ML20244D446

Spent Limestone Monitoring Program Results

ML20244D446
Person / Time
Site:	07000036
Issue date:	04/30/1989
From:	ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
Shared Package
ML20244D325	List: ML20244D321 ML20244D446
References
NUDOCS 8904210344
Download: ML20244D446 (15)

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{{#Wiki_filter:- - - - - - - i SPENT LIMESTONE MONITORING PROGRAM RESULTS COMBUSTION ENGINEERING, INC. HEMATITE PLANT MATERIALS LICENSE #SNM-33 l April, 1989 N0bbk$$$$@B8 7 e

1 l SPENT LIMESTONE MONITORING PROGRAM RESULTS 1.0 Introduction l The Combustion Engineering Hematite Plant uses limestone rock chips in dry scrubbers to remove hydrogen fluoride from the offgas stream of the UF to 6 U0 conversion process. The limestone chips are partially converted to 2 calcium fluoride in the scrubbers, and are referred to as " spent lime-stone" after r moval from the scrubbers. Spent limestone is monitored with an alpha survey meter upon removal, and is released for use as on-site fill material if no alpha activity above background levels are detected. Spent limestone with detectable activity, but not greater than 2 1000 dpm/100 cm, was quarantined in an intermediate storage pile at the southeast corner of Building 255. If the activity level exceeded 1000 2 dpm/100cm, the limestone was packaged for shipment to licensed burial. 2.0 Discussion The above spent limestone handling procedure was initiated in September, 1979, when NRC permission was obtained to use spent limestone with no detectable alpha activity and less than 5x background level beta activity as on-site fill material. A second set of porous metal filters was installed in the offgas line in 1979 to provide backup in case of failure of the primary filters, essentially eliminating incidents causing signifi-cant limestone contamination. This material has been used as fill at two locations; Pile A is approximately 100 yards east of the fenced manufac-turing area, and Pile C is immediately north of the site pond. Prior to September, 1979, all spent limestone with contamination levels 2 less than 1000 dpm/100 cm was accumulated in a pile located in the southeast corner of the fenced area (separated from the intermediate storage area for quarantined limestone by a roadway). The majority of the pre-1979 limestone had no detectable alpha contamination. The pre-1979 spent limestone is identified as Pile B. -

s Locations of the three spent limestone piles are shown on a site map in Figure I. The quarantined limestone has been placed in 55 gallon drums for storage pending further analyses to determine the appropriate method of disposition, and is not included in this report. 3.0 Monitorina Proaram Pursuant to condition #16 of License SNM-33, a monitoring program has been conducted to determine the radioactive content of the spent limestone piles and to assess possible environmental effects (if any) from using spent limestone as fill material in the on-site unrestricted area. The monitoring program consisted of (1) sampling and analysis to determine activity levels and distribution within each pile, (2) soil samples at the downhill edge of the fill areas to measure possible soil contamination by the fill material, and (3) continuous air sampling above each pile to I measure possible air contamination. 3.1 Determination of Activity levels and Distribution 3.1.1 Samolina Sampling locations were determined by superimposing a 5' x 5' horizontal grid pattern on to the surface of each of the three piles. Each horizontal row was identified by number and each vertical row identified by letter. Sampling grid layouts are shown in Figures 2, 3 and 4. A representative sample was obtained from each grid cell by taking a sample at five evenly spaced locations, as shown in Figure 5. The individual samples from each cell were combined into double poly bags and identified by pile and cell location within the pile. The volume of each composite sample was approximately 2 liters. After completion of the grid sampling, core samples were obtained by digging into each pile at the point of maximum thickness and taking a sample at I foot depth intervals. Locations of the core samples are shown in Figure 6. The core samples were also placed in poly bags and identified.

L. l h l -3.1.2 Samole Preparation Each composite and core sample was spread out on a 32" x 40" poly -{ bag and placed in the sun to dry in preparation for milling. Caution was used while drying the samples to avoid the possibility of cross-contamination. The drying area ~ was the roadway along the - south side of the wood bard, approximately 100 yards outside the fenced manufacturing area. After drying, each sample ~ was placed back into it's original poly bag and placed in 55 gallon drum storage. Each sample was thoroughly mixed in the drying process. Milling of the samples was accomplished by using a micropulverizer which was purchased new for this purpose. As each sample was milled, the product was collected in a clean vacuum bag. The milled product was a homogeneous fine powder. A 50 gram sample was removed for analysis from each vacuum bag. 3.1.3 Samole_ Analysis A 0.5 gram sample was weighed into a metal planchet from each 50 gram sample. The sample was then counted using a Tennelec low level gas proportional counting system. Results were calculated using an empirical self-absorption curve which corrected for the change in counting efficiency. caused by the sample mass. The correction factor for alpha absorption in a 0.5 gram sample distributed evenly on the bottom of a metal planchet is 4.45. This factor was verified by comparative analysis with three other laboratories. Results of these analyses are provided in Table 1. Contamination levels, in picocuries per gram, are shown in the same geometrical layout as the sampling grid for each pile. Average contamination levels were: l Pile A 8 pC1/ gram Pile B 15 pCi/ gram Pile C 7 pC1/ gram -

