ML20059A816

Soil Sampling Plan for Phase II of Sva Decommissioning Project

ML20059A816
Person / Time
Site:	07000734
Issue date:	10/21/1993
From:	GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER
To:
Shared Package
ML20059A772	List: ML20059A769 ML20059A816
References
PROC-931021, NUDOCS 9310270136
Download: ML20059A816 (15)

Text

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+CEnn?RAL AFOANCK 4

a SOIL SAMPLING PLAN FOR PHASE 11 OF e

THE SVA DECOMMISSIONING PROJECT l

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N CENERAL ATOMICS SOIL SAMPLING PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 1 OF 14 October 21,1993 1.

Objective To provide a plan for soil sampling during Phase 11 of the SVA Decommissioning Project under which GA will demonstrate compliance with approved soil release ent r ria.

11 Helease Criteria

1. Soil Concentrations The soil release criteria to be used are provided in Table 1 which are taken from the Nuclear Regulatory Commission's Policy issue SECY 81-576, October 5,1981 and previously approved for the GA site and the SVA Decommissioning Project (References 1,2 and 3).

The values in Table 1 are levels above naturally occurring background (section 2.3.1 and 6.3 of Reference 4).

The soil release criteria is 10 pCi/ gram for natural thorium (Th-232 and Th-228 above natural background concentrations).

The limit for enriched uranium (30 pCi/ gram above natural background concentrations) will be applied by adding the U-234 and the U-235 concentrations. The U-234 concentration will be determined by measuring the U-235 concentration by gamma spectroscopy and then using a ratio of 30:1 (U-234:U-235) based on typical uranium isotopic analysis of enriched uranium used in the facility as shown below:

NUCLIDE AVERAGE SPECIFIC ACTIVITY WEIGHTED WEIGHT %

(p curies /g)

ACTIVITY (p curies /g)

U-234 0.98 6129.54 60.069 U-235 93.15 2.14 1.99 U-236 0.40 63.56 0.254 U-238 5.50 0.34 0.0187 TOTALS 100.03 62.33 ar Based on the above, the weighted activity ratio of U-234:U-235 is 30:1.

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& CENERAL h ATOhNCS SOIL SAMPLING PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT PAGE 2 OF 14 October 21,1993 in order to confirm the ratio, contaminated soil from a sunsp located in the North Annex was sent to IT Corporation on April 22,1992 for uranium isotopic analysis. The average ratio of U-234:U-235 from the analysis was found to be about 26:1. The results of the analysis are provided in Attachment 1.

Therefore, the use of the 30:1 ratio is conservative.

It is GA's intent to remediate areas containing elevated activity levels in the soil.

However, in the event that reasonable efforts have been made and soil concentrations continue to remain elevated, GA may apply the criteria described in section 2.2 and section 8.0 of Reference 4 to determine compliance. Reference 4 (section 2.2 and section 8.0) established the guideline that areas of residual activity exceeding the guideline value, known as

" elevated" areas, are acceptable, provided they do not exceed the guideline value by greater than a factor of (100/A)*, where A is the area of residual 2

activity in m, and provided the activity level at any location does not exceed three times the guideline values. In addition, radionuclide concentrations will be averaged to demonstrate the average is at or below guideline values, 2

established as acceptable to NRC. Averaging will be based on a 100 m (10 m x 10 m) grid,

2. Direct Measurements Exposure rates are not to exceed 10 microR/hr above background at 1 m above the surface.

For open land areas, exposure rates (measured at 1 m above the surface) can 2

be averaged over 100 m grid areas. The maximum exposure rates over any discrete area may not exceed two times the limit above backaround in accordance with section 2.2 and section 8.0 of Reference 4. It is GA's intent to remediate all areas where microR readings exceed 10 microR/hr at 1 m above the surface. However, in the event that reasonable efforts have been made and measurements continue to remain elevated, GA may apply the criteria described above and discussed in section 2.2 and section 8.0 of Reference 4 to determine compliance.

Ill. Buildino 37N and Surroundino Area to be Released to Unrestricted Use Figure 1 shows Building 37 (north end) and the immediate adjacent surrounding area (" extended footprint") which includes the area to be released to unrestricted use.

IV. Samole Analysig

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&+ CENERAL aronnes SOIL SAMPLING Pl.AN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT PAGE 3 OF 14 October 21,1993

1. Backaround Concentrations Natural background concentrations in. soil near the SVA (Building 37) site have been established (at the 95% confidence level) and are provided in Table 2.

The locations from which samples were taken are provided in Attachment 2.

2. Uranium and thorium concentrations in soil Uranium and thorium concentrations in soil samples will be determined by using gamma spectroscopy. The U-235 concentrations will be determined using the 144 kev peak or the 186 kev peak. Th-232 concentrations will be determined by averaging the 338 kev and 911 kev Ac-228 peaks. The Th-228 concentration will be determined by averaging the 238 kev Pb-212 peak and the 583 kev TI-208 peak.

