comparison of serpent and evolcode in a sodium fast...

Comparison of SERPENT and EVOLCODE in a Sodium Fast

Reactor loaded with MA

R. Ochoa, M.Vazquez, F. Alvárez-Velarde,

N. García-Herranz, F.Martin-Fuertes, D. Cuervo

1 2012 Serpent International Users group meeting. 19th-21st Sept, UPM, Madrid

Outline

1. Introduction

2. Codes (EVOLCODE)

3. Calculation schemes

4. Models for CONF2, HET2 & HOM4 cases

5. Results: transmutation, reactivity, kinetic parameters, feedback coefficients, power distributions

6. Conclusions

2 2 2012 Serpent International Users group meeting. 19th-21st Sept, UPM, Madrid

As a result of the optimization studies performed in SP2.1, an optimized oxide core with a reduced sodium void reactivity has been defined: CONF2

The assessment of the MA recycling possibilities in this configuration is of major interest

Most of studies use deterministic calculation routes, like ERANOS; it is important to apply realistic tools that offer more accurate results in order to verify the deterministic methodologies and assess the confidence resulting from the simulations

The integration of depletion modules and MC codes provides tools able to model very detailed and complex 3D core geometries using continuous-energy x-sections: EVOLCODE, SERPENT

1. Introduction


1. Introduction

Double Purpose: assessment of the effect of MA loading on reactivity coefficients and kinetics data for the optimised CONF2 configuration

– CONF2: reference case without initial MA (optimised oxide fuelled core)

– HET2-CONF2: lower transmutation case, in which MA produced by the oxide core only are recycled

– HOM4-CONF2: upper transmutation case, in which higher levels of MA are recycled to enable transmutation of waste from thermal reactors

Objectives: – give realistic estimates of reactor core characteristics

– compare the obtained results with the ones computed using other MC-linked depletion codes (EVOLCODE) to assess the confidence resulting from MC simulations


2. EVOLCODE

5

EVOLCODE 2.0 Developed at CIEMAT

MCNPX coupled with ORIGEN and ACAB codes

2012 Serpent International Users group meeting. 19th-21st Sept, UPM, Madrid

3. Calculation schemes

6

Continuos energy Monte Carlo transport calculation: – JEFF3.1.1 cross section library

Burnup Calculations: – Burnup using JEFF-3.1.1 decay data and fission yields libraries

– Fuel irradiation time divided into 5 cycles of 410 efpd

– Control rods on the top of the fissile core

SERPENT EVOLCODE (Parallel 128 cores)

Calculation time of a single burnup step Total calculation time

~8 h proc 3.07GHz 24GB RAM ~48 h*

~2h15m proc 3GHz (2GB/core) ~13h

Running time


SERPENT EVOLCODE

Neutron histories Active cycles

Keff Average statistical uncertainty

150 000 200

10pcm

150 000 200

8pcm

*High memory requirements made parallel calculations not available

4. Models

7

Models – Very detailed heterogeneous models of the three configurations were

developed for SERPENT and EVOLCODE

– Temperatures:

• Fissile fuel : 1227 ºC or 1500 K

• Fertile fuel: 667 ºC or 900 K

• Coolant and structures: 470 ºC or 743 K


4. Models: CONF2


Inner Core: 8 active rows Fresh fuel: Pu: 14.76%w HM U: 85.24 %

Outer Core: 4 active rows Fresh fuel: Pu: 17.15%w HM U: 82.85%

Lower fertile blanket Fresh fuel: U: 100%w

CONF2


HET2 Outer Core: 4 active rows Fresh fuel: Pu: 17.15%w HM U: 82.85%

Inner Core: 8 active rows Fresh fuel: Pu: 14.76%w HM U: 85.24 %

Lower fertile blanket Fresh fuel: U: 100%w

Additional ring of 84 sub-assemblies Fresh fuel: U: 80% MA: 20%


HOM4 Outer Core: 4 active rows Fresh fuel: Pu: 17.15%w HM U: 78.85% MA: 4%

Inner Core: 8 active rows Fresh fuel: Pu: 14.76%w HM U: 81.24 % MA: 4 %

Lower fertile blanket Fresh fuel: U: 96%w MA: 4%


3. Models: Differences between SERPENT and EVOLCODE

12

In the analysis with SERPENT, only 2 axial levels were considered, one for the active core, 100 cm high, and one axial level for the lower blanket, 30 cm high.

