ML20248L832
| ML20248L832 | |
| Person / Time | |
|---|---|
| Issue date: | 06/09/1998 |
| From: | Joseph Holonich NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Rael G ENERGY, DEPT. OF |
| References | |
| REF-WM-62 NUDOCS 9806110401 | |
| Download: ML20248L832 (8) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 2066Hm01
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June 9, 1998 Mr. George Rael, Director U.S. Department of Energy Albuquerque Operations Office ERD /UMTRA P.O. 3ox 5400 Albuquerque, NM 87185-5400 1
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SUBJECT:
ACCEPTANCE OF COMPLETION REPORT FOR RIFLE, COLORADO, VICINITY PROPERTY RF-582
Dear Mr. Rael:
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the Rifle, Colorado, Vicinity Property Completion Report (VP CR) for property RF-582, part of the Interstate 70 right of way southwest of the New Rifle processing site. This VP CR, dated January 29,1997, was submitted by the U.S. Department of Energy (DOE) under letter dated July 17,1997.
Concurrence by the NRC on this VP CR is required because special circumstances resulted in supplemental standards being invoked during remedial action. Because the use of supplemental standards is the reason for the NRC's review, the NRC staff review has been limited to those parts of the VP CR related to the use of supplemental standards.
The DOE proposes the use of supplemental standards to justify leaving contaminated material that extends into the highway berm and under the highway. The extent of contamination j
remaining on the VP is estimated by DOE to be about 63,000 yd$, over an area of about 11,000 t
yd2 The deposit contains material with significantly elevated concentrations of Th-230.
Measured radionuclides concentrations ranged from 0.5 to 228 pCi/g for Ra-226 and from 0.3 to
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6749 pCi/g for Th-230. The highest concentrations, and most of the contamination, are below the ground surface, generally at depths of 4 feet or greater.
The NRC staff reviewed the VP CR, and the details of the review are documented (see enclosure). Based on the review, the NRC staff concludes that information provided by the DOE in the VP CR provides reasonable assurance that supplemental standards for soil cleanup have been properly applied at vicinity property RF-582. Therefore, the NRC staff concurs that the use of supplemental standards and the remediation of this vicinity property were completed in accordance with the EPA standards. The signed NRC Review Form for Supplemental Certification of Vicinity Properfies, showing NRC concurrence, is enclosed.
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G. Rael If you have any questions conceming this letter or the enclosure, please contact the NRC l
Project Manager, Janet Lambert, at (301) 415-6710.
Sincerely, M.
Joseph J. Holonich, Chief 1
Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards
Enclosures:
As stated cc: F. Bosiljevac, DOE Alb E. Artiglia, TAC Alb i
1
s' G. Rael June 9, 1998 If you have ahy questions concerning this letter or the enclosure, please contact the NRC Project Manager, Janet Lambert, at (301) 415-6710.
Sincerely,
[D. Gillen for]
Joseph J. Holonich, Chief Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards
Enclosures:
As stated cc: F. Bosiljevac, DOE Alb E. Artiglia, TAC Alb DISTRIBUTION w/ Encl.:
File Center-NMSS r/f URB r/f PUBLIC ACNW CNWRA JLambert w/o Encl.:
MFederline MLayton CAbrams DOCUMENT NAME: S:\\DWM\\ URB \\DWS\\RF-582.COV OFC URB E
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URA a NAME DSchmid d DGille JHoNcb l
DATE 6/6 /98 6/ 0/98 N
6/i/98 OFFICIAL RECORD COPY l
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U.S. NUCLEAR REGULATORY COMMISSION STAFF REVIEW OF COMPLETION REPORT FOR RIFLE VICINITY PROPERTY RF-582 The U.S. Nuclear Regulatory Comrnission (NRC) staff has reviewed the Rifle, Colorado, Vicinity Property Completion Report (VP CR) for property RF-582, part of the Interstate 70 right of way southwest of the New Rifle processing site (MK-F 1997). This VP CR was submitted by the U.S. Derartment of linergy (DOE) under cover letter (Hamp 1997). Concurrence by the NRC on this VP CR is required because special circumstances resulted in supplemental standards being invoked during remedial action. Because the use of supplemental standards is the reason for the NRC's review, the NRC staff review has been limited to those parts of the VP CR related to the use of supplemental standards.
