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Home My WebLink AboutDRC-2012-001439 - 0901a068802d23ffcc: Director, Air and Toxics Technical Enforcement Program, US EPA Region VIII Jo Ann Tischler, Denison Mines (USA) Corp .. Harold R. Roberts, Denison Mines (USA) Corp. David A. Turk, Denison Mines (USA) Corp. 2 OENISOJ)JJ MINES .. "I l l _I J J J J J J 1. INTRODUCTION During June 2011, Tellco Environmental, LLC (Tell co ) of Grand Junction, Colorado, provided support to Denison Mines (USA) Corporation (Denison Mines) regarding the required National Emission Standards for Hazardous Air Pollutants (NESHAPs) Radon Flux Measurements. These measurements are required of Denison Mines to show compliance with Federal Regulations. The standard is not an average per facility, but is an average per radon source. Tellco was contracted to provide radon canisters, equipment, and canister placement personnel as well as lab analysis of samples for calendar year 2011. The sampling effort commenced on June 6, 2011. Denison Mines personnel provided support for loading and unloading charcoal from the canisters. This report includes the procedures employed by Denison Mines and Tellco to obtain the results presented in Section 9.0 of this report. 2. SITE DESCRIPTION The White Mesa Mill facility is located in San Juan County in southeastern Utah, six miles south of Blanding, Utah. The mill began operations in 1980 for the purpose of extracting uranium and vanadium from feed stocks. Processing effluents from the operation are deposited in four lined cells, which vary in depth. At the time of the June 2011 radon testing, Cell 1 and Cell 4B were used for "liquor" storage, while Cell4A is used for sand tailings/liquor deposition. Cell 2, which has a total area of approximately 270,624 square meters (m2), has been filled and covered with interim cover. This cell was comprised of one region, a soil cover of varying thickness, which required NESHAPs radon flux monitoring. There were no exposed tailings or standing liquid within Cell 2. Cell 3, which has a total area of 288,858 m2, is nearly filled with tailings sand and is undergoing pre- closure activities. This cell was comprised of two source regions that required NESHAPs radon monitoring: at the time of the June 2011 radon sampling, approximately 153,773 m2 of the cell had a soil cover of varying thickness, and approximately 82,239 m2 of exposed tailings "beaches". The remaining approximately 52,846 m2 was covered by standing liquid in "low" elevation areas. The standing liquid level was a little lower than in 2010. Raffinate crystals and residue from the repair of the original Cell4A in 2006 have been placed in Cell 3. The Cell 2 and Cell 3 cover regions were approximately the same size (area) during the 2011 radon flux sampling as they were for the 2010 sampling program; the standing liquid area in Cell 3 was a little smaller in area. Due to worker health and safety concerns expressed by both Denison Mines and Tellco personnel, portions of the unstable and wet beaches and covered areas were not sampled. The areas tested for radon emanation are representative of the disposition of tailings for the 2011 reporting period. 3. REGULATORY REQUIREMENTS FOR THE SITE Radon emissions from the uranium mill tailings at this site are regulated by the State of Utah's Division of Radiation Control and administered by the Utah Division of Air Quality under generally 1 ~I l l l l -1 J J J J J J J were recorded on the same data sheets as the sample placement information. The blank samples were similarly processed. 5.4 Environmental Conditions A rain gauge and a minimum/maximum thermometer were in place at the White Mesa Millsite to monitor rainfall and air temperatures during sampling in order to ensure compliance with the regulatory measurement criteria. In accordance with 40 CFR, Part 61, Appendix B, Method 115: 6. 6.1 6.2 • Measurements were not initiated within 24 hours of rainfall. • No rainfall occurred during any of the sampling periods. • None of the radon measurements presented in this report were performed during temperatures below 35°F or on frozen ground (the minimum air temperature recorded at the site during the collection periods was 42°F). SAMPLE ANALYSIS Apparatus Apparatus used for the analysis: • Single-or multi-channel pulse height analysis system, Ludlum Model 2200 with a Teledyne 3" x 3" sodium iodide, thallium-activated (NaI(TI)) detector. • Lead shielded counting well approximately 40 cm deep with 5-cm thick lead walls and a 7- cm thick base and 5 cm thick top. • National Institute of Standards and Technology (NIST) traceable aqueous solution radium- 226 absorbed onto 180 grams of