In the analysis with EVOLCODE, 11 axial levels were considered, 10 axial levels in the active core, 10 cm high each, and one axial level at the bottom, for the lower blanket, 30 cm high. Moreover, an additional sensitivity case with only 2 axial levels has been also explored for direct comparison with SERPENT.


Energy-dependent branching ratios: influence?

4. Results: MA evolution


Transport σ1G

Burnup σ1G

(n,γ) (n,γ)

(n,γ)*

242Cm

241Am

(n,γ-m)

242Am

242mAm

(n,γ)

β – (83%) ground *

TRANSPORT BURNUP BURNUPσ σ σ= +ground

* groundSERPENT

σBRσ σ

=+

Effect of branching ratios

(99%)


14




15

BR = 0.885 BR = 0.867

Mass SERPENT

Differences EVOLCODE

Mass SERPENT

Differences EVOLCODE

Am-241 142.870 -0.1% 142.872 -0.1% Am-242 0.045 3.8% 0.045 2.2% Am-242m 3.297 -12.1% 3.813 1.6%

Isotopes mass (kg) at 820d (BOC) for CONF2


SERPENT sets constant branching values: BR (Am-241) = 0.885

EVOLCODE accounts for energy-dependent branching: <BR>ESFR= 0.867

A correct branching ratio is needed to predict accurately the inventory produced via isomeric transitions


EFPD 0 410 820 1230 1640 2050 2050

(BOL) (BOC) (EOC) (EOL) (default BR Am241= 0.885)

U235 0.01 -0.32 -0.77 -1.28 -1.77 -2.23 -2.29 U236 - 1.63 1.81 1.85 1.74 1.57 n.a. U237 - 1.14 2.20 2.07 2.20 2.12 n.a. U238 0.02 0.03 0.04 0.04 0.04 0.04 0.04

NP237 0.03 -0.19 -0.45 -0.74 -1.01 -1.28 -1.32 NP238 - 1.95 2.22 2.13 1.68 1.45 1.45 NP239 - -0.72 -0.44 -0.26 -0.31 -0.38 -0.28 PU238 0.02 0.61 1.21 1.56 1.69 1.68 2.85 PU239 0.02 -0.24 -0.40 -0.50 -0.61 -0.72 -0.71 PU240 0.02 0.00 -0.03 -0.06 -0.09 -0.13 -0.13 PU241 0.03 -0.09 -0.26 -0.39 -0.50 -0.57 -0.58 PU242 0.03 -0.04 -0.10 -0.16 -0.22 -0.31 -0.08 PU243 - 0.76 0.48 0.33 0.25 0.01 0.01 AM241 0.02 -0.22 -0.56 -0.94 -1.31 -1.68 -1.74 AM242 - 2.17 2.36 2.48 1.89 1.63 3.97

AM242M 0.34 1.71 2.05 2.04 1.73 1.31 -11.81

AM243 0.02 -0.10 -0.23 -0.35 -0.45 -0.53 -0.68 CM242 -0.90 2.63 2.91 2.94 2.61 2.25 4.47 CM243 1.18 0.67 1.52 2.44 3.00 3.13 5.13 CM244 0.04 0.38 0.61 0.75 0.83 0.85 0.84 CM245 0.06 -0.11 -0.18 -0.14 -0.05 0.05 0.08 CM246 0.72 0.84 0.86 0.82 0.80 0.76 0.80

