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Radiation Processing Facilities: An Environmentally Friendly Option R.M. Brinston international irradiation Association (iiA) Ottawa, Canada Abstract Radiation-processing facilities deliver enormous benefits to society. That these facilities are environmentally friendly or “clean and green” may be one of the best-kept secrets. Over 170 large-scale commercial cobalt-60 irradiators and 21 electron-beam accelerators are used sterilize approximately 45% and 7-10% respectively of the world’s single-use medical disposable products. It makes sense to apply this experience to the irradiation of biohazardous contaminants – specifically the treatment of sewage sludge, biomedical waste, postal mail and other items that might contain highly infectious, harmful microorganisms. The US NRC on August 17, 2007 published an environmental assessment (EA) for the Pa’ina Hawaii food irradiator. This extensive report covers all pertinent information that will be useful to others planning a cobalt-60 irradiator installation. With the “finding of no significant impact”, the NRC reiterates the fact that irradiators are environmentally friendly, as well as safe and secure. Economics matter in any discussion about radiation processing facilities. Presented in this paper is an overview of radiation processing, plus an example of the capital investment and current operating costs of gamma, e-beam and x-ray systems from an experienced operator’s perspective. Anyone considering the installation of a modern irradiation facility has a broad range of factors and options to consider. Seasoned and influential environmental activists are changing their mind on nuclear energy when they examine the largest greenhouse emitter, coal and the world’s increasing demand for energy. This re-think bodes well for the commercialization of radiation processing for treating bio-hazardous contaminants. A preliminary environmental audit demonstrates that irradiation facilities contribute little carbon dioxide (and other green house gases) to global warming. To put it into perspective using the operators’ example the e-beam accelerator would consume electricity thereby generating gases equivalent to about 730 moose belches or a motorist driving 13,000 kilometres per year.

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1) Introduction The international irradiation Association (iiA), formerly the AIII, is the only global not-for-profit, industry supported organization dedicated to providing leadership and assistance to its members in advancing the safe and beneficial uses of industrial radiation processing. The iiA membership has more than doubled in the past couple of years, increasing from 21 to 42 organizations with corporate office located in 20 countries. In addition all IMRP Laureates are life time honorary members. iiA membership includes the leading suppliers of both isotope and machine-based radiation equipment; multi-national healthcare companies; as well as the providers of over 90% of the world’s contract irradiation services. The iiA Board of Directors consists of senior industry executives from Australia, Belgium, Canada, U.K. and USA whose combined knowledge with large-scale applications of ionizing radiation amounts to more than 200 years of experience. The Association’s aim is to serve as a global hub for the collection and dissemination of information and educational materials about all significant matters relating to the radiation processing industry. Since the mid-1950’s radiation has become the preferred method for terminal sterilization of single-use medical healthcare productsi. Today, over 170 large-scale commercial cobalt-60 irradiators and 21 electron-beam accelerators sterilize approximately 45% and 7-10% respectively of the world’s single-use medical disposable products. It makes sense to apply this experience to the irradiation of biohazardous contaminants – specifically the treatment of sewage sludge, biomedical waste, postal mail and other items that might contain highly infectious, harmful microorganisms. In 2004, the market estimate for combination drug-device healthcare products was $5.9 billion, and forecasted to grow to $9.5 billion by the year 2009. Manufactured under highly controlled conditions and in small quantities for just-in-time delivery, these products will likely have an extremely low bioburden. Many require stringent temperature control and have very tight dose tolerance requirements. For example in the case of tissue allografts, there is no such thing as a standard size, shape, or material; plus the small quantities and possible presence of viruses adds complexity. These issues pose unique challenges for any sterilization method. As determined in the iiA-sponsored workshops strong technical and economic incentives exist to determine how best to optimize radiation sterilization to treat these new or next generation drug-device combination healthcare productsii.

