D.09.4 Resource Gammacell 220 Irradiators

Objective

• Establish a roadmap to resource Gammacell 220 irradiators.

Actions

• Establish strategy:

  1. Develop agreements, contracts or indemnification documents such as liability wavers from at least NIST and preferably from other national labs to Nordion (or some other corporate entity) to enable resourcing (replenishing) of Gammacell 220 irradiators, which serve as a critical piece of the US primary standards process and help maintain traceability standards; or

  2. Provide a national strategy to update US infrastructure in regards to self-contained gamma irradiators; or

  3. At a minimum, provide a reasonable protocol for academia, labs and industry for the disposal of partially depleted cobalt-60 sources in existing Gammacell 220 irradiators

• Avoid overreacting to regulations surrounding cesium-137 and cobalt-60 sources and provide a forum for proper education about lifecycle management including upfront and ongoing costs (money, time, personnel, liability), safety and ongoing traceability.

Requirements

• Minimal funds; moderate complexity; logistics and decision makers must
  agree that this is a viable near-term approach.

• Moderate funds; high complexity; depending on scale, the cost to redesign Gammacell 220 irradiators to meet modern needs and enable better future resourcing would likely require upfront investment on the order of 10 million dollars and a long-term commitment to support ongoing research efforts and ongoing regulatory support concerning distributed gamma cells at labs, and in academia

• Moderate funds; unknown complexity

Background

For business reasons, Nordion (Sterigenics), has withdrawn resourcing support for current Gammacell 220 irradiators. There exist myriad Gammacell 220 irradiators across North America that face limited options for resourcing (i.e. replenishing cobalt-60 sources) inside the cells. Some of these irradiators are located in academia and national labs such as at NIST. Maintaining traceability to primary standards at NIST is a major concern so as not to impede commerce. Maintaining research capabilities at national labs and academic sites is of secondary near-term concern, but critical to maintain long-term US competitiveness in research areas concerning ionizing radiation.

Suggested needs for next generation self-contained irradiators:

• Uniform calibration volume with dose control and measurement validation at 1 cm spacing
• Temperature range of −75 C to 75 C with 1 C temperature accuracy
• Dose control within 3% for industry, and within less than 2% for NIST

Resolution

Following recommendations described within MPD D.09.4, this metrology need can be successfully marked as complete, due to initiatives taken at Hopewell Designs, Inc. between 2015 and 2022.

Hopewell Designs, Inc. undertook the endeavor to create, develop, and install the radiation system at the National Institute of Standards and Technology (NIST) that is used to realize the gray (Gy), the standard unit of measurement for radiation dose that all other radiation measurements are compared to (here dose refers to the measure of radiation energy absorbed by the human body). Every measurement made in the field of radiation is traceable through a chain of comparison measurements back to this standard at NIST, and NIST maintains and disseminates this radiation standard for medical, radiation processing, homeland security, and radiation protection applications.

During attendance to the annual CIRMS conference, Hopewell representatives learned that the radiation industry needed a novel system for high dose rate radiation calibration. Development of this system required extensive use of simulation software for ensuring dose rates were appropriate and radiation shielding was adequate. Moreover, simulation of each of the moving components was needed to ensure radiation safety was maintained throughout all transitions, such as the motion of transporting the 5-liter volume, and the process of loading the highly radioactive cobalt sources from the shipping container and into the system.

The development of this system was the culmination of a five-year long commitment from Hopewell Designs. Today, a replacement calibration system is available to the market with the full backing of the cobalt-provider Nordion. This system is turn-key, offers numerous advantages to the legacy GC220 system, and is able to be resourced in place. You can find this system today by searching online for the high dose rate research irradiator, the GR420.