U 0.02 0.03 0.04 0.04 0.04 0.04 0.03 NP 0.03 -0.20 -0.45 -0.73 -1.00 -1.25 -1.29 PU 0.02 -0.10 -0.18 -0.22 -0.29 -0.36 -0.26 AM 0.03 -0.18 -0.43 -0.72 -1.00 -1.26 -1.85 CM 0.06 0.83 1.01 1.06 1.02 0.96 1.28


4. Results: mass evolution

Differences (SERP-EVCD)/ EVCD in %

for the HOM4

4.Results: Actinides evolution


CONF2 HOM4 HET2

SERPENT EVOLCODE SERPENT EVOLCODE SERPENT EVOLCODE

Charged mass (kg)

U 87190.4 87158.7 80676.1 80659.7 101514.2 101483.7 Np 0.0 0.0 650.1 649.9 603.9 603.7 Pu 11855.9 11849.7 11856.8 11854.4 11855.9 11849.7 Am 93.2 93.2 2951.8 2951.0 2835.5 2834.7 Cm 0.0 0.0 253.8 253.6 235.7 235.6 MA 93.2 93.2 3855.7 3854.5 3675.1 3673.9 Discharged mass (kg) U 78017.4 77948.7 72632.4 72605.1 92160.2 92089.6 Np 44.1 43.3 406.0 411.1 583.8 583.5 Pu 13120.8 13209.1 13417.4 13466.4 13711.6 13799.3 Am 338.8 338.3 1900.4 1924.7 2701.7 2703.4 Cm 66.1 65.6 472.0 467.5 333.6 332.0 MA 449.0 447.2 2778.4 2803.4 3619.1 3618.9

Max. relative differences of: 0.06% in charged mass and 1.16% in discharged mass

0.06%

1.16%


CONF2 HOM4 HET2


Transmutation Rate (%) at EOL

U -10.5 -10.6 -10.0 -10.0 -9.2 -9.3 Np - - -37.5 -36.7 -3.3 -3.3 Pu 10.7 11.5 13.2 13.6 15.7 16.5 Am 263.5 263.2 -35.6 -34.8 -4.7 -4.6 Cm - - 86.0 84.3 41.5 40.9 MA 381.7 380.0 -27.9 -27.3 -1.5 -1.5 Mass balance (kg/TWhe) at EOL U -129.5 -130.0 -113.5 -113.7 -132.0 -132.6 Np 0.6 0.6 -3.4 -3.4 -0.3 -0.3 Pu 17.9 19.2 22.0 22.8 26.2 27.5 Am 3.5 3.5 -14.8 -14.5 -1.9 -1.9 Cm 0.9 0.9 3.1 3.0 1.4 1.4 MA 5.0 5.0 -15.2 -14.8 -0.8 -0.8




Transmutation Rates (EOL-BOL)/BOL in %

4. Results: Pu evolution

20

Pu isotopes evolution


Differences lower than 1%

Total Pu increase, % CONF2 HOM4 HET2

(Pu(t)-Pu(BOL))/Pu(BOL) SERPENT EVOLCODE SERPENT EVOLCODE SERPENT EVOLCODE

Period 0-2050 EFPD 10.67 11.47 13.16 13.60 15.65 16.45 Period 820-1230 EFPD 2.05 2.17 2.61 2.66 2.94 3.06

Mass balance (kg) for Pu isotopes at EOL (Pu(EOL)-Pu(BOL))


21

MA evolution


4. Results: transmutation

22

Am isotopes evolution


-1000

-800

-600

-400

-200

0

200

400

Am241 Am242 Am242m Am243 Amtotal

HET2

Inner Outer Blanket Radial ring

-1000

-800

-600

-400

-200

0

200

400


CONF2

Inner Outer Blanket

-1000

-800

-600

-400

-200

0

200

400


HOM4

Inner Outer Blanket

Mass balance (kg) for Am isotopes at EOL (Am(EOL)-Am(BOL))

Total Am increase, % CONF2 HOM4 HET2

(Am(t)-Am(t0))/Am(t0) SERPENT EVOLCODE SERPENT EVOLCODE SERPENT EVOLCODE

Period 0-2050 EFPD 263.5 263.2 -35.6 -34.8 -4.7 -4.6 Period 820-1230 EFPD 19.5 19.5 -8.5 -8.2 -1.0 -1.0

Differences lower than 1% !!

