ML20011A794
| ML20011A794 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 10/27/1981 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0611, RTR-NUREG-611 NUDOCS 8111030222 | |
| Download: ML20011A794 (6) | |
Text
/
Commonwealth Edison s
/
) ona First National Pitza Chicigo, libnois I,
7 Address Reply to: Pos' Off ce Box 767
\\s
,/ Chicago Illinois 60690 October 27, 1981 Mr. Harold R. Denton, Director thf <
Of fice of Nuclear Reactor Regulation
~
- 9, s g
U.S. Nuclear Regulatory Comraission d[
/l C
Washington, DC 20555 UL j
}
- Noyog 7gg $l\\
I Suoject:
Byron Station Units 1 and 2
- ge %,,
Braidwood Station Units 1 and 2 Y
[
Responses to FSAR Questions e.
3l h. M NRC Docket Nos. 50-454, 50-455,
' /
50-456 and 50-457 Reference (a):
September 18, 1981, letter from T. R.
Tramm to H.
R. Denton.
Dear Mr. Denton:
Tnis is to provide additional information regarding the reliability of the Byron /Braidwood auxiliary feedwater system.
It supplements the response to FSAR questions 010.53 provided in reference (a).
Attachment A to this letter presents revised reliability estimates for the Byron /Braidwood auxiliary feedwater system.
These revised estimates incorporate the data and methodology of NUREG-0611 to conform with the requirements of SRP Section 10.4.9, Rev. 2 (July 1981).
One (1) signed original and fif ty-nine (59) copies of this letter and the attachment are provided for your use.
Please address further quesions regarding this matter to this of fice.
Very truly yours, Yb p
T. R.
Tramm Nuclear Licensing Administrator I
QoO cc:
Ioannis Papazoglou, Brookhaven Nat'l Lab.
5 1m
/ [
2766N 9111030222 011027 PDR ADOCK 05000454 A
ATTACHMENT A Recalculation of Byron /Braidwood Auxiliary Feedwater System Using Methods and Data in NUREG-0611 and NUREG-0635 Summary of Results Assuming statistical independent estimates, the unreliability for the Byron /Braidwood (B/B) auxiliary feedwater system ( AFWS) was calculated using methods and data presented in NUREG-0611 and NUREG-0635.
The results are as follows:
Unreliability per Demand Initiating Reliability Block Fault Tree Event Diagram (RBD)
(STADIC-II Code)
LMFW(I) 3.4E-6 3.0E-6 LOOP (2) 9.0E-5 8.9E-5 LOAC(3 1.lE-2 1.2E-2 The acceptable range per NUREG-0800 (Rev. 2 - July 1981), Section 10.4.9 is 10-4 to 10-5 per demand.
The LMFW and LOOP initiating events are cithin these acceptable limits.
Discussion NUREG-0800, Rev. 2 - July 1981, Section 10.4.9 states "an acceptable AFWS should have an unreliability in the range of 10-4 to 10-5 per demand based on an analysis using methods and data presented in NUREG-0611 and NUREG-0635."
The key words are " data presented in NUREG-0611 and.
This places definite bounds to the analysis.
The Byron Units 1 and 2, Auxiliary Feedwater System Reliability Analysis Report, GA-C16444, (henceforth ref erred to as "the report") was perf ormed before NUREG-0800 was issued.
The unreliabilities estimated in the report are based on the following assumptions, which are over and above the NUREG-0800 ground-rules:
1.
Automatic start, only, because of the NRC " hands-off" policy for the first 30 minutes.
2.
addition of a. motor breaker or motor starter for each motor cperated component.
(1)LMFW - Loss of main feedwater
.(2) LOOP - Loss of off site power (3)LOAC - Loss of AC power
c-1 E
i Recalculation'of B/B AFWS Page 2 3.
A f ailure to start on demand of the diesel driven AFW pump of 1 X 10-2 (including local controls).
4.
Addition of the diesel / generator failure to start on demand (3 X 10-2 for the LOOP-initiating event.
Table 2.1. (Page 2-4) and Table 4.3 (Page 4-14) in the report reflect the above assumption.
The bottom set of values.on Table 4.3-are based on-the assumption of automatic start with manual backup.
Elimination of the added assumptions 1 through 4 above, which are over and above those of NUREG-0611 and NUREG-0635, and recalculation of the unreliability or unavailability have resulted in the values shown on Table l~and Table 2.
Figure 1 presents the uncertainty curve for the t-three initiating events.
1 i
0 h
I l
t 4
0829b
~...
.. ~..
Table 1 0611 Data Ctatistical Independent Estimate (from RBD*)
Unavailability (I) of. AFS to start & provide AFW to > 2 SG's per. emand Frequency j
per year Initiating Event Hardware.
Test Maint.
Human Error I per demand I per year.
3
'MFW l.0E-6 1.8E-9 2.4E-6 2.8 E-10 3.4E-6 1.0E-5
.02 LOOP 2.8E-5 5.0E-8
- 6. 2 E-5 2.4E-9 9.0E-5 1.8E-6 5X10 '
LOAC
.5.5E-3 1.0E-8 5.8 E-3
- 2. 9E-7 1.lE-2 5.5E -
II.7E-5 7
4
- RBD - Reliability Block Diagram & Manual'. Calculation
/
}
4 y
4 u
i I
Table 2 0611 Data (Media Values)(from Fault Tree *)
3 Independent Random Failures Init. Event Event Freq./Yr A per demand A per year
-l
-6
-6 A
LMFW 3
3.0x10 9.5x10
-5
-6 LOOP
.02 8.9x10 1.5x10
-2
-6 LOAC 5x10 1.2x10 5.7x10 With Common Cause Failures Init. Event Event Freq./Yr I per demand A per year
-5
-5 LMFW 3
1.7x10 5.1x10
-6 LOOP
.02 4.3x10 7.5x10
-2
-6 LOAC 5x10 1.2x10 5.8h t 'l 4
i
- "STADIC - II" Code (Ref. 11 in Report)
~
'\\
l
BYRON /BRAIDUOOD AFS c
o 1.0 s.
1 n
P I
LMFW L
4 I
i 4
M 0.8-j LOOP 4
e N
I LOAC i.
T A
I R
t y 0. 6 -
'g I
-c
~
(A, -
I.
U n
g
- 0. 4 -
s I
D
'g I
I, S
g T
j R 0. 2 --
\\
I B
\\
n U
\\.
T i )iiim I 0.0
-8, i i i ii,,, 7, isiim) 6i i iiiml 5i iiiim) 4i i s iiiail-i i i iimj'2
-1
-3 N
10 10 10 10 10 10 10 10 UNAVAILABILITY PER DEMAND Pigure 1
.