ML20037A215
| ML20037A215 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/03/1978 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7904170459 | |
| Download: ML20037A215 (14) | |
Text
.~
3
]
')
[p n; UNITED STATES o
y" NUCLEAR REGULATORY COMMISSION a
W ASHINGTON, D. C. 20555
%,*****/
APR 3 1978 Docket No. 50-320 MEMORANDUM FOR:
D. Vassallo, Assistant Director for Light Water Reactors, DPM FROM:
R. Tedesco, Assist'rit Director for Plant Systems, DSS
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON ENVIRONMENTAL QUALIFICATION FOR A MAIN STEAM LINE BREAK INSIDE CONTAINMENT FOR THREE MILE ISLAND, UNIT 2 Plant Name: Three Mile Island Nuclear Station Docket Number:
50-320 Milestone Number: N/A Licensing Stage: 0L NSSS Supplier:
Babcock & Wilcox Architect Engineer:
Burns & Roe Containment Type: Dry Responsible Branch & Project Manager: LWR-2; H. Silver Requested Completion Date: N/A Review Status:
Incomplete The Containment Systems Branch and Power Systems Branch have reviewed the infonnation provided by the applicant in Section S3-42 of the Three Mile Island Unit 2 FSAR related to the adequacy of the environmental qualification of safety related equipment for a main steam line break (MSLB) inside containment. As a result we find that we have a need for additional information before we can complete our review on this plant. A request for information specific to Three Mile Island Unit 2 is enclosed.
The applicant's containment environmental qualification analysis was reviewed using a CSB developed Interim Evaluation Model which is enclosed for transmittal to the applicant for further guidance. We will be using this model in evaluating qtolification profiles for all operating reactor license application reviews while a final position on this m&tter is developed.
Contact:
P. Baranowsky, CSB 492-7711 W Q99++17 W]
Q G
APR 3 1973 D. vassallo The spectrum of break sizes and single failure evaluation to determine the adequacy of the mass and energy release used for the MSLB accident containment environmental analysis will be reviewed by the Analysis Branch.
Ykw Robert L. Tedesco, Assistant Director for Plant Systems Division of Systems Safety
Enclosure:
As Stated cc:
R. Mattson S. Hanauer R. Boyd R. Hartfield S. Varga J. Glynn G. Lainas H. Silver J. Shapaker F. Rosa T. Ippolito F. Ashe F. Eltawila Z. Rosztoczy P. Norian W. Jensen P. Baranowsky r-w w
e
}
1 Containment Systems Branch Request for Additional Infonnation Three Mile Island, Unit 2 Docket No. 50-320 1.
The following information regarding the qualification of equipment identified in Section S3-42 is required, a.
Provide the specific test report (s) which. documents the qualification test data, testing methods and procedures, and results for each component listed as required for a steam line break inside containment.
b.
Describe the cable connection at the component for all components needed during a MSLB.
Describe how these connections have been qualified for the MSLB enviroriment and identify the applicable test reports.
c.
Fan cooler motor and containment purge valve and actuator qualification data is required if these components are required to operate during a MSLB accident.
Provide a table or graph of the actual test data which includes temperature, pressure, moisture content, and chemical spray and.show the duration for which the test parameters were held starting from initial ambient conditions. Where available provide component thermocouple readings taken during the qualification testing.
Provide the test report as requested in "a" above.
d.
For motors enclosed in NEMA IV boxes identify the design specifications and clarify whether motors were tested with or without the enclosures.
Provide the test report as requested in "a" above.
1) e.
Identify the pressure and humidity conditions of the tests performed for the selected electric power, control. and instrumentation cable and terminal connections needed during an MSLB accident. Note that-Section 3.11.2.1 shows substantially lower environmental qualification test conditions than provided in S3-42.
Provide the test reports for these components as requested in "a" above.
f.
Identify the specific transmitters listed as items f(i) thru f(v).
Provide the test reports as requested in item "a" above.
g.
