ML20053E789
| ML20053E789 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/07/1982 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.02, TASK-2.K.3.17, TASK-TM NUDOCS 8206100091 | |
| Download: ML20053E789 (11) | |
Text
- _ - _ _ _ _ _
l BALTIM ORE GAS AND ELECTRIC CHARLES CENTER.P. O. BOX 1475. BALTIMORE, MARYLAND 21203 ANTHum C. LUNDVALL. JR.
Va(C Patssot NT June T, 1982 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attn:
Mr. R. A. Clark, Chief Operating Reactors Branch #3 Division of Licensing
Subject:
Calvert Cliffs Nuclear Power Plant Units Nos. 1 & 2; Dockets Nos.50-31T & 50-318 Response to NUREG-0737 Items II.K.3.2 & II.K.3.17
Reference:
(a) Letter from R. A. Clark to A. E. Lundvall, Jr.
dated 1/20/82, same subject.
(b) Letter from A. E. Lundvall, Jr. to R. A. Clark dated h/13.82, same subject.
(c) Letter from A. E. Lundvall, Jr. to D. G. Eisenhut dated h/26/82, same subject.
(d) Letter from A. E. Lundvall, Jr. to R. A. Clark dated 5/13/82; TMI Action Plan Item II.K.3.17 Gentlemen:
This letter supplements our previous submittals in response to Reference (a) (references (b), (c), (d)). All remaining information requested is provided as an attachment to this letter.
Please note that references (b) and (c) apply to Calvert Cliffs Units 1 and 2, Docket Nos. 50-317 & 50-318. If you have any further questions on this subject, please do not hesitate to contact us.
Very tr
- yours, c m
. ys Attachment ec:
J. A. Biddison, Esquire G. F. Trowbridge, Esquire Messrs.
D. H. Jaffe - NRC R. E. Architzel - NRC wawm P
1 ATTACHMENT Response to Request for Additional Information NUREG 0737 Item II.K.3.2 1.
Q) Provide a justified estimate of how many multiple PORV openings per transient could be expected with each initiator event.
A) Only one PORV opening is expected during a pressurization event in which the PORV's are actuated. As described in Section 3.9 of CEN-lh5, the coincidence of the PORV opening setpoint and the high pressure reactor trip at approximately 2h00 psia on the Calvert Cliffs Nuclear Power Plant insures that the reactor is shutting down as the PORV's are opening, if not before. By the time the PORV's blow down to the reset pressure, the typical post-reactor trip pressure reduction is noted in the licensing and analyses of FSAR pressurization events.
It should be noted that a more realistic best estimate analysis of the pressurization event,
described in CEN-128, " Response of CE NSSS to Transients and Accidents," indicates that PORV's are not challenged when the pressure reduction due to systems such as pressurizer spray and turbine bypass are considered.
2.
Q) The safety failure rate calculated in CEN-lh5 should have taken into account the effect, if any, of the additional challenges to the safety valve when the PORV is blocked intentionally.
If this has not been done, recalculate the safety valve failure rate using the above criteria.
A) As noted above, several plant systems besides PORV's operate to reduce plant pressure preventing safety valve actuation. These include the high pressure preventing safety valve actuation. These include the high pressure reactor trip, turbine trip on reactor trip, i
pressurizer spray, and turbine bypass. Analyses indicate that these systems are effective in preventing challenges to the primary safety valve and, therefore, no additional safety valve challenges would be expected due to the intentional blocking of PORV's.
3.
Q) Submit an analysis of the probability of a small break LOCA caused by the stuck-open safety valve using the calculated safety valve failure rate.
A) Attached.
l
\\
l
i
)
LEGEND l
Figure 1 Assumptions:
1.
Given RCS pressure increase which does not challenge PORV, it
(
vill challenge SRV which is subject to premature operation.
i 2.
Even though reactor trip may occur, if PORV is challenged and 1
fails to open, the SRV vill be challenged.
3.
If PORV is challenged and operates (opens) successfully, no i
challenge to the SRV vill occur (not true for ATWS events).
h.
Multiple openings do not occur (see response to Question 1).
5 Only one SRV will open due to setpoint drift, while both PORV's open on a legitimate demand.
Data:
j High RCS Pressure: 1 per year (IREP Table'C.3.2 for CE Plants)
Challenge PORV's given that RCS High Pressure occurs:
0.1 (IREP Table C.3.2 for CE Plants) i Figure 2 Data:
Failure - Porv to Open, given signal - 3E-3/ demand (IREP p.7-9, Table 7-1).
PORV Blocked Closed - because of infrequent operation and short detection intervals, no analysis performed. Estimate unavailability of lE-3 per valve as conservative. Neither Neither PORV commanded open - see Figure 3.
Figure 3 i
Data:
Failure - Relay to Energire: lE h (IREP Table 7-1).
Failure - Contacts Fail Open: 3E-7 (IREP Table 7-1).
~
LEGEND Continued Figure 3 (continued)
Failure - Aux Logic (2/h): Estimate 1E-5 as conservative.
