ML20199H716
| ML20199H716 | |
| Person / Time | |
|---|---|
| Issue date: | 01/26/1998 |
| From: | Joseph Holonich NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Rael G ENERGY, DEPT. OF |
| References | |
| REF-WM-86 NUDOCS 9802050105 | |
| Download: ML20199H716 (10) | |
Text
-
, Nnuary 26, 1998 A
4
< Mr. George Rael, Director'-
g U.S. Department of Ene gy '
Albuquerque Operations Office ERD /UMTRA' 1
P.O. Box 5400 I I
Albuquerque, NM 87185-5400
SUBJECT:
REVIEW OF COMPLETlON REPORT FOR THE SLICK ROCK, COLORADO, URANIUM MILL TAILINGS REMEDIAL ACTION PROJ _CT SITES
Dear Mr. Rael:
By letter of December 12,1997 the U.S. Nuclear Regulatory Commission transmitted its draft Completion Review Report (CRR) for the Slick Rock, Colorado, Uranium Mill Tailings Remedial Action sites to the U.S. Deparwnt of Energy. The draft CRR included the results of the NRC staffs review of the geotechnicai r.gineering, surface water hydrology and erosion protection, and groundwater protection activities, with the staffs review of the radiological cleanup and control results to follow under a separate cover.
The staff has completed its review of the remedial actions related to the radiological cuanup and verification activities at the Slick Rock processing sites and the d.sposal cell construction activities at the Bur o Canyon disposal site and has identified twelve open issues (enclosed). These issues, along with the previously-identified open issue related to groundwater protection, will need to be resolved prior to NRC's concurrence in the completion of the remetiial action at the Slick Rock sites.
If you have any questions concerning this letter or the enclosure, please contact the NRC Project Manager, Ms. Charlotte Abrams, at (301) 415-5808.
Sincerely, 1
Original Signed By Joseph J. Holonich, Chief Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguaids j L jQ,
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U.S. NUCLEAR REGULATORY COMMISSION STAFF REVIEW OF COMPLETION REPORT FOR SUCK ROCK, COLORADO, UMTRA PROJECT PROCESSING AND DISPOSAL SITES The U.S. Nuclear degulatory Commission staff reviewod the U.S. Department of Energy (DOE)
Completion Report (CR) for the Slick Rock, Colorado, processing and disposal sites. The CR describes the remedial accions (radiological cleanup) and venfication activities performed at the Slick Rock processing sites and the disposal cell construction activities performed at the Burro Canyon disposal site.
The criteria for site cieu,iup (at the processing sites) and radon attenuation (at the disposal site) were generally established in the RAP (DOE,1996) and concurred in by NRC staff in the Technical Evaluation Report (TER; NRC,1996) as providing assurance that the processing sites and disposal cell would meet the U S. Environmental Protection Agency's (EPA's) requirements of 40 CFR 192. The following discussions and comments are based on review of the radiological cleanup and verification and the radon attenuation sections of the CR. In its review, the staff identified twelve comments or open issues that are as follows:
SITE CLEANUP GOMMENT 1: Site-Specific Assessment for Th 230 Supplemental Standard Areas A supplemental atandard from the generic Th-230 protocol was used to determine the acceptability of residual Th-230 concentrations in soil at the Slick Rock sites. The CR does not contain a site-specific dose assessment or ALARA analysis, which are required by NRC as a condition in its approval of the generic protocol.
DISCUSSION Appendix J (page 3, Section 2.5) of the CR indicates that for excavation control and for verification, Th 230 measurements were made and the 1000-year concentration of Ra-226 was determined for comparison with the EPA standards for Ra-226. This conforms to one of the requirements of the generic Th-230 protocol for use of supplemental standards for areas of Th-230 contamination near the surface of the final grade.
In its approval of the generic Th-230 protocol, the NRC imposed aoditional conditions, one of which is applicable to the Slick Rock sites. Tho NRC indicated (Holonich,1994) that, because the generic Th-230 protocol does not consider the volume of Th-230 contamination or the additional health risk from r,ny residual uranium, implementation of the protocol for each site shoeld include a site-spec
- r.nalysis of the health risk, and should emphasize reducing the Th-230 to ALARA levels. The NRC (He sich,1994) noted that the DOE's dose assessme nt included assumptions (e.g., that the cor,ta,unated area involved only one 100 m grid) that the staff cocsidered non-conservative for all sites.
