OPAL Reactor Full 3-D Calculations using the MonteCarlo ...€¦ · OPAL Reactor Full 3-D...

OPAL Reactor Full 3-D Calculations using the

MonteCarlo Code Serpent 2

By Diego Ferraro & Eduardo Villarino Nuclear Engineering Department – INVAP S.E. - Argentina

16th IGORR 2014/IAEA Technical Meeting

17th-21th November 2014 – Bariloche - Argentina

Presentation Overview

1- Introduction – Why using Serpent?

2- Previous Experiences & Motivation

3- Full Core 3-D model for the OPAL Research

Reactor

4- Results & Comparisons with experimental values

and other codes

5- Future works

6-Conclusions

2

16th IGORR 2014/IAEA Technical Meeting - 17th-21th November 2014 – Bariloche – Argentina

1- Introduction – Why Serpent?

• MonteCarlo (MC) Codes are used mainly :

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

•Several MC codes extensive validated are available (MCNP, KENO, etc).

•Usually demand high computational resources applications such as full

core burnup and cell calculations have been prohibitive in the past decades.

•Serpent Code is a brand-new Neutron/photon transport code developed

since 2004 at VTT Technical Research Centre of Finland specifically

oriented for such tasks, including burnup capabilities.

•Serpent 2 enhances geometrical capabilities. Allows burnup calculations, few-

group constant generation, kinetic parameters, flux distributions, etc.

3


2- Previous experiences & Motivation

• 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.

The reactor consists of a compact core of 16 LEU MTR-type fuels, cooled and

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

Reflector Vessel.

Several irradiation facilities in the Reflector Vessel: Cold Neutron Source with

two beams, a thermal neutron source with two beams, 17 vertical irradiation

tubes, 19 pneumatic RIGs , 6 NTDs facilities, space for a HNS.

It was designed, commissioned and performance tested using INVAP´s

calculation line (CONDOR + CITVAP) + MCNP4C.

4



• Previous works: Serpent 1 used as a cell-level code to model FA to obtain

few group constants to be used in core calculations (CITVAP) for the OPAL

Research Reactor, showing a good performance [1].

• Nowadays:

Increase in Serpent Capabilities + Parallelization Complex core models

may be developed, including burnup for Research Reactors.

Encouraged by the past results, a full 3-D Serpent 2 model for the OPAL

Research Reactor is developed in the present work.

Comparisons with experimental results from Commissioning & results

from INVAP´s neutronic calculation line & MCNP.

[1] D. Ferraro, E. Villarino, "OPAL Reactor Calculations using the Monte Carlo Code

Serpent", Proceedings of the 4th International Symposium on Material Testing Reactors

December 5-9, 2011, Oarai, Japan.

5


6

Objective:

Develop a full 3D

core model in

Serpent 2 &

compare results

with other codes &

experimental data

from Reactor

Commissioning



Full 3-D Serpent

Results

INVAP Neutronic Calculation Line:

7

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

Serpent 2 v1.21.

• Automatic Input generation through and spreadsheet.

• First Core configuration is modeled:

3 Fuel types (MTR)

5 CR, Chimney, Reflector Vessel.

• Simplified models for most relevant experimental facilities are included:

17 vertical irradiation tubes.

A simplified model for the Cold Neutron Source (CNS)

2 Cold neutron beams.

2 Thermal neutron beams.

Hot neutron beam.

• Results for these models are compared with experimental data from

Reactor Commissioning & Other codes:

Critical positions (from Reactor Commissioning).

Kinetic parameters.

In-core thermal flux profiles.

Full core burnup (1st cycle). 16th IGORR 2014/IAEA Technical Meeting - 17th-21th November 2014 – Bariloche – Argentina

3- Full Core 3-D model for OPAL RR

8


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

Developed model characteristics:

9


Full model x-y cut core detail


For burn cases, 10 axial subdivisions.

Plates and BP (Cd wires) evolved independent.

Unionized grid optimization to face RAM requirements.

Parallel calculations are compulsory (OMP).

Statistical error (1) <1% (flux) and 10/20 pcm (keff).

Full model x-y cut –centre of core – FA detail NE corner

4 – Results & Comparisons

10

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

Cases Serpent

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!


11

Kinetic Parameters: Measurements from Reactor Commissioning:

Due to detector efficiency requirements, during Commissioning of the OPAL

Reactor, the 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: In 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

Parameter Measurement

Serpent 2

(IFP) MCNP

α [1/s] 38.1 38.8 37.2

In good agreement with calculated and

measured values (<3%).


12

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


Fairly good agreement

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


13

In-Core Thermal Flux:

Measurements from commissioning for at low power

(36kW±6):


Differences with experimental data are below 5/8% in

average and inside the Power Uncertainty.

0.E+00

1.E+11

2.E+11

3.E+11

4.E+11

5.E+11

6.E+11

7.E+11

8.E+11

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

Th

erm

al F

lux

(E

<0.6

25eV

) [

n/c

m2

s]

Axial position [cm]

B1 - MeasuredB1-Calculated Serpent 2 B1 - CONDOR-CITVAP

0.E+00

1.E+11

2.E+11

3.E+11

4.E+11

5.E+11

6.E+11

7.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]

C1 - measuredC1 - Calculated Serpent 2C1 - CONDOR-CITVAP

Channels B1 and C1


14


Fairly good agreement with experimental values (Differences

800/400 pcm)

Full Core Burnup Calculations:

Critical positions for First Cycle burnup.

Real days converted to FPD.

ARO burn at Hot Full Power, saving a restart case. Then Critical CR

positions are modeled using compositions from restart.

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

16 17 18 19 20 21 22 23 24 25 26

Cal

cula

ted

Rea

ctiv

ity [pcm

]

FPD

Serpent 2 Calculated values for Critical positions at Full Power

15

5- Conclusions

• A full 3-D core model was developed in Serpent 2 v1.21 for the

state of art - 20MWth OPAL Research Reactor.

• All main parameters measured during reactor commissioning

were calculated, 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 are feasible in MTR

reactors considering:

High memory resources requirements are expected.

Fuel management capabilities are to be required.


6 – Future Works

16


Encouraged by the results from last sections, it is intended to extend the

burnup calculations to other cycles material management scheme is

compulsory.

Comparisons to experimental data to be extended to the reported

Neutron fluxes in bulk irradiation facilities, placed in the Reflector Vessel.

Questions?

Thanks for your attention!!


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