# Coupled Monte Carlo neutronics and thermal hydraulics for power reactors

## Abstract

The availability of high performance computing resources enables more and more the use of detailed Monte Carlo models even for full core power reactors. The detailed structure of the core can be described by lattices, modeled by so-called repeated structures e.g. in Monte Carlo codes such as MCNP5 or MCNPX. For cores with mainly uniform material compositions, fuel and moderator temperatures, there is no problem in constructing core models. However, when the material composition and the temperatures vary strongly a huge number of different material cells must be described which complicate the input and in many cases exceed code or memory limits. The second problem arises with the preparation of corresponding temperature dependent cross sections and thermal scattering laws. Only if these problems can be solved, a realistic coupling of Monte Carlo neutronics with an appropriate thermal-hydraulics model is possible. In this paper a method for the treatment of detailed material and temperature distributions in MCNP5 is described based on user-specified internal functions which assign distinct elements of the core cells to material specifications (e.g. water density) and temperatures from a thermal-hydraulics code. The core grid itself can be described with a uniform material specification. The temperature dependency of crossmore »

- Authors:

- Institut fuer Kernenergetik und Energiesysteme IKE, Universitaet Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart (Germany)
- Gesellschaft fuer Anlagen- und Reaktorsicherheit GRS MbH, Forschungszentrum, Boltzmannstrase 14, 85748 Garching (Germany)

- Publication Date:

- Research Org.:
- American Nuclear Society, Inc., 555 N. Kensington Avenue, La Grange Park, Illinois 60526 (United States)

- OSTI Identifier:
- 22105849

- Resource Type:
- Conference

- Resource Relation:
- Conference: PHYSOR 2012: Conference on Advances in Reactor Physics - Linking Research, Industry, and Education, Knoxville, TN (United States), 15-20 Apr 2012; Other Information: Country of input: France; 12 refs.

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; BENCHMARKS; CROSS SECTIONS; MODERATORS; MONTE CARLO METHOD; NUCLEAR FUELS; PWR TYPE REACTORS; REACTOR CORES; REACTOR LATTICES; SCATTERING; SIMULATION; TEMPERATURE DEPENDENCE; TEMPERATURE DISTRIBUTION; THERMAL HYDRAULICS; THERMAL NEUTRONS

### Citation Formats

```
Bernnat, W., Buck, M., Mattes, M., Zwermann, W., Pasichnyk, I., and Velkov, K.
```*Coupled Monte Carlo neutronics and thermal hydraulics for power reactors*. United States: N. p., 2012.
Web.

```
Bernnat, W., Buck, M., Mattes, M., Zwermann, W., Pasichnyk, I., & Velkov, K.
```*Coupled Monte Carlo neutronics and thermal hydraulics for power reactors*. United States.

```
Bernnat, W., Buck, M., Mattes, M., Zwermann, W., Pasichnyk, I., and Velkov, K. Sun .
"Coupled Monte Carlo neutronics and thermal hydraulics for power reactors". United States.
```

```
@article{osti_22105849,
```

title = {Coupled Monte Carlo neutronics and thermal hydraulics for power reactors},

author = {Bernnat, W. and Buck, M. and Mattes, M. and Zwermann, W. and Pasichnyk, I. and Velkov, K.},

abstractNote = {The availability of high performance computing resources enables more and more the use of detailed Monte Carlo models even for full core power reactors. The detailed structure of the core can be described by lattices, modeled by so-called repeated structures e.g. in Monte Carlo codes such as MCNP5 or MCNPX. For cores with mainly uniform material compositions, fuel and moderator temperatures, there is no problem in constructing core models. However, when the material composition and the temperatures vary strongly a huge number of different material cells must be described which complicate the input and in many cases exceed code or memory limits. The second problem arises with the preparation of corresponding temperature dependent cross sections and thermal scattering laws. Only if these problems can be solved, a realistic coupling of Monte Carlo neutronics with an appropriate thermal-hydraulics model is possible. In this paper a method for the treatment of detailed material and temperature distributions in MCNP5 is described based on user-specified internal functions which assign distinct elements of the core cells to material specifications (e.g. water density) and temperatures from a thermal-hydraulics code. The core grid itself can be described with a uniform material specification. The temperature dependency of cross sections and thermal neutron scattering laws is taken into account by interpolation, requiring only a limited number of data sets generated for different temperatures. Applications will be shown for the stationary part of the Purdue PWR benchmark using ATHLET for thermal- hydraulics and for a generic Modular High Temperature reactor using THERMIX for thermal- hydraulics. (authors)},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2012},

month = {7}

}