2 The CR does not contain the site-specific dose assessment and ALARA analysis of the residuallevels of Th-230. However, the NRC staff reviewed the Th-230 verification data to determine how many venfication grids were involved in the use of the Th-230 criteria of the generic Th-230 protocol. For this tally, the staff counted grids for which the Th-230 concentration exceeded aither 5 pCilg above background for surface samples or 15 pCi/g above background for subsurface (deeper than 15 cm) samples. Concentration levels less than these values would be reasonably expected to occur with Ra-226 concentrations at the EPA cleanup standards (with the assumption that Th-230 is roughly in equilibrium with Ra-226 in material jnvolved the us/). The staff identified 3 grids at the Slick rock UC site t.:)d 6 grids at the of tailings origin grids next to each other at the NC site. The staff concludes that the grids involved are relatively isolated; therefore, the dose assessment used in supporting the generic Th-230 protocol should be applicable to the Slick Rock sites. The staff cor.cludes that the requirement for a site-specific dose assessment is satisfied by the generic analysis performed to support the generic Th-230 protocol, but that there is not a 1
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justification that the generic Th-230 protocol results in Th-230 concentrations are at ALARA levels.
RECOMMENbATION The DOE should provide a brief discussion of how residual Th-230 has been reduced Al. ARA.
SOIL CLEANUP VERIFICA~.10N G.QMNIENT 2: Potential Underestimation of Ra 226 Concentration The use of a regression using all data obtained for the composite gamma measurement technique, referred to as the Hand-held Gamma Verification System (HGVS), could result in a higher than planned probability that the Ra-226 concentr tion in soils has been underestimated at some venfication grids, and the actual Ra-226 concentration exceeds the EPA standard.
DISCUSSION Use of the HGVS was described in section 2.4 (pages 2 and 3) of Appendix J of the CR and in section 6.2.1.2 of the Remedial Action Assessment (RAA) section of Volume 1 of the CR. The HGVS was used at some locations at the UC and NC processing sites where soil samples were difficult to collect, Mcluding locations of exposed rock. The procedure for verification using the HGVS (procedure OP-003-9)is included as part of Exhibit J.1 to Apper, dix J of the CR. The method is t;ated on a correlation of average
_ gamma radiation count rate (with a shielded instrument) to soil Ra-226 concentration (measured by soil sampling and analysis). For the HGVS, gamma count rates are measured at nine locations above the soil 2
within a venfication grid (100 m area). The average gamma count rate is calculated and this average is used to estimate the Ra-220 concentration in the soil. An initial correlation between the average gamma count rate and the measured soil concentration of Ra-226 was developed, prior to use for venfication measurements, using paimd measurtiments from 40 grid areas. During venfication additional soil samples were obtained from at least 5% of th6 grid locations (38 additional locations), to add data points to the correlation. From the 78 data points, a linear regression was calculated, along with the upper
%unds of one-tailed 95% confidence intervals on the predicted Ra-226 concentrations. To simplify, a straight line was then fit to these upper bounds to provide a linear estimator of the upper bounds. The lincar estimator of the upper bounds was then used dunng verification to ".. conservatively predict Ra-226.. " concentrations based on the average gamma count rate. Thus, for verification measurements, the measured gamma count rate is used to estimate an upper bound (95% confidence) on the Ra-22E concentration in the soil.
3 The final data, regression analysis, and plot sf the data and regression curves for the HGVS measurements are provided in Exhibit J.2 to Appendix J of the CR. These items were reviewed by the NRC staif. Tables J.6b and J.7h nf Appendix J to the CR provide results of the HGVS measurements, including results for the "quaitty control" soil sample measurements. From a review of these tables, it was venfied that soil sample results were available for 38 verification grids, which was greater than 10% of all the HGVS verification grids. Thus, the requirement for soil samples to be obtained from at least 5% of the verification Grids was met. From the data shown in Exhibit J.2, the NRC staff verified that the data from these 38 additional soil samples were incluoed in the development of the regression and the linear estimator of the upper bound curve.
