# Coupled transient tutorial with MSCS

Jump to: navigation, search

This tutorial describes how to use Serpent 2.1.29 to solve a simple reactivity insertion transient for a 3x3 rod unit cell with a central AIC control rod. We will solve the coupled neutronics-fuel temperature problem for an accidental fast removal and return of the control rod. We will not solve heat conduction in the fuel, but will use an adiabatic approximation instead: all heat is modelled as remaining at the place of deposition.

The XY and XZ cuts of the geometry we want to simulate are shown below:

The details of the transient we want to simulate follow: In the beginning of the transient, the system (made critical by soluble boron) is operating at a power level of 1.0 W with the delayed neutron precursors at their stable concentrations. The control rod is removed from the system with an instantaneous upward velocity of 100 000 cm/s, which is maintained until the control rod is completely removed from the geometry. After this, the control rod is inserted back with 5% of the removal speed until the initial position is reached again.

In order to simulate the transient, we will need to first generate the source distributions for neutrons and delayed neutron precursors in the beginning of the transient. As we want to start the transient from the critical state (starting from subcritcal or supercritical states is not currently supported), we will need to create a critical model of our system.

Let's start with the following input:

Colors in the input correspond to:

• Comments
• Control words
• Name definitions
• Name references

Initial input for 3x3 rod 3D unit cell

``` /****************
* Main options *
****************/
```
```% --- Link XS-libraries
```
```set acefile "./sss_endfb71.xsdata"
```
```% --- Neutron population and criticality cycles:
```
```set pop 10000 50 50
```
```% --- Total power for normalization (1 W):
```
```set power 1
```
```% --- Use reflective boundary condition in XY, black in Z
```
```set bc 2 2 1
```
```% --- Add geometry plots
```
```plot 2 500 1000
plot 3 500 500
```
```% --- Add mesh plots (flux + fission power)
```
```mesh 3 500 500
mesh 2 500 1000
```
```% --- Temperature mesh plots
```
```mesh 10 3 500 500
mesh 10 2 500 1000
```
```/*******************
* Pin definitions *
*******************/
```
```% --- Empty lattice position:
```
```pin 99
cool
```
```% --- Fuel pins (same type but treated separately)
```
```pin 1
fuel1  0.60579
void   0.62103
Zirc2  0.71501
cool
```
```pin 2
fuel1  0.60579
void   0.62103
Zirc2  0.71501
cool
```
```% --- Control rod
```
```pin CR
AgInCd  0.43310
void    0.43688
ssteel  0.48387
cool    0.56134
zirc    0.60198
cool
```
```% --- Control rod guide thimble
```
```pin GT
cool    0.56134
zirc    0.60198
cool
```
```% --- Control rod bottom surface
```
```surf sCR pz 0.0
```
```% --- Move control rod surface to starting position
```
```trans s sCR 0 0 -3.54
```
```% --- Control rod universe C definition
```
```cell CRb C fill GT -sCR
cell CRt C fill CR  sCR
```
```/***********************
* Geometry definition *
***********************/
```
```% --- Assembly lattice
```
```lat 100 1  0.0  0.0 5 5 2.5
99 99 99 99 99
99  1  2  1 99
99  2  C  2 99
99  1  2  1 99
99 99 99 99 99
```
```% --- Geometry boundary (50 cm high cuboid)
```
```surf  9  cuboid  -4.6875 4.6875 -4.6875 4.6875 -25 25
