ML20215F217
| ML20215F217 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 10/02/1986 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 2204K, 8761002, IEIN-84-90, NUDOCS 8610160124 | |
| Download: ML20215F217 (5) | |
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!' _ ' Commonwealth Edison 72 West Adams Street Chicago, Ilknois kV 2 Address Riply to: Post Office Box 767 U Chicago, Illinois 60690 0767 October 2, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Supplemental Information on Environmental Effects on Main Steam Line Break Outside Containment - Information Notice 84-90 NRC Docket Nos. 50-454/455 and 50-456/457 References (a): September 10, 1986 letter from A. D. Miosi to H. R. Denton.
(b): July 22, 1986 letter from A. D. Miosi to H. R. Denton.
Dear Mr. Denton:
The purpose this letter is to provide you additional information as discussed with members of your staff on September 24, 1986 concerning information provided in references (a) and (b). Attached is a report which provides a parallel evaluation based on component surface temperature which demonstrates that the components in question are qualified using this conservative approach.
Should you have any questions concerning this matter, please contact this office.
One signed original and fifteen copies of this letter and report are provided for your review.
Very truly yours, Me A. D. Miosi Nuclear Licensing Administrator i
la Attachment l
8610160124 061002 cc:
J. Stevens DR ADOCK 0500 4
l 0M 2204K
r Feferences: 1) 2EC: "etter, A.D.
Miosi to H.R.
Centen, Evaluation of Environmental Effects of Main Steam Line Break Outside
' 22-96.
0:ntainment (IE Infcrmation Motice 94-90),
- 2) CECO letter, A.D.
Miosi te H.R.
Denten, Supplemental Information on Environmental. Effects of Main Steam Line
,Ereak Outside Containment IE Information Notice 94-90, 9-10-96.
The two. referenced letters provided information on the potential for increased environmental qualification requirements due to the postulated higher temperature (superheated) steam conditions as identified in IE Ho 1ce 94-90.
These letters addressed the predicted transients and the effects of an extended qualification transient and the potential for adverse long term (post-isolation) effects of increased temperature.
This submittal addresses the margins in the qualification review with respect to Section C.4 of Regulatory Guide 1.99, Rev.1 and clarifies the location and value of-temperatures determined for the equipment using thermal lag analysis.
Marcins Regulatcry Guide 1.89 presents 4 points to be considered in a justification for margins of less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> in the qualification testing.
These are addressed individually in the following section:
- 1) Consideration of a Spectrum of Breaks.
As described in Reference 1,
a full spectrum of break sices was considered to insure that the most severe combination of temperature and time at temperature was used for the evaluation of extension of qualification.
2)Need for Eculement Later in Event or for Recovery.
Reference 2 discussed the need for any of the equipment following the closure of the HSIV (Main Steam Isolation Valves).
None of the equipment exposed to the increased temperatures is used to mitigate the event or recover from the event.
?) Potential for Failed Eautoment to Adverselv Affect Safety or Mislead the Operator.
Reference 2 discussed the failure modes of the equipment in the Safety Valve Room and the Steam Tunnel.
No failure mode exists that would result in adverse safety effects or would degrade other safety equipment.
After the postulated event of Main Steam Line Break, nonelof the instruments or equipment would te used by the operator to mitigate the event and any erronecus signals would not affect the operator actions since there is no act ion to be t aken based upon these signals.
4)Marcin Available to Account for Uncertainties and Inaccuracies.
The calculations and analyses utilized conservatism throughout the evaluation of input parameters and t he select ion of calculat ional-
f.
Te:hni;2es.
These renservatisms are listed and explained in Se:::en 6 cf Reference 1..
Because the conservatism has been s:stematically added with each of the successive assumptions needed to pred::t the transient-ter g er ature and the ilme of MSIV
- s:laticn. no additions; arbitrary ::nservatism is required i:
Insure that a sufficient qualification ::me is used.
Thermal Lac Calculations Thermal lag analysis was performed for three components which are part of *he MSIV actuator: the hydraulic actuator cylinder, the pneumatic reservoir. and the NAMCO limit switch.
In Reference
- 1. results of an analysis wh::h determined the temperature transient at the surface cf; the non-metallic parts of these components were reported.
The predicted temperatures were well below the established allowable temperature for the materials used in the parts and it was concluded that no concern about the adequacy of the components existed.
Subsequent discussion with the NRC reviewer revealed that the review of the calculation would be delayed because of the difficulty anticipated by the NRC in evaluating a analysis of the local temperature at one part in contrast to analyses of component surface temperatures which had been submitted previously.
Although the original calculations described in References 1 and 2 are felt to be' an adequate technical basis to close the issue of Steam Line Break EQ effects, CECO and S&L have reviewed the calculations te determine the surface temperatures of the components in question.
A parallel evaluation based on component surface temperature demonstrates that the components in question are qualified using this more conservative apprcach.
Each ccmponent is.medeled as a set of nodes connected to each other and to the atmosphere by apprcpriate heat transfer equations.
With the predicted atmospheric temperature as a boundary condition, transient calculations are completed for the models.
As expected.
large temperature drops occur at the surfaces, while temperatures are relatively constant through highly conductive metal'lic parts.
Because of the differences in the components the models are quite similar for the hydraulic cylinder and the pneumatic reservoir, and different for the limit switch.
The temperatures predicted for the non-metallic parts (seals) of the cylinder and reservoir were actually the inner surface temperature of the metal shell of the components.
An evaluation of the temperature gradient across the shell demonstrates that the temperature differential across the wall of the component is on the order of 1'F.
Th.is difference is net significant.
Therefore the previously supplied curves (Figures 3 through 6 of Reference 1) can be used as component surface temperatures rather than the temperature of individual parts.
As a result the previous conclusion that the components are qualified is valid under the more conservative approach of using component surface temperatures.
The limit switch calculation was somewhat more complicated in that a
7-.
suris:e temperature was :alculated for *he ;henolic contact block inside *he metal h0using
- f. bronze housing with a stainless steel cover plater of the device.- Because *he bicck is, to some extent, isolated from the housing, there is some difference in temperature between the repor*ed value of the b10ck surface temperature (Figure ~ in Reference 11 and the h:using surface temperature.
Figure A is revisirn or.
Ficure 7 to include the surface temperature of the housir.g.
The NAMCO lim 1*
switch has been qualifie:1 for about 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> at ?40' T wi t h peaks as high as ?91"F.-
The revised curve in Figure A peaks at ?5'"E with only a *otal of less than *hree minutes above 340"F.
Essed on the above discussion and the informa*1cn in References 1 and 2,
1*
is concluded tha* the MSIV is qualified and the components for which thermal lag analysis was performed are qualified based both on the component surface temperature and the 1ccal temperature of non-metallic parts.
05/22/86 08:53:17 500 t
0.3 FT BREAK o BRONZE HOUSING l
-t-STAINLESS STEEL PLATE 102% POWER LEVEL 450.-
300 GPM AFW FLOW RATE VALVE HOUSE TEMPERATURE 400.-
~
g f
350.I S
C t
i i
o-j" EXTERIOR 0 PH WRL 8
g 250. -
y e
r s
4 200.-
PHENGLIC CONTACT BLOCM MSIV ISOLRTION y,
(1576 6 SEC1 150.-
i t
100
.0 2
.4
.6 8
1.0 12 1.4 1.6 1.8 2.0 1000 X TIME AFTER MSLB (SECONDS)
FIG A: TEMP RESPONSE INSIDE NAMC0 LIMIT SWITCH HOUSING, CASE 2 (REVISED FIG. 7 0F REFERENCE D