ML20133C098
| ML20133C098 | |
| Person / Time | |
|---|---|
| Issue date: | 12/31/1996 |
| From: | Joseph Holonich NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Sena R ENERGY, DEPT. OF |
| References | |
| REF-WM-65 NUDOCS 9701070033 | |
| Download: ML20133C098 (7) | |
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Mr. Richard Sena, Acting Director Environmental Restoration Division Uranium Mill Tailings Remedial Action Project U.S. Department of Energy 2155 Louisiana NE, Suite 4000 Albuquerque, NM 87110
SUBJECT:
STATUS OF COMPLETION REVIEW FOR THE FALLS CITY URANIUM MILL TAILINGS REMEDIAL ACTION PROJECT SITE
Dear Mr. Sena:
The U.S. Nuclear Regulatory Commission staff has reviewed the U.S. Department of Energy's (DOE) letters of August 14 and September 13, 1996, that provided responses to NRC issues and page changes for the Falls City Completion Report.
Enclosed is the status report of the five open issues. As indicated, in order to complete NRC review of the Completion Report, DOE should provide additional information on Issues Ib and 2.
The NRC staff has also reviewed DOE's submittal of September 13, 1996, that responded to concerns raised by Concord 011 Company in letters dated January 26 and February 14, 1996. DOE contends that only one of the four 1
issues raised by Concord is linked to the certification of the Falls City i
site. However, NRC staff has dewratned that.all four issues relate to site i
certification and that these must ise resolved before NRC can concur that the Falls City site meets the applicable standards.
The NRC staff has begun review of the DOE letter of December 20,'1996, that provides additional response to Concord's concerns. DOE has indicated that additional infomation still is to be provided on the U-238/Ra-226 ratio value i
used on vicinity property FC-0026, the 1992 visit to the Bargmann Tract, and the Tordilla Creek sediment sampling. DOE also has indicated that it will provide any field notes or other documentation of DOE's examination of seeps or springs, and that the DOE Grand Junction Office will be notified to include g
the presence of seeps and springs in their inspection agenda. To ensure
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implementation of this latter commitment, NRC staff anticipates that a change I
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will be made to the Falls City Long-Tem Surveillance Plan inspection checklist (agenda).
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Mr. Richard Sena 2
If you have any questions, please contact the NRC Project Manager, Elaine Brummett at (301) 415-6606.
Sincerely,
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Loriginal signed by Dani61 H.'Gfilen for:]
Joseph J. Holonich, Chief Uranium Recovery Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards
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i EVALUATION OF DOE'S RESPONSE TO FALLS CITY, TEXAS, CONPLETION REPORT ISSUES i
On March 8,1996, NRC staff provided DOE with the Draft Corgletion Review Report containing four issues on site cleanup and radon attenuation, and one issue concerning the inadequate vegetation density on the topslope of the cell. These issues were addressed by DOE's response dated August 14, 1996.
l The status of the issues is discussed below.
ISSUE la Address 28 specific grid blocks (each containing 25 verification grids) that do not appear to have sufficient Ra-226 values presented in either Appendix H, or in Appendix J, and were not represented on maps of mineralized areas in Attachment 1 of Appendix H.
DISCUSSION: DOE stated that page two of Appendix H indicates characterization j
efforts demonstrated that the areas were mineralized sediment.
DOF riso i.
referred to Attachment 3 and Table H.1 in Appendix H and added that Block X-48 i
was mostly outside of the limits of contamination.
Revisions (two sentences added) to the Remedial Action Assessment Section and Appendix H were provided.
NRC staff determined that the page revisions in Response Attachments 1 and 2 did not completely address the issue. The response should have indicated that the unorganized data in Table H.1 is represented by a grid block in Figure H.1 (indicates mineralized sediment) of Attachment 3 to Appendix H.
Staff notes that grid block B-40 is not represented in that data, but apparently is represented by one data point in the table titled " Designated Windblown Re-characterization Data North Section of Parcel A," in Attachment 3.
Therefore, after detailed examination, staff considers that adequate data for these grid blocks is contained in the CR.
STATUS: This issue is closed.
ISSUE lb Justify, in Appendix B calculation 20-439-04-01, why elevated levels of Th-230 were left in place. Also, page 12 of the Remedial Action Assessment (CR Volume 1) states that residual Th-230 in excess of established guidelines was found to exhibit all the characteristics of in situ mineralized material and, therefore, was left unexcavated.
