1. M. I. Al-Jarallah Future Power Production System 1 Presentation by: M. I. Al-Jarallah Department of Physics King Fahd University of Petroleum & Minerals Dhahran-Saudi Arabia Contact: 009 663 860 2281 Email: mibrahim@kfupm.edu.samibrahim@kfupm.edu.sa Homepage: http://faculty.kfupm.edu.sa/phys/mibrahim Future Power Production System

2. M. I. Al-Jarallah Future Power Production System 2 1.Introduction 2.Advantages & Disadvantages 3.Available ADSs and Those in The Design Stages 4.Diagrams of the Facilities 5.Target, Fuel, Coolant and Accelerator Types 6.The Physics of Spallation 7.Applications of ADSs 8.Conclusion

3. M. I. Al-Jarallah Future Power Production System 3 Neutrons resulting from interaction of relativistic projectiles with extended targets [e.g. protons on lead], can be used for energy production and nuclear waste transmutation, in sub- critical nuclear assemblies. These systems are known as Accelerator Driven Systems [ADS], and are also called AD Sub-critical Reactors [ADSR]. They are designed to replace or supplement conventional nuclear reactors as neutron sources. –In such system, an accelerator produces an energetic and intense proton beam [several hundred MeV to a few GeV, 5 – 100 mA], which is made interact with a cooled target consisting of lead or other high mass nuclei to produce fast neutrons through Spallation Process. Spallation Process is the nuclear reaction of high energy protons with nuclei. –These neutrons can then be moderated and used for some of the same purposes as the neutrons that are produced in a reactor through the fission process. Similar ideas were first proposed more than fifty years ago ! 1. Introduction

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5. M. I. Al-Jarallah Future Power Production System 5 A) Advantages of an ADS over conventional reactors: 1.Greater efficiency in neutron production 2.Greater safety in operation 3.Less production of unwanted radioactive materials in particular, Pu or other transuranium actinides by using thorium fuel. Thorium is more abundant than Uranium, it generates much less transuranic actinides among the radioactive waste and the risk of nuclear proliferation is negligible. Thorium based thermal reactor cannot operate in a satisfactory way on a self sufficient 232Th – 233U cycle. Evidently an external supply of neutrons remove the above mentioned limitations. 2. Advantages and Disadvantages of ADS

6. M. I. Al-Jarallah Future Power Production System 6 B) Disadvantages of ADS compared with existing reactors: 1.The need to construct accelerators that are considerably more powerful than existing one. 2.The need to accurately determine many as yet unknown or poorly known nuclear data for the target and other material used in the system 3.The need to develop chemical separation and partitioning methods that are specific to the process in an ADS.

7. M. I. Al-Jarallah Future Power Production System 7 Because of the mentioned problems, only a few ADS are in use or have been designed to some degree of details at the present time. These are: The SING facility at the Paul Scherror Institute [PSI] in Villigen, Switzerland, makes uses of the 590 MeV, 1.5 mA proton beam from PSI cyclotron: (n th = 10 13 cm -2 s -1,) Russian facility in the Joint Institute for Nuclear Research, Dubna, Russia (GeV). MYRRHA: A multipurpose ADS being developed jointly by Belgian Nuclear Research Center and Ion Beam Applications [350 MeV, 5 mA proton beam]. The Spallation neutron facility to be built at Oakridge National Laboratory [ORNL] in cooperation with several other U.S. national laboratories, will have about twice the neutron flux in, SING facility the European Spallation Neutron Source [ESS] and a Japanese facility with similar design features, will have an order of magnitude higher thermal neutron flux of SING facility. 3. Available ADS and those in the Design Stage

8. M. I. Al-Jarallah Future Power Production System 8 Fig. 1 Schematic View of the Target System

9. M. I. Al-Jarallah Future Power Production System 9 Fig. 2 Schematic Diagram of a Separate High Energy Target

10. M. I. Al-Jarallah Future Power Production System 10 Fig. 3 Scheme of the Target and Fuel Spheres

11. M. I. Al-Jarallah Future Power Production System 11 Fig. 4 Diagram of a Beam Driven Liquid Cooled ADS Without Separate Target.