This vicinity proprty (VP) is part of the right of way for Interstate 70, southwest of the New Rifle processing site. The property consists of a four lane paved highway with a median separating the eastbound and westbound lanes. The Colorado River is along the southern boundary of this VP. This vicinity property is adjacent to vic?nity property RF-475, and designation of this vicinity property resulted from a spillover investigation during remediation of RF-4/5. The residual radioactive material contamination on this VP appears to be part of a large deposit primarily (initially) on RF-475. The deposit contains material with significantly elevated concentrations of Th-230 and elevated concentrations of Ra-226. The deposit on this VP extends into the Interstate highway berm and under the highway.
Some of the contaminated material on this VP was removed during remediation, Nt DOE proposes the use of supplemental standards to justify leaving some of the contaminated material that extends into the berm and under the highway. As indicated in Appendix B to the VP CR, test pits, with soil sampling, were used to characterize the approxin' ate extent of contamination. Test pits were piaced in the highway median and on the north side of the highway, but test pits could not be excavated south of the highway due to the proximity of the river. Thus, the full extent of contamination is not known. In Appendix B of the VP CR, the 3
extent of contamination remaining on the VP is estimated to be about 63,000 yd, over an area 2
of about 11,000 yd The external exposure rates at 1 m above the ground surface range from 8 to 17 pR/ hour over the contaminated areas. Radionuclides concentrations measured in test pit samples ranged from 0.5 to 228 pCi/g for Ra-226 and from 0.3 to 6749 pCi/g for Th-230. The highest concentrations, and most of the contamination, are below the ground surface, generally at depths of 4 feet or greater.
USE OF GENERIC THORIUM-230 CRITERION AS SUPPLEMENTAL STANDARD in the area where contamination has been remediated on this VP, the DOE has used a supplemental standard for Th-230 contamination, to determine the adequacy of remedial action.
Concentrations of Th-230 were measured in the soit verification samples, in addition to the usual Ra-226, and the results were used to calculate the Ra-226 concentration that would be present in 1000 years (abbreviated RC-1000 in the VP CR). The 1000-year Ra-226 concentrations were then compared to the U.S. Erivironmental Protection Agency (EPA)
Ra-226 standard of 15 pCi/g above background (for soils deeper than 15 cm), to determine if concentrations were acceptable. Though the VP CR did not indicate that this process was the use of a supplemental standard for Th-230 contamination, the criterion of comparing the 1000-year Ra-226 concentrations to the EPA standard for Ra-226 is one criterion that was suggested in the DOE's generic Th-230 protocol (Chernoff 1993). The NRC staff interpret this criterion to i
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NRC Rwiew of VP CR for RF-582 2
June 1998 j
be a generic supplemental standard for Th-230 contamination that was used for determining the I
adequacy of Th-230 cleanup and the acceptability of existing Tn-230 concentrations at the Rifle i
sites and associated vicinity properties. For the area of this VP for which remediation was I
performed, ten 100 m2 verification grids were sampled, all of which were subsurface (to be backfilled). Of these, the concentrations of Th-230 were greater than 15 pCi/g above background in two grids, but for all grids the calculated 1000-year Ra-226 concentrations were j
less than 15 pCi/g above background. Thus, for the remediated area, the verification samples indicate that the generic Th-230 supplemental standard was met.
