AN ALTERNATIVE PROPOSAL FOR A HIBRID REACTOR (SUB-CRITICAL

FACILITY COUPLED WITH AN ACCELERADOR)

Sergio A. Pereira and Adimir dos Santos

Schematic representationof Rubbia’s EnergyAmplifier

RUBIA’S PROPOSAL

• a cyclotron like this is not possible nowadays• with one spallation point, the central fuel elements will achieve higher temperature and burn with higher radial power density• to start the reactor, the lead must be liquid - aprox. 4 months• Pressure vessel - 30m high• structural problems during earthquakes• the vapor generator and core maintenance is remote and very difficult, due to the liquid lead

• more than one point of spallation: - reduce the requirement of proton energy and current of the accelerator, - to make a flatter power density distribution.• the subcritical core is replaced by a concept of a solid lead calandria with the fuel elements in channels cooled by Helium: - allows on line refueling or shuffling, - utilization of a direct thermodynamic cycle (Brayton), which is more efficient than a vapor cycle• the utilization of He as coolant: - more realistic, since the gas cooled reactors technology is well established, - more efficient from the thermodynamic view, allowing simplification and the utilization in high temperature process like hydrogen generation

Objectives

CalculationLAHET/HETC

Heat generatedin the spallation region and their

products

Angular, spatial andenergetic distribution

of the neutron and photon sources

Spallationregion

dimension

MCNP-4C

NJOY

Cross section andenergy deposition

KERMA

Power,Power distribution,Keff,Energy deposition,etc ...

TRANSM

Methodology to be usedon simulations

L

APb

First thermal barrier:area- Ael temp - T1

Second thermal barrier:area - AHe

temp. - T2

He cooling pipe ( THe )

FuelElement

Tel (800-850°C)

elel ATTq )( 41

4

PbPb AL

TTkq 21

HeHe ATThq )( 2

(radiation)

(conduction)

(convection)

Experimental and calculated results of JEZEBEL experiment

Experimental and calculated results of THOR experiment

Comparison betweenproton been resultsobtained with FLUKAand LAHET

Comparison betweenEA parameters obtainedwith FLUKA and LCS

Cylindrical fuel elementrepresentation with ahexagonal fuel roddistribution

Alternative conceptwith 3 spallationregions

Radial power density distribution of the 3 spallation sourcesconfiguration

Final results

CONCLUSION

• the methodology utilized reproduces with good accuracy the benchmark results

• in order to keep the lead solid, the solution of using pipes with helium between the fuel elements guarantees that the temperature will stay well below the limit (328 C)

•the proposed conception possesses a gain of 70. For a 1GeV proton• the gain is 110 which is closer to Rubia ( 120)

•using a tree spallation source configuration we achieved a formfactor smaller than 2, when compared with 7, in the case with one central spallation source configuration.

FUTURE WORK

• Fuel burnup

• Nuclear Data for Th-232 and U-233

•Nuclear Data for the Spallation Process

•Experimental Support . Closest to the Desirable is MYRRHA . Still in the design stage.