Clarify that there are no external prescurizer safety relief valve t
actuation features required during a MSLB which may be subject to the containment environme'nt.
2.
As part of the containment response analysis for a MSLB inside containment provide the following information.
a.
Provide the results of the single active failure evaluation which specifically identifies those containment safety systems and components relied upon to limit the containment temperature / pressure response to a MSLB accident. This evaluation should include, but not necessarily be limited to, the loss or availability of offsite power (whichever is worse), diesel generator failure when loss of offsite power is evaluated, and loss of containment heat removal systems (either partial or total).
l
+
l l
I
()
3-
.)
b.
Justify the assumptions made regarding the time at which active containment heat removal systems become effective.
Include consideration of actuation sensors and setpoints, activation delay time, and system delay time (i.e., time required to come into operaticn). This information should be provided in conjunction to item "a" above.
c.
Justify the selection of the worst case for environmental qualification considering time duration at elevated temperatures as well as the maximum temperature.
In particular provide the results for the spectrum of break sizes analyzed and referred to in Section 15B.1.
Provide the pressure, temperature, saturation temperature, and steam generator blowdown data as a function of time for the worst case analysis for environmental qualification.
3.
Tne following information is required describing the component thermal analyses performed as part of the environmental qualification. Each component needed during an MSLB should be addressed explicitly.
a.
Provide external and sectional diagrams of each component analyzed showing principle dimensions, materials of construction, and cross sections modeled for analysis.
l b.
Provide a detailed description of each th?rmal model indicating basic assumptions and showing the model mock up with principle dimensions, materials, and material thernal properties.
1 e
e e--
,3 q'
_4 c.
Justify the use of an external convective flow velocity of 30 ft/sec. Alternatively, use the correlation provided in the CSB Interim Evaluation Model.
d.
Provide a plot of surface temperature, heat flux, and heat transfer coefficient for each component thermal analysis for as many points on the component as necessary to justify qualification.
e.
Additional information is required to justify the natural convection heat transfer assumption for penetration connectors.
(1) Provide an appropriate set of containment layout views which indicates the location of postulated steam line breaks relative to those connectors for which the natural convection assumption has been used.
(2) Identify those obstructions which will obviate the direct
- /.
flow of steam to the component'.
(3) Provide the design specifications (pressure, temperature, external flow, and any others of relative importance) of the penetration terminal connector boxes.
(4) Provide an appropriate set of views of the boxes to show the location, orientation, and principle dimensions of these boxes and the size and location of the steam ingress points relative to the connectors located within.
y-__
.~\\
. J (5) Provide a more detailed discussion of the technical basis for the assumption of natural convection heat transfer only within the boxes.
(6) Identify the specific point on the component wnich was analyzed and justify that this location is the most critical or conservative with regard to potential component failure.
(7) Provide information sufficient to show that the component environmental qualification test resulted in a thermal transient equal to or more severe than that calculated for the thermal analysis at the specific point analyzed. This should include a description of the test configuration, test data and thermocouple locations, and basis for assessing component surface temperature during the test at the point of analysis.
4.
Provide pressure and temperature qualification profiles which show the component peak calculated surface tenperature(s) and the qualification test temperature.
If the component peak test temperature was held for a short duration (e.g., less than approximately 10 minutes) or if test conditions were not at the steam saturation temperature provide justification that the qualification temperature has been properly derived (i.e. that the test chamber tenperature is the component qualification temperature).
~
The profiles should be provided for each component needed during an MSLB. Use this information to justify component qualification to the postulated MSLB accident environment.
(
l
3 s
CSB Interim Evaluation Model Environmental Qualification for Main Steam Line Break Inside Containment (Operating License Applicants Only)
Analyses of main steam line break (MSLB) accidents inside PWR dry-type containments have predicted temperature transients which exceed the qualification tenperature of some safety related equipment. As a result there is a concern regarding the capability of this equipment to survive such an event to assure safe plant shutdown. This concern is ' elated to Issue 25 of NUREG-0153 dated September,1976.
