OPAL Reactor Full 3-D Calculations including...

OPAL Reactor Full 3-D Calculations including

refueling

5th International Serpent User Group Meeting in Knoxville , USA, 13-16 Oct 2015

By Diego FerraroNuclear Engineering Department – INVAP S.E. - Argentina

Presentation Overview

1- Introduction – Why using Serpent in INVAP?

2- Serpent coupling with INVAP Calculation line

3- OPAL Reactor: Full 3-D Serpent model

4- Full 3-D model in Serpent with Refueling

using diverse approaches

5-Conclusions

2

5th International Serpent User Group Meeting in Knoxville, USA, 13-16 Oct 2015

1- Introduction – Why Serpent?

• Monte - Carlo Codes are used mainly in the Nuclear Engineering Department:

Criticality Calculations (Reactors, Fuel Storages)

Shielding Calculations (Coupled N,P)

Ex-Core Facilities design & performance evaluation in RR

Code to Code comparisons

Detailed flux profile calculations

• INVAP deterministic Calculation Line (CONDOR CP/HRM cell code +

CITVAP finite differences diffusion core code) is coupled with MCNP/Serpent

through NDDUMP code (internal development) Evaluations can be

performed with burnup dependence

• NDDUMP can handle composition changes: fuel management &

thermalhydraulic feedback & control rod position3


1- Introduction – Why Serpent?

• Original motivation to use Serpent (2010) in INVAP:

Obtain condensed parameters (macroscopic XS) for in-core and ex-core

devices with high heterogeneity for Research Reactors.

Additional comparisons for burnup dependent cell-level calculations for MTR

including burnable poisons with a different physical approach.

• Today’s motivation to use Serpent in INVAP:

Increase in Serpent Capabilities + Parallelization Complex core models

can be developed and compared with other calculations.

Core-level Calculations using compositions obtained from other codes.

Additional comparisons including burnup at cell-level calculations for diverse

fuel designs (both MTR or NPP) using a different physical approach.

Full core MonteCarlo calculations including refueling for Research Reactors.

4


2 –Coupling with INVAP Calculation Line

5

+ External code

(developed in C)

to perform

simple refueling

using Serpent 2

restart file

(NEW)


INVAP neutronic Calculation Line:


• The OPAL Research Reactor.

State of art 20MWth multi-purpose open-

pool type Research Reactor located at Lucas

Heights, Australia.

It was designed and built by INVAP between

2000 and 2006 and it is owned and operated

by ANSTO.

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Irradiation facilities in the Reflector Vessel: Cold Neutron

Source (+ two beams), a thermal neutron source (+ 2

beams), 17 vertical irradiation tubes, pneumatic RIGs, 6

NTDs facilities.

It was designed, commissioned and performance tested

using INVAP´s calculation line (CONDOR + CITVAP) +

MCNP4C.

Data available in IAEA Research Reactor

Benchmarking Database (Tech. Report Series Nro 480).

Compact core of 16 LEU MTR-type fuels with Cd wires as BP, cooled and

moderated by light water and reflected by heavy water contained in a

Reflector Vessel.


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Previous works:

• A 3-D full core model for OPAL Research Reactor was developed for

Serpent 2 v1.21. Automatic Input generation through and spreadsheet.

• Main components for first Core configuration were modeled:

3 Fuel types (MTR), 5 CR, Chimney, Reflector Vessel.

• Simplified models for most relevant experimental facilities are included:

17 vertical irradiation tubes

Simplified model for the Cold Neutron Source & Cold neutron beams.

2 Thermal neutron beams.

• Results for these models are compared with experimental data from Reactor

Commissioning & Other codes:

Presented in 16th IGORR 2014/IAEA Technical Meeting: “ OPAL Reactor

Full 3-D Calculations using the MonteCarlo Code Serpent 2” – D. Ferraro

and E. Villarino – Nov 2014

Critical positions (from Reactor Commissioning).

Kinetic parameters.

In-core thermal flux profiles.

Full core burnup (1st cycle).