Indicate the location of this material and provide, or reference the data substantiating that i.t is in situ material.
DISCUSSION: DOE added a footnote to the Appendix B calculation Th-230 data sheet, referencing an explanation in the Remedial Action Assessment, Section D, because this is the same material / deposit. Text was added to page 12 (Section D) of the Remedial Action Assessment to indicate the location of the elevated Th-230 and to refer to analyses in Appendix H.
NRC staff could not find where the elevated Th-230 deposit was evaluated in the Completion Report (CR).
STATUS: This issue remains open until DOE indicates how this nterial was determined to be in situ mineralized material.
Enclosure
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ISSUE Ic Indicate what surface areas were determined to contain in situ mineralized deposits without the use of the Ra-226/U value; given the evidence of oxidized in situ deposits with high Ra-226/U values, l
indicate where these sediments were located and how they were i
distinguished from tailings;- provide the data for the 75 soil samples and the rigorous statistical analysis referred to on page 2 j
of Attachment 2 in Appendix H; and indicate if the method for distinguishing tailings when the Ra/U was between 2 and 4 with i
measured U-235 values was utilized and how the method is justified given the low and variable level of U-235.
i DISCUSSION: DOE stated that the Pnciographic Index and memos in Appendix H i
indicate where and how visual examinations ; wetimes in conjunction with Ra/U values) were used to determine in situ mineralized deposits; the oxidized deposits were identified in subpile and some windblown areas as discussed in Appendix H; and information on the samples is provided as page changes for
! of Appendix H.
DOE also indicated that the method was used and i
is justified because the system's minimum detectable concentration for U-235 i
was less than the background value and because empirical data supports use of i
the method.
Based on the data and discussion of the analytical method provided by DOE, the NRC staff considers the procedure to be adequately justified.
STATUS: This issue is closed.
ISSUE 2 Appendix H (page 4) indicates that 150 x 150-foot grids were used to obtain characterization data in the mineralized areas to save time.
However, it appears this grid size was also used in several areas after tailings removal. DOE should provide discussion in the CR to justify the use of larger verification grids in certain areas.
DISCUSSION: DOE stated that 150 x 150 foot-grids were used for re-rharacterization and not verification of EPA standards.
For example, RRM was deposited in a former open pit mine. DOE also indicated that after removal of the material, the EPA criteria no longer applies, and instead the area must be characterized for in situ mineralized sediment.
NRC staff does not agree that the EPA criteria no longer applies in the example cited in DOE's response. Also, staff discussed with DOE during a site visit on May 12, 1993, that we do not agree that the use of 150-foot grids is appropriate to demonstrate that the RRM has been removed to meet the EPA standards and that only in situ material remains. This means information, not necessarily Ra-226 analysis, should be provided on each 100 square meter area.
DOE's discussion of the visual identification of in situ material does not indicate if spot checks were done, or if the geologist walked a grid pattern in order to support verification of RRM cleanup.
In addition, DOE's use of the term "re-characterization" in the CR does not change the fact that verification of RRM cleanup is required for these areas.
STATUS: To close this issue, DOE should justify that sufficient information has been provided to verify that RRM removal from the open pit mines, or other areas of in situ mineralized material, meets the EPA standards.
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ISSUE 3a The Remedial Action Plan (RAP) radon barrier design incorporated an additional 6 inches of barrier to allow for shrinkage cracking l
because the Plasticity Index of the barrier soil is greater than 30, but this is not included in the final (CR) design.
In addition, the l
RAP and CR radon flux models utilize a long-term moisture content l
for the radon barrier derived from the Rawls and Brakensiek j
i equation, based on an organic content of 6.5 percent. CR Appendix E l
indicates that all 67 radon barrier samples taken during 4
construction had an organic content of less than 1 percent. Use of i.
this lower organic content value in the equation would have resulted in a lower (more conservative) long-term moisture content for the barrier material. Therefore, the CR should demonstrate how the j
average measured Plasticity Index and organic content values for the j
l radon barrier, obtained during construction, impact the long-term j
radon flux.
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DISCUSSION:
DOE stated that shrinkage cracking was addressed in the preliminary cover design because the erosion protection was to be a bedding i
j layer and riprap.