2) An Environmental Assessment One of the most famed microbial reduction applications, food irradiation is gaining acceptance especially in the USA. Americans alone now consume approximately 18 million pounds of irradiated ground beef and poultry, around 8 million pounds of irradiated fruits and vegetables and approximately 175 million pounds of irradiated spicesiii. Commercial facilities presently irradiating food for human and animal consumption in the USA include Food Technology Services Inc. (FTSI) Mulberry, Florida process beef, produce and spices; Sadex Inc, Sioux City, Iowa has an increasing animal feed and supplement business. Hawaii Pride, Keaau, Hawaii treats produce destined for the mainland. The two largest contract service providers, Sterigenics and STERIS Isomedix both have multiple facilities that irradiate a variety of spices, ingredients and garlic. On 17 August 2007, the United States Nuclear Regulatory Commission (NRC) published in the Federal Register a “finding of no significant impact” in the environmental assessment (EA) conducted for the compact Pa’ina Hawaii compact food irradiatoriv. The licensing of panoramic or underwater irradiators

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does not require an environmental assessment. However, through a process involving the judiciary the NRC entered into a settlement agreement with the Concerned Citizens of Honolulu to hold public meetings and conduct this assessment. This extensive report by the government covers the pertinent environmental impacts and concludes these findings:

• Irradiators occupy a small amount of space; • There is very little, if any noticeable noise; • Virtually no emissions of air effluents; • No significant impact on water quality or use; • Public and occupational health impacts expected well below regulatory standards; • The proposed irradiator would have no significant impacts from transportation of the cobalt-60

sources or additional products; and • The irradiator would satisfy several needs related to the control of invasive pest species damaging

to agriculture.

In a new section they state, “NRC safety and security requirements, imposed through regulations and orders, and implemented by the licensee, in combination with the design requirements for panoramic and underwater irradiators provide adequate protection against successful terrorist attacks on irradiator facilities”. Appendix C contains public comments on the draft environmental assessment. This EA will be useful to others planning a cobalt-60 irradiator installation.

3) Safety and Security of Irradiation Facilities For over fifty years, both cobalt-60 irradiators and accelerators have an outstanding record of accomplishment. Security concerns associated with cobalt-60 are groundless. The design of industrial irradiation facilities, stringent control over the shipping of source in massive containers, and the detailed safety and security plans irradiator owners have implemented ensure gamma irradiation continues to be safe and effective and make cobalt-60 virtually useless as a tool of terrorism. Life-cycle source tracking coupled with stringent import and export controls are in place with Cobalt-60 suppliers and users to control the location and disposition of all sources. The industry has consistently regarded safety and security as a top priority and has fulfilled that priority with regulatory rigor.

4) Economics Matter: Technology Fundamentals Economics matter greatly to anyone considering the installation and efficient operation of a new irradiation facility – either a cobalt-60 gamma system or an accelerator for e-beam or X-ray treatment. All irradiation facilities are capital intensive. Many designs exist, all customized to deliver the desired dose of ionizing energy into the product in a safe and efficient manner. The literature contains many papers with economic analyses and websites can provide a wealth of information. Careful thought goes into selecting the design proposal and understanding the factors which optimize capital investment and operating costs; specifically type of product and goal of the treatment, volume throughput and growth projections, specific geographic cost inputs and company corporate accounting practices. Typical industrial radiation processing facilities have four basic components:

• Energy source consisting of either an accelerator or cobalt-60;

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• Radiation cell and entrance maze constructed of thick concrete walls, and in the case of cobalt-60 a pool of water, which all act as a biological shield;

• Material handling system to move the product into, though and out of the radiation cell; and

• Safety systems to protect workers, public and the environment. First, it is important to understand the fundamental difference between accelerators, machine-based facility and cobalt-60 a radioisotope facility. Because accelerated electrons are charged particles with a mass, they are limited in their penetrating power. Gamma or X-rays are photons of energy, like light with no mass or charge, but of sufficiently higher energy to penetrate and subsequently generate secondary electrons.

