1 / 28

The Canadian Experience

The Canadian Experience. Estimating Radiation Hazards to Biota at Uranium Mines. Dr. Steve Mihok, Directorate of Environmental and Radiation Protection and Assessment PROTECT Workshop – Vienna, June 27, 2007. Regulatory Framework – NSCA (2000).

sierra
Télécharger la présentation

The Canadian Experience

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Canadian Experience Estimating Radiation Hazards to Biotaat Uranium Mines Dr. Steve Mihok, Directorate of Environmental and Radiation Protection and AssessmentPROTECT Workshop – Vienna, June 27, 2007

  2. Regulatory Framework – NSCA (2000) • CNSC - “Regulate … to prevent unreasonable risk to the environment…”, Applicant - “Make adequate provision for the protection of the environment …”, “… control releases …” • CNSC Regulatory Policy P-223- consistency with other Canadian policies, acts, … • CEPA – legal framework for managing “toxic” substances • CEAA – pre-licensing, assessment of likely, significant, adverse effects for defined “projects” • FTSMP – promotion of pollution prevention • MMER – As, Pb, Ni, Zn, Ra-226 … “permission to pollute”- CNSC license conditions for emerging issues (U, Mo, Se)- PSL2 decision on uranium as a “toxic substance” for biota at certain facilities, resultant MOU with Environment Canada • S-296, Environmental Management Systems ~ ISO 14001

  3. Hazard Assessment - How results are used • EMS - Programs and Procedures for Environmental Protection- Context and predictions for spatial and temporal effects / ”aspects” - Needs for operational controls on quantities, timing and locations of releases • Effluent Monitoring Program- Requirements for procedures to verify that controls are effective- Performance indicators / targets, administrative controls & action levels • Environmental Monitoring Program - Need for, and the scope of, activities to verify that releases are having the predicted effects (Pathways Contaminant Monitoring vs Biological Effects Monitoring) • Remediation of Contaminated Sites- Clean-up criteria and priorities for many historical sites$$$ • Emerging issues at all sites- Long-term contamination of groundwater, sediments, unexpected pathways

  4. Uranium Mining in Canada – Geography

  5. CNSC – Federal RegulatorSaskatchewan Environment – Provincial Regulator JEB open pitMcClean Lake Mine Northern Boreal Forest – MANY Lakes & Rivers

  6. Decommissioned & Abandoned Mines Some sites with minimal Decommissioning Elliot Lake, OntarioQuirke TMA

  7. Recent Mining-related EAs / ERAs • New High Grade Ore Mine – Cigar Lake • Operating Mines – McClean Lake Sue E, Key Lake, McArthur River, Rabbit Lake Pregnant Soln • Decommissioning – Cluff Lake • Historical Mines –Beaverlodge, Port Radium, Lorado, Gunnar, Madawaska, Dyno, ongoing … • Remediation – Port Hope / Port Granby “Mounds” • 2007+ – DeLoro (received), Midwest (guidelines) • Typical Consultants – e.g. SENES, Ecometrix

  8. CNSC Approach - Radiation Hazards for Biota • Published by Environment Canada & Health Canada as a PSL2 Assessment in 2004 – Chemical Toxicity of Uranium • Refined from literature reviews in the late 1990’s • Following Environment Canada’s risk quotient approach for assessment of any hazardous substance (safety factors) • Simple, conservative dose coefficients and biota geometry (Amiro, 1997), conservative alpha RBE 40, tritium RBE 3 • Effects benchmarks chosen for the most sensitive species using data on chronic reproduction or mortality effects, “similar” to UNSCEAR/IAEA except for fish • Conservative in estimating exposure (benthos), secular equilibrium (30% Rn-222), choice of transfer factors …

  9. Licensee Approach - Delegation of Technical Work • CNSC is not prescriptive - guidelines only, no standards • What has worked out well- Risk is being identified to set priorities- Practical needs of licensing are being met- Data gaps are being addressed in “FUPs” • What has not worked well- ERA “numerical” results are easy to manipulate, and hence, very tedious to review and interpret- There are many data gaps on exposure or effects- Physical models do often under-predict sediment levels - Pathways are still generic; exposure of wildlife is only just now starting to be verified with measured data • Licensees still question ERA interpretation, prefer to react to “dead bodies” rather than prevent risk

  10. A “Typical” ERA – Predicting the future Rabbit Lake • an old mill with sites already at ecological risk • proposal to mill Cigar “pregnant” solution from McClean Lake mill via a new haul road

  11. Valued Ecosystem Components • Chosen to balance public interest and to capture exposure pathways, set in consultation with “Environmental Quality Committees” • Similar logic for aquatic biota, fish species and benthos

  12. Typical Pathways – Wateras a driver Watershed model calibrated via Kd Whole fish data needed Carex, the wrong species “Muskrats do not eat roots”, and other nonsense Interpretation of Beyer et al. feces data Kd or transfer factor approach Almost no data