The above results were not corrected to subtract the contributions from naturally occurring radioisotopes which were in _ the fresh limestone prior to use in the - dry scrubbers. Naturally occurring uranium levels in the fresh limestone have been measured in the 3 to 5 parts per million range. 3.2 Soil Samolina Downhill of Fill Areas Quarterly soil samples have been collected at the downhill edge of the two fill areas to measure possible soil contamination resulting from the use of the spent limestone as fill material. Collection of these samples, beginning with the second quarter of 1985, has been incorporated into the routine site soil sampling program. The location north of the site pond is designated as Soil Station 11, and the location east of the fenced manufacturing area is designated as Soil Station 10. These samples are sent to a contractor laboratory for analysis. Results are shown in Table 2. 3.3 Air Samplina Continuous high-volume air sampling was conducted to measure possible air contamination resulting from spent limestone surface dust suspension. Weekly samples were collected at the center of, and approximately 1 meter above, each of the three piles. The weekly samples were composited on a quarterly basis and analyzed by a contractor laboratory. Results are shown in Table 3. The lower limit of detection was less than 10-16 pCi/ml. Results include natural background from ambient dust loading and any contribution from normal operating stack emissions. 4.0 Conclusions The sampling program to determine alpha activity levels of the post-1979 spent limestone demonstrates that this material is well below the 30 picocuries per gram limit for release for unrestricted 'use specified in the Branch technical position paper on residual radioactivity levels. The two piles of fill material averaged 7 and 8 pCi/g with no individual grid cells significantly above the limit. The pre-1979 pile, averaging 15 j pCi/g, is only 50% of the limit, but is twice the level of the spent

1 i 4. \\ limestone generated since the backup filters were installed in the UF 6 conversion offgas line. Thus, the combination of backup filters and present survey ~ techniques result in spent limestone which has significant-ly lower contamination levels than that previously generated. Soil sampling results from the contractor laboratory, 'although somewhat variable, show that no significant buildup is occurring in the soil downhill of the fill material areas. Air sampling results show that direct inhalation of suspended dust by an individual residing full time on the uncovered spent limestone fill material would result in a lung dose less than the 25 mrem annual limit. Atmospheric diffusion, covering the material with soil and less than full time residence, will further reduce the actual lung dose that. would be received. Based on the results of the above monitoring program of the spent lime-stone, it is our conclusion that release of this material under Option 1 of the Branch technical position paper would h' ave no significant adverse environmental impact. 4 i t -s-j