From the NRC staffs brief review of the data, plot, and regression for the KGVS method, includirg a comparison of the data obtained during verification activities (the 38 additional soil sample data poir ts) to the data obtained orior to verification (the 40 initial data points), it appears that the data obtained during verificatiot ( ativities exhibit significantly greater vari ability than do the initial data This could be an indicationhiat the ihitial data points were not propar) representative'of the areas for Which the HGVS procedure was to bu used. By grouping the new data and the initial data together for the regression analysis, as described in tae CR, the greater variabiSty in the data obtained from verification sampling (which would seem to be me most representativo) is eff.ctively diluted (reduced) by the lester vanability in the initial data. Thus, the regression developed in the CR may underestimate the actual variability in 2
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verification sampling results for the HGVS technique, and may underestimate the value of the upper bound (95% confidence) on Ra-226 concentrations at particular gamma count rates. The result may be that the upper bound values are associated with a lower (lowr
- tr,an 95%) confidence level than was intended. This could result in a higher than planned probabilit, mat the Ra 226 concentration has been underestimated at some verificatica grids, and that the actual Ra-226 concen2ation exceeds the EPA standard.
RECOMMENDATION The DOE should provide addrtional discussion of this aspect of the HGVS regression, and revise the regression to use only the newer data points obtained during veriiication sampling.
I COMMENT 3: Clarification of HGVS Discussion The description of the HGVS needs to be clarified.
DISCUSSION Section 6.2.1.2 (page 8) of the RAA section of Volume 1 of the CR, states that the average gamma count rate for a grid was ".. compared with the gamma count rate corresponding to the appropriate EPA standard (e.g.,5 or 15 pCi/g Ra-226 plus background)." Actually, the average gamma count rate for a verification grid was compared to a count rats for which tne upper bound (95% confidence) of the predicted Ra-226 concentration was equal to the appropriate EPA standard plus background.
RECOMMENDATION The DOE should clanfy this discussion.
GQ1BENL4: No Verification Measurement for Grid F-0110 The CR did not provide data from any verification measurement for Location F-01-10.
DISCUSSION There is no verification mea 3urement for Location F-01-10, because this grid was on a natural rock cliff side and could not be sampled due to safety hazards. No additional information about this grid, that might be helpful in deciding whether the grid meets the EPA standard for Ra-226, was provided in the CR.
RECOMMENDATION The DOE should provide additional information to support a dL.sn that this grid is likely to meet the stancards Cf the sdandard has been met). Such additional information minht include similarities between the subject grid and the surrounding grids which were verified, information about the remedial action (if any) performed on the subject g;id, and physical characteristics of the soil or rock surface of the grid that might relate to the potential for contaminated material to remain on the grid. If the DOE concludec that the standards have not been met, that information should be included in the CR.
COMMENLE: Lack of statistical analyses of offsite laborato y QA data The CR presnts the results of the analyses from an offsite laboratory to support the quality of verification results for the Stick Rock sites, but no statistical analyses of these data have been presented.
DISCUSSION Three types of laboratory results for measurements of Ra-226 cnd Th-230 in soil are described in section 4 of Appendix J of the CR: (1) OA measurements by an offsite laboratory, (2) onsite gamrna spectrometry opposed crjstal system (OCS) quality control samp;es for the HGVS sampling, and Q) s > suits of a blind z' g sample testing prog,am implemented to provide qudty assufance (QA) data. During1he early part of the project, the QA measurements from the offsite laboratory were compared to the results from inc Slick Rock onsite laboratory. The average Ra-226 concentrations from these analyses were 2.7 pCi/g for the offsite anal)ses and 2.3 pCi/g for the onsite analyses. The CR does not describe any statistical comparisons of these two averages and the individual data were not provided; therefore, it is unclear 3
3 whether the difference in means is significant. The difference may be an indication of an underbias in analy$es made by the OCS (the OCS average is about 15% less than the offsite average). Such an underbias would be somewhat consistent with results of the OCS quality control (QC) measurements, discussed below, which also appear to show an underbias in the OCS results.
