ML19289E622
| ML19289E622 | |
| Person / Time | |
|---|---|
| Issue date: | 04/04/1979 |
| From: | Varga S Office of Nuclear Reactor Regulation |
| To: | Taylor J BABCOCK & WILCOX CO. |
| References | |
| NUDOCS 7904210786 | |
| Download: ML19289E622 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 v;
APR 4 1979 Mr. James H. Taylor Manager, Licensing Babcock & Wilcox Company Nuclear t'ower Generation P. O. Box 1260 Lynchburg, Virginia 24505
Dear Mr. Taylor:
SUBJECT:
REVIEW 0F TOPICAL REPORT BAW-10070 In order to complete our review of the subject report, we require adequate responses to the enclosed requests for additional information.
If you have any questions on this matter, please contact us.
Sincerely,
')l Steven A. L)(h
%e Illkts Varga, C i Light Water Reactor Branch No. 4 Division of Project Management
Enclosure:
As stated cc: Mr. Robert B. Borsum 7735 Old Georgetown Road Bethesda, Md.
20014 ee 7904216?f(,
Request for Additional Information on BAW-10070, POWER TRAIN The responses furnished to NRC questions of March 23, 1976 concerning the POWER TRAIN code have been reviewed, and further information or clarification of points presented in the response are needed to assist completion of the topical report review.
In addition, general information needs are included in this request concerning the application and verifica-tion of the code.
A.
Information on Prior Responses 1.
Response to Question 3 The requested description of the plant protective system modeled in POWER TRAIN is limited to identification of the trip parameters used.
Information concerning the manner of considering protective instrumentation response, protective system logic and response, and controlled component response characteristics have not been presented.
Provide a block diagram type schematic of the protective system modeled in POWER TRAIN including all input instrumentation, output control signals, and output controllers.
In addition, describe the modeling of the plant control system action that may take place before protective action is initiated. A discussion of the manner in which such action is considered in the slower accident transients should also be provided in connection with the description of the protective system function for these transients.
-2 In the response to Question 4, reference is made to an ICS system concerning feedwater controls. This sytem, which evidently is part of or interacts with the plant protective system is not described in the report.
Provide a description of this system, the normal system functions, and where the system is modeled in connection with POWER-TRAIN analyses.
2.
Response to Question 4 The information provided in this response does not respond to the request made concerning Twi.
Identify the limit information against which a judg-ment is reached with respect to Twi for the turbine trip transient.
This information was requested in the original request for additional information.
It is also requested that the dependence on mass flow rate of the Twi limit be furnished.
In connection with the sample results shown on Figure B-1, provide the following additional information:
a) Discuss and justify the apparent lack of cold leg transport delay at the reactor inlet.
b) Discuss the apparent transport delay occurring in the core resulting from the use of a single node core coolant mixing model such as would be obtained from equations 3.3-2 and 3.3-3 in the report.
3 3.
Response to Question 7 Describe the valve vendor supplied data used as a basis for determining spray, relief, and pilot valve flow rates, and describe the method used for quantitatively determining these parameters for POWER-TRAIN calcula-tions.
General Information 1.
Identify the accidents analysed for plant licensing applications that are performed with the POWER TRAIN code.
Also identify all other codes used, if any, to provide input data to POWER TRAIN for these analyses in addition to the COMANCHE and PUMP codes, and describe all data transfer between codes.
2.
Because of the limited core noding detail used in POWER-TRAIN, limiting DNBR, and limiting clad and fuel temperatures during accident transients can only be roughly estimated.
Describe the manner by which these and other limiting parameters are determined for SAR analyses on the basis of POWER-TRAIN results.
3.
The course of accident transients can be appreciably influenced by various plant control systems in addition to the protective system.
These con-trols are not described in the report, but some of their actions may be included in POWER-TRAIN analyses as indicated in some responses to questions.
As a result, it is not certain if their normal response is considered to be completely included in accident analyses using POWER-TRAIN.
Provide a discussion of how the reactor, pressurizer, feedwater, steam generator and turbine controls response is considered in SAR analyses.
4.
The steam generator is described in generality with respect to the finite difference eauations used to compute the unit thermodynamics.
The model
.. detail used in accident analyses, the heat transfer regimes and corre-lations modeled, and the unit hydrodynamics are not presented.
Provide descriptions for each of these aspects of the steam generator model to enable a more ade: Jate understanding of the OTSG model.
5.
A sample application of the POWER-TRAIN code to an accident transient as submitted in an SAR is required.
The computed results should be graphically presented for the primary system parameters, and all con-trols and protective system action should be described or identified in a discussion or on output graphics used to present results of the sample calculation.
6.
Sensitivity of results to uncertainties in primary controlling para-meters in the plant design, such as flow rate, power level, system pressure, coolant volumes, reactivity coefficients, etc., should also be determined from analytical studies using the computer program for off-design conditions.
7.
Verification studies using POWER-TRAIN to simulate plant or experimental system transients including protective and control action are also re-quired to provide a degree of assurance that the computer program provides reasonably accurate predictions of accident transients for the SARs.
Previous verification studies conducted by B&W with POWER TRAIN on plant startup transients, load swings, load rejections, etc., would be applicable for this purpose, and should be furnished in response to this information request. The comparisons between experimental measurements and POWER TRAIN
~..- results presented in the response to Question 4 in the first round request for additional information, and in the response to Question 2 of the second round request are inadequate for this purpose as the comparisons concern only minor perturbations to the steam generator portion of a plant simulation.
POWER TRAIN verification should be based on comparisons with several plant parameters, such as, primary and secondary flow rates, temperature and pressure profiles along flow paths, pressurizer inventories, protective, and reactor, steam generator, and pressurizer control systems response, secondary steam conditions, etc., to be considered adequate.