  13. Radiation Hazard – Common practices • Conservative DCFs from Amiro (1997) • Discussion of RBE values, alpha from 5-40Discussion of dose benchmarks, PSL2 vs others • Variable treatment of secular equilibrium, Thorium may not be considered, Radon at 1%, 10%, 30% … • Benthos screening done against LEL/SELs, some use of Thompson et al. recent benchmarks • Considerable diversity in how uranium chemical toxicity is addressed, both exposure and effects

  14. Dealing with uncertainty • SENES –probabilistic approach with mostly order of magnitude, log-normal distributions for transfer factors, many fixed parameters, occasionally using a tiered approach with further data collection • ECOMETRIX –screening approach, use of expected and bounding / maximum scenarios • ALL -minimal discussion of whole body versus organ doses, species-specific biology, review of toxicity literature, ecological context of impacts “Adaptive Management” & FUPs

  15. Radiation effects – Rabbit Lake EASR (2006) Po-210 and benthos

  16. Reality Checks - Tissue Concentrations • Waterfowl: Cluff Lake (5), Rabbit Lake (4), Elliot Lake (2), some very high levels on TMAs, almost no bone data • Benthos: McClean Lake (2, creek), Cluff Lake (4, shallow lakes), Elliot Lake (2, lakes), Port Hope (harbour & creek)- dragonflies, crayfish, snails, tubificids, pooled samples… • Fish:much better data, different trophic levels, small and large fish, some fish ageing data, recent whole body data, some flesh vs bone comparisons, almost no organ dataAnalysis of Po-210 is expensive – often missingE.G. Wildlife – no request by regulator = no radionuclide data

  17. Reality Checks – Ecology • Moose exposure/diet is adjusted for low density, and large home range to produce low, low risk…BUT, BUT… Useful N =Zero? • Aerial surveys of moose have all been done in winter - In summer some moose have literally fallen into TMAs • Moose appear to live on macrophytes in early summer, this high level of sustained exposure is ignored in yearly averaging • Fecal data from mule deer at a metal mine in BC indicate very high exposure to tailings, what happens at uranium mines?

  18. Setting Priorities – Radionuclides or ??? U

  19. Uranium Chemical Toxicity • No benchmark for birds (1 study with metallic form) • Mammalian physiological benchmarks approach background based on kidney toxicity; chronic reproductive benchmark is at lowest level studied • Bioavailability and environmental chemistry is poorly documented in soils, sediments, water • Allometric scaling of CTV for wildlife species relative to mouse / rabbit greatly affects results [Sample et al. 1996 vs 1999 coefficients] • Uranium OFTEN FLAGS FOR RISK at near-field siteS depending on how the model is set up

  20. Rabbit Lake Mine – Benthos & Uranium Small lakes/ponds are often the first receiving water body.Upper Link Lake is an “outlier” in the LEL/SEL statistical analysis; it greatly affects STATISTICS for Hyallela despite overall N = 20,000

  21. Orders of MagnitudeRQ=1 or 10?

  22. Waterfowl / Benthos – TMAs / Pits Rabbit Lake B-Zone 1992

  23. Importance of organ doses from Po-210 to waterfowl RQ>>1??

  24. The long term Watershed models tell us that most far-field environments should return to background in about 100 yearsWhat do we know about wildlife exposure now?

  25. Bone doses may be critical ~ Ra = Rn? = Pb = Po

  26. ERA Interpretation – how to get a low RQ Real examples of Muskrat exposure to Uranium • ↓ 2x - use “default” sediment ingestion rate of 1%[ignore recent measured values (1.6-3.5%)] • ↓ 2x adjust the CTV for a 28 g mouse to a “large” muskrat by the lowest of two allometric exponents suggested by Sample • ↓ 5-10x have the muskrat only eat shoots of macrophytes (Carex!) and not roots, ignore literature and/or data • ↓ 2-4x calibrate the watershed model to agree with shoots of macrophytes, present “fit” on a log scale to make it look good • ↓ ?x – choose your transfer coefficients wisely …

  27. Putting it all together – A typical decision point • Benchmark = 1 mGy/d, RBE = 10, Radon @30% • Whole body dose, Amiro (1997) DCFs • Probabilistic Transfer, beaver, moose etc. all with very low RQs for radiation Coefficients • Generic diets, home range, exposure scenarios… • Highest RQ for near field = 0.43 (expected) for the scaup, = 1.54 (95th percentile),Muskrat hazards • BUT - Se, Mo flagging for risk, many species with RQs > 1 for NOAELs, effects extending into the far field for years Proceed with licensing the project – YES or NO? Set license conditions for improved effluent treatment? Insist on a major Follow-up Program to measure actual risks?

  28. Future – Uranium @ $150+ per lb? • High Grade Ores(predicting effects) • Athabasca Basin(old mills, new mines) • Northern Mines (Nunavut, Labrador) • Climate Change(Wildlife, First Nations) Woodland and BarrenGround Caribou

More Related