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k i TABLE 1 i Spent Limestone Sample Analysis Results (picocuries per gram) LlHE$iONE PILE "A" I A B C D E F G H I J K L M N O P Q 1 10 10 9 7 5 7 2 12 7 4 18 1 4 2 1 9 9 3 9 9 13 9 5 2 9 2 9 9 5 4 22 25 22 1 12 12 to -1 2 7 1 4 -1 5 6 12 16 6 15 18 12 16 18 6 2 to 5 1 10 7 6 10 13 9 to 7 810 to 5 2 2 15 2 7 8 13 8 7 2 2 7 15 7 8 5 5 6 -1 7 12 9 13 5 12 4 4 13 to 12 8 CORE SAMPLES: 1 ft: 8 2 ft: 12 3 ft: 18 3E392533333 333 E E35 3 5 3 33 3 3 33 33333 3 3 3 33 3 3 3 333 33 25E3 E3333333 3 3 3 333 E E E E E E S E E E EERSESEEEEEEEEEEEErsESEEE 3 i LIMESTONE PILE "0" A B C D E F G H I J K L M N O P Q R S T U V W 15 12 18 15 15 2 10 6 5 8 5 20 12 10 5 12 6 16 9 14 9 3 8 10 3 8 2 12 3 2 2 5 6 -1 5 22 7 8 22 15 12 13 10 9 16 9 15 6 31010 5 8 5 13 8 13 9 18 13 6 15 3 14 12 19 18 8 13 6 12 9 9 8 10 10 6 10 8121717131616 8 7 { 11 8 10 13 8 8 9 23 13 6 6 10 6 9 15 6201218 81311 10 15 14 23 24 12 12 3 15 15 12 15 17 17 14 14 16 19 15 14 14 14 9 26 25 64 20 21 30 51212131910 5 13 12 to 8 9101320 8 37 30 57 41 25 16 9 12 3 9 8 6 8 1 50 20 20 to 13 29 7 26 39 29 16 21 16 10 13 4 21 18 10 7 13 6 8 8 4 13 18 { 6 34 36 35171310 to 36 8 10 25 14 25 8 4 3 to 5 27 13 25 11 13 23 17 12 17 047162730242011 4 20 25 25 17 21 14 6 20 13 14 13 11 21 20 11 6 '3 4 17 13 16 21 23 71816 6 61617 2 28 25 20 20 48 2511 to 201416 4132 1 68 20 26 18 27 24 14 18 CORE SAMPLES: 1 ft: 6 2 ft: 12 3 ft: 25 4 ft: to 3E3E8333E333333333E352335E3333RE3883SS8333333883353333333323-*-*-*EBBSSESSE RSEFFSSESSESSESBSBSEEES LIMESTONE PILE "C" A B C D E F G H I J K L M Sf O P Q R S T U V W X Y Z AA BB CC 00 EE 1 74 2 21215 75 7 12 5 to 1 2 2 to 15 22-1 5 1 5 13 10 9 7 15 10 7 510 5 7 3 12 2 2 13 12 75 5 2 9 9 4 5 5 2274-1 4 74 4 9 59 7 5 -1 16 75 9 5 4 1 4 7 12 5 74 1 5 5 5 15 1 2 10 21 9 15 7 9 2 2 9 2 2 to 10 1 10 7 13 5 1 to 6 71216 1 1 5 4 74 4 9 to 9 -1 5 -1 4 74 4 2 4 5 72 7 12 7 15 15 12 2 1 4 7 7 5 4 5 12 2 5 12 12 5 2 4 4 7 774 8 19 5151216 4 75 9 5 13 74 1 5 5 7 to 5 -1 4 5 1 to 4 2 9 9 13 76 4 9 9 5 10 4 2 412 5 5 4 -1 2 5 2 4 77 10 5 916 9 7 12 9 to 10 13 12 2 5 2 5 to 4 5 1 9 2 7 l 11 12 15 7 5 to 9 13 13 9 9 13 9 2 9 2 9 12 9 4 1 9 9 12 4 22 to 18 -13816 9 5 9 13 1 9 5 12 1 52 5 13 15 12 13 74 77 2 2 2 4 4 7 12 7 1 to 5 15 5 14 15 15 18 to 4 5 5 4 4 1 13 2 4 7 1 4 9 2 7 15 7 13 10 -1 5 7 2 4 9 2 9 5 51812 9 10 16 2 13 12 2 1 9 5 9 17 1 2 5 8 4 18 5 4 5 CORE se PLES: 1 ft: 14 2 ftr 14 3 ft: 4 4 ft: 6 5 ft: 11

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TABLE 2 r SPENT LYMESTONE FILL - DOWNHILL LIMESTONE MONITORING (Picocuries per gram) $0!OSTATION!.10.k' IEast Of Pl5riC ' ~ Alpha : 1985 1986 1987 1988 First Quarter 11 28 30 1 Second Quarter 10 14 57 22 Third Quarter 5 14 54 12 Fourth Quarter 8 30 18 18 Beta First Quarter 15 160 94 Second Quarter 40 33 150 140 Third Quarter 19 26 160 26 Fourth Quarter 36 120 38 43 S0!LiSTATIOW;11f [ North'.! offs,Ite' Pond ;j Atpha 1985 1986 1987 1988 First Quarter 9 13 67 Second Quarter 11 7 41 23 Third Quarter 6 54 34 37 Fourth ouarter 36 53 23 28 Beta First Guarter 22 34 55 Second Quarter 28 50 56 54 Third Quarter 23 84 61 58 Fourth Quarter 47 85 53 51

TABLE 3 l t i l l QUARTERLY COMPOSITE AIR SAMPLING AB0VE LIMESTONE PILES i Concentration (x10-15 Ci/ml)- Inside Fence East West 1985 July - September 4.7 2.6 8.3 October - December 7.8 3.9 2.7 1986 January - March 1.6 1.8 2.0 April - June-1.2 1.0 July - September l 9.5 6.0 5.6 ^ October - December 8.8 7.6 5.8 1987 January - March 6.5 3.3 4.4 April - June 5.8 4.0 2.0 l July - September 3.1 2.8 2.4 October - December j 6.6 4.4 3.8 i i

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