The Physics of Spallation Processes

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2.4. CONCEPTS OF TRANSMUTATION 252.4 Concepts of transmutationIn the last years on several international conferences the physics, technologies and economicaspects of energy generation and transmutation of nuclear waste by AcceleratorDriven Systems (ADS) were discussed and published in great detail [Bow92, AIP94,Bow96b, Ven96, Rub96b, Rub95, Rub97, Fil97, Pab97, ENEA01]. As for example the InternationalAtomic Energy Agency IAEA [IAEA97] reviews explicitly the existing projectsand international activities as e.g. the JAERI OMEGA project in Japan, the Los Alamosand Brookhaven National Laboratory ADS projects, the CERN-group conceptional designof a high power energy amplifier, the ADS program in Russia and France as well as theEuropean community projects. The physics design of ADS and the design of the so-calledEnergy Amplifier (EA, cf. sect. 2.5) is expatiated in detail also in several comprehensivecompilations of the AIP (American Institute of Physics) conference contributions 346[AIP94] and the Proc. of the 2nd Int. Conf. on Accelerator Driven Transmutation (ADT)held in Kalmar, Sweden [Ven96, Rub96b].Figure 2.11: Accelerator driven transmutation of radioactive waste.Scientists are divided on the choice of geological repositories for long lived waste disposal.It is in fact impossible to guarantee the integrity of this kind of storage for futuregenerations. A definitive solution to the problem would be the complete elimination ofthe most offending isotopes with the help of nuclear reactions which would allow longlivedelements to ”transmute” into stable ones. The application of high intense protonAccelerator driven systems for the Transmutation of long lived radioactive Waste (ATW)
26 CHAPTER 2. RESEARCH WITH NEUTRONSis discussed as an alternative to the controversial storage and could strongly influence thedebatable fuel cycle and future energy production.ATW as schematically shown in Fig. 2.11 is a technological approach to a possible reductionof the hazards of permanent spent nuclear fuel disposal. It utilizes three ”buildingblocks”, (1) a linear accelerator capable of delivering a proton beam with mega-Watts ofbeam power, (2) a subcritical nuclear assembly where the proton beam is converted byspallation reactions into an intense neutron flux, with which fissile isotopes and longlivedfission products are transmuted into short- lived radio-isotopes or stable nuclei, and(3) a chemical process for treating nuclear waste to isolate long-lived radio-isotopes andtransuranics for initial or recycle irradiation.The research on transmutation is not only aimed at the destruction of transuranicselements, which represent the most toxic part of nuclear waste, but it is also devoted tothe elimination of the most dangerous fission fragments. Most of these elements have alifetime that rarely lasts more than decades or centuries. This means that, by eliminatingthe few most offending long-lived fission fragments, one could dispose the rest in controlledsecular repositories for a few centuries to eliminate all danger completely. The biggestachievement would be the elimination of the need for geological repositories.Table 2.6: Most dangerous fission fragments produced annually by one GWe power reactor.The volume of inert material is indicated on the right in which the elements shouldbe diluted, to be considered as dangerous as industrial or medical radioactive waste,and to be stored in uncontrolled surface repositories, according to American regulations.The elimination of iodine and technetium, the most dangerous isotopes, would allow aconsistent reduction in the volume of storage waste.Radio Isotope Half life Weight Radio-toxicity Class A dilution(kg) (Sv) (m 3 )99 Tc 211.000 years 16,61 27670 947,65129 I 15,7 million years 8,09 19580 178,47135 Cs 2,3 million years 34,12 9870 39,3293 Zr 1,53 million years 26,11 2380 18,75125 Sn 100.000 years 1,19 3200 9,6579 Se 650.000 years 0,3 745 0,59By examining the radio-toxicity of long-lived fission fragments, it is clear that the mostoffending are few in number. In particular, 129 I and 99 Tc are by far the most dangerous fortheir solubility and mobility in the biosphere. These light elements cannot fission like thetransuranics, so a different technique has to be adopted to eliminate them. The techniqueconsists of artificially accelerating their natural decay by using neutrons again. The goalis to let the dangerous elements capture a neutron, in order to increase their energy andbecome unstable, as they will rapidly decay in stable elements. This process also occursin reactors, but it is not efficient enough and the eliminated quantities are smaller thanthe produced ones.The solution to this problem has been suggested by Physics Nobel prize laureate CarloRubbia and his research on so-called ADS (Accelerator Driven System). The secret is to
Page 1 and 2: The Physics of Spallation Processes
Page 3 and 4: AbstractA recent renascence of inte
Page 5 and 6: Contents1 Introduction 12 Research
Page 7 and 8: CONTENTSvNeutron multiplicity distr
Page 9 and 10: 2 CHAPTER 1. INTRODUCTIONThe emphas
Page 11 and 12: 4 CHAPTER 1. INTRODUCTIONinverse ki
Page 13 and 14: 6 CHAPTER 2. RESEARCH WITH NEUTRONS
Page 15 and 16: 8 CHAPTER 2. RESEARCH WITH NEUTRONS
Page 17 and 18: 10 CHAPTER 2. RESEARCH WITH NEUTRON
Page 31: 24 CHAPTER 2. RESEARCH WITH NEUTRON
Page 37 and 38: Chapter 3Neutron productionNeutrons
Page 39 and 40: 32 CHAPTER 3. NEUTRON PRODUCTIONthe
Page 41 and 42: 34 CHAPTER 3. NEUTRON PRODUCTIONrad
Page 43 and 44: 36 CHAPTER 4. THEORY/MODELStype par
Page 45 and 46: 38 CHAPTER 4. THEORY/MODELSFor inci
Page 47 and 48: 40 CHAPTER 4. THEORY/MODELS2. the d
Page 49 and 50: 42 CHAPTER 4. THEORY/MODELSSpallati
Page 51 and 52: 44 CHAPTER 4. THEORY/MODELSTable 4.
Page 53 and 54: 46 CHAPTER 4. THEORY/MODELS⎡ ⎛(
Page 55 and 56: 48 CHAPTER 4. THEORY/MODELScross se
Page 57 and 58: 50 CHAPTER 4. THEORY/MODELSFigure 4
Page 59 and 60: 52 CHAPTER 4. THEORY/MODELSenergy F
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76 CHAPTER 6. EXPERIMENTSacquisitio
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78 CHAPTER 6. EXPERIMENTSof target
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80 CHAPTER 6. EXPERIMENTSspread of
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82 CHAPTER 6. EXPERIMENTSrelated to
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84 CHAPTER 6. EXPERIMENTSprogram of
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88 CHAPTER 6. EXPERIMENTSFigure 6.1
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90 CHAPTER 7. RESULTS AND COMPARISO
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Chapter 8ConclusionThe studies perf
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144 CHAPTER 8. CONCLUSIONthe incide
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Bibliography[Aba01] A. Abanades et
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148 BIBLIOGRAPHY[Bau86] W. Bauer et
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150 BIBLIOGRAPHY[Bow91] D.R. Bowman
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152 BIBLIOGRAPHY[Col68] W.A. Colema
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154 BIBLIOGRAPHY[ENEA01] A European
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156 BIBLIOGRAPHY[Fil01] D. Filges,
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158 BIBLIOGRAPHY[Gol99b] F. Goldenb
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160 BIBLIOGRAPHY[Her01] C.M. Herbac
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166 BIBLIOGRAPHY[Lip94] V. Lips et
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174 BIBLIOGRAPHY[Vio85] V.E.Viola e
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Author: Frank Goldenbaum currently
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