Samples will be counted for a minimum of 15 minutes. A 15 minute count is sufficient to detect the uranium-235 gamma ray (144 or 186 kev peak) and gamma rays from the various Thorium daughters at levels below the release criteria. The results will be compared to the release limits.

Estimated detection limits for a 15 minute count are as follows:

U-235 is < 0.3 pCi/g Th-228 is < 1.5 pCi/g Ra-228 is < 1.5 pCi/g V. Sample Collection Soil samples will be collected from within the extended footprint area (see Figure 1), including from underneath the concrete slab, from underneath and around the drain lines and from exposed soilin the area extending from the concrete slab to the boundary of the extended footprint. Grids will be established for the purpose of referencing the locations of samples and measurements. The 10 m x 10 m grid system to be used is shown in Figure 2.

1. _G.enera!

A 15 cm " surface" soil sample will be collected with a sample size of approximately 1 kilogram. The sampling locations will be identified on drawings. The samples will be properly logged, labeled, packaged and tracked.

All debns (grass, rocks, sticks, and foreign objects) will be removed from the sample. Samples will be dried and counted by gamma spectroscopy. Results will be reported in pCi/g for each radionuclide.

An "affected" area is an area having potential for radioactive contamination or having known radioactive contamination. As applied to the SVA

CENERAL ATOMICS SOIL SAMPLING PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT PAGE 4 OF 14 October 21,1993 Decommissioning Project, all exposed soil will be classified as "affected"

2. Underneath the concrete slab Biased samples will be collected from underneath the concrete slab (under cracks and/or drains where the soil appears affected; i.e., discolored, odiferous or otherwise abnormal or suspected of contamination).

Scanning (along the surface of the soil) will be performed to identify locations of elevated activity levels. Areas of suspected activity, identified by scanning or visual inspection, will be evaluated to determine their activity levels and the extent of contamination. Cleanup will be performed, as required, and the scanning repeated until remediation is accomplished as demonstrated by additional soil sarnpling, analysis and comparisons with the guidelines.

After scanning and remediation of known contaminated areas, systematic soil sampling will be performed on a triangular grid with a sampling interval of 5 m on a side as shown in Figure 3. Additional remediation will be conducted if release criteria are not met, if elevated areas (areas above release criteria) are identified during the final survey, they will be evaluated for acceptability using NUREG/CR-5849 averaging methods, regardless of whether or not remediation will be conducted.

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3. Underneath the drain knes When collecting samples from underneath the drain lines (in the trenches created during removal of the drain line), biased samples will be collected as follows:

1) Soil samples will be collected from underneath and around any drain lines which appear broken, corroded or otherwise deteriorated.

2) Soil samples will be collected whenever exposure rates are elevated (measured using microR meters and/or Nal (TI) detectors /ratemeters).

3) Soil samples will be collected if the soil appears affected, i.e., discolored, odiferous or otherwise abnormal.

In addition, systematic samples will be collected approximately every 5 m (about every 15 feet) from underneath the drain lines. The drain lines are located about one (1) to three (3) feet below the concrete surface underneath the production floor. The production floor area is about 120 feet (east and west) x 160 feet (north and south). There are a total of 12 lines running west to

9 d CENBEFAL 9 AFOMBCE 4

SOIL SAMPLING PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 5 OF 14 '

October 21,1993 east, therefore a total of about 100 samples will be collected. in addition, there are about 350 feet of arterial feeders running between the 12 lines; samples will be collected every 5 m (below arterial feeder lines), if possible. Thus, approximately 20 samples will be collected under these arterial lines. Soil will not be back-filled into trenches unless approved by the Nuclear Regulatory Commission (which will be deemed to signify approval by the State of Califomia).

4. Subsurface Samoles I

Remediation of soil will continue to a depth required to reduce the concentrations to levels below the release criteria. A final sample (s) after remediation will demonstrate that residual activity is below the release criteria.

Subsurface samples underneath the concrete slab may be collected to a depth j

of three (3) feet. Subsurface samples will be collected in biased locations and will include: 1) each location (larger than 5 m ' ) where soil contamination above the guidelines was discovered and remediated and 2) any location where i

exposure rate measurements were elevated (greater than two times the external radiation exposure limit, above background). These measurements will be made using a microR meter or Nal (TI) detector /ratemeter.

l Subsurface samples will also be collected underneath drain lines in a total of l

eight (8) locations to a depth of about fifteen (15) feet. If necessary, based on the results of the analyses of these samples at these depths, additional sampling at further depths and/or at other locations will be conducted.

l In addition, at least six (6) subsurface samples (to a depth of 15 feet) will be collected in the north end of the building (North Annex area). There are no underground drain lines in this area, but historical data indicates that the area was used as an outside storage area prior to the addition of the annex.

l Subsurface samples may also be collected in other suspect locations, if warranted by exposure rate measurements or remediation efforts.

5. Outside Areas of the Building Scanning (along the surface of the soil) will be performed in all exposed soit j

locations to identify locations of elevated activity levels. Spacing intervals l

between scanning paths should be such that a minimum of 50% of the surface i

is scanned.

l Systematic soil sampling from all exposed soil locations will be performed on the 5 m triangular grid pattern shown in Figure 3.

