Investigation of solution techniques for large sparse band width matrix equations of linear systems

Includes bibliographical references (leaves 107-108

WOSUB : a subchannel code for steady-state and transient thermal-hydraulic analysis of BWR fuel pin bundles.

The WOSUB-codes are spin-offs and extensions of the MATTEO-code [1]. The series of three reports describe WOSUB-I and WOSUB-II in their respective status as of July 31, 1977. This report is the first in a series of three, the second of which contains the user's manual [2] and the third [3] summarizes the assessment and comparison with experimental data and various other subchannel codes. The present report introduces the drift-flux and vapor diffusion models employed by the code, discusses the solution method and reviews the constitutive equations presently built into the code. Wherever applicable, possible exteriors of the models are indicated especially with due regard of the findings presented in [3]. Overall, the review of the model and the package of constitutive equations demonstrate that WOSUB-I and II constitute true alternatives for BWR bundle and PWR test bundle calculations as compared to the commonly applied COBRA-IIIC, and COBRA-IIIC/MIT codes which were primarily designed for PWR subchannel and core calculations, respectively. In fact, the incorporation of the drift flux and the vapor diffusion pro- cesses into a subchannel code has to be cdnsidered.a major step towards a more basic understanding and a well balanced engineer- ing approach without the extra burden of a true two-fluid two- phase model. Recommendations for improvements in the various areas are indicated and should serve as guidelines for future develop- ment of this code which in light of the encouraging results pre- sented in [3] seems to be highly warranted. The WOSUB-code is still in the stage of evolutionary development. In this context, the review reflects the achieve- ments as of July 1977.Topical report for Task 3 of the Nuclear Power Reactor Safety Research Program sponsored by New England Electric System, Northeast Utilities Service Co. under the M.I.T. Energy Laboratory Electric Power Program

WOSUB : a subchannel code for steady-state and transient thermal-hydraulic analysis of BWR fuel pin bundles. Volume III. Assessment and Comparison

The WOSUB-codes are spin-offs and extensions of the MATTEO-code [1]. The series of three reports describe WOSUB-I and WOSUB-II in their respective status as of July 31, 1977. This report is the third in a series of three, the first of which [2] contains all the information about the models, solution methods and constitutive equations and the second [3] being the user's manual of the code. This report summarizes the assessment of the WOSUB- code against experiments and compares its results with the results of other subchannel codes. The following experiments are used for the purpose of the assessment of the code under steady-state conditions: 1) 9-rod GE-tests with radially uniform and non- uniform peaking factor patterns. 2) 16-rod Columbia tests with slight power tilts. 3) Planned 9-rod Swedish tests with very strong power tilts. 4) Actually performed 9-rod Swedish tests with power tilt. 5) 9-rod GE-CHF experiments. The comparison with these data shows that WOSUB is capable of predicting the lower-than-average behavior of the corner sub- channel and the higher-than-average behavior of the center subchannel for both quality and mass flux. None of the other well-known subchannel codes is indeed capable of specifically predicting the correct corner subchannel behavior. These codes seem to inherently suffer from major deficiencies associated with their incorporated mixing models. Therefore, it is con- cluded that only improved models for the description of two- phase flow phenomena are capable of handling these situations and that the vapor drift flux model together with the vapor diffusion model as incorporated into WOSUB is doing a good job. The fact that WOSUB does not perfectly match the experimental results over the whole spectrum of experimental evidence can be attributed to the vapor diffusion model which was originally fitted to air-water test results in a geometry consisting of two subchannels only. Obviously, this geometry leads to over- emphasizing the importance of the vapor diffusion as compared to what actually happens in a multi-rod geometry. WOSUB gives the user the option of calculating the critical power as a function of the boiling length - a concept which is especially useful to easily account for axially nonuniform power profiles and which closely resembles the procedure now used by GE. Furthermore, the code determines four heat transfer coefficients around the circumference of the fuel pin, thus giving the user the possibility of selecting the minimal one for the purpose of hot spot calculations. Overall, the assessment and comparison presented in this volume show that the WOSUB-code has to be considered a valuable tool for BWR bundle and PWR test bundle analysis with a potential for further improvements. The commonly used concept of power-to-flow ratio fails to explain most of the test data used for comparison in this report. The WOSUB-code is still in the stage of evolutionary development. In this context, the results presented in this present report have to be considered preliminary. They reflect the development as of July 1977

WOSUB : a subchannel code for steady-state and transient thermal-hydraulic analysis of BWR fuel pin bundles. Volume II. User's Manual

WOSUB (Computer program).The WOSUB-codes are spin-offs and extensions of the MATTEO- code [ 2 ]. The series of reports describe WOSUB-I and WOSUB-II in their respective status as of July 31, 1977. This report is the second of a series of three reports describing the WOSUB code. It gives a detailed description of the input data, flow charts, and output, and contains the list- ings of WOSUB-I and WOSUB-II. For the purpose of future ex- tensions parameters, common blocks and variables used in the code are listed in full detail. WOSUB-I and WOSUB-II are subchannel computer codes for the steady-state and transient analysis of the thermal-hydraulic characteristics of Boiling Water Reactor (BWR) fuel rod bundles. Both codes are also applicable'to analyze PR bundles, especially when these are ducted--a situation which most often arises in experimental set-ups. The main difference between WOSUB-I and WOSUB-II is that the former is designed to analyze small bundles, whereas the latter is capable to handle symmetric sections of today's large- sized BWR bundles. In addition, WOSUB-II does not contain all of the additions made in WOSUB-I yet, because it is deemed appropriate to introduce these into the smaller code first, before they are implemented into the bigger one. Both codes are still in the stage of evolutionary develop- ment. Thus, changes are to be expected in the near future. There- fore, it should be noticed that this report reflects the develop- ment as of July 1977 only.opical report for Task 3 of the Nuclear Power Reactor Safety Research Program sponsored by New England Electric System, Northeast Utilities Service Co. under the M.I.T. Energy Laboratory Electric Power Program