E-Beam High-energy accelerators in the range of 5 to 10 MeV, with power levels from 25 kW to 350 kW (or higher) with beam width up to 1.8 m are suited for bulk product irradiation. The energy level dictates product thickness, acceptable minimum and maximum dose, and the current determines the dose rate. Listed below are several key equations. vvi Penetration:

d = (0.524 E – 0.1337) / ρ Where, d is penetration depth in cm, E is beam energy in MeV, ρ is density in g/cm3

Irradiating product from opposite sides increases the depth of treatment and improves the dose uniformity ratio (DUR), if selected correctly.

d = (E - 0.32) / (2.63 x ρ) for one-sided e-beam irradiation d = (E - 0.32) / (1.19 x ρ) for two-sided e-beam irradiation

Dose Uniformity Ratio:

DUR=Dmax/Dmin Where, D is Dose in kGy at minimum amount to achieve the desired effect (e.g.

sterilization); at the maximum the product still functions as intended.

Power: P= E x I

Where, P is Beam Power (kW), I is the average beam current (mAmps)

Throughput:

T=P/ D x f Where, T is the maximum throughput in kg/sec, f is energy absorption efficiency (%)

Line speed:

L= (P x f) /(D x d x A) Where, L is line speed in kg/ sec, A is the cross sectional area of the product

irradiated in the direction of travel of the conveyor, t is time in seconds.

Figure 1 illustrates the relative dose depth distribution for three different beam energies and gamma rays from cobalt-60. X-rays would be similar to gamma rays.

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Figure 2 illustrates the dose depth distribution of 10 MeV electrons first on one side and then the other side to achieve the desirable dose uniformity. Note if the product is thicker the dose in the center will be lower, hence a wider dose uniformity ratio. With thinner product, there will be a higher dose the center and perhaps even greater than the Dmax of a single sided irradiation.

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In any practical situation, there is power loss between the scan horn and the product, as well as some electrons spill over the edge of the package, and others need to pass right through the package so that the far side gets an adequate dose. This is the energy absorption efficiency (f) adjustment factor. Figure 3 illustrates an e-beam irradiator design where product is typically treated one box at a time and then flipped it to irradiate the other side. Furthermore, because these are accelerated electrons with mass and charge, there may be backscattering or edge effects and shadowing phenomena in heterogeneous products.

Designers build an accelerator facility with the maximum capacity needed up front; the machine may be turn on or off depending on the amount of product requiring processing. Because these are sophisticated machines, they typically require more maintenance than a gamma facility. In the literature, some authors conservatively assume 7,000 operating hours per year, but 8,000 hours is a more common assumption.

X-ray When accelerated electrons hit a very dense material such as tungsten or tantalum target, the metal atoms in the target stops the electrons and causes the emission of high energy x-rays of various energy levels but never exceeding the maximum of the parent electrons. The generation of x-rays only happens by turning on the parent electron beam. Figure 4 illustrates a conceptual x-ray irradiator design for treating a pallet of product.

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As an emerging technology x-ray facilities are still in the conceptual stage with limited commercial success because the efficiency of electron to x-ray conversion is relatively low. With 5 MeV electrons, the conversion is just under 8% into a forward stream of high energy x-rays. The latest 7 MeV 1000 kW accelerator developed by IBA offers a power conversion of about 11%, and with a multi-pass system of 2 stacked pallets could theoretically process approximately 15.5 m3/ hourvii with a DUR of 1.5 at 25 kGy and product density of 0.15 gm/cc. The advent of higher power accelerators with x-ray conversion capabilities offers the possibility of different industrial configurations and material handling systems to treat product on pallets, in tote box containers or in a carrier system. Product throughput and dose uniformity will vary depending on the accelerator and material handling system selected. A reasonable assumption for accelerators operating in the x-ray mode is 8,000 hours per year, but this needs proving with actual operating experience. In addition to the electrical consumption when processing product, analysts should include an allowance for maintenance costs around $200,000 to $230,000 per year. A special consideration is bombarding materials with high energy electrons or x-rays can induce radioactivity. Extensive theoretical and practical research has shown that sensible limits of 10 MeV electrons and 7.5 MeV x-rays are safe for the diversity of irradiated products treated today.

