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Medical Isotope Production without Highly Enriched Uranium 9 Conversion to LEU-Based Production of Molybdenum-99: General Approaches and Timing The objective of this chapter is to describe and discuss general approaches and timing for conversion to low enriched uranium (LEU)-based production of Mo-99. Like the preceeding two chapters, this chapter is intended to support the discussion of conversion feasibility that appears in Chapter 10. GENERAL APPROACHES FOR CONVERSION Highly enriched uranium (HEU)-based Mo-99 producers have two basic options for converting to LEU-based production: Brownfield: Convert an existing processing facility from HEU-based production to LEU-based production, or convert an unused facility that contains hot cells to LEU-based production. Greenfield: Construct a new processing facility that is designed specifically for LEU-based production. For the purposes of this discussion, a “processing facility” is a facility that contains hot cells and ancillary support equipment to receive and process irradiated LEU targets (see Chapter 2), recover and purify Mo-99, and manage wastes. The facilities upstream and downstream of this processing facility—that is, the reactor used for target irradiation and the facility used to prepare technetium generators—are likely to
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Medical Isotope Production without Highly Enriched Uranium be usable for either HEU- or LEU-based production with little or no modifications.1 Brownfield Conversion The major advantage of Brownfield conversion is its potential cost effectiveness: It is substantially less costly to replace process equipment in an existing facility2 than to construct a new facility. However, if not properly managed and scheduled, conversion of an existing processing facility could interrupt ongoing Mo-99 production activities and result in unnecessary cost, time, and personnel radiation exposures. The best current example of a successful Brownfield conversion is the Mo-99 processing facility in Argentina. As discussed in Chapter 7, the facility operator, Comisión Nacional de Energía Atómica (CNEA), was able to convert to LEU-based production in the same set of hot cells that were being used for HEU-based production. Moreover, this conversion was made without interrupting Mo-99 production. This conversion was possible for two reasons: First, conversion did not require substantial changes to existing target dissolution and Mo-99 recovery processes; consequently, substantial equipment modifications were not required. Second, CNEA produces Mo-99 only once a week, and so there was sufficient hot cell down time to perform the necessary process development and conversion work. Conversion within a single set of hot cells might be more difficult when substantial process changes are required: major equipment modifications or replacements might be needed, and cross-contamination of processing lines could occur. Such conversion would also be more difficult when production is carried out more than once a week.3 Regulatory requirements may also be a barrier to conversion within the same set of hot cells. As noted in Sidebar 8.1, the Food and Drug Administration (FDA) supplemental New Drug Application approval process requires three full-scale production runs of Mo-99 on the equipment that will be used for commercial production. The process equipment must be set up for those runs but cannot be used for commercial production until FDA approval is obtained. Such approval could take several months. 1 For example, the rigs used to irradiate targets in the reactor might need to be modified if the LEU targets have a different geometry than the HEU targets they are replacing, but changes to the reactor facility itself would likely not be required. 2 This statement assumes that major facility modifications are not required. It could be costly to make major modifications to an existing facility to accommodate new process equipment. 3 Mo-99 could be shut down to allow for conversion if Mo-99 could be purchased from other sources until regulatory approvals were received to restart production with the new process.
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Medical Isotope Production without Highly Enriched Uranium In cases where conversion cannot be made within the same set of hot cells, Brownfield conversion may only be possible if there are additional hot cells available in the facility or nearby. Research and development (R&D) could be carried out in hot cells in other facilities as well. Those hot cells could be used initially to carry out the R&D needed to support conversion and would eventually become the new LEU-based processing facility. This facility could be run in parallel with the HEU-based processing facility as long as needed to complete the conversion process. The two production facilities could be run in parallel, for example, to shake out the new process and train personnel. As will be discussed in Chapter 10, at least three of the existing large-scale Mo-99 producers (Mallinckrodt, Institut National des Radioéléments [IRE], and MDS Nordion) could likely convert using this approach. Greenfield Construction Greenfield construction is advantageous primarily because it would not interfere with current Mo-99 production activities, and also because the new facilities can be custom-designed to meet current and projected future Mo-99 production needs. However, construction is likely to be substantially more expensive. There are no recent examples of Greenfield construction for Mo-99 production. The Australian producer (Australian Nuclear Science and Technology Organisation [ANSTO]) is in the process of converting from an inefficient LEU-based process to a more efficient process using technology that was engineered and scaled up by the Argentine company Investigaciones Aplicadas Sociedad del Estado (INVAP) and CNEA from the CNEA-developed LEU-based process (see Chapter 3). ANSTO’s existing hot cell facility was substantially refurbished by INVAP (which also constructed the Open Pool Australian Lightwater [OPAL] reactor) as part of this conversion process. The new LEU-based processing facility designed and being constructed near Cairo, Egypt, by INVAP is an example of a Greenfield facility. However, this country is not an existing Mo-99 producer and plans to produce primarily for its own domestic needs and possibly to supply other countries in the region. TIMING FOR CONVERSION The time required for conversion will depend largely on which approach (Brownfield or Greenfield) is used. Both approaches share some common development steps that would require about the same amount of time, most notably for target design and fabrication and process development and testing (Chapter 7). Once this testing is completed, the setup and testing
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Medical Isotope Production without Highly Enriched Uranium of process lines in the facilities and regulatory approvals4 would also take about the same amount of time. However, the time required to construct or convert the facility itself would be substantially different as discussed in the following two subsections. Greenfield Construction Greenfield construction generally requires much longer lead times than Brownfield conversion. The exact timing would depend on the nature of the facilities to be constructed as illustrated with the following two examples: Construction of a new reactor and processing facility, the latter consisting of hot cells and ancillary support equipment; or Construction of a new processing facility at or near an existing reactor. In the first case, the reactor and processing facility would likely be constructed concurrently. After construction is completed, cold commissioning of the processing line and pretraining of staff would be carried out. Hot commissioning of the processing line would normally be carried out once the reactor is operational and the first targets are irradiated. The time interval between the start of construction and commissioning of reactors built during the past two decades (e.g., Egyptian Testing Research Reactor II [ETRR2] in Egypt, Forschungsneutronenquelle Heinz Maier-Leibnitz [FRM II] in Germany, and OPAL in Australia) has been 6 to 8 years.5 Production facilities might be constructed in less time, but of course they could not be operated until after the reactor was commissioned. This construction and commissioning time interval does not include the preconstruction period, which begins with the decision to build, extends through the tender solicitation and selection process, and ends with the award of a construction contract. This typically requires another 2–3 years. Up to an additional 1–2 years6 would be required to obtain regulatory approvals to produce Mo-99 (see Chapter 8). The estimate of the total time required to bring new Mo-99 production to market is thus 9–13 years. This estimate does not account for any unanticipated startup delays as has oc- 4 Regulatory approvals could take longer if the producer had no previous experience with Mo-99 production. 5 Isotope production reactors (Maple reactors) were constructed in Canada but were never commissioned; see Chapter 3. 6 The longer time period could apply if Mo-99 is being produced for export because Mo-99 producers would have to help their customers obtain regulatory approvals in customers’ home countries.
