Transcript Nuclear Thermal Rockets

Nuclear Thermal Rockets
Brice Cassenti
University of Connecticut
Nuclear Energy
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Relativity
Fission energy
Radioactive decay
Cross-sections
Nuclear thermal rockets
Relativistic Energy
• For all particles
m02 c 4  m 2 c 4  p 2 c 2
E02  E 2  p 2 c 2
E  mc 
2
• For photons m
0
• For
m0 c 2
1  v / c 
2
0
 h 
E  pc  h  
2  
 2 
v / c  1
1 2
2
E  m0 c  mv
2
Binding Energy
Fission of 92U235
Energy
Value (MeV)
Fission fragment kinetic energy
166.2
Neutron kinetic energy
4.8
Prompt X-rays
8.0
b particles from fragment decay
7.0
g particles from fragment decay
7.2
Antineutron from fragment decay
9.6
Total released energy
202.8
1
235
236
139
94
1
n

U

U

Ba

Kr

3
n
0
92
92
56
36
0
Fission Process
Radioactive Decay
• Consider uranium alpha decay
238
234
4
U

Th

He
92
90
2
• Decay rate is proportional to number left
N  N 0 e  t
t mean  1 / 
t half 
ln 2


0.692

• Activity measured in Sieverts
Fission Fragment Decay
Fission Fragment Size
Neutrons Emitted
Neutron Energy
Cross-Section
• Cross-section = s
dI
 snI
dx
I  I 0 e snx
• Units
– 1 barn=10-24cm2
Uranium Fission Cross-Sections
Some Cross-Sections in barns
Nucleus
Absorption, sa
Capture, sc
Fission, sf
Scattering, ss
235
92U
687
107
580
10
1065
315
750
9.6
233
92U
585
52
533
?
238
92U
2.75
2.75
0
8.3
U (natural)
7.68
3.50
4.18
8.3
94Pu
239
Note : s a  s c  s f
Neutron Moderator
Scattering Cross-Sections
Reactor Schematic
Nuclear Thermal Propulsion
• Solid Core
– 850-950 second Specific Impulse
• Gas Core
– 1800-1950 second Specific Impulse
Solid Core Schematic
NERVA Program
NERVA Core & Fuel Rods
Core Layout
Gas Core Rocket
Nuclear Light Bulb
References
 Bussard, R.W., and R.D. DeLauer, Nuclear Rocket Propulsion, McGraw-Hill
Series in Missile and Space Technology, McGraw-Hill Company, Inc. 1958.
 Cork, J.M., Radioactivity and Nuclear Physics, D. Van Nostrand Company, Inc.,
New York, 1950.
 El-Genk. M.S., (editor) A Critical Review of Space Nuclear Power and
Propulsion 1984-1993. American Institute of Physics, New York, 1994.
 El-Wakil, M.M., Nuclear Power Engineering, McGraw-Hill Book Company, Inc.,
New York, 1962.
 Harper, W.R., Basic Principles of Fission Reactors, Interscience Publishers, Inc.,
New Your, 1961.
 Muhkin, K.N., Experimental Nuclear Physics, Mir Publishers, Moscow, 1987.
 Murray, R.L., Nuclear reactor Physics, Prentice-Hall, Inc., Englewood Cliffs, NJ,
1957.
 NASA, Nuclear Thermal Propulsion Workshop, NASA Conference Publication
10079, Cleveland, OH, July 10-12, 1990.