4. Results: Reactivity

23

Reactivity


1

1.005

1.01

1.015

1.02

1.025

1.03

1.035

1.04

0 410 820 1230 1640 2050Time (days)

K-eff evolution

CONF2-EVOLCODE CONF2-SERPENT HOM4-EVOLCODE

HOM4-SERPENT HET2-EVOLCODE HET2-SERPENT

4. Results: kinetic parameters

Mean Generation Time – Calculated by SERPENT as:

• RECIPVEL / NSF

• IMPL_PROMPT_LIFETIME / IMPL_KEFF

– Compared with ERANOS, an order of magnitute higher

Effective delayed neutron fraction – Provided by default in SERPENT

– EVOLCODE: Modified MCNPX version, tracking the delayed neutrons by fission and obtaining their multiplication


CONF2 HOM4 HET2


βeff @ BOC, pcm 373 370 350 346 372 368 βeff @ EOC, pcm 367 362 345 338 365 359

SERPENT ERANOS

2.0566E-06 4.12E-07

1*f vν

Λ =Σ

lk

Λ =

4. Results: feedback coefficients

25

Doppler constant Computed by comparison of the nominal and perturbed state Nominal state: fissile mediums temperature is 1500 K Perturbed state: same fuel isotopic composition, fissile mediums at 2500 K

(inner and outer core; fertile blanket remains at 900 K)


Sodium void Two cases on the base of different voided regions involving only inside

wrapper zones, while outside wrapper remains normally flowed Core void: active core (inner + outer) Reactor voided: active core (inner+outer)+UGP+plug+Na plenum

4. Results: feedback coefficients

26

BOC


EOC

CONF2 HOM4 HET2


Doppler, pcm -891 -827 -562 -594 -762 -783 Core void worth, pcm 1476 (3.96$) 1516 (4.10$) 1714 (4.9$) 1712 (4.95$) 1527 (4.11$) 1517 (4.12$) Reactor void worth, pcm 719 (1.93$) 767 (2.07$) 1036 (2.96$) 1061(3.07$) 781 (2.1$) 743 (2.02$)

CONF2 HOM4 HET2


Doppler, pcm -727 -772 -570 -629 -723 -717 Core void worth, pcm 1636 (4.5$) 1654 (4.6$) 1778 (5.2$) 1746 (5.2$) 1622 (4.5$) 1626 (4.5$) Reactor void worth, pcm 896 (2.4$) 922 (2.5$) 1145 (3.3$) 1095 (3.2$) 907 (2.5$) 875 (2.4$)

Differences lower than 10% !!

27

CONF2

HET2

t = 0 days

HOM4

4. Results: power distribution

28

HET2

t = 410 days

HOM4

CONF2


29

HET2

t = 820 days

HOM4

CONF2


30

HET2

t = 1230 days

HOM4

CONF2


31

HET2

t = 1640 days

HOM4

CONF2


32

HET2

t = 2050 days

HOM4

CONF2


Detailed models of CONF2 without and with MA loading have been developed for SERPENT and EVOLCODE

Code comparison: – results predicted by the two codes are very close in keff

estimations before activation of burnup models.

– After a typical long irradiation period of 2050 EFPD, discrepancies between EVOLCODE and SERPENT are quantified in the order of 3% concerning isotope masses, 600 pcm top in keff, and 10% concerning reactivity parameters.

– The fuel depletion models likely explain the observed differences

5. Conclusions


Core performance: – SERPENT has proven to be a reliable tool to analyze core

physics problems of Fast Reactors: transmutation, core performance, etc.

5. Conclusions


Thanks for your attention

35 2012 Serpent International Users Group meeting. 19th-21st Sept, UPM, Madrid

comparison of serpent and evolcode in a sodium fast...

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