RECOMMENDATION If the DOE intends to use the offsite laboratory QA analyses of Ra-226 to support the quality of the venfication results for the Slick Rock sites, statistical analyses of the QA data should be performed.
QQNIMENT 6: Inappropriate comparison of OCS results to HGV9 results The comparison of the average OCS result for HGVS grids to the average HGVS result for those grids is Inappropriate, because tne HGVS results are estimates of an upper bound on the Ra-226 concentrations.
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DISCUSSION The aserage Ra-226 concentration of the OCS QC samp:ss taken for the HGVS measurements was compared to the average HGVS Ra-226 concentration. From the 38 paired measurements of HGVS and soil samples, the average Ra-226 concentration from the OCS measurements on soil samples was indicated to be 3.2 pCi/g, while the average Ra-226 concentration from the HGVS measurements was indicated to be 5.1 pCi/g. The NRC staff believes that this comparison is not relevant, because the Ra-226 concentratio,is from the HGVS measurements are actually estimates of an upperbound(95%
confidence) on the Ra-226 concentration, rather than a best estimate of the coricentration.
RECOMMENDATION The DOE should revise the discussion of these data in the CR to provide a meaningful comparison, i' an analysis of these data is desired. (If the comparison is correct and appropriate, it would indicate a severe underbias h the OCS results.)
COMMEN77: Lack of statistical analysis of hlInd sample data The CR presents the results of the blind sample testing to support the quality of verification results for the Stick Rock sites, but no statistical analyses of these data have toen presented.
OlSCUSSION For the blind sampling program, test soil samples were pepared from material collected at several DOE t
I project sites, and samples were sont to the Yankee Atomic Environmental Laboratory (YAEL) and the Slick Rock onsite laboratory for ana;yses of Ra-226 and Th-230. Table J.2 of Appendix J to tile CR shows the results of the blind analyses by the onsite and offsite laboratories and the YAEL. The CR indicates that there was good agreement between boih the onsite and offsite laboratories with YAEL's results.
However, the CR did not describe any statistical comparisons of these blind analysis results, so it is unclear whether the differences in individual results are significant.
RECOMMENDATION in order to use the blind sample analysis results to support the quality of the verification results for the Slick Rock sites, the DOE must perform appropriate statistical analyses of the blind sample data.
COMMENT 8: Low Blas in Results from OCSs SRK-2 and SRK-4 Results of the OC analyses on OCS instruments SRK-2 and SRK-4 show an apparent low bias for these instruments.
I~I DISCUSS lON The CR (section 6.2.2.2 of the RAA section o' Volume 1 and section 2.3 of Appendix J) indicated that a performance criterion for operation of the gamma spectrometry system (the OCS) used for Ra-226 verification muasurements was that, at the concentrations of the standards (5 pCi/p), the Ra-226 verification must be performed such that the analytical results are within plus or minus 30 percent of true 4
i concentrations, at the 95 percent confidence level. Appendix J of the CR briefly describes the measurements made and the results used to show compliance with this criterion. The error limits were empi6cally determined, using a NationalInstitute of Standards and Technology traceable reference material with a Ra-226 concentratior; of 5.12 pCi/g that was routinely analyzed during the verification piocess. It appears that these measurements were performed multiple times per day, as more than 2000 of these OCS quality control (OC) checks were per<ormed.
Table J.1 cf Appendix J of the CR provices a summary of the OCS OC measurements, ir:cluding the mean and two standard deviation value of the OCS measurements for each OCS instrument used for the Stick Rock verification analyses. This summary is repeated in Table 1, below. As indicated by the mean value plus and minus two standard deviations, the 95% confidence intervals of the OCS measurements were within 30% of the true value. Thus, the NRC agrees that the performance criterion for the operation of the OCS was met for the systems used at the Slick Rock sites.
Table 1. Summary of Slick Rock Site OCS QC Measurements Average OCS number result i 2s
- Number of checks SRK-2 4.7 1 0.9 1012 SRK-4 4.7 1 0.9 1002 NAT 1
- 5.1 i 0.7 169 NAT-2
- 5.4 t 1.0 95 NAT-3
- 5.2 1 0.8 118 Here i 2s means plus or minus 2 standard deviations (though the CR used the term sigma). Note that the true concentration of the standard used for the OC checks was 5.12 pCi/g.