activated charcoal. • Ohaus Model C501 balance with O.l-gram sensitivity. Sample Inspection and Documentation Once in the laboratory, the integrity of each charcoal container was verified by visual inspection of the plastic container. Laboratory staff documented damaged or unsealed containers and verified that the data sheet was complete. All of the 300 sample containers received and inspected at the Tellco analytical laboratory were verified as valid; no samples were lost. 6.3 Background and Sample Counting The gamma ray counting system was checked daily, induding background and radium-226 source measurements prior to and after each counting session. Based on calibration statistics, using two 4 l l "l l .1 _I ." j J J J J J J sources with known radium-226 content, background and source control limits were established for each Ludlum/Teledyne counting system with shielded well (see Appendix A). Gamma ray counting of exposed charcoal samples included the following steps: • The length of count time was determined by the activity of the sample being analyzed, according to a data quality objective of a minimum of 1,000 accrued counts for any given sample. • The sample container was centered on the NaI detector and the shielded well door was closed. • The sample was counted over a determined count length and then the mid-sample count time, date, and gross counts were documented on the radon flux measurements data sheet and used in the calculations. • The above steps were repeated for each exposed charcoal sample. • Approximately 10 percent of the containers counted were selected for recounting. These containers were recounted within a few days following the original count. 7. QUALITY CONTROL (QC) AND DATA VALIDATION Charcoal flux measurement QC samples included the following intra-laboratory analytical frequency objectives: • Blanks,S percent, and • Recounts, 10 percent All sample data were subjected to validation protocols that included assessments of sensitivity, precision, accuracy, and completeness. All method-required data quality objectives (EPA, 2009) were attained. 7.1 Sensitivity A total of fifteen blanks were analyzed by measuring the radon progeny activity in samples subjected to all aspects of the measurement process, excepting exposure to the source region. These blank sample measurements comprised approximately 5 percent of the field measurements. The results of the blank sample radon flux rates ranged from 0.03 to 0.15 pCi/m2 -s, with an average of approximately 0.07 pCi/m2 -so 7.2 Precision Thirty recount measurements, distributed throughout the sample sets, were performed by replicating analyses of individual field samples (see Appendix B). These recount measurements comprised approximately 10 percent of the total number of samples analyzed. The precision of all recount measurements, expressed as relative percent difference (RPD), ranged from less than 1 percent to 8.7 percent with an overall average precision of approximately 2.7 percent. 5 ", ! ·1 , 1 J J J ,J 7.3 Accuracy Accuracy of field measurements was assessed daily by counting two laboratory control samples with known Ra-226 content. Accuracy of these lab control sample measurements, expressed as percent bias, ranged from approximately -1.2 percent to +2.0 percent. The arithmetic average bias of the lab control sample measurements was approximately +0.4 percent (see Appendix A). 7.4 Completeness All 100 samples from the Cell 2 Cover Region were verified, representing 100 percent completeness for that region. All 100 samples from the Cell 3 Beaches region were verified, representing 100 percent completeness for that region. All 100 samples from the Cell 3 Covered Region were verified, representing 100 percent completeness for that region. Altogether, all 300 samples from 300 sample locations were verified during this sampling program, representing 100 percent completeness overall. 8. CALCULATIONS Radon flux rates were calculated for charcoal collection samples using calibration factors derived from cross-calibration to sources with known total activity with identical geometry as the charcoal containers. A yield efficiency factor was used to calculate the total activity of the sample charcoal containers. Individual field sample result values presented were not reduced by the results of the field blank analyses. In practice, radon flux rates were calculated by a database computer program. The algorithms utilized by the data base program were as follows: Equation 8.1: pCi Rn-222/m2sec = [Ts* A *b*~.5(d!9i.75)] where: N = net sample count rate, cpm under 220-662 keY peak Ts = sample duration, seconds b = instrument calibration factor, cpm per pCi; values used: 