JUSTIFICATION FOR NONROUTINE USE OF SUPPLEMENTAL STANDARDS FOR
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THORIUM-230 AND RADIUM-226 CONTAMINATION IN SOIL I
The VP CR indicated that the justification for the use of supplemental standards to leave contaminated material on the VP was based on the high cost of remediation relative to long-term benefits (as allowed in criterion (c) of 40 CFR 192.21) and based on the presence of l
radionuclides other than Ra-226 and its decay products (per criterion (h) of 40 CFR 192.21), in this case Th-230. The NRC staff believes that the Ittter basis is more important for this VP, as j
Th-230 is the primary wntaminant in the material that is intended to remain. The staff believes 1
. hat considerations of cost relative to long-term benefits are relevant to the determinations of
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the acceptability of the remaining contamination, as part of the ALARA evaluation that is required. Criterion (c) is also relevant to the residual levels of Ra-226 that exceed 15 pCi/g j
above background.
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The VP CR included two evaluations of the radiation doses to people who spend time on these l
sites. First, the standard assessment for VPs was performed, which considers only radiation j
doses due to exposures to extemal gamma radiation and fails to consider internal exposures.
'l Second, because of the relatively high concentrations of Th-230 found, an additional assessment to consider internal and external exposures was performed and is documented in Addendum 1 to Appendix B of the VP CR.
The NRC staff evaluated this latter assessment. The assessment included the estimation of doses for two scenarios: (1) a "long-term exposure" scenario, with an individual assumed to occupy the location of the maximum surface radionuclides concentrations, and (2) a "short-term unusual exposure" scenario, with a construction or maintenance worker assumed to be i
exposed to the maximum subsurface radionuclides conce.ntrations during repair or construction i
work on the roadway. For the occupancy (long-term) scenario, maximum surface radionuclides l
concentrations, of 156 pCi/g of Th-230 and 1.5 pCilg of Ra-226, were assumed as the source term. For the worker (short-term) scenario, maximum subsurface concentrations, of 6749 pCi/g of Th-230 and 161 pCilg of Ra-226, were assumed. In both cases, the exposure pathways i
considered were inhalation of resuspended contaminated soil and direct external exposure.
l Similar modeling parameter values were genera!!y used, with two exceptions: (1) for the mass 3
loading in air (for resuspension), a value of 0.0002 g/m (indicated to represent normal 3
conditions) was used for the occupancy scenario, while a value of 0.0006 g/m was used for the worker scenario; and (2) the thickness of contamination was assumed to be 1 ft for the occupancy scenario and 1 m for the worker scenario. Results of the assessment were estirrated dose rates of 11 prem/ hour for the occupancy scenario and 1.4 mrem / hour for the worker scenarso. The DOE conclusions, in the VP CR, were that due to the location of the contaminated material, it would be unlikely for anyone to spend enough time on the site (occupancy scenario) to receive a dose of 100 mrem in a year, and it would be unlikely for a
NRC Raview of VP CR for RF-582 3
Juna 1998 worker to spend enough time working with the highly contaminated materials to receive a dose of 500 mrem in a year.
The general approach to evaluating Th-230 contamination has usually involved evaluating the maximum Ra 226 concentration that would be present over 1000 years (see Chernoff 1993),
but this was not done for the dose assessment. The calculated 1000-year Ra-226 concentrations for samples from the test pits are listed in Table B.T4 of Appendix B to the VP CR. The maximum 1000-year Ra-226 concentrations are 56 pCi/g for the surface samples and 2467 pCi/g for the subsurface samples. The NRC staff considered a revised dose assessment, using the same methods and the two scenarios described in the VP CR, but using the maximum 1000-year Ra-226 concentrations and Th-230 concentrations as the source term.
