III. Neutron Generator Evaluation
a) Our Goal
The goal of this project is to design a portable, shielded neutron collimator. The
first step in doing this is to find a commercially available neutron source that will meet the
needs set forth by the project. We found several companies that specialize in producing
neutron generators for various purposes. When selecting the generator there are a
number of criteria to keep in mind.
b) Important Criteria
Neutron Flux is the number of neutrons per second the generator produces. We
want to get as much neutron flux as possible from our selected generator to make
Neutron energy is the energy of the neutron produced by the generator. The two
most common energies are 2.5 MeV from a Deuterium-Deuterium reaction and 14.1 MeV
from a Deuterium-Tritium reaction. These neutrons will be used to excite the target to
determine if explosive materials are present. Different energies of neutrons excite
different elements, so we must determine what is necessary for our design. We also
need to remember that higher energy neutrons require more shielding.
The life of a neutron generator is usually reported in years, and is based off an
average run time every day. This usually goes until refueling or maintenance is needed.
It is important to minimize the size of our generator as much as possible. This
allows for more collimating and shielding material in a smaller space.
The weight of the neutron generators needs to be considered as well. The lighter
it and its power source is, the better off we are.
Both the initial cost of the generator as well as the cost of maintenance and
refueling of the generator needs to be considered as well.
c) Generator Information
VNIIA or the All-Russia Research Institute of Automatics is a Russian company
that produces approximately 10 models of neutron generators. These vary greatly in flux,
size, and cost. However, their operating life is very short compared to other companies,
and their models are not easily refuel-able.
Thermo Electron Corporation produces several neutron generator models as
well. However, only one of their models is of an appropriate size to be considered for this
project. Their refueling and maintenance programs are very good and relatively
NSD Fusion is a German company that produces generators to fit your needs.
They gave us some examples of models they have produced in the past and told us there
is some flexibility in what they produce, but we were able to get a good idea of their
capabilities from the models we were given.
EADS Sodern is a French company that produces 3 different models of neutron
generators. They have excellent operating life and neutron fluxes.
Adelphi is a new company to the neutron generator market, and should have
several models of generators available next fall sometime. They are using a new
technology based on research done by Lawrence Berkley National Labs. The information
we have gotten says that their models will be able to produce neutrons with a flux of
several orders of magnitude higher than any of the other models we have found.
d) Evaluation of Generators
Neutron flux is by far the most important criteria for deciding upon a generator.
Also, we decided that a deuterium-deuterium reaction will not excite the particles we
wanted to see. Finally, many of the VNIIA generators had very short operating lives. We
felt that this would greatly hinder the performance of the system and eliminated them
from our list. We further narrowed down our field of neutron sources to eight generators
by eliminating others with low neutron flux or low neutron energies.
VNIIA Thermo NSD Fusion EADS Adelphi
Comparison specs Units
Neutron Flux N/s 1.00E+09 5.00E+08 1.00E+08 1.00E+08 2.40E+08 5.00E+08 1.80E+10 1.00E+10 1.00E+13
Neutron energy MeV 14.1 14.1 14.1 14.1 14.1 14.1 14.1 14.1 14.1
Operating Life Hours 500 500 500 1200 25000 25000 25000 4000
Cost per unit $ $52,000.00 $50,000.00 $105,000.00 $64,375.00 $70,000.00 $70,000.00 $85,000.00 $55,000.00 $300,000.00
Table 1: Reduced Table of Neutron Generators
A larger version of this spreadsheet is available in the appendix.
Decision Matrix VNIIA Thermo NSD EADS Adelphi
High End Model
Comparasion specs Units Weight Datum
Neutron Flux N/s 4 - - - - - - + Datum +
Neutron energy MeV 3 S S S S S S S Datum S
Cost per unit $ 2 + + - - - - - Datum -
Operating Life Hours 1 - - - - + + + Datum S
Total + 1 1 0 0 1 1 2 Datum 1
Total S 1 1 1 1 1 1 1 Datum 2
Total - 2 2 3 3 2 2 1 Datum 1
Weighted + 2 2 0 0 1 1 5 Datum 4
Weighted - 5 5 7 7 6 6 2 Datum 2
-3 -3 -7 -7 -5 -5 3 0 2
Table 2: Neutron Generator Weighted Decision Matrix
We used a decision matrix to help refine our choices. We added the Adelphi
generator on later after we received its information. The Decision Matrix highlights our top
three neutron generators.
e) Our Top Three Neutron Generators
Dr. Dunn gave us the number of 1x10 neutrons at the target to achieve an ID of
explosive material. In order to get an idea of how long this would take with each
generator we applied the formula:
Neutrons = Source Power x Area of target / (4 x x r ) x time
Applying this for our three generators at 2 and 5 meters from a 0.5m x 0.5m target gave
us this table. From the table we can see that the only reasonable ID time is give to us by
the Adelphi generator.
Generator 2 m (sec) 5 m (sec)
Adelphi D-T Generator 20.106176 125.6636
EADS Genie 35 20106.176 125663.6
NSD High End model 11170.09778 69813.11111
Table 3: Time for ID of target (no collimator)
The Adelphi neutron generators use a new technology developed by
Lawrence Berkley National Labs using pure ions in the form of an RF plasma.
Their generators have fluxes several orders of magnitude greater than any
others, but their operating life is unknown, they will not be available for 8-10
months, and they will be much more expensive than the other generators. The
Adelphi generator is still our number one choice because the large flux it is able
EADS Sodern Genie 35
The EADS Sodern Genie 35 is our number two choice because of its low
cost and good flux. It also has an excellent operating life.
NSD Fusion D-T High End Model
The NSD neutron generator is an improved spherical Inertial
Electrostatic Confinement (IEC) device. It has exceptionally long life due to its
plasma target over a solid target. Most of their models spec for over 20,000
hours of use. This might be slightly less due to the gaseous build up from Tritium,
but can go for as long as 36 months to 5 years without needing service.