0.1713, for M-01lD-21 and 0.1718, for M-02/D-20 d = decay time, elapsed hours between sample mid-time and count mid-time A = area of the canister, m2 6 l l l l l _I ·1 J J j J J j 9.2 Site Results Site Specific Sample Results (reference Figure 2 and Appendix C) (a) The mean radon flux for each region within the site as follows: Cell 2 -Cover Area Cell 3 -Cover Area -Beach Areas -Standing Liquid 18.0 pCi/m2-s (based on 270,624 m2 area) 9.5 pCilm2-s (based on 153,773 m2 area) 31.4 pCilm2 -s (based on 82,239 m2 area) ° pCilm2-s (based on 52,846 m2 area) Note: Reference Appendix C of this report for the entire summary of individual measurement results. (b) Using the data presented above, the calculated mean radon flux for each cell (pile) is, as follows: Cell 2 = 18.0 pCilm2-s (18.0)(270,624) 270,624 Cell 3 = 14.0 pCilm2-s (9.5)(153,773) + (31.4)(82,239) + (0)(52,846) 288,858 The weighted average radon flux rate as shown above for Cell 3 was calculated in accordance to Subsection 2.1.3 (a) of the EPA's Method 115, which states "Water covered area -no measurements required as radon flux is assumed to be zero". As shown above, the arithmetic mean radon flux for each cell at Denison Mines White Mesa milling facility is below the NRC and EPA standard of 20 pCi/m2 -so No condition or unusual event occurred during the measurements that could significantly affect the reported results. Appendix C is a summary of individual measurement results, including blank sample analysis. Sample locations are depicted on Figure 2, which is included in Appendix D. The map was produced by Tellco. 8 l l l l I l l II I -I .1 : 1 _I .1 J J J J J J Appendix A Charcoal Canister Analyses Support Documents A L-L-L-L-L-.: L- DENISON MINES (USA) CORPORATION WHITE MESA MILL, BLANDING, UTAH 2011 NESHAPs RADON FLUX MEASUREMENTS CELLS 2 & 3 SYSTEM DATE Bkg Counts (1 min. each) 1.0. #1 #2 #3 M-01/D-21 6/10/2011 154 149 155 M-01/D-21 6/10/2011 139 111 149 M-01/D-21 6/11/2011 139 137 159 M-01/D-21 6/11/2011 152 140 155 M-01/D-21 6/12/2011 127 121 133 M-01/D-21 6/12/2011 129 116 135 M.:01/D-21 6/10/2011 154 149 155 M-01/D-21 6/10/2011 139 111 149 M-01/D-21 6/11/2011 139 137 159 M-01/D-21 6/11/2011 152 140 155 M-01/D-21 6/12/2011 127 121 133 M-01/D-21 6/12/2011 ,129 116 135 M-02/D-20 6/10/2011 132 144 137 M-02/D-20 6/10/2011 145 155 133 M-02/D-20 6/11/2011 130 145 137 M-02/D-20 6/11/2011 160 151 146 M-02/D-20 6/12/2011 137 132 149 M-02/D-20 6/12/2011 124 127 137 M-02/D-20 6/10/2011 132 144 137 M-02/D-20 6/10/2011 145 155 133 M-02/D-20 6/11/2011 130 145 137 M-02/D-20 6/11/2011 160 151 146 M-02/D-20 6/12/2011 137 132 149 M-02/D-20 6/12/2011 124 127 137 I ~---.J~~~ ACCURACY APPRAISAL TABLE Source Counts (1 min. each) AVG NET YIELD FOUND SOURCE KNOWN % BIAS #1 #2 #3 cpm cpm/pCi pCi 10 pCi 10483 10233 10476 10245 0.1713 59805 GS-04 59300 0.9% 10302 10313 10293 10170 0.1713 59368 GS-04 59300 0.1% 10405 10222 10374 10189 0.1713 59478 GS-04 59300 0.3% 10353 10241 10280 10142 0.1713 59208 GS-04 59300 -0.2% 10321 10250 10373 10188 0.1713 59473 GS-04 59300 0.3% 10468 10430 10346 10288 0.1713 60058 GS-04 59300 1.3% 10417 10430 10179 10189 0.1713 59482 GS-05 59300 0.3% 10367 10387 10265 10207 0.1713 59584 GS-05 59300 0.5% 10312 10516 10420 10271 0.1713 59959 GS-05 59300 1.1% 10324 10336 10604 10272 0.1713 59967 GS-05 59300 1.1% 10489 10437 10161 10235 0.1713 59751 GS-05 59300 0.8% 10347 10315 10420 10234 0.1713 59743 GS-05 59300 0.7% 10348 10316 10285 10179 0.1718 59247 GS-04 59300 -0.1% 10410 10448 10337 10254 0.1718 59686 GS-04 59300 0.7% 10428 10460 10343 10273 0.1718 59796 GS-04 59300 0.8% 10278 10337 10144 10101 0.1718 58793 GS-04 59300 -0.9% 10231 10346 10310 10156 0.1718 59117 GS-04 59300 -0.3% 10263 10200 10195 10090 0.1718 58731 GS-04 59300 -1.0% 10370 10524 10504 10328 0.1718 60118 GS-05 59300 1.4% 10545 10468 10359 10313 0.1718 60029 GS-05 59300 1.2% 10164 10382 10289 10141 0.1718 59028 GS-05 59300 -0.5% 10533 10578 10519 10391 0.1718 60483 GS-05 59300 2.0% 10247 10343 10296 10156 0.1718 59115 GS-05 59300 -0.3% 10161 10182 10230 10062 0.1718 58566 GS-05 59300 -1.2% AVERAGE PERCENT BIAS FOR ALL ANAL YTICAL SESSIONS: 0.4% A-1 II I '1 , .... 1 1 I i T ; • I -I ! . I ' I I . I . ! II ·1 .. I J J J j J J BALANCE OPERATION DAILY CHECK I I )I Balance Model: . 0 ba. lit ~ po r-t-0 -':j f'tiln, S .. N .. I;L 307 Standard Weight (g): ---..!::;l..:::::....=;O---:CA::....;.:....-O __ . _______ _ Date Pre-check (g) Post-check (9) O.K. ±O.1 %? By [, lio/ /1 ';1-00.0 2..,00,.0 Ye5 I~~~ ..... If U> /11/ " :;;..oO~ 0 " 1J2?/~_ ;2..00 ~O ye6 ~/r2/J) I ~~1-7-00 ~O '2--00;0 yea 7 -( , A-6 -'-1 I· I '~I ~~l -I -"'-1 -I "1 . -I I . _ .. 1 ! , .1 rJ ~,I .J .j _J J AppendixB Recount Data Analyses B