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Medical Isotope Production without Highly Enriched Uranium curred for some recently constructed reactors (see discussion of the Maple and OPAL reactors in Chapter 3). In the second case, there is little experience to draw on, in fact none for a large-scale producer of Mo-99 during the last several decades. The Argentinean company INVAP is finishing construction and starting commissioning of a turnkey integrated facility for producing Mo-99 from LEU targets irradiated in ETRR2, but to the committee’s knowledge this is not now planned to be large-scale production. Such a facility, using proven technology,7 can be designed and constructed in 2–3 years. An additional 1–2 years would likely be required for cold and hot commissioning, training of staff, and regulatory approvals. Two U.S.-based organizations are seeking partners for Greenfield construction of Mo-99 production facilities in the United States: The Missouri University Research Reactor (MURR) is seeking support to construct a facility for LEU-based production using its existing multipurpose reactor (Chapter 3). MURR estimates that it could take 3–4 years to fund and construct this facility. MURR estimates that additional time, perhaps another year, would be required for process commissioning and associated regulatory approvals. Babcock & Wilcox (B&W) is seeking a radiopharmaceutical partner for a medical isotope production reactor and associated processing facilities at its Lynchburg, Virginia, site (Chapter 3). The company estimates that construction would require 5 years if the regulatory issues described in Chapter 3 can be addressed in a timely manner. Again, additional time, perhaps 6 to 18 months, would be required to transition to this or any other new isotope production facility into production because of FDA approval protocols. For these Greenfield construction examples, the minimum time required to bring new Mo-99 production to market ranges from about 4 to 9 years. Brownfield Conversion Brownfield conversion shares some similarities with the second case for a Greenfield construction, except that the processing facility already exists. The time required to convert the facility is probably less than building a new facility from scratch. As noted previously, two recent examples of such conversions are CNEA (Argentina) and ANSTO (Australia).8 The time for conversion of the CNEA facility was very short (on the order of 7 This facility will produce Mo-99 using the CNEA-developed process that was scaled up and engineered by INVAP. 8 ANSTO was a Brownfield conversion in the sense that its existing hot cell facility was refurbished to accommodate a new LEU process.
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Medical Isotope Production without Highly Enriched Uranium a year) but, as discussed previously, this conversion was unique because it did not require major changes to the target dissolution and Mo-99 recovery processes. Conversion of the ANSTO facility began in January 2007 and is still under way.9 Facility commissioning has been delayed because of startup problems with the OPAL reactor. As noted previously, ANSTO was carrying out low-activity Mo-99 production trials but had not yet commenced commercial production when this report was being finalized. The time required for a Brownfield conversion will depend on the nature of that conversion. If the conversion requires the refurbishment of existing hot cells, it could require as little as 1–2 years once the process development work is completed. Personnel training and regulatory approvals would take an additional 1–2 years. On the other hand, if existing facilities can be adapted to an LEU-based process, the conversion time could be reduced to the time required to modify the process equipment, train staff, and obtain regulatory approvals. This could be as little as a few months to about 2 years once the process development work is completed. FINDINGS This chapter provides a description and discussion of some general approaches to converting from HEU-based to LEU-based production of Mo-99. The chapter also describes the timing requirements for such conversion. On the basis of this information, the committee finds that: There are two general approaches for converting from HEU-based production to LEU-based production: Brownfield (conversion within an existing processing facility or an unused facility with hot cells) or greenfield (construction of a new processing facility). Brownfield conversion is generally less expensive and takes less time but could interfere with ongoing Mo-99 production operations. Greenfield construction is generally more expensive, but the facility can be custom-designed to meet current and projected Mo-99 production needs, and conversion would not interfere with ongoing Mo-99 production activities. Brownfield conversions can be carried out in as little as a few months to about 2 years once the necessary process development work is completed. Greenfield construction can require 9–13 years from the decision to build to startup of Mo-99 production if a new reactor and processing facility are constructed or about 4–6 years for construction and startup of a new processing facility. 9 Although physical installation began in 2007, substantial effort had begun prior to this date including planning and preparatory work which was initiated in 2005.