These are Naturita site OCS instruments, that were used for some of the Slick Rock venfication analyses.
From the data shown in Table J.1 of the CR (see Table 1 above), the NRC staff has evaluated the significance of the differences between the mean OC measurements for OCSs SRK 2 and SPK-4 and the true mean concentrtn of the reference material. Using a Student's t test, the mean concentrations measured by the two OCSs are signi'icantly different from the true mean concentration (p<0.05). Since the measurements were apparer,Jy performed et quality control messurements, the NRC staff concludes that the performances of OCSs SRK-2 and SRiu may not have been v ithin reasonable bounds. The CR has not provided any analysis of the?e means of the QC measurements and has not provided any analysis of poter.tial corrections that could be performed to account for the apparent low bias in results frm OCSs SRK-2 and SRK-4.
The NRC staff estimated the impacts of such potential ccrrections, as follows. The results for OCSs SRK-2 and SRK-4 rppear to be biased !ow by approximately 8.2%, and a correction factor would be 1.09 (5.12 pCi/g + 4.7 pCi/g). From the CR it cannot be determ;ned wnich verification measurements for Ra-226 were made using OCSs SRK-2 and SRK-4; therefore, th] staff looked at all verification restts (a worst case). From this review, staff determined that there couto be 27 venfication grids (^.5 of which were surface samples, with less than 15 cm of backfill) for which the corrected results would exceed the EPA standards for Rn-226 in soil. Of these, the highest corrected concentration is 17.2 pCi/g and the surface
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sample would hyeia corrected concentration of 7.0. Thrgefore, the GPA stand rd fog Ra-226 may not have been met for all verification grids (about 27 gride mi;nt exceed the stand 1).
RECOMMENDATION DOE should proviu analyses and discussion of the apparent low bias in results from OCSs SRK-2 and 5
SRK-4, and should discuss potential co tections to data from these OCSs.
COMMENT 9: Frequency of Th-230 Measurements The documentation provided in the CR is insuf5cient to determine whether the Th-230 sampling frequency criteria have been met.
DISCUSSION The RAP (DOE,1G96) indicated that venfication for Th-230 contamination (here Th-230 contamination means Th-230 in excesr 4 Ra-226 contamination) would be performed using the UMTRA Project generic Th-230 protocol. The protocol (Chemoff,1993) provides the following scheme for verification samplirr for Th-230. In processing site areas that are suspected of meferentially mobilizing thorium contamination over radium contamination, based on process knowled), - 5 other sources such as previous sampling data,100% of the (100 m ) grids are to be sampled and ai,syzed for Th-230. In subpile areas,10% of the 2
grids are to be sampled, and, in area 9 where process knowledge and enaracterization data indicate no potential for preferential mobilization, grids will not be sampled for Th-230. Also, if any verification samples exceed the generic Th-230 criteria of the protocol, the surrounding eight grids will be examined to determine if those grids also exceed the criteria.
Section 2.5 of Appendix J of the CR describes the Th-230 verification sampling performed at the Slick Rock processing sites and indicates that Th-230 sampling was conducted on a minimum of 10% of the subpile grids at both of the sites. The CR also ind cates that there were no raffinate ponds at the sites (raffinate ponds are one type of locatien that would be suspected of preferential mobilization of thoriuni over radium). However, there is no information to indicate whether or not other areas suspected of Th-230 contamination have had 100% verification sampling coverage. In its review of the RAP (NRC, 1996), the staff indicated that several locations on the Slick Rock NC site had elevated levels of Th-230 with Ra-226 levels less than 15 pCi/g, which may indicate areas of preferential mobikzation of Th-230. In addition, the CR contained no information to indicate shether any venfication samples had shown Th-230 conce.itration exceeding the generic Th-230 criteria.
The documentation provided in the CR is insufficient to determine whether all the Th-230 sampling frequency criteria have been met. It appears that at least 10% of subpile areas were sampled for Th-230, but it is not cleat whether all areas suspected of preferential Th-230 contamination have been sampled for Th-230 with 100% grid coverage. It is also not clear whether any verification samples showed Th-230 contamination greater than the generic Th-230 protocol criteria, which would require Th-230 analyses for the surrounding eight verification grids.