12. M. I. Al-Jarallah Future Power Production System 12 Fig. 5 Diagram of the Fuel Assembly

13. M. I. Al-Jarallah Future Power Production System 13 Fig. 6 Diagram of Spherical Fuel Pellets in a Fluidized Bed Configuration

14. M. I. Al-Jarallah Future Power Production System 14 Fig. 7 Global view of the present design of MYRRHA

15. M. I. Al-Jarallah Future Power Production System 15 Fig. 8 MYRRHA in a confinement building that is inaccessible during operation

16. M. I. Al-Jarallah Future Power Production System 16 A) Target Types: Solids or liquids can be used as fuel. The requirement for both is high neutron yields and for solids they should have high fusion temperature: Lead [fusion 327 o ] heavy target is considered practical Solid Tungsten Solid [metallic, oxides, nitrides, carbides, etc.] Lead – Bismulth liquid targets 5. Target, Fuel, Coolant and Accelerator Types:

17. M. I. Al-Jarallah Future Power Production System 17 1.Higher heat removal capability due to the fact that the heated material is transported rather than the heat. 2.Higher spallation material density in the volume due to absence of cooling channels which tend to dilute the target the more the higher the power density. 3.No or minimum amount of water with its associated problems in the proton beam. 4.No life time limit caused by radiation damage in the target material. 5.Significantly lower specific radioactivity in the target material due to the target mass used and perfect mixing, making an emergency cooling system unnecessary. 6.The inside pressure in the target can be significantly lower than in water cooled system, putting less stringent requirements on the ca`sing wall. The advantages of liquid metal targets over volume cooled solid targets:

18. M. I. Al-Jarallah Future Power Production System 18 B) Fuel Types: Solids [metallic, oxides, nitrides, carbides, etc.] Molten Salt [Fluorides or Chlorides] C) Cooling Agent Gas Molten Metal [Sodium, Lead, or Lead, Bismulth] Molten Salts [Transparent to visible light, and thus allow visual inspection] D) The Accelerator System Cyclotron: more compact and thus require less space and more economical. However there is current limitation: 5 – 10 mA. LINACS: Current  100 mA

19. M. I. Al-Jarallah Future Power Production System 19 6. The Physics of Spallation The physics of spallation is in fact rather complex because of the large range of energies involved, and efforts are still going on in various locations to develop models that reproduce all the pertinent experimental observations. During the spallation process not only n’s but also protons and other light nuclei are emitted from the excited nuclei. As a consequence, the residual nuclei are not only neutron–poor isotopes of the parent nucleus that decay, mainly by internal p  n conversion and  + emission, into lower Z elements, but these elements are also created directly in the spallation process.

20. M. I. Al-Jarallah Future Power Production System 20 About 90% of the n’s released from thick targets in a spallation reaction can be described by characteristic energies around 1 – 2 MeV and are emitted more or less isotopically. Their spectral and angular distributions thus resemble closely to those of fission n’s [Figure 9 ]. The small fraction cascade n’s whose energy can reach up to that of the primary particles driving the reaction, are emitted mainly in the forward hemisphere relative to the proton beam. They are difficult to moderate and thus constitute the main problem in shielding and activation in a spallation neutron source.

21. M. I. Al-Jarallah Future Power Production System 21 Fig. 9 Calculated neutron spectra for fission and for spallation in a tungsten target

22. M. I. Al-Jarallah Future Power Production System 22 Fig. 10 Chain of Possible Reactions Starting from Initial 232 Th fuel. Cross Sections are for Thermal Neutrons in Barns.

23. M. I. Al-Jarallah Future Power Production System 23 Fig. 11 Time Evolution of the Composition of an Initial, Thin Thorium Slab Exposed to a Constant Thermal Neutron Flux of 1.0 x10 14 cm -2 s -1.

24. M. I. Al-Jarallah Future Power Production System 24 Fig. 12 Chain of Possible Reactions Starting from initial 238 U fuel.

25. M. I. Al-Jarallah Future Power Production System 25 Fig. 13 The Evolution of the Composition of an Initially Slightly Depleted Uranium Fuel.

26. M. I. Al-Jarallah Future Power Production System 26 1.Production of Energy: a credible alternative to fast breeder and fusion reactors. They give a unique opportunity to improve the social acceptability of fission energy. 2.Nuclear Waste Processing: Transmutation, which by neutron capture, transforms a radioactive nucleus into a stable one. Incineration which amount to nuclear fission following neutron capture [transuranic elements such as Pu and minor actinides: Np, Am, Cn. They have high radiotoxicities due to this dominant  decay. They have long lifetimes, up to 25000 years for 239 Pu]. At least one incineration reactor for four PWRs would be needed if one wants to incinerate completely plutonium and minor actinides. 3.Production of radioisotopes for medical and industrial purposes. 4.Production of tritium 7. Applications of ADSs:

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29. M. I. Al-Jarallah Future Power Production System 29 It is evident that ADS are now accepted by sponsoring agencies and by members of the nuclear community as valuable new tools in basic research and in applications. This will require new technologies of immediate relevance for ADS development. A first demonstration prototype of several tense of MW could be build within 5 – 7 years. An industrial realization would probably require at lest 15 years. 8. Conclusion:

30. M. I. Al-Jarallah Future Power Production System 30 Thank You