In the final design, the topslope erosion protection is 30 inches of growth medium and 6 inches of topsoil (vegetative cover). Thus shrinkage cracking of the radon barrier is unlikely and the 6-inch allowance was not considered.
i DOE also indicated that the long-term moisture content for the radon barrier in the RAP and CR radon flux models was based on the lower bound of 15-bar moisture content (11 capillary moisture tests), because this methodology is considered most important in the NRC Standard Review Plan and is more i
appropriate than the equation, due to its empirical nature.
DOE concluded i
that the plasticity index and organic content values would not impact the i
long-term radon flux.
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The first part of DOE's response is acceptable to staff, but the latter part l
is incorrect. NRC's Standard Review Plan for Title I Sites (June 1993) does i
not give preference to the capillary moisture test (ASTM D-3152 or D-2325),
i but does indicate that proposed long-term moisture values will be compared to appropriate in situ values.
In addition, DOE's data from other sites has demonstrated that the 15-bar moisture test does not always provide conservative results. Also, NRC staff notes that Remedial Action Plan (RAP)
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calculation 20-438-03-01 (sheet 34) indicates that the calculated long-term i
moisture for the radon barrier material was 24 percent.
In contrast, the capillary moisture tests resulted in 38 percent and the in situ value was 35 percent. Therefore, the final CR radon flux calculation used a conservative (calculated) barrier moisture value.
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l STATUS: This issue is closed.
j ISSUE 3b The CR final radon flux calculation utilized the 1000-year Ra-226 levels resulting from the 3-inch layer of Th-230 material placed on the top slopes in only one location, not in all top slope locations i
as was done in the flux calculation attached to PID 15. DOE should explain why the calculations are different.
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DISCUSSION: DOE indicated that when PID 15 was prepared, placement of i
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I windblown and Th-230 elevated material was not complete, and it was estimated that a 3-inch-thick layer of Th-230 material would cover most of the topslope.
The CR radon flux model was based on measured in-place values, except for a 3-inch layer of Th-230 material assumed for location #13 because the top layer l
was not sampled in that area. DOE pointed out that for all samples with elevated Th-230, the 1000-year Ra-226 value was used in the radon flux calculation. After additional review,.NRC staff agrees that the Th-230 material was adequately represented in the final radon flux model.
STATUS: This issue is closed.
i ISSUE 3c Page AA-35 of calculation 20-439-04-01 (CR Appendix B) indicates that the Ra-226 levels of radon barrier and growth medium are 4.2 and 4.7 pCi/g, respectively. The column headings for these data indicate Ra-226 values are corrected. DOE should explain why and how the Ra-226 values were corrected.
If the Ra-226 level of the cover material is significantly above background, as indicated, then it is inappropriate to use a zero Ra-226 value in the DOE radon model.
DISCUSSION: DOE stated that the Ra-226 values (obtained by the Opposed Crystal System) were corrected for moisture and emanation to estimate the 20-day value. To be conservative, the radon barrier Ra-226 value was used in the CR radon flux model.
STATUS: This issue is closed.
ISSUE 4 CR Appendix H (Post Remedial Site Conditions) does not mention the demolition of structures and disposal of debris.
DOE should revise Appendix H to include discussion concerning the site structures.
DISCUSSION: DOE indicated that this issue is adequately addressed in Volume I of the CR, Remedial Action Assessment (Section B), and in Appendix E.
NRC staff notes that the only structure mentioned in Remedial Action Assessment Section A (Pre-Remedial Action Site Conditions), is the mill building foundation.
Section B only states that debris was demolished and placed in the tailings embankment. However, Appendix E indicates that all contaminated material nnd debris resulting from demolition of foundations and associated structures were cut or broken up to meet size specifications.
STATUS: Although CR Appendix G or H (pre and post-remedial conditions) should be the place to address the status of any mill buildings, the staff considers this minor issue closed.
ISSUE 5 Based on staff site visits, it appears that adequate vegetation density has not been maintained following DOE's approval of the construction activities. The staff noted the presence of several areas on the top of the cell where the vegetation density is not adequate. It is our understanding that DOE has reseeded several areas to increase the vegetation density. DOE has not provided any additional information on the success of the reseeding, and'the staff has not yet verified that the necessary density has been achieved.
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o DISCUSSION: DOE reseeded several areas to increase the vegetation density and provided information and photographic documentation of the success of the reseeding in the Final CR. NRC staff verified that the necessary density has been achieved during a site visit on June 21, 1996.
STATUS: '.nis issue is closed.
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