Failure - Loss of 125 VDC: Estimate from NUREG-0666 p. 37 (Probability of DC bus Failure) x (Mean Failure Exposure Time) x (1 + Demand Probability) < lE-6 Minimum Cut Sets:
(Loss of 125 VDC at 1C06) + (RPS hux Logic Failure) + (63X -1102 Coil Fails to Energize) + ((HS lh02 Contacts Fail Open) + (h2 (Sch 1Blhh9) Relay Fails to Energize)) * ((HS lh0h Contacts Fail Open) +
(h2 (Sch 1Bohh9) Relay Fails to Energize))
Figure h Data:
Safety Valve (PWR) FaiF close: 3E-3 (Table 7.1, IREP) (given that it is open).
Figure 5 Data:
SRV Fails to Open:
3E-3/ demand (IREP Table 7.1)
Figure 6 Assumptions:
- Both SRV'e are open - since the setpoints for each are different, there is a high probability that only one vill open during the transient, meaning that the other is already closed. For simplification, this is ignored.
Data:
SRV Fails to Reclose, given that it is open:
3E-3.
(Table 7.1, IREP)
The value for BWR primary safety valve should approximate the code safety valve failure rate better than that given for PWR since " Fail to Reclose" is based on B&W PORV's.
I
p
/
LEGFND-Continued
/
Figure 7 Data:
Failure - SRV Opens Prematurely: From Table 7.1, IREP (SRV Standby Failure Probability ) x (Mean Failure Exposure Time) = 2E-2 A more realistic assessment was performed by C-E.
This value was found to be approximately one order-of magnitude too high based on operating -
experience data.
Figure 8 Data:
s See Figure I.
4
?
3 u
t Y
s t
s
?
l 1
a
,1 s
.I t
/
[
l SM Al.L LOCA AS A RESULT OF S RV's Fall TO RECLOSE
^l
/
TRANSIENT-CHALLENCIS ISRV PORV PORV SLOCR 3RV SRV OUTCOME HI RC$ PRESS PORvi OPER RECLOSE CLOSED OPEN RECLOSE FICfl0M i
a s
t a
.994 NO LOCA q
.9999 i
.99
- j NO LOCA 1
GE-3
/
gg.g POR Y LOCA g,
$RV LOCA (SE-8) l PER YEAR 9E-6 NO LOCA
/
/
/
NO LOCA 4E-2 3E-3 O.9 SRV LOCA
- 1. l E 4 i
ho LOCA FIGURE I i
/
. -%. s IE-4 BOTH PORV'S Fall TO OPEN NEITHER PORV GIVEN SIGNAL SOTH PORV's E
COMMANDED BLOCKED N I NE OPEN l PORV OPENS CLOSED n
O I
I I
I GIVEN SIGNAL GIVEN SIGNAL N'll PORY N'12 PORY N*ll PORV N'12 PORY DLOCKED BLOCKED FAILS TO OPEN FAILS TO OPEN CLOSED CLOSED LF LF LF LF 3E-3 3E-3 IE-3 IE-3 FIGURE 2
4 IE-4 NEITHER PORV COMMAND OPEN o
LOSS OF LOSS OF SIGN AL TO SIGNAL TO PORV il PORV 12 (b
(b HS I402 4 2 RELAY 63X-180 2 63X - 110 2 42 RELAY HS 1404 CONTACT S FAILS TO CONTACTS l-2 CONTACTS 3 4 FAILS TO CONTACTS Fall OPEN ENERGl Z E FAllTO CLOSE Fall TO CLOSE ENERGlZ E Fall OPEN 8
8 8
8 rs n
s
,E..
,E.T
,E.,
,E..
l LOSS OF RPS AUX 63 X - IlO 2 63 X-IlO 2 RPS AUX LOSS OF 125 VDC LOGIC FAILS COIL F AILS COIL FAILS LOGIC FAILS 125 VDC AT ICO6 2 /4 TO ENERGlZE TO ENERGlZE 2/4 AT ICO6 O
8 8
8 8
O BE-6 IE-5 IE-4 IE-4 IE-5 IE-6 FIGURE 3
1/2 PORV'S Fall TO RECLOSC SE-3 I
I N'll PORV N'12 PORV FAILS TO FAILS TO RECLOSE RECLOSE LF LF 3E-3 3E-3 FIGURE 4 BOTH SRV'S Fall TO O PEN l
l 9E-6 l
I I
N* ll SRV N *lE SRV FAILS TO OPEN FAILS TO OPEN l
LF LF 3E-s 3E-s FISURE 8 l
l
T t/2 SRV'S Fall TO RECLOSE SE-3 NS Il SRV N* 12 SRV FAILS TO FAILS TO CLOSE CLOSE 8
8 3E-3 3E-3 FIGURE 6 1/2 SRV'S OPENS PREMATURELY ew 4E-2 N* 11 SRV No 12 SRV OPENS OPENS PREM ATURELY PREMATURELY O
O 2E-2 2E-2 i
FIGURE 7 I
I 1 SRV FAILS TO RECLOSE 8
3E-3 FIGUR E 8 e
y,.
7
,-... - -.