Coupled Neutronics and Thermal-Hydraulics Simulations Using Monte Carlo and CFD

Volkan Seker, Justin W. Thomas and Thomas J. Downar Purdue University

Nuclear Engineering Building 400 Central Drive West Lafayette, IN,47907

vseker@ecn.purdue.edu ; jthomas@anl.gov ; downar@ecn.purdue.edu

Presented by : Dinan Andiwijayakusuma, S.Si

Paper R E V I E W

12/04/23 BATAN-Computational Division 2

Major Work

A major part of the work was to develop and implement methods to update the cross

section library with the temperature distribution calculated by STAR-CD for every region

12/04/23 BATAN-Computational Division 3

Decription the Work

MCNP --> was used to simulate the transport of neutrons through the system

STAR-CD --> solves the 3-D momentum and energy transport equations

NJOY --> Generated Cross Sections Data using data from CFD solution

12/04/23 BATAN-Computational Division 4

Interface

Written by FORTRAN90 with utilized two PERL script

Execute MCNP (output : “mcnp2star.dat”) Execute STAR-CD (output : “star2mcnp.dat”) Rewritten “xsdir” with new generation cross-

section identifiers,temperatures, library names dan library paths.

The Script running until the Eigen Value and flux are convergen

12/04/23 BATAN-Computational Division 5

Initialization

Stand alone CFD run with input initial power profile --> to obtain initial temperature distribution for MCNP cross-section library

MCNP run with standard library to obtain inital source

12/04/23 BATAN-Computational Division 6

Iterative Process

The iterative calculation : MCNP (input power) --> output power distribution

--> mcnp2star.dat STAR-CD (read mcnp2star.dat) --> output

temperature,density and volume each cell --> star2mcnp.dat

NJOY (read star2mcnp.dat) --> generate new CS library --> update MCNP input (new density & new temperature)

Proses tsb berulang (iteratif) sd tercapai keadaan konvergen

12/04/23 BATAN-Computational Division 7

Iterative Process

Proses tsb berulang (iteratif) sd tercapai keadaan konvergen

12/04/23 BATAN-Computational Division 8

Three Techniques for updating Cross Section

Terkait dengan “Major Works” untuk update

Cross-Section, maka ada 3 teknik/pendekatan : Perform ENJOY calculation for each nuclide in

each region Pre-generate a library for each nuclide with

small temperature increment (2K - 5K) Pre-generate a library for each nuclide with

larger temperature increment (25K - 50K)

12/04/23 BATAN-Computational Division 9

Result

GEOMETRY

12/04/23 BATAN-Computational Division 10

Result

CFD MESHING

Arah Axial : Tinggi 240cm di-diskritisasi menjadi 600 layer, shg masing2 layer 0.4cm

Arah Radial di diskritisasi sama utk masing2 layer,yaitu 2240 cells

Total cells : 600x2240= 1.344.000 CFD cells

12/04/23 BATAN-Computational Division 11

Result

MCNP MESHING

Azimuthal meshing = 8mesh

Axial meshing = 12mesh Jumlah total MCNP cells:

6720 with tallies performed dalam 1920 cells pada daerah fuel

12/04/23 BATAN-Computational Division 12

Result

Computing run-time for a single MCNP :

siklus aktif = 300,

neutron per-siklus = 500.000 neutron

running on cluster 30 nodes (spek PC: 3GHz Pentium 4 Processors RAM 2GB)

dibutuhkan waktu 6 jam Untuk total 12 iterasi dibutuhkan 100 jam

12/04/23 BATAN-Computational Division 13

Result

Percobaan I, dengan distribusi suhu konstan (300oC) diperoleh hasil :

Terdapat selisih MCNP lebih besar 74pcm

Perbandingan Hasil MCNP dengan DeCART Code*) :

*) deterministic transport code

12/04/23 BATAN-Computational Division 14

Result

Percobaan II, dengan distribusi variable suhu diperoleh :

Terdapat selisih McStar lebih besar 66pcm, perbedaannya tidak terlalu jauh dengan kasus suhu konstan

Perbandingan Hasil MCNP-STARCD (McStar) dengan DeCART/STARC-D Code*) :

*) deterministic transport code

12/04/23 BATAN-Computational Division 15

Result

12/04/23 BATAN-Computational Division 16

Result

12/04/23 BATAN-Computational Division 17

Result

Perbedaan hasil eigen-value utk harga k-eff :

Case I -->Temperature constant : 74 pcm

Case II --> Variable temperature : 64pcm Perbedaan hasil Power Density :

Case I -->Temperature constant : 3,2%

Case II --> Variable temperature : 4%

12/04/23 BATAN-Computational Division 18

Conclusion

Secara umum Coupling MCNP-CFD sangat baik, namun karena waktu komputasi yang sangat lama, maka metode ini belum bisa menggantikan coupling Deterministik DeCART-CFD.

Metode Coupling MCNP-CFD ini bisa digunakan sebagai audit-tools untuk verifikasi hasil perhitungan dengan metode deterministik pada kasus-kasus yang lebih spesifik.

12/04/23 BATAN-Computational Division 19

Future Works

Dengan pertimbangan akurasi tinggi pada metode coupling MCNP-CFD namun dengan waktu komputasi yang lama, maka :

Perlu dikembangkan metode yang bisa mempercepat waktu komputasinya, misal dengan teknik variance reduction

Infrastruktur komputasi yang mampu menunjang sehingga diperoleh waktu komputasi yang cepat

12/04/23 BATAN-Computational Division 20

Terkait dengan USPEN 2010

Mempelajari requirement input masing2 SW (Neutronik-->mis:MCNP & TH-->mis:COBRA)

Mempelajari output yang dihasilkan masing2 SW (Neutronik-->mis:MCNP & TH-->mis:COBRA)

Mempelajari teknik update cross-section, yaitu

1. Mempelajari teknik NJOY mengenerate library cross-section data

2.Mempelajari penyiapan library cross-section data secara manual dengan kenaikan suhu tertentu

Mempelajari teknik komunikasi data yang memungkinkan untuk ketiga komponen tsb

12/04/23 BATAN-Computational Division 21

Terkait dengan USPEN

MCNP Input :1. Geometry Properties2. Material Properties3. Source Card4. Tally Card

MCNP Output :Neutron Fluks Distribution(Converted to Power Distribution)

CFD (FLUENT) read MCNP outputPower Distribution as Heat Source

sebagai bagian input dari CFD(FLUENT)

CFD output :Temperature and density of every cells.This data used to update cross-section

New Cross-SectionLibrary Data

requires a mesh mapping or interpolation scheme between the meshes used in

12/04/23 BATAN-Computational Division 22

Output

12/04/23 BATAN-Computational Division 23

NEXT STEP

SP 1 : NEUTRONIK

SP 2 :THERMALHYDRAULIC

SP-3 :GENERATE CROSS-SECTION

SP-4 :INTERFACE TO INTEGRATED

12/04/23 BATAN-Computational Division 24

CLOSING

Any Suggest..???