Designing Radioactive Laboratory Exhausts: How Do I Know It`s Safe?

John Alberico, RWDI

Emissions from radioactive exhausts can pose a serious health problem - both acute and chronic. Once the contaminated emissions leave a laboratory building, they must be properly dispersed to ensure the safety and well-being of the people exposed to them. Re-entrainment of exhausts containing radioactive emissions is a continuing challenge for laboratory designers - the exhausts systems can be underdesigned causing unsafe conditions, or overdesigned leading to additional capital and maintenance costs and an aesthetically unpleasing design.

The assessment of radioactive emissions from laboratories on the environment typically involves several steps:

  1. estimating the emissions of radioactive material,
  2. developing design criteria for these emissions that are based on meeting regulatory limits that ensure the safety of people exposed to the emissions (i.e,, short-term and annual dosage limits),
  3. conduct dispersion modeling to predict the impacts at sensitive locations, and
  4. if necessary, modify the stack design to ensure the design criteria are met.

The under- or overdesign of these exhaust systems is typically the result of adopting dispersion models (e.g., COMPLY, CAP88). While these models are convenient for calculating exposures, they are not well-suited for estimating near-field dispersion, particularly in highly-urbanized environments.

Instead of modeling dispersion using these regulatory models, dedicated numerical dispersion models (e.g., ASHRAE) and physical wind tunnel dispersion modeling can be used to develop more accurate dispersion estimates. This leads to stack and intake designs that can meet exposure limits, ensure the safety of the people exposed to the emissions, and potentially result in less costly designs.

This presentation will outline the methodology used to assess radioactive emissions and how do develop exhaust systems that will ensure the safety of people that may be exposed to the emissions based on dispersion models that better model the near-field regime around buildings (e.g., ASHRAE or Wind Tunnel). Case studies will be presented to demonstrate the benefits of the proposed methodology. Better design practices can help to meet long-term and short-term dosage limits.

Learning Objectives

  • Participants will acquire an understanding of radioisotope regulatory limits.
  • Participants will acquire an understanding of how radioisotope hood stack designs can benefit from improved dispersion modelling involving numerical disperion and wind tunnel modeling.
  • Participants will learn advantages and disadvantages of different design strategies for meeting the regulatory limits.

Biography:

John is a Principal at RWDI with more than 25 years of experience. He is a Canadian Certified Environmental Professional.

John's area of technical expertise is in exhaust and dust dispersion, and wind flow around buildings, which has included involvement in several hundred projects providing expert consultation, and conducting both numerical and wind tunnel modeling. His primary focus has been in the institutional, healthcare, higher education and pharmaceutical sectors.

 

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