RECOMMENDATION The DOE should p ovide additional description of the Th-230 sampling frequencies so that it can be determined if the sampling entena provided in the generic Th-E0 protocol have been met.
NONROUTINE APPLICATION OF SUPPLEMENTAL STANDARDS COMMENT 1.0: Lack of Justification for Applicability of Supplemental Standards Under Criterion (a) of 40 CFR 192.21 Appendix K of the CR does not contain sufficient justification for the applicability of criterion (a) of 40 CFR 192.21 to the contamination remaining around the gas pipeline on the Slick Rock UC site.
DISCUSSION h"
Three areas witbnkhe gas pipeline right of-way through he Slick Rock UC site are under don' sideration for application of supplemental standards. These areas are referred to as the Gas Plant Area, S8 Road Area, and Madame Curie Area. Drawings provided in Appendix K show that the pipeline lies generally 2-4 ft below the ground surface, and that contamination is thought to remain above the pipehne; although, it appears that only limited characterization of the remaining contamination has been performed. In 6
performing remedial actions near the pipeline, excavation of contaminated materials was performed no closer.than 10.ft from the pipeline location. Because of standard precautions about allowable slopes foi excavations, contaminated material was left in the slopes away from the pipeline at distances greater than 10 ft. In addition, six inches of contaminated material was removed from the surface above the pipeline (in a 20-ft band,10 ft to either side of the pipeliae). Because of precautions taken for the maximum slopes and, because th6 county road was required to remain open, an araa undertying the county road is includa.J in the supplemental standards area. Leaving contaminated material near the pipeline and under the county road has been proposed by the DOE based on nsks of injury to workers if the material were excavated.
The EPA ciaanup standards,40 CFR 192.21, specify enteria that may be used to determine applicability of supplemental standards. Page 4 of Appendix K of the CR indicates that criterion (a) of the EPA Standards at 40 CFR 192.21 is applicable to the pipeline right of way. This criterion (hereafter, Criterion a) states:
(a) Remedial actions required to satisfy Subparts A or B would pose a clear and present risk of injury to workers or to members of the public, notwithstanding reasonable measures to avoid or reduce risk.
Appendix K of the CR, does not provide justification for the applicability of criterion (a) for the application of
- supplemental standards in the gas pipeline area. However, in section K.4.1.1 of Appendix K of the CR, the description of the alternative remedial action of complete remediation mentions that the attemative would include such precautions as purging the gas from the pipeline before work, excavation using small equipment and hand excavation, and some hand backfill after excavation. These pr9 cautions would appear to be ' reasonable measures" to reduce risks to workers working next to a gas pipeline. If these measures are reascnable and would reduce risks to workers to acceptable levels, then it appears thu cnterion (a) would not be applicable.
Altematively, the pipeline could be purged, but the CR indicates that the costs of such purging are unreasonably high relative to long-term benefits. In section K.4.1.1 of Appendix K (ou pages 8 and 9) of the CR, the following statements are made:
If the pressure in the pipeline is not removed the hazards of excavating around the pipeline would be too great. If the pressure is removed from the pipeline, the owner, KN Energy, will have to be compensated for the gas re'essed and potential lost revenue.
Thic option would have iequired a substantial amount of work and monies compared to the amount of benefits received from remediation.
In a letter from R. D'Arezzo of MK-Ferguson, dated November 4,1996 (Exhibit K.2 of Appendix K to the CR), a similar statement is made: "The pressure could be removed from the pipeicie but the cost of doing so would be unreasonably high relative to long-term benefits."
In section K.5 of Appendix K to the CR, the reasons for rejecting complete remediation of the contamination (referred to as Altemative 1) v.ere described as follows.
Complete remeolatian of the contamination soil (Altemative 1) was rejected due to the health c.nd isafety risks ysociated yvith working on/near the high, pressure gas pipel.ne and closing tile only
' access toadto the canyon. It was also rejected due !g the re!'octance of the owner of the '
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easement to allow full access to the area.