Results of this revised assessment were estimated dose rates of 78 prem/ hour for the occupancy scenario and 4.2 mrem / hour for the worker scenario, which are about 7 tirnes and 3 times greater than the results reported in the VP CR for the occupancy scenario and worker scenario, respectively, The NRC staff agrees with the DOE's contention that the assumptions used in the dose assessment tend to overestimate the potential dose. In particular, for the occupancy scenano (surface concentrations considered), it is unlikely that an individual at the VP would spend all the time at the location of the highest concentration. Likewise for the worker scenario
. (subsurface concentrations considered), it is unlikely that a worker would only be exposed to the soil containing the highest concentrations; rather a worker would likely be exposed, on average, to soils with concentrations lower than the maximum concentrations. From these assessments, the NRC staff concludes that while the potential exists for a worker in the future to be exposed to residual contaminants and to receive a significant radiation dose, it appears unlikely that a worker would receive 9 dose greater than 100 mrem / year.
The DOE also described the additional costs of complete cleanup of the residual contamination.
The VP CR indicates, in Appendix B, that the cost for removing the remaining contamination is estimated to be about $3,600,000. For use of supplemental standards for radionuclides other than Ra-226, the standards of 40 CFR 192.22 require that the levels of such other radionuclides are reduced ALARA. The NRC staff concludes that the cost of complete remediation of the l
Th-230 and Ra-226 contamination exceeds a reasonable cost, given the potentiallong-term benefits (reduction in dose) of the additional cleanup. Thus, the NRC staff agrees with the DOE that it is appropriate to leave the contamination on the VP, with the use of a supplemental standard.
NRC STAFF CONCLUSION The staff concludes that information provided by the DOE in the VP CR provides reasonat.-e assurance that supplemental standards for soil cleanup have been properly applied at vicinity property RF-582. Therefore, the NRC staff concurs that the use of supplemental standards and the remediation of this vicinity property were completed in accordance with the EPA standards.
l REFERENCES Chemoff A.1993. Letter to J.J. Surmeier, Uranium Recovery Branch, Division of Low-Level Waste Management & Decommissioning, Office of Nuclear Material Safety and Safeguards, U.S Nuclear Regulatory Commission, regarding thorium-230 cleanup protocol, dated I
NRC Rwiew of VP CR for RF-582 4
Juns 1998 December 22,1993. U.S. Department of Energy. Albuquerque Field Office, Uranium Mill Tailings Remedial Action Project Office, Albuquerque, New Mexico.
Hamp S.C.' 1997 ' Vicinity Property No. RF-582, Interstate 70 Right of Way, Rifle, Colorado.
Letter to J.'J. Holonich, Uranium Recovery Branch, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, dated July 17,1997. U.S. Department of Energy, Albuquerque Operations Office, Environmental Restoration Division, f
Albuquerque, New Mexico.
MK-F (MK-Ferguson Company and Rust Federal Services, Inc.).1997. Vicinity Property Completion Report at RF-582, Interstate 70 Right of Way, Rifle, Colorado. January 29, 1997.
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VP No.: RF-582 l.'.
NRC Ravisw Form l..' '
for Suppl:m:ntal Certification of Vicinity Properties The Department of. Energy (DOE) has determined that the remedial action at the following vicinity property (VP) has been completed and thereby complies with supplemental standards invoked by DOE under 40 CFR, Subpart C, specifically Subsections 192.21 and 192.22.
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NRC concurrence for the Radiological Engineering Assessment (REA) given on:
[X ]
Supplemental standards were not in the REA, special circumstances required that l
supplemental st dards e involved during remedial action.
'o 1
/7 /997 1
Steven C. Hamp', DOE Cert ation Officer ate
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Based on the information and certification provided by the DOE, the NRC:
M concurs that the rernedial action at the subject VP has been completed under its authority provided by the Uranium Mill Tailings Radiation Control Act (UMTRCA), Section 104(f)(1) and as described in the Memorandum of Understanding (MOU), Appendix A, Section 3.4.
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concurs, as above, except for the following conditions:
1.
2.
3.
[] See attached sheets for any additional provisions.
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needs additionalinformation to make a concurrence decision. This information consists of:
[ ] See attached sheets for any additional informational needs.
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. ABDL s J,Ju NRC Concurring Official anb Title
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- Date Joseph J. Holonich, Chief Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards L
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