ML20045E855
| ML20045E855 | |
| Person / Time | |
|---|---|
| Issue date: | 06/09/1993 |
| From: | Brummett E NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Gillen D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-65 NUDOCS 9307060145 | |
| Download: ML20045E855 (5) | |
Text
F JUN 0 S 1993 NEMORANDUM FOR:
Dan Gillen, Section Leader Remedial Action Section LLUR/LLWM/NMSS 1
FROM:
Elaine Brummett, Project Manager Special Issues Section LLUR/LLWM/NMSS
SUBJECT:
FALLS CITY, TEXAS, URANIUM MILL TAILINGS REMEDIAL ACTION PROJECT SITE VISIT On May 12, 1993, I visited the Falls City, Texas, UMTRA Project site to view the excavated areas; discuss verification procedures in areas with naturally elevated Ra-226 and Th-230; observe gamma readings in verified, windblown, and borrow areas; and review construction and verification progress to date.
Enclosed, for your information, is the trip report from my visit and the follow-up conversation notes.
If you need any additional information regarding the issues discussed in the report, please contact me at 504-2533.
OftfGNAL SIGNED BY Elaine Brummett, Project Manager Special Issues Section LLUR/LLWM/NMSS
Enclosures:
As stated f
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1 TRIP REPORT FOR SITE VISIT / MEETING AT FALLS CITY. TEXAS. UMTRA PROJECT SITE Date:
May 12, 1993 Place:
Falls City, Texas
Purpose:
To view the site conditions and discuss several technical and regulatory issues concerning soil cleanup and verification, and background radiation levels Attendees:
Department of Energy W. Woodworth, Site Manager Morrison-Knudsen ES
.@gmedial Action Contractor)
D. Carlson, H.P. Manager T. Stanford, Site Const. Manager L. Patrick, Site H.P. Manager Nuclear Reaulatory Commission E. Brummett, Site Project Manager Discussion:
W. Woodworth and I met the evening of May 11, 1993, to discuss travel arrangements, issues to be covered, and site tour details. We left San Antonio about 5:30 a.m. and drove in separate cars to the UMTRA Project Falls City site. We arrived at 7 a.m., and after my site safety training, I started l
the tour with Woodworth and the Remedial Action Contractor (RAC) staff noted above.
We walked around the excavated portion of the borrow area and pits #3 and #5.
We noted that the natural soil is visually different from the tailings, saw q
lignite seams, took gamma counts to estimate Ra-226 levels, compared photographs of pit #3 from mining days with the current excavation outline, and noted stakes at 150-foot centers at lower portions of the pits where soil samples were taken.
We observed: windblown areas; pit #4 which was partially filled and lined and now is being used as a retention basin; earthwork
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operations on top of the embankment; locations off the SE corner of the embankment where samples were taken that indicate elevated Th-230; and the lab where technicians were using the opposed crystal system and the germanium system to analyze soil samples.
There was some discussion of issues during the tour; then Woodworth and I met to elaborate on and summarize the discussions:
1.
Verification in areas with naturally elevated Ra-226 and/or Th-230 l
High-grade uranium ore was removed from this site, and the low-grade deposits remain near the surface in some spots and around most of the deep portions of the pits (old surface mines).
To verify cleanup in these 4
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I areas, the RAC first uses visual cues, such as texture, color, and structure (layers). The RAC staff indicated that the State of Texas geologist agrees with them on this visual method. One soil sample is then taken every 150 feet (similar to site characterization) and analyzed for Ra-226.
If there is more than 15 pCi/g in the sample, the U/Ra is determined by the germanium system to decide if the elevated Ra-226 is due to in-situ mineralized deposits (background).
Large areas have already been verified with these procedures. This method is also used to determine if areas that were designated windblown, based on the Ra-226 concentration, are really contaminated, or if the readings were due to the naturally elevated background.
The RAC's draf t document that explains and justifies the use of these procedures at the Falls City site, had been given to me April 22, 1993.
DOE had asked me to comment before the document is finalized for formal NRC review.
I pointed out several concerns I had with the document.
While one might agree that it is not practical to do regular Ra-226 verification sampling in areas where background Ra-226 levels vary greatly and average 200 pCi/g; 40 CFR 192.12(a) indicates that the Ra-226 concentration is to be averaged over 100 square meters to provide reasonable assurance that remedial action has been accomplished.
I said that since NRC must concur that DOE has met the EPA standards at this site, the Completion Report should indicate how tht: intent of the standards has been met.
I suggested that the discussion of verification incorporated into the Completion Report, should include the RAC and state geologists' reports, details on the procedures, data characterizing background, and explain references to other VMTRA Project sites that used alternate grid sizes (Riverton Th-230 90x90 foot verification grids applied only to supplemental standard for the saturated zone).
2.
Th-230 plume off SE corner of the embankment Results of samples (9-11 feet deep) at or in water table:
1600 pCi/g at base of embankment 1000 pCi/g in ditch where apron will be 600 pCi/g 100 feet farther south Several other samples around these had lower levels of Th-230. At the end of construction, there should be 18.2 feet of fill over the 1600 pCi/g spot, so the radon flux should not be a problem.
The RAC staff wondered if the contamination could remain because it would be within the fence and so have restricted access.
I said NRC staff would need to review the data and a discussion of the issue before making a recommendation.
3.
Naturally elevated Ra-226 levels in the radon barrier borrow area The highest reading was 19 pCi/g (at a depth of 15 feet).
The RAC guideline allows up to 60 pCi/g for any sample, as they assume mixing of the occasional " hot spot" will still result in a low average value. The RAC will monitor and sample during excavation.
The EPA standard only 2
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addresses estimated radon flux from RRM, but DOE is concerned about meeting NESHAPS flux measurements.
4.
Mine overburden material as fill for pit #3 Parcel B is a vicinity property that contains pit #3, another smaller pit (without tailings backfill), and a large mound of overburden which was moved for access to the underlying ore.
The subcontractor plans to move the overburden pile to fill pit #3.
The RAC said the material averages about 8 pCi/g Ra-226 and they will monitor Ra-226 levels during excavation.
I indicated that the overburden characterization data could be summarized in the Completion Report and assurance that the overburden does not contain mine wastes (barrels of fuel, tires, etc.) should be provided.
3
I' FOLLOW-UP DISCUSSIONS ON FALLS CITY SITE ISSUES Date: May 13, 1993 E. Brummett, M. Layton, and D. Gillen - NRC The issue on the Th-230 plume seems to be resolved by the supplemental standard in the RAP.
Using the final grade elevation, DOE can estimate the radon flux and then calculate the radon progeny concentration in a slab-on-grade house and compare that to the 0.02 WL EPA standard.
M. Layton said the ground water is Class III, and the supplemental standard is based on the health effects from contamination of neighboring wells.
DOE should be able to show that the elevated Th-230 would not reach the neighbors' well.
The naturally elevated Ra-226 in the radon barrier material and in the backfill material for pit #3 does not seem to be a problem, but we will discuss it with NRC legal staff.
Only the issue of 150-foot verification grids remains a problem.
NRC staff will comment after DOE submits a formal discussion of this issue with the information requested.
Date: May 14; 1993 E.Brummett, NRC and W. Woodworth, DOE I pointed out that the Th-230 plume could remain if the elevated material would be covered by enough fill so that the estimated radon progeny concentration did not exceed the EPA standard.
W. Woodworth thought some of the material would not have enough cover, so he would recommend that the elevated Th-230 be excavated.
Woodworth said the RAC would revise the draft submittal on the 150-foot verification grids.
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