Gamma Deliberately produced in a nuclear reactor, cobalt-60 emits two gamma rays with fixed energies of 1.17 and 1.33 MeV as it decays to stable nickel-60. This decay is a well understood natural phenomena and is a constant process over time, with cobalt-60 having a half-life of 5.25 years. In gamma facilities, owners install an initial cobalt-60 load of say 1 million curies (1 MCi) which is contained in double-encapsulated stainless steel sources (45.12 cm long x 1.11 cm diameter and up to 14,000 curies each). Typically, facilities once a year add cobalt-60 for decay replenishment at 12.3% and growth in product volumes requiring irradiation. Removal of the cobalt-60 sources occurs at the end of their useful life, which is typically 20 to 25 years and returned to the manufacturer for re-cycling or disposal.

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It is important to note that gamma rays are very penetrating and travel in all directions radiating out from the cobalt-60 source rack. Figure 5 illustrates a typical gamma irradiator design the popular JS10000 multi-pass hanging-tote irradiator by MDS Nordion has a maximum source rack capacity of 5MCi and can process can process product with a density of 0.15 gm/cc at 25kGy at a rate of approximately 4.4 m3/ hourviii with 1 MCi of installed cobalt-60.

MDS Nordion also offer several different pallet designs, while these machines have a lower throughput they offer labour savings and less product handling. The throughput is a function of the irradiator design, minimum required dose, acceptable dose uniformity ratio, product density and total activity installed cobalt-60 activity. Time is the only process control variable. Note the cobalt-60 constantly decays whether exposing product to it or not, hence facilities operate 24 hours per day, 7 days per week and achieve 8,600 operating hours per year. Shutdowns are short for routine maintenance and source replenishment. Due to a simpler mechanical operation, the maintenance costs associated with a gamma facility are about 20 to 30% of an accelerator based facility. MDS Nordion, Canada and REVISS Services (UK) are the two primary suppliers producing cobalt-60 which comes from a number of different reactors around the world. There are several unique costs associated with the use of cobalt-60; specifically warranty, transportation, installation, and disposal by the supplier. In a general economic analysis consider these costs included in the price of the cobalt-60. It is also important to note that the gamma radiation industry and irradiator owners are strictly regulated using security measures that meet International Atomic Energy Agency (IAEA) guidelines as well as stringent national authorities like the U.S. Nuclear Regulatory Commission (NRC). The licensing cost of a gamma irradiator may be higher and will vary depending on the specific site location, but it is relatively insignificant in the overall budget.

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To compare radiation processing systems using basic physics: 1 kW of electron or x-ray radiation equals 67,578 curies of cobalt-60 (or 1 MCi is equivalent to 14.8kW of electrons or x-rays). While this provides a direct comparison of the source power, it neglects the efficiency of delivering the ionizing radiation dose to the product. One must look at the facility design and performance tables supplied by the irradiator manufacturer to compare systems. In Figure 6: the first chart (left hand side) contains the data for different accelerator systems operating in the X-ray modeixxxi processing totes or pallets of product and the second chart (right hand side) two different cobalt-60 gamma irradiator concepts, loaded with 1 MCi and then operating at the maximum capacity. Because each radiation processing system is custom built facility designers generate confidential performance tables for throughput and dose uniformity based on proprietary data. Many factors influence the selection of an irradiation facility, including technical factors; such as density, dose uniformity, shipping box size, product scheduling, volume throughput and growth, and local economic factors; such as labour and electricity costs.

In summary:

• E-beam is ideally suited for products that are low density, homogeneous, packed in relatively thin boxes, tolerant of high dose rates and wider dose uniformity.

• Gamma is suited for products of any density, heterogeneous in composition and packaged in a variety of configurations that fit within the pallet, carrier or tote system.

• X-ray is an emerging technology that still needs to prove the claim that its electrical cost and efficiency is equivalent to cobalt-60 gamma radiation.

