Report on Defense-Related Legacy Uranium Mines in the United States

Transcription

1 Report on Defense-Related Legacy Uranium Mines in the United States David S. Shafer, PhD, Acting Director of Site Operations Office of Legacy Management US Department of Energy October Technical Meeting of the International Atomic Energy Agency (IAEA) Regulatory Supervision of Legacy Sites Initiative Technical Meeting

2 The U.S. Congress directed the U.S. Department of Energy (DOE) to prepare a report on defense-related uranium mines. Work on report started in January Report is due in July Focus is on mines that provided uranium ore for atomic energy defense activities of the U.S., namely the Atomic Energy Commission Report will evaluate impacts, prioritization, feasibility, and costs associated with environmental and public health impacts of AUMs. Federal agencies may be designated responsible parties for cleanup of mines. Uranium mines have never been regulated in the U.S. as part of the nuclear fuel cycle. Aerial view of U mine and milling waste at the Northeast Church Rock Mine, New Mexico. 2

3 Defense-related uranium mines are part of a larger issue of abandoned or inactive mines in the U.S. More than 150,000 abandoned or inactive hard rock mines exist in the western U.S., not including Alaska. Even if all U mines are considered, they are less than 5 percent of all abandoned mines However, in the Four Corners region (Arizona, Colorado, New Mexico, and Utah), the majority of abandoned mines are uranium. Why does the U.S. have legacy uranium and other types of mines? Most of these mines were established under the General Mining Law of 1872, which did not require reclamation or remediation. The 1872 General Mining Law promoted mining as a way for Euro-Americans to settle the western U.S. Because remediation of mines was not required, the operators or licensees of most mines is often not known or no longer exist. Not until 1976 did agencies who manage public land in the U.S. have strong regulatory authority to manage mines, including requiring surety bonds for closure of them. Population growth in the western U.S. means that many more people live near abandoned mines. 3

4 The timeframe for defense related U mines is well known. Domestic uranium mining supported defense activities from 1947* until 1970 in the U.S. (Atomic Energy Commission) * A small amount of uranium was obtained from reprocessing vanadium tailings purchased by the Manhattan Engineer District (MED) in the 1940s. MED also purchased ore from foreign locations. 4

5 DOE Office of Legacy Management (LM) is writing a summary report backed by four technical reports. Given time and resources we are maximizing the use of existing information from other agencies. Data is also being used from: Approximately 200 mines reclaimed by DOE in Colorado Almost 90 mines visited this year to collect site specific data There will be a summary report with supporting information and data contained in four technical reports: 1. Location and status of reclamation/remediation of mines. 2. Assessment of impacts to public health and environment. 3. Potential cost and feasibility of reclamation and/or remediation. 4. Ranking of priority for reclamation and remediation. 5

6 Federal and state records to identify location and status of defense-related uranium mines. Our primary source of information is from U.S. Atomic Energy (AEC) records. 4,213 documented claims (listed by state and county only). We have used other federal databases to validate locations and statuses. EPA Technologically Enhanced, Naturally Occurring Radioactive Materials (TENORM) and Uranium Location Database. EPA Region 9 Navajo Nation (NN) AUM screening reports. The NN is the largest reservation for Native Americans in the U.S. U.S. Geological Survey Mineral Resources Data System. U.S. Bureau of Land Management (BLM) Abandoned Mine Site Cleanup Module (AMSCM) Worked with state and tribal Abandoned Mine Lands (AML) programs. We have received information from 12 states and the Navajo Nation. Two major laws/programs under which mines are being reclaimed in the U.S. Surface Mine Control and Reclamation Act (SMCRA) of Superfund or the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). 6

7 How many Defense Related AUMs exist and what data do we have on them? Total Number of Mines: 4,213 Number of Mines with Data* Percent of Total Location 3, U Ore Produced 4, Land Ownership 3, Cost if reclaimed Gamma Radon 3 <1 * Without input from field verification results from 89 mine site visits. Similar to other legacy sites, data on many AUMs is lacking or not centralized. AUM data is often grouped with data on other hard rock mines. 7