The NRC has identified this matter as a Category A Technical Safety Activity and is currently pursuing a program to resolve this concern.
In the meantime it is required that you perform an evaluation of the containment environmental conditions associated with a MSLB accident as well as a LOCA and justify that the essential equipment needed to mitigate these accidents have been adequately qualified.
Since the NRC generic effort on this concern is still in progress, we are providing the. analytical assumptions which are acceptable for the interim period. These models and assumptions are acceptable for the spectrum of MSLB accidents.
1.
Containment Environmental Response a.
Heat transfer coefficient to heat sinks.
The Uchida heat transfer correlation (data) should be used while in the condensing mode. A natural convection heat transfer
3 coefficient should be used at all other times. The application of these correlations should be as follows:
(1) Condensing heat transfer q/A = hu. (T -T) s y
where q/A = the surface heat flux h
= the Uchida' heat transfer coefficient u
T
= the steam saturation (dew point) temperature 3
T,
= surface temperature of the heat sink (2) Convective heat transfer q/A = hc. (T -T,)
y where h = convective heat transfer coefficient c
T = the bulk vapor temperature.
y All other parameters are the same as for the condensing mode.
b.
Heat sink condensate treatment When 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 atmosphere is superheated a maximum of 8% of the condensate may be transferred 1
.. s,,
L./
to the vapor region. The revaporization should be calculated as follows:
M = X q / (h -h )
r y t where M = revaporization rate r
X = revaporization fraction (0.08) q = surface heat transfer rate b = enthalpy of the superheated steam y
h = enthalphy of the liquid condensate entering l
the sump region (i.e., average enthalpy of the heat sink condensate boundary layer) l I
c.
Heat sink surface area The surface area of the heat sinks should correspond to that l
used for the containment design pressure evaluation, i
l l
I 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 MSLB accident. This evaluation W
e-
. g =, i as g6. e e. e, e.e e
~
4 should include, but not necessarily be limited to, the loss or availability of offsite power (whichever is worse), diesel generator failure when loss of offsite 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 con 2ainment heat removal systems become effective should include consideration of actuation sensors and setpoints, activation delay time, and system delay time (i.e., time reg ' red to come into operation).
f.
Identification of mast 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 l
break sizes analyzed and single failures evaluated.
l 2.
Safety Related Component Thermal Analysis 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 thennal stressing, temperature-related degradation, steam or chemical interaction at elevated temperatures, or other thermal effects could
+.
e.
se, g
a
?
result in failure of the compartment electrically or mechanically.
The heat transfer rate to components should be calculated as follows:
a.
Condensing heat transfer rate
- I
-T,)
q/A = hcd s
where q/A = component surface heat flux h
= condensing heat transfer coefficient cd
= the larger of 4x Tagami Correlation or 4x Uchida Correlation T
= saturation temperature (dew point)'
s T, = component surface temperature 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.
f l
/^
i 6-i The velocity used in the evaluation of Reynolds number may be determined as follows:
V = 25 BD VCONT where V
= velocity in ft/sec M
= the blowdown rate in Ibm /hr BD 3
VCONT = 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 coefficient must be fully justified whenever used.
3.
Evaluation of Environmental Qualification The component peak surface temperature (s) (Tcs) should be computed using items 1 and 2 above. The component qualification temperatere (Tcq) should be determined from the actual environment test conditions.
Where components have been " bathed" in a saturated steam or steam /afr 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 l
l point or for short durations (e.g., less than 10 minutes), the qualification tenperature must be justified by experimental thermocouple readings on the component surface or analyses which minimizes the heat flux to the component.
1 e
66 e
e
T- -- -n.
(-
7 If the component surface temperature, Tcs, is less than or equal to the component qualification temperature, Tcq, the component may be considered qua.lified for an MSLB environment during the interim period.
If the component surface temperature is greater than the qualification temperature, then (a) provide additional justification that the component can operate in environments equal to or greater than that which would result in the calculated peak surface tenperature, 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, Tcq' o.
O e
---,4.
...,