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5) Economics Matter: One Example Illustrative is one example of the capital investment and current operating costs from an operator’s perspective with experience in managing of a variety of radiation processing facilitiesxii. The 46-page presentation by Sterigenics gives general information on basic physics and processing overview, design and operational parameters and technical performance characteristics.

i) Capital Investment In this example, the accelerator facility costs in the neighbourhood of US$10 to $12 million dollars. This large facility has a single radiation source (IBA Rhodotron® TT300, 10 MeV 200 kW) with three separate beam lines going into two adjacent concrete radiation cells and the operator has the choice to send product into one cell or the other. In one cell the machine operates in a 10 MeV electron beam (e-beam) mode where product in thin boxes passes under the scanning horn, while this mode is considerably faster it has important depth dose limitations. In the other cell, the machine normally operates in the 5 MeV x-ray modes where product in tote moves on a conveyor past the x-ray target in a single row, using a top-to-bottom interchange and external front to back rotation to achieve optimum dose uniformity. For a standard absorbed dose of 25 kGy on a product of 0.15 gm/cc density at 120 kW beam power the (double-sided) throughput would be approximately 14.4 m3/ hourxiii xiv in the e-beam mode. A gamma irradiator facility costs between $4 to $6 million dollars and with the purchase of cobalt-60 at $2.00 per curie for 1 MCi add another $2 million to the capital cost. In this case, there would be only one concrete radiation cell and the conveying system would be a highly-efficient product overlap, multi pass continuous automatic tote system.

ii) Annual Operating Costs In this paper the author presents general economic considerations with the operational cost example normalized to 1.2 million cubic feet (34,000 m3) of product with 0.15 g/cm3 density and requiring a 25 kGy delivered dose.

• E-beam with 10 MeV electrons, power input about 285 kW, operated 8,700 hours: 2,480,000 kW-h x $0.12/ kW-h = $297,600

• X-ray from 5 MeV electrons, power input approximately 1000 kW, operated 8,700 hours: 8,700,000 kW-h x $0.12/ kW-h = $1,044,000

• Gamma from cobalt-60 130,000 curies/ year x $2.00/ ci = $260,000

This example excludes any ancillary costs, e.g. cooling systems. It does not take into account the depreciation of the capital investment. When undertaking an economic analysis it is a challenge to compare facilities, radiation power ratings and product throughput. There exists a wide diversity of radiation processing facilities, equally matched by a diversity of applications and requirements. Of course everyone uses their own set of assumptions and in any detailed analysis would rely on proprietary information with performance guarantees which are not typically published in the open literature.

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6) Environmental Activism Re-Think Patrick Moore, avid environmentalist and co-founder of Greenpeace, makes the case for nuclear energy in an interesting article entitled, “Nuclear Re-think”xv. His views have dramatically changed and he makes the point that “nuclear energy is the only non-greenhouse-gas-emitting power source that can effectively replace fossil fuels while satisfying the world’s increasing demand for energy.” Coal provides cheap electricity but generates 9 billion tons of carbon dioxide (CO2) per year greenhouse gas emissions and causes acid rain, smog, respiratory illness, mercury contamination. In contrast 441 nuclear plants operating globally avoids the release of nearly 3 billion tons of CO2. Wind and solar are environmentally friendly but cannot be built to replace large base load coal-fired plants. Hydroelectric plants have already been built to capacity. Mr. Moore makes the point that attitudes are changing amongst even the staunchest environmentalists. And he discusses the five myths and facts associated with nuclear energy. Bottom line is nuclear energy is clean, cost-effective, reliable and safe.

7) Irradiation Facilities: An Environmental Footprint In an environmental audit of radiation processing facilities it is possible to take the electrical consumption from the economic example above and calculate the related CO2 emissions. This would cover the bulk of the contributions since the power consumption of the machinery would be relatively small. In a comprehensive environmental audit this would be included as well as the contribution from construction of the concrete shield and so forth. Table 1 illustrates the CO2 emissions from the generation of electrical power in the United Statesxvi. (Note in 1999, they estimated the emission of 2,245 million metric tons of CO2. During this same time period the generation of electricity in millions of kWh was 2,584,779 from all fossil fuels and 1,106,294 from non-fossil fuelled sources.)