8 In practice, there are different objectives implied by reclamation versus remediation of legacy uranium mines. Reclamation Remediation * Physical hazards, e.g., open shafts, are mitigated Waste rock is recontoured to reduce erosion and improve drainage Clean soil is placed over waste rock, primarily to revegetate the site Radiological exposure may be indirectly reduced Radiological exposure/metal toxicity is directly addressed Soil or overburden thickness attenuates gamma or radon exposure to risk-based levels Waste rock and soil is removed and disposed of in offsite or onsite disposal cells Ecological impacts are mitigated *Includes actions identified for reclamation. 8

9 Mine reclamation in Colorado: mine adits closed, waste rock stabilized, and clean soil put down to help revegetate the site. Before The Radium No. 8 Pit Mine is located in near Slick Rock, Colorado. After The mine complex was reclaimed in The After picture was taken in August 2011, 2 years after the site was reclaimed. Radiological exposure was probably reduced, but was not the primary objective of the reclamation. 9

10 We know the location of all but 7 mines that produced over 1,000 tons of ore for the AEC. Size of Mine Tons of Ore* Number of Mines Known Locations Unknown Locations Small ,931 1, Small/Medium 100 1, Medium 1,000 10, Medium/Large 10, , Large 100, , Very Large >500, Unknown Size Total 4,213 3, There are 580 mines with unknown locations; the majority of these are small (i.e., <100 tons). Unknown location means we know the state and county but do not have latitude and longitude. * multiply tons x 0.91 to convert to metric tones 10

11 The majority of unknown defense-related uranium mines are located in Utah and Colorado. However, 85% of the unknown mines produced 100 tons or less or ore. State Total Known Locations Unknown Locations COLORADO 1,518 1, UTAH 1,378 1, ARIZONA WYOMING NEW MEXICO SOUTH DAKOTA TEXAS UNKNOWN CALIFORNIA NEVADA NORTH DAKOTA MONTANA WASHINGTON IDAHO OREGON 4 4 OKLAHOMA 2 2 ALASKA 1 1 FLORIDA 1 1 NEW JERSEY 1 1 PENNSYLVANIA 1 1 Total 4,213 3,

12 The number of mines in a state does not necessarily equate with U ore production. More ore was mined in New Mexico than the other three Four Corners (Arizona, Colorado, New Mexico, and Utah) states combined. Wyoming is second in ore produced. Source: AEC records. 12

13 Navajo Nation Concerns about impacts of uranium mining on the Navajo Nation is one of the reasons the report is being prepared. Largest AUM in the U.S. is on land of the Acoma Pueblo Indians in New Mexico. Detail area 13

14 Roughly 79 percent of all defense-related uranium mines are on public lands managed by federal agencies. Agency Number of Mines Bureau of Land Management 2,049 Unknown 732 State, county, and private 533 U.S. Forest Service 373 Bureau of Indian Affairs 448* Department of Energy 43** National Park Service 28 Bureau of Reclamation 3 Department of Defense 2 Fish and Wildlife Service 2 Total 4,213 *Includes mines claims on NN **On land withdrawn from BLM 14

15 There are a variety of physical hazards, pathways for exposure to radiation, and ways that environmental media can be contaminated at uranium mines. 15

16 Physical hazards at abandoned mines can present immediate health risks. About 25 people die each year due to accidents at abandoned mines in the U.S. Falling down a 100m shaft is an acute exposure (to the ground). Physical hazards of an abandoned mine can include open shafts and tunnels, subsidence, collapsing infrastructure. Public land agencies frequently address physical hazards before radiation and toxicological hazards at mines. Example of a phased approach to legacy site remediation Data also shows that sealing tunnels and shafts can reduce radiological exposure to radon. 16

17 What clean-up standards are used for abandoned uranium mines in the USA? What exposure scenarios are used? There is no single radionuclide concentration that is used as a clean-up standard at AUMs Concentration standards for related sites (e.g., the Uranium Mill Tailings Radiation Control Act {UMTRCA}) have been used. Concentration of Ra226 < 0.185Bq/g in top 15cm of soil over an 100m2 area; concentration of Ra226 < 0.555/g below 15cm depth of soil. A risk based standard is most commonly used, based on the increased cancer risk from exposure to radionuclides. Acceptable probability of increased cancer risk is 1 x 10 (-4) to 1 x 10 (-6) for all pathways in the U.S. Superfund or CERCLA Program, although higher end of risk range is rarely used as a goal. Hazard Ranking < 1 for other hazardous constituents (e.g., at uranium mines might include arsenic, selenium, molybdenum, etc.). What exposure scenarios are being used for the report? Recreational user (up to two weeks per year at a mine site) (public land) Occasional visitor (up to one hour at a time) (public land) Residential (mainly on tribal land, living on mine waste, 350 days/year, for 30 years) 17

