Not Just Fusion: Exploring TWDEC Technology for Fission Fragment Direct Energy Conversion

Transcription

1 Not Just Fusion: Exploring TWDEC Technology for Fission Fragment Direct Energy Conversion A. G. Tarditi Electrical Power Research Institute, Knoxville, TN

2 Introduction Fission fragments direct energy conversion has been considered in the past for increasing power plant efficiency [1-4] and for space propulsion [5-6] These concepts were focused on the direct conversion of the charged fragments utilizing high-voltage DC electrodes. [1] S. A. Slutz et al.,phys. Plasmas 10, 2983 (2003) [2] P. V. Tsvetkov, et al., Trans. American Nucl. Soc., 91, 927 (2004) [3] and 2004 annual reports [4] R. Clark and R. Sheldon, AIAA (2005) [5] G. Chapline and Y. Matsuda, Fusion Technology 20, 719 (1991) [6] P. V. Tsvetkov, et al., AIP Conference Proceedings 813.1, 803, (2006)

3 Introduction (II) Considering a different approach: direct energy conversion of charged fission fragments kinetic energy into alternating current via a traveling wave coupling This approach was first conceived application to fusion reactions (Traveling Wave Direct Energy Converter, TWDEC [7-9]) [7] Momota H. et al. Fusion Technology, 35, 60 (1999) [8] Momota, H., Miley, G.H., AIP, Conf. Proc., 608, 834, (2002) [9] Yasaka Y. et al., Nucl. Fusion 49, (2009)

4 Previous Work on Fission DEC

5 Previous Work on Fission DEC Fission fragments direct energy conversion has been considered in the past for increasing power plant efficiency [1-4] and for space propulsion [5-6] These concepts were focused on the direct conversion of the charged fragments utilizing high-voltage DC electrodes. [1] S. A. Slutz et al.,phys. Plasmas 10, 2983 (2003) [2] P. V. Tsvetkov, et al., Trans. American Nucl. Soc., 91, 927 (2004) [3] and 2004 annual reports [4] R. Clark and R. Sheldon, AIAA (2005) [5] G. Chapline and Y. Matsuda, Fusion Technology 20, 719 (1991) [6] P. V. Tsvetkov, et al., AIP Conference Proceedings 813.1, 803, (2006)

6 Previous Work on Fission DEC Figure 2. Schematic of proposed Fission Fragment Rocket. Fissile dusty plasma fuel is confned to dust chamber, where RF induction coils heat the plasma. Fission fragments are collimated by the magnetic field either to collection electrodes for power, or exit the reactor for thrust.

7 Previous Work on Fission DEC

8 Previous Work on Fission DEC Early JPL work:

9 Comparison w\fusion Design Momota-Miley Design [8] : Direct Energy Converter D- 3 He IEC fusion core (several units, each 10 MW/6,000 kg) : D- 3 He IEC units: power=10 MW, weight=6,000 kg TWDEC (pair) total weight=35,000 kg TWDEC power in=250 MW, power out=150 MW (h=0.6) Length=150 m, Diameter=6.6 m Heat removal 100 MW radiator panel 50x140m, temperature 600 K Specific mass: a=0.14 kg/kw

10 TWDEC Fission Conceptual Design Exploring of DEC configurations that could be implemented within a nuclear fission core Collecting and collimating a beam of charged fission fragments (e.g. thin solid core for optimal fragment extraction, [1]) Consider application to gas core (e.g. vortex confinement, [7]) [7] Sedwick, AIAA Journal of Propulsion and Power, Vol 23, No. 1, Jan-Feb 2007.

11 TWDEC Fission Conceptual Design Charged fission fragments (positively charged, about 20 electron charges) are magnetically collected and focused Fission fragment beam of relatively low density, to avoid significant space charge effects.

12 TWDEC Fission Example 235 U => 140 Xe + 94 Sr + 2n Consider a 100 MeV 140 Xe fragment with a +20e charge 140 Xe fragment speed v Xe = m/s For a inter-electrode TWDEC distance of d=1 m the frequency of the AC power is f 0 =v Xe /2d=5.85 MHz Alternating-gradient beam focusing

13 TWDEC Fission Example Solenoidal magnetic field B 0 = 0.5 T: Xe fragment gyroradius= 1.71 m B Collimated Fragment Beam Fragment at reduced drift speed into TWDEC Side injection can reduce drift speed and TWDEC frequency Bunching can provide the non-adiabatic injection required to capture the ions.

14 TWDEC Fission Example 235 U => 140 Xe + 94 Sr + 2n Consider a 100 MeV 140 Xe fragment with a +20e charge 140 Xe fragment speed v Xe = m/s Consider a magnetic field B 0 = 0.5 T: Xe fragment gyroradius= 1.71 m For a inter-electrode TWDEC distance of d=1 m the frequency of the AC power is f 0 =v Xe /2d=5.85 MHz In real life multiple products must be considered

15 TWDEC Fission Challenges In real life multiple fragment products (different masses and energies) must be considered Multiple channels may be required for efficiency Electron flow must be dealt with

16 Summary Fission fragments leave thin fissile fuel elements Fragments carry large positive charge ( 20 e) and are collimated into a beam by a magnetic field Traveling Wave DEC converts fragment energy into AC electric power