Table 1: CO2 emission from the generation of electrical power

Fuels Average Output Rate (pounds of CO2 per kWh)

Average Output Rate (gm of CO2 per kWh)

Coal 2.095 950 Petroleum 1.969 893 Natural Gas 1.321 599 Other Fuels (municipal solid waste, tires…)

1.378 625

US Average 1.341 609 Table 2 illustrates the consumption of electricity in the radiation processing facility and the generation of CO2 as per the different facility types. With nuclear and other non-fossil fuels as the electricity source the generation of CO2 and greenhouse gases would be zero.

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Table 2: Irradiation Facilities and contribution to CO2 emission from consumption of electricity (metric tons per year) E-Beam X-Ray Gamma Coal 2,360 8,270 - Petroleum 2,220 7,770 - Natural Gas 1,490 5,210 - Other 1,550 5,440 - US Average 1,510 5,290 - It is important to put this into perspective with respect to the issue of global warming. In Norway each Moose produces approximately 2.1 metric tons of CO2/yearxvii and they have a population of 125,000 or 6% of the total world’s population. An accelerator operating in the e-beam mode or x-ray mode would be equivalent to 730 or 2,520 moose. In other words a small output of greenhouse gas for a tremendous benefit of eliminating highly infectious, harmful microorganisms

8) Conclusions Innovative irradiator design concepts are routine to experience engineers and physicists. They all have safety systems that are integrated with irradiator operations and designed to protect the worker, public and environment. All comply with applicable international and domestic regulatory standards. There is a choice of technology, e-beam, gamma or X-ray. Facilities are custom built and the process is economical, especially as the capacity increases. Overall radiation processing is a great untold environmental story. It is green and clean and offers many benefits to humankind.                                                             i AdvaMed Statement to The National Academy of Sciences” Nuclear and Radiation Studies Board, January 29, 2007 ii Masefield, J., Brinston R., “Radiation Sterilisation of Advanced Drug-Device Combination Products” Medical Device Technology, March/ April 2007, 12-16 iii Eustice, R and Hunter, R. General Correspondence. iv Federal Register / Volume 72, No. 159/ Friday, August 17, 2007/ Notices, pages 46249-46251 and Final Environmental Assessment related to the Proposed Pa’ina Hawaii, LLC Underwater Irradiator in Honolulu, Hawaii. (Docket No. 030-36974) v Chmielewski, A.G., T. Sadat, and Z. Zimek, “Electron Accelerators for Radiation Sterilization”, IAEA (in publication) vi IA-X Accelerator Specialists http://www.iaxtech.com/index.html vii IBA Correspondence, Performance of a Multipass C-ray System based on a TT1000 Rhodotron viii MDS Nordion JS10000 Brochure http://www.mds.nordion.com/products/sterilization.htm ix Meissner, J. X-Ray Sterilization, Managing Risks, IMRP 2003 Presentation, September 2003 x Stichelbaut f., J-L Bol et al, A high-performance X-ray system for medical device irradiation, Radiation Physics and Chemistry, Vol. 76, Issues 11-12 Nov. Dec. 2007 xi Meissner, J. X-ray Sterilization using a Tote Box Irradiator, IMRP 2006 Poster presentation, Kuala Lumpur xii Smith, M. V.P. Radiation Services Sterigenics, “Comparison of Radiation Processing Technologies” presentation to US National Academy of Sciences, Nuclear and Radiation Studies Board, Committee on Radiation Source Use and Replacement, October 27, 2007 xiiixiii Cleland, Marshall R, “The Anthrax Attacks on the United States Postal Service: Sanitizing the Mail, Ion Beam Applications, Edgewood, NY 11717 www.iba-worldwide.com/industrial/pdf/Anthrax.pdf?article=82 xiv United States General Accounting Office (GAO), “Report to Congressional Requesters, Diffuse Security Threats, Technologies for Mail Sanitization Exist, but Challenges Remain” April 2002. xv Moore, Patrick, “NuclearRe-think”, IAEA Bulletin 48/1, September 2006 xvi US Department of Energy, Environmental Protection Agency (EPA) Report, July 2000 xvii Norway’s Moose Population in Trouble for Belching, August 21, 2007 http://www.spiegel.de/international/zeitgeist/0,1518,501145,00.html