ML19289F218
| ML19289F218 | |
| Person / Time | |
|---|---|
| Issue date: | 02/28/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19289F217 | List: |
| References | |
| WCAP-8986, NUDOCS 7906040422 | |
| Download: ML19289F218 (4) | |
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ENCLOSURE
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Topical Report Evaluation Report
Title:
Perturbation Technique for Calculating ECCS Cooling Performance Report Number:
WCAP-8986 Report Date:
February 1977 Originating Organization:
Westinghouse Electric Corporation Summary of Topical Report The topical report describes a procedure to be used when operational or design changes occur in a plant, or generically in a class of plants, to minimize the amount of reanalysis of the limiting LOCA required to assess compliance with Appendix K of 10 CFR 50.
The procedure is based on pre-computed PCT sensitivity to specific parameter variations taken one-a t-a-time.
Application of the pre-computed PCT sensitivity coefficients when a plant parameter change occurs would consist of adding the PCT change, or perturbation, produced by the parameter change to the existing PCT deter-mined for the original plant design from LOCA analyses using the approved Westinghouse Evaluation Model; or stated symbolically:
I PCT = PCT + APCT PCT = Perturbed Peak Clad Temperature p
p PCT = LOCA Analysis Peak Clad Temperature APCT = PCT Perturbation 5
APCT = Cp AP Cp
= Perturbation Coefficient for Parameter P AP
= Change in Parameter P from the Original.
LOCA Analyses 2236 006 7906040pjg
Application of the technic /!e'would be limited to changes of less than 100 F in PCT. The perturbation coefficients developed for this use would be based on known conservatisms to ensure conservative application of the technique.
T Perturbation coefficients for power peaking, Fq, upper head tempera-ture, Tuh, and steam generator uniform tube plugging are presented in the report. An example of the application of the technique to a three loop (17x17) plant is also demonstrated in the report.
In this example,.
the combined perturbation effects of all three of these parameters is demonstrated. Changes in upper head temperature and steam generator tube plugging are assumed, and the effect on PCT is determined by super-position of the two APCTs on the original LOCA PCT. U:ing the power peaking perturbation sensitivity coefficient, the reduction in tne per-turbed PCT to conform to the allowable limit is obtained by determining
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T the change required to Fq to produce the necessary APCT to maintain PCT f
within the limit.
This example also serves to demonstrate. the interre-lationship on LOCA PCT between various plant parameters.
i Summary of Staff Evaluation
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Review of this topical report was restricted to evaluation of the technique
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only, and not to the assessment of the adequacy of the perturbation coeffi-
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cients presented in the report.
Such a review will be the subject of a staff, evaluation when the coefficients proposed for licensing applications are submitted, and will require detailed information on the data base used to i
determine the coefficients, and on the conservatism contained in each coefficient.
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Application of the technique has thus far assumed a linear relationship between the various perturbation coefficients as was demonstrated in the example application of the technique in the report. The possibility of non-linear interrelationships or effects on PCT were not apparently investigated in determining the sensitivity coefficients presented in the report so that the linearity, or superposition, assumption used in the example has not been confirmed, thus far.
The coefficients shown in the report are also based on LOCA data developed prior to finding of 'he metal-water reaction rate error t
contained ;n Westinghouse's ECCS Evaluation Model.
t Staff Position Application of a perturbation technique to LOCA analyses to determine changes in PCT produced by parametric changes will provide means for efficient and expeditious review of such changes, and is approved in principle.
However, because of the complex system interactions occur-ring in a LOCA, many of which may be non-linear such is may be encountered with clad swelling and rupture, the application of such sensitivity techniques will require a considerable data base for acceptance. The validity of superposition of individual perturbations to PCT when more than one perturbation change occurs has not been demonstrated in the P
report, or in the additional information submitted in response to staff t
requests for information.
6 2236 008 O
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Applicanility of the coefficients for plant operating or accident conditions (e.g., linear power density, core rated flow, pressure loss and temperature rise, LOCA-PCT, etc.) outsioe the ranges used in the data base for the coefficients will require mathematical as well as computational demonstration.
Extrapolation of coefficients between plant types as was shown on Figure 1 of the report will not be acceptable, and will require a data base for confirmation for each plant type. The linearity of the coefficients within the range of applications proposed for each coefficient where a single value is T
used, such as was given for F, will also require demonstration, and q
all coefficients must be based on results obtained with the corrected metal-water reaction rate model.
For acceptance of the concept of a perturbation technique, the linear superposition assumption used as a basis for this technique requires mathematical demonstration and proof which have.,not been presented in this report.
Such proof would consist of a LOCA calculation containing single and multiple parameter perturbations to compare PCT results with results obtained from the perturbation technique.
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