```
```% --- Cell definitions:
```
```cell  1  0 fill 100  -9          % Pin lattice
cell 99  0 outside    9          % Outside world
```
```/************************
* Material definitions *
************************/
```
```% --- Fuel materials:
```
```% Fuel1 3.6 wt % enrichment (double density)
mat fuel1   -10.307 tmp 300 rgb 100 0 0
92235.03c	-0.03173362
92238.03c	-0.84975585
8016.03c        -0.11851053
```
```% --- "Zircaloy-2" [PNNL-15870, Rev. 1]
% Xe18 commented because of lack of XS data
```
```mat Zirc2 -6.56 tmp 300 rgb 200 200 200
8016.03c  -1.19376E-03
8017.03c  -4.83282E-07
24050.03c  -4.16117E-05
24052.03c  -8.34483E-04
24053.03c  -9.64457E-05
24054.03c  -2.44600E-05
26054.03c  -5.62862E-05
26056.03c  -9.16258E-04
26057.03c  -2.15389E-05
26058.03c  -2.91667E-06
28058.03c  -3.35317E-04
28060.03c  -1.33612E-04
28061.03c  -5.90496E-06
28062.03c  -1.91358E-05
28064.03c  -5.03067E-06
40090.03c  -4.98111E-01
40091.03c  -1.09835E-01
40092.03c  -1.69731E-01
40094.03c  -1.75753E-01
40096.03c  -2.89183E-02
50112.03c  -1.27668E-04
50114.03c  -8.84175E-05
50115.03c  -4.59485E-05
50116.03c  -1.98205E-03
50117.03c  -1.05596E-03
50118.03c  -3.35857E-03
50119.03c  -1.20129E-03
50120.03c  -4.59450E-03
50122.03c  -6.63830E-04
50124.03c  -8.43778E-04
```
```% --- Zircaloy for control rod
mat zirc   -6.56000E+00 tmp 300 rgb 200 200 200
8016.03c  -1.19376E-03
8017.03c  -4.83282E-07
24050.03c  -4.16117E-05
24052.03c  -8.34483E-04
24053.03c  -9.64457E-05
24054.03c  -2.44600E-05
26054.03c  -5.62862E-05
26056.03c  -9.16258E-04
26057.03c  -2.15389E-05
26058.03c  -2.91667E-06
28058.03c  -3.35317E-04
28060.03c  -1.33612E-04
28061.03c  -5.90496E-06
28062.03c  -1.91358E-05
28064.03c  -5.03067E-06
40090.03c  -4.98111E-01
40091.03c  -1.09835E-01
40092.03c  -1.69731E-01
40094.03c  -1.75753E-01
40096.03c  -2.89183E-02
50112.03c  -1.27668E-04
50114.03c  -8.84175E-05
50115.03c  -4.59485E-05
50116.03c  -1.98205E-03
50117.03c  -1.05596E-03
50118.03c  -3.35857E-03
50119.03c  -1.20129E-03
50120.03c  -4.59450E-03
50122.03c  -6.63830E-04
50124.03c  -8.43778E-04
```
```% --- "Steel, Stainless 304" [PNNL-15870, Rev. 1]
```
```mat ssteel -8.00000E+00 tmp 300 rgb 100 100 100
6012.03c  -3.95366E-04
% 6013.03c  -4.63372E-06
14028.03c  -4.59332E-03
14029.03c  -2.41681E-04
14030.03c  -1.64994E-04
15031.03c  -2.30000E-04
16032.03c  -1.42073E-04
16033.03c  -1.15681E-06
16034.03c  -6.75336E-06
16036.03c  -1.68255E-08
24050.03c  -7.93000E-03
24052.03c  -1.59029E-01
24053.03c  -1.83798E-02
24054.03c  -4.66139E-03
25055.03c  -1.00000E-02
26054.03c  -3.96166E-02
26056.03c  -6.44901E-01
26057.03c  -1.51600E-02
26058.03c  -2.05287E-03
28058.03c  -6.21579E-02
28060.03c  -2.47678E-02
28061.03c  -1.09461E-03
28062.03c  -3.54721E-03
28064.03c  -9.32539E-04
```
```% --- AIC from BEAVRS
```
```mat AgInCd -10.160000 tmp 300 rgb 5 255 5
Ag-107.03c 2.3523e-02
Ag-109.03c 2.1854e-02
In-113.03c 3.4291e-04
In-115.03c 7.6504e-03
Cd-106.03c 3.4019e-05
Cd-108.03c 2.4221e-05
Cd-110.03c 3.3991e-04
Cd-111.03c 3.4835e-04
Cd-112.03c 6.5669e-04
Cd-113.03c 3.3257e-04
Cd-114.03c 7.8188e-04
Cd-116.03c 2.0384e-04
```
```% --- Coolant (0% void fraction):
```
```mat cool     -0.99999  moder lwtr 1001 tmp 300 rgb 150 150 255
1001.03c     0.66667
8016.03c     0.33333
```
```% --- Thermal scattering data for light water:
```
```%(HinH20 at 273K)
therm lwtr lwj3.00t
```