ML17296A251
| ML17296A251 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/08/1978 |
| From: | Parr O Office of Nuclear Reactor Regulation |
| To: | Vanbrunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| NUDOCS 7811200199 | |
| Download: ML17296A251 (12) | |
Text
k II and STH 50-530 NOV 08 1978 Distribution Docket Fi.le NRC PDR Local PDR LWR 43 File D. Vassallo
-52B F ~ Williams
- 0. Parr R. Stright M. Rushbrook Mr. E. E. Yan Brunt, Jr.
ELD Yice President Construction Projects Arizona Public Service Company P."0.
Box 21666 Phoenix, Arizona 85036 IE (3)
S.
Brown BCC:
Dear Mr. Yan Brunt:
SUBtlECT:
ENVIRONMENTAL QUAL'IFICATIOH OF SAFETY RELATED EQUIPMENT Recent analyses of the main steam line break accident inside PWR dry-tape containments have predicted temperature transfents which exceed the loss-of-coolant accident qualification temperature of some safety-related equip-ment.
As a result, there is a concern regarding the capability of this equipment to perform the functions required for a safe plant shutdown following the steam line break.
We are pursuing a program to resolve this concern on a generic basis.
Since the generic effort is not complete, we have developed interfmI criteria to be used for Operating License applications.
We have noted that the criteria in Appendix 6D of the. P~lo Verde Nuclear Generating Station (PVHGS) 1 y PSAR are not consistent with our interim evaluation model.
In order that you have definitive guidance on this matter, which will be a major revfeA area for the PVNGS FSAR, a copy of our model Is attached for your Information and use.
Sincerely, Original Signed by Olan Parr Olan D. Parr. Chief Light Water Reactors Branch Ho.
3 Division of Project Harenagement Enclosune:
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cc:
Arthur C. Gehr, Esq.
Snell
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- Pheonix, Arizona 85073 Charles S. Pierson Assistant 'Attorney General 200 State Capitol 1700 West Washington Phoenix, Arizona 85007 David N. Barry, Esq.,
Senior Counsel Charles R. Kocher, Esq., Assistant Counsel Southern California Edison Company P.
O.
Box 800
- Rosemead, California 91770 Dr. Stanley L. Dolins Assistant Director Energy Programs (OEPAD)
Office of the Governor 1700 West Washington Executive Tower - Rm.
507
- Phoenix, Arizona 85007
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'nclosure CSB Interim Evaluation Model Environmental gualification for Loss-of-Coolant Accidents and Hain Steam Line Breaks Inside Containment
'Operating License Applicants Only)
Analyses of the main steam ne rea li break (NSLB) accidents inside PMR dry-type containments have pre c e em di t d temperature transients which exceed the LOCA qualification temperature of some safety related e uipment.
As a result there is a concern regarding the capa y
bilit of this equipment to survive such an event to assure safe plant shutdown.
This concern is related to Issue 25 of NUREG-0153. dated SeptemBer, 1976.
The NRC has identi if ed th s matter as a Category A Technical Safety ram to resolve this concern.
In Activity and is currently pursuing a program to the meantime it is require a
ea d th t each applicant for an operating license perform an evaluation o
e con f th ontainment environmental conditions associated with a MSLB accident as well as a LOCA and ju y
ustif that the essential equipment ne eded to
'tigate these accidents have been q
ade uately qualified.
ml Since e
ncern is still in progress, we are Since the NRC generic effort on this concern e ui ment response pr oviding the ana y ca a
1 ti 1
ssumptions for containment and eq p
which are acceptab e
or e
1 f th interim period.
These models and assumptions are acceptable for the spec rum f
th pectrum or LOCA and NSLB accidents.
Acceptable er release for input to the methods for calculating the mass and energy con'n the attached sunmary on mass and energy containment analysis are provided in e a release methods.
1.
Containment Environmental Response.
a.
Heat transfer coefficient to heat sinks.
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The Tagami condensing heat transfer cor'relation should be used for a
LOCA with the maximum heat transfer rate determined at the time of peak pressure or the end of primary system blowdown.
A rapid transition to a natueaI convection, condensing heat transfer correlation should follow.
The Uchida heat transfer correlation (data) should be used for HSLB accidents while in the condensing mode.
A natural convection heat transfer coefficient should be used at all other times when not in the condensing heat transfer mode for both LOCAs and MSLB accidents.
