ML19254E942
| ML19254E942 | |
| Person / Time | |
|---|---|
| Issue date: | 06/01/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19254E937 | List: |
| References | |
| NUDOCS 7911050086 | |
| Download: ML19254E942 (4) | |
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ENCLOSURE 2 Evaluation of Report TVA-TR78-03 Report Number:
TVA-TR78-03 Repcrt
Title:
Three Dimensional LWR Core Simulation Methods Report Date:
June 1, 1979 Originating Organization:
Tennessee Valley Authority Reviewed By:
Reactor Physics Section, Core Performance Branch The Tennessee Valley Authority has submitted a serie.4 of topical reports describing the methods to be used in performing the neutronics analysis of reactor cores for light water power reactors. These methods are to be used for both boiling water and pressurized weter reactors. Report TVA-TR78-03 is one of this series. We have reviewed this report and have prepared the following evaluation.
1.
Summary of Report Report TVA-TR78-03 describes a, cree-dimensional steady-state resctor core simulator with thermal-hydraulic feedback.
The output of this simulator code (called CORE) will be used for core design analysis, fuel management, and the optimization of operating strategies.
The reactor core is reprecented as a three-dimensional array of rectangular nodes, each having homogeneouw internal properties. Neutronic coupling between nodes is treated by a synthetic kernel approximation to the response matrix method. Nodal neutronic preperties are determined by multi-variable Lagrangian interpolation of input table sets of lattice physics data obtaiaed from IVA's LATTICE code which has been reviewed and approved. Nodal water 1268 322 06 1911050
. density, exposure, fuel temperature, control fraction, soluble boron content and history effects are included. Either transient or equilibrium xenon effects can be represented, although the algorithms for transient xenon calculations are not presented.
The neutron tracking model, boundary conditions, iteration strategy, thermal-hydraulic models including flow distribution and coolant density eZiects, and effective fuel temperature model are all described.
The sanner in which the lattice physics data are represented is also presented along with a discussion of the algorithms used for reactivity depletion. Finally, various auxiliary calculations, such as thermal limits, simulated incore detec*.or calculations, and fuel management (shuffle) features are described or referenced.
2.
Summary of Evaluation We have reviewed the core modeling methods, the neutron tracking techniques and the derivation of the nodal coupling coefficients. These methods are state-of-the-art and are acceptable. We have reviewed the thermal-hydraulic models employed to determine flow distribution, heat sources distribution and coolant conditions and find them to be acceptable. Effective fuel temperatures are calculated by a fit to values obtained from the LATTICE code. This is an acceptable procedure.
The u >e of fitting techniques to obtain the parameters to be used for each node in the calculation as a function of local conditions is routinely used in the industry for such purposes. Its use in the CORE code is acceptable.
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. Two methods of reactivity depletion-forward step and power-exposure are employed in CORE. In the first method the core average exposure is incremented in steps and the nodal properties are assumed to remain fixed during the step. Nodal properties are recomputed at the end of the step in preparation for the next step. This procedure is widely used and is acceptable.
The second method is used when a particular end-of-cycle power sh>?e (e.g.,t i Haling distribution) is desired. The end of cycle effective multiplication factor and beginning of cycle nodal parameters are input along with an estimate of the exposure 1ength and the power distribution.
The depletion calculation is performed and the calculation iterated to converge the effective multiplication factor and the power distribution.
This procedure is acceptable.
Finally, we have reviewed the auxiliary calculations used to obtain Jimulated incore detector readings and to perfonn fuel managemer+ studies.
These calculations are state-of-the-art and are acceptable. Several critical heat flux correlations are referenced. Use of an approved correlation will be required when such calculations are perfonned for licensing actions.
The equations for treating transient xenon are not presented. Before the code is used to perform xenon transients in licensing action such equations will be required, either in a supplement to the present report or as a part of the verification document for such calculations.
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Evaluation Procedure We have reviewed topical report WA-TR78-03 within the guidelines provided by the Standard Review Plan, Section 4.3.
We conclude that sufficient information is provided in the report to permit a knowledgeable person to ascertain that the methods and techniques described are state-of-the-art.
4.
Regulatory Position On the basis of our review we conclude that topical report Ft-TR78-03 may be referenced in licensing actions by the Tennessee Valley Authority for the description of its core simulator. When thermal power limits are deter-mined by WA, the approved correlation by which such limits are determined must be described.
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