66 Page 5 cc: Mr. W. M. Troskoski, Resident Inspector U. S. Nuclear Regulatory Commission Beaver Valley Power Station Shippingport, PA 15077 U.S. Nuclear Regulatory Commission c/o Document Management Branch Washington, DC 20555 Director, Safety Evaluation & Control Virginia Electric & Power Company P.O. Box 26666 One James River Plaza Richmond, VA 23261 i
,l llll i
,l l,
j l
4 EN
?
IL T
E S
N ET 6
IL 6
T 1 -
S W
R ET O
3 A tP L
7 6 iD B
3 8 F
n
- 8 W
M N
H -
U I
o I
U A
C S O
,N L
M R
N T V V n
I F
O O oe M
M Y
is I
U L
M M tn M
P N
P ae I
U tc IM S
Si r
L R
E C.
re, W
B, w43 O
A C
o30 3
P 5
5 P3 -
V 7
7 8 6
3 A
2 8
O 4
y08 6
M_C e5 N
H I
C S l
n I
A l.i
=
R V V aot T O O VNe M M l
rtl S
eeu P
vkB M
C U
ac 1
P eoE BDI
+
NG I
H G
C R
g A
B l
H 1
C 9v P
/
- S N
C O
I L
P t
T 6
I S
M E
'7 T
U N
M 2
C P
H E
M C
J N
I I
N O
I I
C B
T A
1 Y
C C
E T
T s
J P
E a
N T
F s
A 3
g H
A i
I C
S S
YT D
E A
F E
A g
H A S 1
3 H
- D 6
G P A 7
I v
E 2
H H
S H t
(
C A
W sa O
gS A
l L
s[
1
-P Q
9(I HC
~Dv es O a u
ls A
V 5
kN O
7 2
M H
C S
S P
S ;
P
" c O
P O
O : O L
O O
L L
O P
G G
E M
E G
E L
R U L
E L
T O S L
D D
O S T
1 L
T L
H P M C T O
O O
O O A N O O R E O C
H C
T L F R C O
O 0
T T
h
\\
\\
l l
i
.