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Full model x-y cut – 4 cm below core centre

Full model x-y cut – 4 cm below core centre

Full model y-z cut – CR and CNS details

Previous model characteristics:



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Critical points:† Measurement from Reactor Commissioning (CR calibrations):

-700

-600

-500

-400

-300

-200

-100

0

0 5 10 15 20 25 30

Cal

cula

ted

rea

ctiv

ity [

pcm

]

Case Number

Calibration CR 1&4

Calibration CR 5

Calibration CR 2&3

CasesSerpent

2 [pcm]MCNP [pcm]

CONDOR-

CITVAP [pcm]

CR 1 & 4 -400 -360 -300

CR 5 -340 -370 -130

CR 2 & 3 -500 Not Calculated -240

All 74 cases -420 -390 -220

Calculations

Cold w/o Xe,

1st Core Fresh.

Comparison with other codes (from Commissioning):

Fairly good

agreement!


†Ref. 16th IGORR 2014/IAEA Technical Meeting – “ OPAL Reactor Full 3-D Calculations using the MonteCarlo

Code Serpent 2” – D. Ferraro and E. Villarino


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Kinetic Parameters:† Measurements from OPAL Reactor Commissioning:

Neutron decay constant was measured for a 15FA core configuration using

the Feynman-α method.

This configuration was modeled with Serpent. IFP method was used.

Kinetic Parameters for 16 FA configuration: The final 16FA was

calculated and compared with calculations:

Good agreement

with Calculated

values (<4%).

Kinetic Parameter CONDOR-CITVAP MCNP Serpent 2 (IFP)

βeff [pcm] 768 770 766

Λ [μs] 171 172 177

α [1/s] 45 45 44

Kinetic

ParameterMeasurement

Serpent 2

(IFP)MCNP

α [1/s] 38.1 38.8 37.2

Good agreement with calculated and

measured values (<3%).





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In-Core Thermal Flux:†

Measurements from commissioning at low power (36kW±6)

Modeled in Serpent considering CR positions

Mesh detectors included

Overall power set to 36kW

Relevant positions considered

Axial profiles included

0.E+00

5.E+10

1.E+11

2.E+11

2.E+11

3.E+11

3.E+11

4.E+11

4.E+11

5.E+11

5.E+11

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

Ther

mal

Flu

x (

E<

0.6

25eV

) [

n/c

m2s]

Axial position [cm]

A2 - measured

A2 - Calculated Serpent 2

A2 - CONDOR-CITVAP

0.E+00

5.E+10

1.E+11

2.E+11

2.E+11

3.E+11

3.E+11

4.E+11

4.E+11

5.E+11

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

Th

erm

al F

lux

(E

<0

.62

5eV

) [

n/c

m2

s]

Axial position [cm]

D2 - measuredD2 - Calculated Serpent 2 D2 - CONDOR-CITVAP

Positions in FA in D2 and A2





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4- Full 3-D model in Serpent with

Refueling using diverse approaches

New challenge:

• Can we perform full 3-D Burnup calculation in Serpent for a state of art

Research Reactor including refueling?

To perform this task an external code that operates with the Serpent 2

restart file was developed

• The results obtained were compared for cycles 7 to 12 of OPAL reactor

using the diverse approaches available in INVAP Calculation line:

1. CONDOR (HRM- 2D) + CITVAP (finite difference diffusion 3-D) model.

2. CONDOR (HRM- 2D) + CITVAP (finite difference diffusion 3-D) model

compositions inserted in Serpent 2.1.24 model using NDDUMP code.

3. Full 3-D Model in Serpent 2.1.24, including refueling using an external

code that operates with restart file to perform refueling.


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20 axial subdivisions.

Plates and BP (Cd wires) evolved independent in CONDOR.

69 energy groups at cell level, 3 groups at core level.

¼ FA Condor cell model CITVAP model x-y cut



1- CONDOR (HRM- 2D) + CITVAP (finite difference diffusion 3-D) model


Standard cell + core level approach.

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10 axial subdivisions, no division in plates or Cd wires radii for

each axial zone



2- CONDOR (HRM- 2D) + CITVAP (finite difference diffusion 3-D) model

compositions inserted in Serpent model using NDDUMP code

Compositions from CONDOR+CITVAP

are inserted in Serpent input using

INVAP’s developed NDDUMP code.


