By David Cole and Brandyn Leaper
The Port Hope Area Initiative (PHAI) is the Government of Canada’s response to the community-recommended solutions for the remediation and safe, long-term management of historic low-level radioactive waste in the municipalities of Port Hope and Clarington, Ontario.
The waste was the result of uranium and radium processing operations in Port Hope, Ontario, from the 1930s to the 1980s. The Eldorado refinery, on the shores of Lake Ontario, began refining radium-226 from pitchblende ore taken from Port Radium in the Northwest Territories, later transitioning to the refining of uranium ore. Process residues were deposited at the Welcome Waste Management Facility in Port Hope until the mid-1950s, then switching to the Port Granby Waste Management Facility that continued to accept waste until the late 1980s.
The Port Granby Project involves the construction of a new, secure long-term waste management facility and supporting infrastructure. This is in preparation for the excavation and relocation of approximately 450,000 m3 of historic low-level radioactive waste and marginally contaminated soil from the Port Granby Waste Management Facility to the newly constructed facility. The Project is regulated by a Nuclear Waste Substance Licence granted by the Canadian Nuclear Safety Commission (CNSC), which periodically audits and reviews the progress of the work.
Canadian Nuclear Laboratories (CNL) is delivering the PHAI on behalf of Atomic Energy of Canada Limited, a federal Crown corporation. Wood–Environmental and Infrastructure Solutions has been contracted by CNL to execute this project, ensuring it is within compliance with all Canadian laws and regulations. A comprehensive radiation protection program is a necessary aspect of this remediation project and is the key to a successful nuclear remediation project.
Structure of the Port Granby Radiation Protection Program
A radiation protection (RP) program has been developed to meet contractual and regulatory requirements for this project. The scope of the RP program includes:
- A high-level radiation protection plan that specifies responsibilities, authorities, limits, reporting and program assessment requirements.
- A suite of standard operating procedures that describe how the radiation protection program is implemented on a day-to-day basis.
- A comprehensive training program that addresses training needs of both workers and visitors.
- Comprehensive means to measure and record radiation doses and radiation hazards.
- Response to unusual circumstances, incidents and emergencies.
- Ongoing auditing by internal resources, CNL and the CNSC.
Radiation hazards and mitigation
The following potential radiation hazards have been identified at the Port Granby Project site as part of this remediation project:
- External (gamma) radiation fields.
- Inhalation hazards.
- Mitigation methods have been developed in response to each of the identified hazards.
External (gamma) radiation fields
Protection from gamma radiation is typically based on three principles: minimizing the time spent near the radiation, maximizing the distance between the individual and the radioactive material, and having some sort of shielding between the individual and the radioactive material. These principles are implemented to the extent practical and feasible.
For example, excavator operators are discouraged from holding buckets of waste material near the cab for extended periods of time unless absolutely necessary (reducing the time factor and increasing the distance from the radioactive source).
No workers are required to be standing immediately in the vicinity of the excavation work (increasing the distance factor and reducing their exposure time). Workers do not enter the radiation-controlled area unless required to do so (reducing the exposure time and distance between them and the waste material)
Routine monitoring of the site is performed daily to measure gamma radiation fields. Results of these surveys are used to notify workers of areas of elevated radiation and to determine safe working times.
All workers are provided with dosimeters that provide a permanent record of their radiation dose. Real-time monitoring of worker radiation doses is also performed to gain further insight into the doses that workers receive during their daily tasks. This allows on-site radiation protection staff to adjust the RP program in real time.
There are three independent methods used for monitoring radon levels and the radon hazard.
Environmental radon monitors are placed at strategic locations around the site. These are exchanged quarterly and provide an insight into the radon hazards at key locations within the site.
There is continuous real-time monitoring of radon levels using an electronic radon monitor. Key personnel are provided with individual passive radon monitors. These are provided by a commercial supplier and are exchanged monthly.
The project is mandated to operate with the goal of “no visible dust”. As such, in the event that dust is observed, action is promptly taken to eliminate it. Those actions could include wetting of material or stopping any operation that may be producing airborne material.
To enhance visible monitoring, continuous real-time dust monitoring is provided by the environmental monitoring group. These monitors will provide an alarm if elevated dust levels are detected.
All site heavy equipment has enclosed operator cabins with their own air circulation and filtration system. Operators are required to use these air systems while operating their equipment to prevent material from entering through windows during operations.
A small battery-operated portable air pump and filter is deployed daily to monitor for radioactive airborne particulates. The pump and filter is rotated through various locations on a weekly schedule.
All work involving radioactive material is performed within a demarcated “radiation control area”. Personnel access to this area is strictly controlled through a single access control point, which is a dedicated trailer configured to meet the radiation protection needs.
This trailer includes washing and contamination monitoring facilities. Workers don and doff dedicated site clothing that is cleaned and inspected on site before returning to circulation. Site personal protective equipment includes high-visibility coveralls, boots, gloves, and hard hats, hearing and eye protection.
All vehicles and equipment leaving the radiation-controlled area must exit through a controlled gate and are scanned for possible contamination. Two decontamination facilities (capable of accommodating large construction equipment) are available on site. These are essentially vehicle wash facilities that contain all wash water and overspray. In addition, a vehicle wheel wash facility is available for rapid removal of material from the underside and wheels of any equipment. Water from this system is trapped and later treated on site.
Routine monitoring of the dedicated waste haul road between the excavation and emplacement (a distance of about 700 m) is performed using a ScanPlotSM trailer. This consists of a large trailer-mounted radiation detector connected to a real-time display. This trailer is routinely pulled along all the roads to measure levels of contamination. All waste hauling is confined to a dedicated roadway within the site. No waste is transported on public roads.
No eating, drinking or smoking is permitted in the radiation-controlled area except for specially designated areas. Routine contamination monitoring is performed in these designated areas to ensure worker safety and that the spread of contamination is not occurring. There is a dedicated lunch room that is routinely monitored for contamination each day and is situated well away from the waste hauling operations.
Radiation protection program effort
There is a total staff of five staff dedicated to the site RP program. As of October 2017, the total RP effort included:
- Approximately 1,100 gamma radiation surveys.
- Approximately 2,800 contamination surveys.
- RP training to over 250 individuals.
- Issued over 650 dosimeters (each worn for a one-month period).
- Completed over 156 daily radon checks and deployment of over 200 personal radon dosimeters.
- Placing eight quarterly long-term area radon monitors for a full year.
- Completed over 70 localized air-monitoring samples.
Effectiveness of the radiation protection program
Effectiveness of the RP program is continuously evaluated through audits, oversight and review processes. These reviews have consistently shown the RP program is highly effective at ensuring worker exposure is minimized in keeping with the principle of ALARA (As Low as Reasonably Achievable).
- Measured radon levels were essentially the same as background levels. That is, no consistent elevated levels of radon have been observed.
- Analysis of all filters showed zero detectable radioactivity in the air.
- There were no contamination incidents. That is, there have been zero incidents of finding contamination in areas beyond the radiation controlled area.
- There has been no detectable contamination measured on the internal haul route roadways and there has been no release of radiological material from the construction site.
- For nearly all (99%) site workers, the yearly dose received has been below a detectable level, with only four individuals receiving a measureable dose. Those doses that were measurable were less than 1% of the permissible annual limit (for individuals who are designated as nuclear energy workers, as all site workers are).
- This paper was reviewed by staff at Canadian Nuclear Laboratories.
David Cole and Brandyn Leaper are with Wood – Environmental and Infrastructure Solutions. This article
appears in ES&E Magazine’s February 2018 issue.