Based on the above, Appendix K to the CR indicated that there were risks associated with working r, ear the gas pipeline, but did not provide details about those risks (the NRC staff assumes the major risk is the 7
O risk of explosion of gas). Appendix K mentioned actions that would mitigate the risks associated with workinsg around the gas pipeline, i.a did not provide any justification for why such measures would not be reasonable. The other arguments presented, such as about the high cost of implementing risk-reducing measures and the reluctance of the owner of the gas pipeline nght-of-way easement to allo"t full access to the area, are not appropriate to demonstrating the applicability of critorion (a). Appendix K also indicated that tue retson for application of supplemental standards to contamination remaining under the county road was safety risks associated with closing the county road. No justification for this reasoning was provided.
RECOMMENDATION DOE must provide justification for the application of criterion a. The justification should address why measures to reduce risks to workers working around the gas pipeline are not reasonable, and should address safety risks associated with closing the county road.
RADON ATTENUATION FOR DISPOSAL CELL COVER COMMENT 11: Lack of Sampling on Disposal Cell Side Slopes for Radium Concentration and Radon Emanation Fraction None of the sampling locations for Ra-226 concentration and ladon emanation fraction on the disposal cell were on the side slopes of the disposal cell, although, it appears that roughly 30% of the total surface area of the disposal cellis on the side slopes.
DISCUSSION No sampling appears to have been conducted on the side slopes of the dicposal cell and the CR did not contain information to demonstrate that the Ra-226 concentrations from locations on the top slopes would be representative of the concentrations on the side slopes as well.
RECOMMENDATION Although it appears unlikely that Ra-226 concentrations ;n materials on the side s' res of the disposal cell are high enough that the radon flux standard would be exceeded, the DOE should provide additional information or justification for the use of the Ra-226 measurements as representative of the entire surface of the disposal cell.
QQMMENL12: Ra-226 Concentrations in Radon Barrier and Frost Barrier Material The CR does not provide data to support the conclusion that the Ra-226 concentrations in the radon barrier and frost barrier materials are at background levels.
DISCUSSION in the NRC's review of the RAP radon barrier design (NRC,1996), one of the conditions imposed, to which tha DOE committed, was to measure the Ra-226 concentrations in the radon barrier and frost bamer materials to assure that concentrations are at background levels es was assumed in the modeling.
In calculatior, number 11-535-03-00 (Volume 3, page 7, of the CR) it is stated that " Radon barrier and frost barrier materials are clean with a Ra-226 and emanation fraction equal zero." Based on this statement it appears that the Ra-226 concentretion and radon emar'ation fraction of the radon and frost ba.ner materials are at background levels and ere modeled as zero. However, no data have been provided to justify the statement.
RECOMMENDATION The DOE should provide the measurement data or other information to indicate that the Ra-226 concentration in the radon barrior and frost barrier materbls are at background levels.
REFERENCES Chernoff A.1993. Letter to J.J. Surmeier, Uranium Recovery Branch, Division of Low-Level Waste 8
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s Management & Decommissioning Office of Nuclear Material Safety and Safeguards, U S. Nuclear Regulatory Commission, dated December 22,1953. U.S. Department of Energy Albuquerque Field Office, Uranium Mill Tailings Remedial Action Project Office, Albuquerque, New Mexico.
Holonich J.J.1994. Review of UMTRA Project TMrium-230 Generic Protocol. Letter to A.R. Chemot1, Uranium Mill Tailings Remedial Action Project Office, U.S. Department of Energy, dated July 5,1994.
U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety and Safeguards, Division of Waste Management, High-Level Waste and Uranium Recovery Projects Branch, Washington, D.C.
U S. Department of Energy 1996. Remedial Action Plan and Site Design for Stabilization of the inactive Uranium Mill Tailings Sites al Slick Rock, Colorado. Final report, dated May 1996. Report DOE /AL/62350 21F, REV. 2 Jacobs, Albuquerque, New Mexic7.
U.S. Department of Energy.1997. Slick Rock, Colorado, NRC Copy, Final Completion Repod. Volumes 1-3, dated June 1997.
NRC.1996. Final Technical Evaluation Report for the Remedial Action at the Slick Rock, Colorado.
Uranium Mill Tailings Processing and Disposal Sites. Dated September 1996. NRC, Division of Waste Management, Washing'on, D.C.
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