ANDREA macro code is a program developed in UJV since 2005. It serves for calculations of reload design and safety analyses of WWER reactors. The program is standardized according to edict VDS-030 of Czech State Office for Nuclead Safety for analyses of reactors WWER-1000.

The program solves a two-group diffusion equation with help of contemporary nodal method which ensures sufficient accuracy and speed of calculations. It enables to work with an arbitrary axial nodalization, the calculations can be carried out in one sixth of a reactor core or in a full core manner. The program has simple free-formated input files with the possibility of using templates for effectivity of the work.

## Flexibility and automatization

ANDREA offers a wide range of integrated computational sequencies, e. g. for calculations of reactivity coefficients, control rod worths and for an automatic seach for the end of cycle. The course of a calculation may be controled in wide details and it is possible to modify all computational parameters without necessity of repeating the calculation, including the transition between the full-core and the sixth-symmetric calculation. Also the simple and expressive composition of the input files with the possibility of using the templates contributes to the effectivity of work with ANDREA.

## Integrated system of data preparation

For preparation of macroscopic data there is a robust infrastructure at your disposal, which is parameterising the results of calculations of a convenient micro code into a simply usable library. There is a set of tools prepared for processing the HELIOS code results, neveretheless the flexible architecture of the libraries enables to use also other computational tools, eventually. The user's demandingness of the data preparation is minimized while using the graphical user interface QUADRIGA.

## Lucid outputs

The output files are in XML format which enables their automatic processing at ease (e. g. for groovy safety analyses). There is the embedded module ASTRID which converts the output into the graphical and user-convenient form in the HTML format. The user interface ADÉLA for reload design follows up the code ANDREA and it enables an effective reload design in a graphical environment by the *point-and-click* method.

The program ANDREA carries out the calculation according to the user-defined paths (Path). Each path is hereat constructed by variant number of steps (Step) where proceed:

- calculations of states (State)
- calculations of burnup
- reloads or calculation's symmetry transitions

The solver of the program (Solver) is used for the state computation. Iterations proceed untill the convergence of the solver and acquirement of the target value of the effective multiplication factor, which is reached by modification of a selected parameter (boric acid concentration, control rods position, ...). In case of burnup calculation the same iteration scheme is used. The calculation is divided into two steps. In the first one the burnup is proceeded inside the iterations thereby the original powers are used (predictor), whereas the second one uses the final powers (corrector).

Solution of the two-group diffusion equation is carried out with the help of an advanced nodal method using a conformal mapping of hexagonal homogeneous node onto a rectangular node and a transversal integration for the transfer of 3D diffusion equation into four 1D diffusion equations related by the transverse neutron leakage terms. The used methodics of solution counts in the inhomogeneous burnup of fuel assemblies (burnup gradient). To get the pin-wise powers, a reconstruction of the flux layout in the homogenised node interior is carried out first and then a map of precalculated pin-wise powers for given burnup is used for reconstruction of the actual powers of the fuel pins.

The results of the computational code ANDREA with usage of libraries computed by HELIOS program were verified by comparison with operational data and with results of other codes.

A comparison of standardised HELIOS code with the MCNP code approved very good agreement in case of determination of pin-wise powers, even in case of fuel assemblies with burnable absorbers. The comparison approves HELIOS to be a very convenient tool for preparation of the libraries for ANDREA macro code.

Implementation of the nodal solution of ANDREA code was verified by benchmarks published in literature. A very good agreement in multiplication factors and the deviations up to 2 % in nodal powers and 1.5 % in radial powers approved advisability of this implementation. Verification of pin-wise reconstruction with the results of MCNP code for cores with variant fuel types lead to assesment of the uncertainty in pin powers.

The program ANDREA was also qualified based on the operational data. Accuracy of computation of the boric acid concentration was acceptable, the concentration had not exceeded the defined design limit in 93 % of the cases and in any case had not exceeded the safety limit. Uncertainty of the prediction of assembly-wise power layout was determined to be 2.6 % and 3.44 % in case of nodal power layout, respectively.

The program ANDREA was also qualified based on the operational data, when the boric acid concentration was being compared with the measured data. The accuracy of predictions of assembly-wise and nodal power layout was assesed based on the comparison of predicted and measured currents of SPD detectors.

The program was standardised according to edict VDS-030 of Czech State Office for Nuclear Safety for reload design and safety analyses of fuel charges of reactors WWER-1000.

Our partners and customers are given access to the support center, where they can find support for our software products (user guides, updates, issue solutions). If you don't have access information, please ask for them via
e-mail.

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## Commercial services

### Training

We offer trainings for working with the program ANDREA fitted to your needs

### Development of specific features

If you need further improvements or a specific functionality of the program ANDREA, we will design and implement the needed module for you order.

In case you are interested in our services, please,
contact us.

## Examples of input and output files

One of the advantages of the program ANDREA is the lucidity and simplicity of input files. Format of the input data is highly expressive; it is very easy to understand it and, due to suitable default values, the input file is mostly relatively short.

Example of a complete input file

Frequently repeating parts of the input files (e. g. geometry description, nominal operational parameters, definitions of types of fuel assemblies) can be moved to
**templates**
and the current input essentially simplifies and shortens.

Example of a typical input file of the first core load (using the templates)

The inputs for the follow-up reloads contain mostly just a definition of the reload scheme and a description of the calculation process.

Example of a typical input file of a follow-up core reload

Being a component of the program ANDREA there is also the module ASTRID which converts a standard text output into the interactive HTML format.

Example of a graphical output