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Characterization of the SAFARI-1 Characterization of the SAFARI-1

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Characterization of the SAFARI-1 Characterization of the SAFARI-1

Material Testing Reactor

B.M Makgopa

Radiation and Reactor Theory

South African Nuclear Energy Corporation (Necsa) Pelindaba, Pretoria

53 rd Annual Conference of the South African Institute of Physics (SAIP), 8-11 July 2008, y ( ), y ,

University of Limpopo

(2)

Outline Out e

1. Purpose of the study

9 SAFARI-1 Reactor Core layout 9 SAFARI 1 Reactor Core layout

9 Support for PBMR Fuel Research and Development

2. Tools and Software

9 OSCAR-4

9 MCNP

9 OSMINT

3. Results and Discussions

9 Core Flux and Power Distributions

9 Flux and Power Distributions in B6, D6, F6

4. Conclusions and Future Work

(3)

Purpose of the Study u pose o t e Study

9 SAFARI-1 Reactor Core Layout

F l bl

Fuel assembly

Control assembly

Flux trap

1 2 3 4 5 6 7 8 9

A B

Solid aluminium

Hollow aluminium C

D E

Solid beryllium

Hollow beryllium F

G H

Solid lead

(4)

Tools and Software oo s a d So t a e

9 OSCAR4 – Overall System for CAlculation of Reactors

» a core depletion code that is based on nodal diffusion methods

9 MCNP – Monte Carlo N-Particle code

» for neutron, photon and electron transport

» capability to model very complex geometries

9 OSMINT – Oscar4-MCNP INTerface

» links OSCAR and MCNP

t f t i l i t i f OSCAR t MCNP

» transfer material isotopics from OSCAR to MCNP

» generating a core that is correct in space and time

(5)

Proposed Fuel Pebble Irradiation Rig oposed ue ebb e ad at o g

9Fuel pebble

» 6 cm in diameter 9Graphite cup

9Helium gas flow g

9Stainless steel capsule 9Helium gas flow

9Stainless steel rig

9Stainless steel rig

9Aluminium water box

(6)

The Proposed Rig and the Fuel Pebble

9Fuel pebble 9Fuel pebble

» 2.5 cm radius – fuel region

» ~ 15 000 coated fuel particles on a 3-D triangular lattice

» 3 cm radius non-fuel shell (graphite)

» 3 cm radius non fuel shell (graphite)

9Coated fuel particle

» low enrichment (<10% 235 U) – UO 2 fuel kernel

» Carbon buffer layer

» IPyC/SiC/OPyC – TRISO-type fuel

(7)

Results and Discussions I esu ts a d scuss o s

Global Effects (Core)

1x10

4

1 00E+014 rig out

i i

7x10

3

8x10

3

9x10

3

(W /cm

3

) 6.00E+013

8.00E+013 1.00E+014

tron s/cm

2

.s)

rig in

4x10

3

5x10

3

6x10

3

Ne ut ro n h eat in g

2.00E+013 4.00E+013

Neu tro n flux (n eu t

9 Fl d i th th l 1%

-30 -20 -10 0 10 20 30

2x10

3

3x10

3

Axial length of the core (cm) 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10

0.00E+000

Energy (MeV)

9 Flux decrease in the thermal energy range <1%

9 Flux increase in the epithermal and fast energy range <2%

9 Axial neutron heating increase (~4%) – pronounced in the region of the core centerline

the core centerline

(8)

Results and Discussions II esu ts a d scuss o s

Local Effects (Specific to B6, D6 and F6)

3.00E+014 B6

D6 3.00E+014

3.20E+014

B6 D6

2.00E+014 2.50E+014

trons/cm

2

.s)

D6 F6

1.60E+014 1.80E+014 2.00E+014 2.20E+014 2.40E+014 2.60E+014 2.80E+014

u trons/cm

2

.s )

D6 F6

5.00E+013 1.00E+014 1.50E+014

Ne ut ron fl ux (ne u

2.00E+013 4.00E+013 6.00E+013 8.00E+013 1.00E+014 1.20E+014 1.40E+014

Neutr on flux (n e u

9 rig out (left hand side figure) and rig in (right hand side figure)

1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 0.00E+000

Energy (MeV)

