Dectection of Induced Fission in Sealand Containers [pres. slides]

26 Pages·2005·4.621 MB·English

Detection of Induced Fission
in Sealand Containers
John T. Mihalczo, John S. Neal,
Paul A. Hausladen, and Sara A. Pozzi
Oak Ridge National Laboratory
US/RF Workshop on Detecting Nuclear and Radioactive
Material in a Civilian Maritime Environment
November 1-3, 2005
Sandia National Laboratory, New Mexico
Outline
• Detection Possibilities
• Coincidence Measurements
− Between Detector
− With Source
• Detectors
• Matrix of Sources and Potential Measurements
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
2
Detection Possibility from Fission
• Prompt Neutrons
• Prompt Gamma Rays
• Delayed Neutrons
• Delayed Gamma Rays
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
3
Delayed Neutron Data of Keepin,
Wimmett, and Zeigler for 235U
-1
Group Relative Yield Decay constant (sec )
1 0.038 0.0127
2 0.213 0.0317
3 0.188 0.115
4 0.407 0.311
5 0.128 1.40
6 0.026 3.87
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
4
Delayed Gamma Data for 235U
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
5
Comparison Between ORNL Irradiation
Measurements and 235U Delayed
Gamma Decay Model Predictions
10000
600 sec Irradiation
)
s
p
c
(

S
T
N
U 60 sec Irradiation
O
1000
C

R
O
T
C
E
T 600 sec Irradiation (Data)
E
D 600 sec Model Results
60 sec Irradiation (Data)
60 sec Model Results
100
1 10 100 1000
TIME (s)
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
6
Distribution of Prompt Neutron Numbers
for Thermal Fission of 235U
Number of neutrons Fraction of emissions
0 0.0313
1 0.1729
2 0.3336
3 0.3078
4 0.1232
5 0.0275
6 0.0038
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
7
Thermal Neutron Induced 235U
Multiplicity of Prompt Gamma Rays
from the Negative Binomial Distribution
of Valentine
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
8
Sources of Coincidence Counts
• Prompt Fission Chains Induced by the Source
− During or Immediately After the Pulse
• Delayed Neutron induced Fission Chains from
Previous Prompt Fission Neutrons
− Between Pulses
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
9
Multiplet Measurement For an 18.75
kg HEU Uranium Metal Annular
Cylinder
NMIS Multiplicity: Cf-252 Measurement of HEU Casting
1E+9
1E+8 measured
1E+7 Poisson
1E+6
1E+5
1E+4
1E+3
1E+2
1E+1
1E+0
1E-1
1E-2
1E-3
Source-casting-detector configuration Multiplet Measurement in 1997
1E-4
1E-5
1E-6
1E-7
0 1 2 3 4 5 6 7 8 9
Multiplet
Deviation from Poisson distribution is an indication
of fissile presence and mass
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
10