Question 6 of 7: Radiation Survey Plan for an Abandoned Uranium Mine

Question 6: Radiation Survey Plan for an Abandoned Uranium Mine (10 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Given. An inhabited town adjacent to an abandoned uranium mine, with public concern over perceived elevated radiation levels; the deliverable is a one-page memorandum outlining a survey plan.

Find. A structured monitoring plan: what pathways/media need surveying, what instruments and sampling protocols to use, and against what regulatory benchmarks the results should be judged.

Approach. Work through the standard uranium-mine legacy-site exposure pathways — direct external gamma, radon and its progeny, surface/soil contamination, and water — and match each to an appropriate Canadian (CNSC/Health Canada) survey method and benchmark, then present the whole plan in memo form.

1. Memorandum — survey plan for the abandoned uranium mine site.

   To: [Supervisor, Radiation Protection Bureau]   From: [Surveying Officer]   Re: Proposed radiation survey plan — abandoned uranium mine near [Town]

   1. Purpose and scope. This memo proposes a baseline environmental radiation survey of the town and the abandoned mine site to respond to the mayor's concern, establish whether public exposure exceeds Canadian regulatory limits, and identify any remediation or ongoing monitoring needs. The survey will cover four exposure pathways: direct external gamma radiation, radon gas and its short-lived progeny, surface/soil contamination, and surface/groundwater quality.

   2. External gamma survey. Perform a walkover gamma dose-rate survey using a calibrated portable scintillation or GM survey meter, on a systematic grid covering the town, the mine site itself (waste rock piles, tailings, adits), and undisturbed background reference locations well outside any plausible influence of the mine. Record dose rate ($\mu$Sv/h) with GPS-tagged locations to build a contour map, and flag any location whose dose rate is statistically elevated above the local background reference.

   3. Radon and radon-progeny survey. Uranium mine sites and their tailings are major radon (${}^{222}$Rn) sources. Deploy passive integrating radon detectors (alpha-track or activated-charcoal canisters, minimum 90-day integration where feasible) in a representative sample of homes and other occupied buildings in the town, particularly those closest to the mine and those with basements or slab-on-grade construction. Compare results to the Health Canada guideline of 200 Bq/m$^3$ annual average indoor radon; any building at or above this level triggers follow-up and mitigation guidance.

   4. Surface and soil survey. Collect soil samples on a grid across the mine site, tailings/waste-rock areas, and the town (including any areas where mine material may have been used as fill or aggregate), and analyze for uranium, radium-226 and daughter-product activity concentrations by gamma spectroscopy/alpha spectrometry. Perform surface swipe (smear) surveys of accessible mine structures for removable alpha/beta contamination.

   5. Water survey. Sample the town's drinking-water supply (wells and any surface-water intake) and any surface water draining the mine site, analyzing for dissolved uranium and radium-226, compared against Health Canada's Guidelines for Canadian Drinking Water Quality (uranium maximum acceptable concentration 0.02 mg/L).

   6. Instrumentation and QA. All survey meters and laboratory analyses will use instruments with current calibration traceable to a national standard, with field blanks, duplicate samples, and a documented chain of custody for every sample.

   7. Benchmarks and next steps. All results will be compared against the CNSC Radiation Protection Regulations public dose limit (1 mSv/year above background) and the Health Canada radon and drinking-water guidelines noted above. A summary report with recommendations — further monitoring, access restriction, or remediation, as warranted — will follow within [X weeks], with results communicated transparently to the mayor and residents.