18 Estimates of Potential Radiological Risk for AUMs Exposure to waste-rock piles assumed upper confidence level of 2.6 average Becquerel per gram (Bq/g) radionuclide concentrations; available data ranges from 0.1 to 5.6 Bq/g Scenario and Exposure Duration Cover Thickness Small Mine Offsite Resident (30 years) (minimum 200m away from mine) Onsite Recreationist (14 days) Onsite Occasional Visitor (1 hour) Small/ Medium Mine Medium Mine Medium/ Large Mine Large Mine Very Large Mine No cover m cover m cover No cover m cover m cover No cover m cover m cover Exposure to potentially contaminated ground surface assumed 2.6 Bq/g radionuclide concentration Scenario and Exposure Duration Small Mine Small/Medium Mine Medium Mine Medium/Large Mine Large Mine Very Large Mine Offsite Resident (30 years) Exposure to mine adits based on measured radon levels of 0.01 to 131 working levels (WL) is to for 1 hour of exposure U.S. Environmental Protection Agency recommended indoor radon standard is 0.02WL Note: A working level is a measurement of the radon daughter concentration: working level traditionally refers to the dose a miner would receive in 1 month (1 WL) 18

19 What is the Impact of AUMs on Surface Water and Groundwater in the USA? Most AUMs in the USA are in arid and semi-arid regions Comparatively few (approximately 10%?) have contaminated potential drinking water supplies or impacted aquatic resources. However, the mines that have are or will be among the most complex and expensive AUM cleanup sites. Midnite Mine, Spokane Indian Reservation in Washington State. Yellow Cat Mine, Utah, impacts on surface water 19

20 LM is mostly using existing forums and meetings to obtain input stakeholders, including regulators and the public. Interstate Mining Compact Commission (IMCC) Western Region Hardrock/Noncoal Symposium EPA Uranium Contamination Stakeholder Workshop (NN) Annual National Mining Association/NRC Uranium Recovery Workshop March 27 and 28 April 16 and 17 May 1 and 2 Salt Lake City, Utah Gallup, New Mexico Denver, Colorado Four Corners Southwest Partnership for Abandoned Mine Lands (AML) 2013 National Association of AML Programs IAEA Regulatory Supervision of Legacy Sites Annual Technical Meeting Meetings with federal, state, and tribal agencies and interested public to get comments on draft topic reports. July 30 and 31 September 22 through 25 October 22 through 24 November Flagstaff, Arizona Daniels, West Virginia Vienna, Austria Participation in these forums has been extremely valuable in developing rela Webinars will be used to collect comments on draft reports. Webinars 20

21 LM has provided a web-based approach to gather public input. Click Here 21

22 Preliminary Conclusions for Abandoned Uranium Mine Report For AUMs on public lands, a focus on safety hazards over radiological exposure is warranted given the number of accidents at mines. For recreational users and occasional visitors to mine, increased radiological exposure is not a significant health concern, unless radon emissions are concentrated. The sealing of shafts and adits at AUMs for addressing safety hazards can also significantly reduce exposure to radon and radon progeny at certain mines. Recommendation that radon exposure be a priority criteria for closing safety hazards at AUM mines. For offsite residents, radiological exposures can be a health concern at large and very large mines. However, all AUMs in these categories are currently being remediated. in these in these Sealed adits at the Skyline Mine, Arizona 22

23 Preliminary Conclusions (continued) Tribal Nations typically have few controls on where people live and build homes. If people live on mine waste or use it to build homes, risks can be high. Remediation of AUMs on the Navajo Nation will not address all health concerns from U since it occurs naturally at high levels across the region Photo from U.S. EPA Non-radiological constituents, especially other metals (As, Mn, Mo, Cd) as well as other constituents (e.g., Se, SO4) add significantly to the potential health risks posed by AUMs. However,. It would be a mistake for the USA to put all of its mine remediation efforts into AUMs since they represent only 5 percent of abandoned hard rock mines. Other types of abandoned mines have similar safety risks and have other contaminants of concern similar to AUMs. Agencies need to keep better records on AUM reclamation and remediation. It is difficult to assess to what degree issues with AUMs have been addressed. 23