The application of these correlations should be as follows:
C (1) Condensing heat transfer q/A = h nd where q/A = the surface heat flux h
d
= the condensing heat transfer coefficient cond T
= the steam saturation (dew point) temperature 5
T
= surface temperature of the heat sink w
(2) Convective heat transfer q/A =
h 'Tv - T )
where h
convective heat transfer coefficient c
T
=
the bulk vapor temperature.
v All other parameters are the same as for the condensing mode.
b.
Heat sink condensate treatment Mhen 'the containment atmosphere is at or below the saturation temperature, all condensate formed on the heat sinks should be transferred directly to the sump.
When the at'mosphere is superheated a maximum of SX of the condensate may be assumed to remain in the vapor region.
The condensed mass should be calculated as follows:
X '
/ (h -h
)
where H
d mass condensation rate cond
= mass condensation fraction (0.92) q
= surface heat transfer rate h
= enthalpy of the superheated steam V
hL
= enthalphy of the liquid condensate entering the sump region (i.e., average enthalpy of the heat sink condensate boundary layer).
c.
Hect sink surface area The surface area of the heat sinks should correspond to that used for the containment design pressure evaluation.
d.
Single active failure evaluation Single active failures should be evaluated for those containment safety systems and components relied upon to limit the containment temperature/pressure response to a LOCA or MSLB accident.
This evaluation
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should include, butnot necessarily be limited to, the loss or availability of offsite power (whichever is worse), diesel generator failure when loss of of%site power is evaluated, and loss of containment heat removal systems (either partial or total).
e.
Containment heat removal system actuation The time determined at which active containment heat removal systems become effective should include consideration of actuation sensors and setpoints, actuation delay time, and system delay time (i.e., time required to come into operation).
- f. Identification of most severe environment The worst case for environmental qualification should be selected considering time duration at elevated temperatures as well as the maximum temperature.
In particular, consider the spectrum of break sizes analyzed and single failures evaluated.
2.
Safety Related Component Thermal AnaIysis Component thermal analyses may be performed to justify environmental qualification test conditions less than those calculated during the containment environmental response calculation.
The thermal analysis should be performed for the potential points of component failure such as thin cross sections and temperature sensitive parts where thermal stressing, temperature-related degradation, steam or chemical interaction at elevated temperatures, or other thermal effects could
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result in failure of the component electrically or mechanically.
The heat transfer rate to components should be calculated as follows:
a.
Condensing heat transfer. rate q/A h
{T
= T )
where q/A component surface heat flux h
d
= condensing heat transfer coefficient cond the larger of 4x Tagami Correlation or 4x Uchida Correlation T
= saturation temperature (dew point) s T
= component surface temperature w
b.
Convective heat transfer A convective heat transfer coefficient should be used when the condensing heat flux is calculated to be less than the convective heat flux.
During the blowdown period, a forced convection heat transfer correlation should be used.
For example:
NU C (Re) where Nu Nusselt No.
Re = Reynolds No.
C,n = empirical constants dependent on geometry and Reynolds No.
The velocity used in the evaluation of Reynolds number may be determined as follows:
V = 25 BD CONT-where V
velocity in ft/sec HBD the bl owdown rate in 1 bm/hr CONT = containment volume in ft After the blowdown has ceased or reduced to a negligibly low
- value, a natural convection heat transfer correlation is acceptable.
- However, use of a natural convection heat transfer coefficientmust be fully justified whenever used.
3.
Evaluation of Environmental gualification The component peak surface temperature(s)
(T
) should be computed using items 1 and 2 above.
The component qualification temperature (T
) should be determined from the actual environment test conditions.
cq Where components have been "bathed" in a saturated steam or steam/air environment for extended periods (e.g.,
10 minutes),
the qualification temperature is the test chamber temperature.
For components subjected to test conditions substantially removed from the steam saturation point or for short durations (e.g., less than 10 minutes), the qualification temperature must be justified by experimental thermocouple readings on the component surface or analyses which minimizes the heat flux to the component.
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If the component surface temperature, T, is less than or equal to the component qualification temperature, T, the component may be cq considered qualified for an NSLB environment during the interim period.
If the component surface temperature is greater than the qualification temperature, then (a) provide additional justification that the ccmponent can operate in environments equal to or greater Chan that which would result in the calculated peak surface temperature, or
{b) provide a requalification package for the component, or (c) provide appropriate protection to assure that the component will not experience a surface temperature in excess of the qualification temperature, T
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