1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 -2.00E+013

0.00E+000

Energy (MeV)

9In B6, flux decrease ~50% at 1e-7 and ~20% at 1e-6 (thermal region) 9 Also in B6, ~50% increase in the fast neutron flux

9 neutron flux in D6 is insignificantly perturbed by insertion of the rig in B6,

similarly in F6 the perturbation in the neutron flux due to rig insertion was found

similarly in F6, the perturbation in the neutron flux due to rig insertion was found

to be very little

(9)

Results and Discussions III esu ts a d scuss o s

Local Effects (Specific to B6, D6 and F6)

600 B6

B6 D6

400 450 500 550

W /c m

3

)

B6 D6 F6

10

4

(W /c m

3

)

D6 F6

200 250 300 350

Neut ron Heat ing (W

10

3

N eutro n he ating

-30 -20 -10 0 10 20 30

100 150

Axial Length of the Irradiation Position (cm)

-30 -20 -10 0 10 20 30

10

2

Axial length of the irradiation position (cm)

9 rig out (left hand side figure) and rig in (right hand side figure) 9Neutron heating in D6 and F6 remains unchanged

9 In B6, the amount of neutron heating increases by two orders of magnitude g y g

(10)

Results and Discussions IV Results and Discussions IV

Local Effects (Specific to B6, D6 and F6)

1.30E+015 B6

D6

1.30E+015 B6

D6

8.00E+014 9.00E+014 1.00E+015 1.10E+015 1.20E+015

o tons/cm

2

.s)

D6 F6

8.00E+014 9.00E+014 1.00E+015 1.10E+015 1.20E+015

o tons/cm

2

.s)

D6 F6

3.00E+014 4.00E+014 5.00E+014 6.00E+014 7.00E+014

Photon flux (p h o

3.00E+014 4.00E+014 5.00E+014 6.00E+014 7.00E+014

Photon flux (p h o

9 rig out (left hand side figure) and rig in (right hand side figure)

-30 -20 -10 0 10 20 30

2.00E+014

Axial distance with respect to the core centerline (cm)

-30 -20 -10 0 10 20 30

2.00E+014

Axial distance with respect to the core centerline (cm)

9 rig out (left hand side figure) and rig in (right hand side figure)

9In B6, axial photon flux is decreased by ~ 50% due to absorption of photons in the rig materials)

9 The magnitude of the photon flux in D6 and F6 is only slightly perturbed in the

region of the core centerline

(11)

Results and Discussions V esu ts a d scuss o s

Local Effects (Specific to B6, D6 and F6)

B6 4 5 B6

3 0 3.5 4.0 4.5

W /cm

3

)

B6 D6 F6

3 0 3.5 4.0 4.5

W /c m

3

)

F6 D6

1.5 2.0 2.5 3.0

P ho to n He ating ( W

1.5 2.0 2.5 3.0

Phot n heating ( W

-30 -20 -10 0 10 20 30

0.5 1.0

P 1.5

Axial Length of the Irradiation Position (cm)

-30 -20 -10 0 10 20 30

0.5 1.0

Axial length of the Irradiation position (cm)

9 rig out (left hand side figure) and rig in (right hand side figure)

9In B6, axial photon heating is increased by over 50% due to absorption of photons in the rig materials)

Axial Length of the Irradiation Position (cm) Axial length of the Irradiation position (cm)

9 The magnitude of the photon heating remains almost unchanged in D6 and

F6.

(12)

6. CONCLUSIONS 6. CONCLUSIONS

• It is required to irradiate fuel pebbles at very high temperature environment in the SAFARI-1 core – to simulate the high

temperature in the PBMR core

• For such high temperatures to be confirmed as can achieved in the SAFARI-1 core, we require neutronic as well as thermal hydraulic calculations

• So far, the increase in the amount of neutron heating and photon heating in position B6 of the core when this rig is inserted gives hope that the envisaged high temperature environment can be achieved – pending thermal hydraulic

l l ti

calculations

(13)

FUTURE WORK FUTURE WORK

• Extend the rig to contain up to four pebbles and study its impact on the core parameters

• Investigate heat deposition variations in water and helium to better explain some of the striking phenomena

• Use high temperature cross sections for the fuel pebble

materials – to account for doppler effects

(14)

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