A Description of SureBeam Food Irradiation Facilities
R. B. Miller
SureBeam Corporation, 9276 Scranton Road, Suite 600, San Diego, CA 92121
Abstract. SureBeam Corporation now has several facilities in operation for the sole purpose of food irradiation.
The accelerators installed at these facilities operate at nominal electron kinetic energies of 5 and 10 MeV, with average
power capabilities ranging from 15 kW to 150 kW. Both electron beam and x-ray irradiation can be provided.
Material handling systems include both roller conveyors and overhead power-and-free systems for transporting
products through the irradiation zone. These facilities will be described and their capabilities summarized.
depends on many factors, not the least of which
are the ratio of the treatment cost to the value of
the treated product and “public acceptance” of
irradiated foods. In addition, food irradiation
installations can require significant capital
investment that may not have a sufficiently
attractive payback potential for investors.
The essential elements of an acceleratorbased irradiation facility include the accelerator
system itself, a scanning system to uniformly
irradiate the product, and a material handling
system that moves the product through the beam
in a precisely controlled manner. Auxiliary
equipment for the accelerator system includes
vacuum and cooling subsystems.
Extensive radiation shielding is necessary to
reduce the external dose to acceptable levels, and
a safety system is necessary to prevent accidental
exposure of personnel during accelerator
operation. Parameters that affect the dose
distribution must be continuously monitored and
precisely controlled with process control
software. On-site dosimetry is also required for
initial product qualification and process
validation, and for periodic process monitoring.
The volumes of food that can be processed with
a modest accelerator system can be quite large,
and the facility must therefore have adequate
warehouse space for both incoming and outgoing
product.
It is usually necessary to maintain both the
warehouse and irradiation cell areas at reduced
temperatures, implying a significant HVAC
(heating, ventilation and cooling) capability.
The in-coming product area is usually physically
separated from the out-going area by a physical
barrier to prevent commingling of non-irradiated
and irradiated product. In addition, ionizing
radiation produces ozone in air, and some means
Food irradiation has generally come to
describe the use of ionizing radiation (e.g.,
energetic electrons and x-rays) to decrease the
population of, or prevent the growth of,
undesirable biological organisms in food. The
many beneficial applications include for
example, the disinfestation of insects in fruits
and grains, the inhibition of sprouting in potatoes
and onions, the delayed ripening of fresh fruits
and vegetables, and the enhanced safety and
sterilization of fresh and frozen meat products,
seafood, and eggs.
With special regard to food safety, bacteria
such as Salmonella enteridis, Listeria
monocytogenes, Campylobacter jejuni and
Escherichia coli serotype O157:H7 are the
primary causes of food poisoning in
industrialized countries. In 1999, food-borne
illnesses were responsible for an estimated 5000
deaths in the USA alone. Ionizing doses in the
range of only 1-5 kilogray (kGy) can virtually
eliminate these organisms from food, without
affecting the food’s sensory and nutritional
qualities, and without inducing radioactivity.
Recognizing this fact, members of the World
Health Organization’s Food Safety Unit have
described food irradiation as possibly the most
significant contribution to public health to be
made by food science and technology since the
pasteurization of milk.
The SureBeam Corporation was established
as a food irradiation company following the
approval by the US government of the irradiation
of fresh and frozen meats. The total estimated
US food production volume is almost 150 billion
pounds, and the total worldwide food production
is nearly two trillion pounds.
While this
potential food irradiation market is huge, the
attractiveness of this business opportunity
CP680, Application of Accelerators in Research and Industry: 17th Int'l. Conference, edited by J. L. Duggan and I. L. Morgan
© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
871
energies of 5 and 10 MeV, with average power
capabilities ranging from 15 kW to 150 kW.
Both electron beam and x-ray irradiation can be
provided. Material handling systems include
both roller conveyors and overhead power-andfree systems for transporting products through
the irradiation zone. A summary of SureBeam’s
US facilities is presented in Table 2.
for ozone elimination is usually required.
Adequate electrical power must be available to
support all of these functions. With all of the
auxiliary equipment, warehouse space, and
radiation shielding, the footprint of the
accelerator system typically occupies only a
small fraction of the total facility floor space.
The choice of electron beam vs x-ray
processing depends on the areal density (density
times thickness) of the product and the
anticipated mass throughput of product. To
eliminate nuclear activation concerns, the
maximum kinetic energy of the accelerator is
limited by regulation to 10 MeV for electron
beams, and 5 MeV for x-rays. From penetration
considerations, the largest areal density that can
be treated by double-sided electron irradiation at
10 MeV is about 8.6 g/cm2. Products having
areal densities in excess of this amount (pallets
of fresh produce, whole chickens and turkeys, for
example) must be processed using more
penetrating x-rays.
The mass throughput (dM/dt in kg/s) of an
accelerator-based system is proportional to the
average beam power (P in kW), and inversely
proportional to the minimum required dose (Dm
in kGy, with 1 kGy = 1 kJ/kg). Introducing a
throughput efficiency factor, η
dM/dt = η P/Dm
Figure 1. Line drawing of the SB 5/150 linear
accelerator system with scan horn and x-ray
converter.
Table 1
SureBeam SWG Linac/Modulator Summary
(1)
Throughput efficiencies of 0.5 are typical of
electron beam installations, but 0.03-0.035 is
more typical for x-ray installations, primarily
because of the inefficiency of bremsstrahlung
generation at 5 MeV. The SB 10 MeV/18 kW Sband accelerator system is therefore capable of
processing over 40,000 lbs of ground beef per
hour at a typical minimum required dose of 1.5
kGy.
To achieve comparable throughput
processing rates with x-rays requires much
higher average beam power. To satisfy this need
we have developed an axially-coupled, standingwave, 5-MeV L-band accelerator system with a
maximum average power capability of up to 150
kW (see Figure 1). The first machine of this
design has been recently installed in our Chicago
Service Center, and is currently undergoing
validation testing. A summary of SureBeam
linac and modulator systems is presented in
Table 1.
SureBeam Corporation now has several facilities
in operation for the sole purpose of food
irradiation. The accelerators installed at these
facilities operate at nominal electron kinetic
Desgn.
Coupl.
Freq.
RF
5/15
10/18
5/150
10/150
SideSideAxialAxial-
S-band
S-band
L-band
L-band
Kly.
Kly.
Kly.
Kly.
Energy
Store
PFN
PFN
Induct.
Induct.
Switch
Thy.
Thy.
IGCT
IGCT
Table 2
SureBeam US Facility Summary
Loc.
Accel.
(KE/P)
Material
Handling
Thruput
(lbs/hr)
Appl.
Sioux
City
10/15
(x2-u/d)
5/15
Roller
2-pass
w/transl.
Food
Safety
Hawaii
5/15
Chicago
10/15
(x2-u/d)
5/150
Los
Angeles
10/15
(x2-u/d)
5/15
(x2)
10/15
(x2-u/d)
5/15
O/H PF
2-pass
w/rot.
Roller(e)
O/HPF(x)
2-pass
w/rot.
Roller(e)
O/H PF(x)
2-&4-pass
w/rot.
Roller
2-pass
w/transl.
60,000
@2kGy
1500
@2kGy
6,000
@0.5kGy
Texas
A&M
872
60,000
@2kGy
6000
@5kGy
60,000
@2kGy
1200
@5kGy
-
Disinfes
tation
Food
Safety
Food
Safety
Res.