ML20235K246
| ML20235K246 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 09/23/1987 |
| From: | Hunsader S COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| 3610K, NUDOCS 8710050013 | |
| Download: ML20235K246 (3) | |
Text
,
- 3. J A - ym Commonwealth Edison.
l One First N*.:ional Plaza. Chicago, Illinois
_l._ ;] ~.L e ;;
v Address R: ply to: Post Office Box 767
\\
(/, : Chicago, Illinois 60690 0767 I.'
September 23, 1987 l
Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTN: Document Control Desk l
Subject:
Byron Station - Unit 2 Initial Test program Results Containment Ventilation System NRC Docket No. 50-455 Reference (a): February 6, 1987 S.A. Varga letter to D.L. Farrar Reference (a) requested that additional information be provided to
- demonstrate that the enhanced performance of the RCFC's, observed from testing, does not affect the assumptions regarding RCFC performance contained in the ECCS containment back pressure analysis or acceptable Appendix K evaluation.
In an effort to prolong the life of the steam generators by allowing plant operation at a lower primary water temperature (Thot) than originally designed, the most limiting accident cases were reanalyzed for an operating range (rather than a single operating point) and formalized in report form by Westinghouse. FSAR Chapters 6 and 15, which describe the various accident analyses performed, will be updated based upon these analyses. This information has not, yet, been formally submitted to the NRC but it is advantageous to use certain information relating to assumptions made for RCFC performance during various accidents because of the use of state-of-the-art computer codes for hydraulic system analysis and the use of leak before break criteria.
The following analysis for RCFC performance utilizes information contained in the Westinghouse T ot Reduction h
Licensing Report.
i 8710050013 B70923 DR ADOCK 050 5
j
u F
' T.E. Murloy Septembar 23, 1987 T ot Reduction Final Information contained in the Byron /Braidwood h
Licensing Report (WCAp-11386, Rev. I and WCAp 11387, Rev. 1) yields the following:
Revised FSAR Fig. 15.6-12 and 15.6-12a give the peak containment pressure of 24 psig, occuring approximately 20 seconds after the start of an accident.
~ Revised FSAR Fig. 15.6-7 and 15.6-7a give the peak clad temperature in the most limiting case of 1871*F, occuring approximately 56 seconds after the start of an accident.
Revised FSAR Table 6.2-54 lists the assumption that all.4 RCFC's operate and can start 15 seconds after the start of an accident.
Revised FSAR Fig. 6.2-27 gives the peak containment temperature of approximately 225'F.
Using the data contained in the above (Thot) Licensing Report, one can also determine the amount of energy given off to the containment atmosphere from the start of an accident to the time that peak clad temperature is reached. FSAR Tables 6.2-51 and 6.2-52 will show that from 0 to 56.2 seconds after the start of an accident, approximately 342.1 x 106 BTU are released to the containment. From FSAR Fig. 6.2-25, which remains unchangea, one RCFC is capable of removing 98 x 106 BTU /hr or 0.027 x 106 BTU /sec.
If we assume that the RCFC's remove heat at this rate, then from the time 15 seconds to 56 seconds, the RCFC's can remove approximately 4.47 x 106 BTU.
(This calculated capability is high, but the purpose of the Appendix K analysis is to demonstrate that peak clad temperature limits can be achieved with safeguard equipment operating at their absolute maximum capability to lower containment pressure to its lowest value).
The performance of the RCFC's was shown for 100*F service water temperature in reference (a). The Appendix K analysis, however, assumes 45'F service water. The Wyle Laboratories data shows that at the higher I
containment air temperatures, the heat removal from the RCFC's is in the l'
form of latent heat (condensation). Since this is true, it was assumed that for containment air temperatures of 225'F, the RCFC's will remove the same amount of heat, whether the temperature of the service water is 100*F or 45'F.
Using the RCFC performance data in reference (a), at a containment 6 BTU /hr air temperature of 225*F, one RCFC is capable of removing 115 x 10 or 0.32 x 106 BTU /sec. Four RCFC's are capable of removing 0.128 x 106 BTU /sec. Again, assuming that the RCFC's remove heat at this rate, then, from the time 15 seconds to 56 seconds, the RCFC's can remove approximately 5,25 x 106 BTU.
6 BTU more than that The RCFC's can remove approximately 0.78 x 10 assumed in the Appendix K analysis (5.25 x 106 - 4.47 x 106 BTU), in the time it takes to reach peak clad temperature. At 24 psig pressure (38.7 psia), the heat of condensation for saturated steam is approximately 935 BTU /lbm. Due to the RCFC performance difference, an extra 835 lbm of steam will be condensed.
At a specific volume change of approximately 10.9 ft 3/lbm, this yields a volume difference of approximately 9100 ft.3 The free volume of the containment is 2.809 x 106 ft.3 The volume difference of the condensed steam means that the pressure in the containment L______-_--__________-___-__-________-___-___________-____________-_____-____-_____________-__________
-/'
b --
1.
T.E. Murley.
dn' gji - September 23, 1987-3 4
ti t-i will be reduced'by,9I,90/2,809,000 or by 0.324%.,This corresponds to a ll
- pressure reductiom obarproximately 0.078 psi. ' Thin is well within the uncertainty,in calculating containment pressure transients due to heat removal from structudt' heat.3 sinks. The enhanced performance of the RCFC's has a negligible impact on the assumptions used in the Appendix K analysis.
~ In'suinmary, enhanced RCFC performance does not negate the assumptions used in the Appendix K analysin and t::.= calculated reak clad l-temperature 'd belos the~ accept'a'.1/js licit.
\\' s/
5 i
,.4 Please address any queat hns concerniry this matter to this office.
i l-i l
Nery truly yours, I
S. C.'Ifunsader l
-Nuclea'r Licensing Administrator 6.,$ ' [..
i
,. t I
3 es 1-t,
,S j.
yy
+
/
3 cc:
L. Olshan e'
(
i,.3 (
l Byron Resident Tr;spector l
NRC - PIIT
,.[4 4
t l
> t
/
1 k.
l i
\\
s f
)
u t
s y
l' t
\\
s 1
d i
r j
1' 1
LL i.-
(
e 3610K
)I 1
g h
Y 4
e l
a