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10 axial subdivisions

Automatic division of depletion

zones: division in plates & Cd

wires

4 radii for each Cd wire

9760 depleted materials

Parallel calculation (OMP)



3- Full 3-D Model in Serpent, including refueling using an external code

that operates with restart file

Full Serpent model + external refueling using

Restart file processing.


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3- Full 3-D Model in Serpent, including refueling using an external

code that operates with restart file (cont)

How do we perform refueling

Burn with

SerpentSave restart file

(f.e. rest1.res)

Get a new restart

file where refuel

compositions are

included using a

ad-hoc code

(f.e. rest2.res)

Read restart

file in Serpent

(rest2.res)

Details to be considered:

moving different FA types

easy input to process restart file


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Obtained results for Cycles 7 to 12 – All Rods Out:

Good Agreement between 3 approaches !

Differences in Serpent in NDDUMP due to Cd wires modeling

Full 3-D modeling in Serpent + Refueling is possible for RR

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165

Exce

ss R

eac

tivi

ty [

pcm

]

FPD

Serpent full 3-D model - 9760 materials

Serpent Calculation using CONDOR-CITVAP Compositions (obtained with NDDUMP)Condor + CITVAP


Cycle 07

Cycle 12

3 types of FA with

diverse U load BP1 FA type

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We can also check measured critical positions (f.e. Cycle 12) using

the Serpent restart file and reported CR positions.

Very good agreement with experimental results (< 1000 pcm)!

Full 3-D modeling in Serpent + Refueling + critical position

check is possible for RR


-1500

-1250

-1000

-750

-500

-250

0

250

500

750

1000

1250

1500

1750

2000

135 140 145 150 155 160Re

acti

vity

[p

cm]

FPD

Cycle 12 - burn with Serpent - critical CR positions

Some CR

positions with

Xenon not in

equilibrium

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Further comments (regarding calculation aspects) in Serpent:

1. Calculation time:

For each cycle 6E4 min of [email protected] 15h in a 64CPUs node in (OMP mode)

Full 6 cycles can be calculated within 1 week in a 64CPUs node in (OMP mode)

2. Memory Requirements:

3. Factors affecting efficiency:

Case Full Serpent model Serpent + NDDUMP model

# burn materials 9760 None

MAT_MEMSIZE [Mb] 56521.80 1243.01

XS_MEMSIZE [Mb] 2633.57 643.23

0.0E+00

1.0E+04

2.0E+04

3.0E+04

4.0E+04

5.0E+04

6.0E+04

0.00

0.20

0.40

0.60

0.80

1.00

1.20

26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Tota

l CP

U t

ime

[min

s]

OM

P F

ract

ion

Burnup FPD

Cycle 08 OMP Fraction

Cycle 08 - no depout 3 OMP Fraction

Cycle 08 Total running time

Cycle 08 - no depout 3 Total running time


Depout

Mesh plots

Others...

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5- Conclusions

• All main parameters for OPAL Reactor measured during commissioning

were calculated in past works, good agreement was encountered compared

with experimental data and with results from INVAP deterministic

Calculation line and independent MCNP models.

• Full core calculations including burnup and refueling can be carried

out for MTR reactors using Serpent:

A code to perform refueling using Serpent restart files was developed

and tested.

Good agreement with other calculation schemes & experimental data.

High memory & CPU resources requirements.

• Serpent 2 can be used as independent Calculation Line at diverse

levels: Cell, Full Core, Full Core using external compositions, etc.


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• A Validation effort can be carried out by Serpent Users? How

can we contribute?

• Detailed Data is available in IAEA or CEA framework for

several Research Reactors & NPP (IAEA benchmarking

database Series 480 + IAEA CRP for burnup + NEA

International Handbook of Evaluated Reactor Physics

Benchmark Experiments - IRPhEP, etc) Should users

develop a Serpent benchmarks database?


5- Conclusions

Questions?

Thanks for your attention!

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