ML20142A037

Forwards Controls for Environ Pollution Results of Isotopic U Content of Soil Samples from Unrestricted Area Along W/ Corrected Results

ML20142A037
Person / Time
Site:	07000371
Issue date:	02/24/1986
From:	Berger J OAK RIDGE ASSOCIATED UNIVERSITIES
To:	Crow W NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
26546, NUDOCS 8603190251
Download: ML20142A037 (4)

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February 24, 1986

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Mr. William Crow 1

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Washington, DC 20555 Subj ect : ADDITIONAL ISOTOPIC URANIUM ANALYSIS - UNC SOILS

Dear Mr. Crow:

In my letter of Octot c 16, 1985, isotopic uranium analyses, performed on 10 samples from the UNC restricted area were described. The conclusion reached from these analyses was that the U-234/U-235 activity ratio was approximately 32.7.

In comparison, UNC's vendor laboratory, Controls for Environmental Pollution (CEP), had previously reported much lower ratios, which were inconsistent with literature values and also common sense.

Because of these large dif ferences, I carefully reviewed our procedures and identified an error in the computer program, which reduces the average ratio by about 20%, i.e. f rom 32.7 to 26.1.

I also provided aliquots of the same 10 samples to UNC's vendor for analysis. The CEP results are presented on the attached table along with the corrected ORAU results.

It is apparent from this table that with exception of samples 3489 and 3608, there are significant dif ferences between nost ORAU and CEP results.

In most cases the CEP analyses indicate lower levels of U-234 and U-235 and higher levels of U-238 than determined by ORAU. An exception is sample 3599, for which CEP reported higher levels than ORAU. These results demonstrate the non-homogeneity that is present in the soils at the UNC facility and the problem of homogenizing the soil samples by laboratory techniques such as ball milling and blending.

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dif ferences were also observed between U-235 analyses by alpha spectrometry and gamma spectrometry, which provides an average concentration over a much larger sample size. This problem is believed due to the physical and chemical form of the uranium and the matrix in which it is contained. The two exceptions were samples obtained from the lagoon wall area, where the contaminant would be expected to be more homogenously distributed, because of its dif ferent physical and chemical form after waste treatment activities.

Despite the differences in the individual analyses, it should be noted that the CEP results provide U-234/U-235 ratios similar to those determined by ORAU.

The average ratio of the 10 samples is 21.2 for CEP: analyses as compared to the

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r-Mr. William Crow February 24, 1986 revised ORAU ratio of 26.1.

This seems to contradict the earlier CEP findings of a much lower U-234/U-235 ratio.

Sincerely, l

James D. Berger Program Manager Radiological Site Assessment Program JDB:vol Attachment cc: Jerry Roth, Nuclear Regulatory Commission, Region I 1

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e ISOTUPIC URANIUM CONTENT OF Soll SAMPLES FROM UNC RESTRICTED AREA Sample Analytical Uranium Concentrations (pCi/g)

ID Laboratory U-234 U-235 U-238 U-234/U-235 3457 ORAU 10.7 + 2.la 0.51 + 0.50 1.34 + 0.73 21.0b CEP 2.18 + 0.32 0.12 + 0.06 0.73 + 0.05 18.2 3468 ORAU 17.7 + 2.9 0.30 + 0.41' O.96 + 0.67 59.0b CEP 3.13}0.46 0.17}0.08 1.16}0.20 18.4 3478 ORAU 152

+2 6.94 I 0.54.-

2.59 + 0.29 21.9 CEP 16.5. + 3.0

-0.69 + 0.10 6.51 + 1.00 23.9 3489 ORAU 8.89 + 0.94

~ 0.'5'1 + 0.25 0.41 + 0.20 17.4 CEP 10.4 [1.0 0.50'[0.12 3.76'[0.45 20.8 3496 ORAU 15.9 + 1.9 0.38 + 0.34

' O.79 + 0.43 41.8b CEP 2.38[0.28 0.14[0.05 0.76[0.10 17.0 3539 ORAU 29.3 + 2.7 0.50 + 0.40 0.60 + 0.39 58.6b CEP 2.96 + 0.36 0.13 + 0.06 1.18 + 0.20 22.8 3584 ORAU 31.8 + 2.3 0.85 + 0.41 1.02 + 0.41 37.4 CEP 2.40[0.36 0.17[0.08 0.93[0.30 14.1 3599 ORAU 9.19 + 1.54 0.34 + 0.34 0.14 + 0.19 27.0b CEP 30.7'[3.7 1.26[0.13 9.94[1.00 24.4 3602 ORAU 461

+5 16.6 + 1.0 4.46 + 0.28 27.8 CEP 6.28[0.75 0.24[.0.08 1.98[0.30 26.2 3608 ORAU 6.09 + 1.02 0.25 + 0.29 0.40 + 0.26 26.5b CEP 6.03 + 0.48 0.23 + 0.05 1.78 + 0.21 26.2 aErrors are 2a based only on counting statistics.

bNot used in average because of large relative error.

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