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CENERAL ATOMIC 5i SOIL SAMPLING PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 6 OF 14 October 21,1993 1

At least two (2) subsurface samples will be collected to a depth of about fifteen (15) feet. If necessary, based on the results of the samples at these depths, additional sampling at further depths and/or at other locations will be conducted.

VI Comparisons After the averages satisfy the guideline values and conditions, the results will be further evaluated to determine whether the data for each survey unit provides a 95% confidence level that the true mean activity meets the guidesnes using equation 8-13 of reference 4 (this equation is recommended by the Environmental Protection Agency as a method to test data, relative to a guide'ine value, at a desired level of confidence).

The test will be applied to three (3) groups of samples. The first group will be the samples collected from the grid pattern shown in Figure 4. The second group will be the samples collected every 5 m from underneath the drain lines and the third group will be the subsurface soil samples.

Vll Direct Radiation Measurements To determine compliance with the external radiation limit of 10 microR/hr at 1 m above the surface, exposure rate measurements will be taken at 1 meter at all systematic soil sampling locations (after soil remediation has been completed).

The results will be compared with the release criteria shown in Table 1 (and discussed above).

A calibrated microR meter will be used to determine exposure rate measurements in microR/hr. A pressurized ion chamber (PIC) will be obtained in order to verify the calibration of the microR meters.

Vlli Phase ll Final Survev Report All survey results will be documented and provided to the Nuclear Regulatory Commission and the State of California in a final report. Note: For areas where remediation was conducted, the report willinclude the results of surveys conducted prior to the area being remediated as well as the final survey results.

+CENERAL ATOMICS SOIL SAMPLING PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 7 OF 14 October 21,1993 l

REFERENCES 1.

Nuclear Regulatory Commission, Policy issue SECY 81-576, October 5,1981.

2. Asmussen, Keith E., Letter No. 696-1896 to John W. N. Hickey, " Decontamination Guidelines for GA's SVA Decommissioning Project", dated April 14,1992.

3. Hickey, John W. N., Letter to General Atomics, ATTN: Dr. Keith E. Asmussen, License No. SNM-696 Amendment No.18, dated March 31,1992.

4. Manual for Conducting Radiological Surveys in Support of License Termination (Draft for Comment), NUREG/CR-5849, ORAU-92/C57, Oak Ridge Associated Universities, June 1992.

CENERAL ATOMICS SOIL SAMPLING PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT PAGE 8 OF 14 October 21,1993 Table 1.

Radionuclide Concentration Limits For Soil And Exposure Rate Limits.

From Option 1 NRC Policy Issue (SECY 81-576)

Rattionuclide Concentration (pCilg)*

Natural Thorium (232Th & 22sTh) with daughters present and in equilibrium 10 Enriched Uranium (Soluble and 30 Insoluble)"

External Dose Limit = 10 pR/hr (above background levels) at 1 m above surface If more than one radionuclide exists, the sum of the fractions of the concentratians will be calculated a follows:

[.C1 L,

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C, = The average soil concentration of radionuclide i.

L, = The maximum soil limit for i (pCilg).

The sum of the fractions must be less than one in order for the soll to meet the release criteria.

" The 23sU concentrations determined by gamma spectroscopy will be used to ensure that concentrations for enriched Uranium are below the given limit. The ratio of U to 23sU is thirty to one (30:1) for the SVA facility.

234

SOIL SAMPUNG PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 9 OF 14 October 21,1993 Table 2.

Baciigmund Radionuclide Concentrations (pCVg) in Soil '

Sample Co-60 Cs-137 Th-228 Ra-226 Ra-228 U-238 U-235 ID

• AJ ND' ND 1.28 i 0.07 1.0210.10 1.47 i 0.14 1.98 10.31 0.15 i 0.03 G2 ND 0.12i0.03 0.92 t 0.07 0.8610.59 1.01 i 0.12 1.86 i 0.29 0.12 i 0.02 AC ND ND 1.2910.07 1.1410.12 1.34 i 0.14 2.27 i 0.27 0.20 i 0.03 BKG-1 ND ND 1.40 i 0.16 0.92 0.23 1.44 0.28 2.0610.48 0.19 i 0.06 BKG-2 ND ND 1.54 i 0.15 1.07 i 0.11 1.57

• 0.27 2.30 i 0.45 0.17 i 0.05 BKG-3 ND ND 1.4010.14 0.8210.17 1.6210.26 ND 0.19 i 0.05 BKG-4 ND ND 0.67i0.09 0.7210.14 0.84 i 0.17 1.1510.37 0.09 i 0.04 BKG-5 ND ND 1.5110.16 1.0410.22 1.79 i 0.31 2.77 i 0.67 0.12 i 0.06 BKG-6 ND ND 0.68 i 0.09 0.7210.13 0.76 i 0.16 ND 0.08 i 0.03 BKG-7 ND ND 1.17 i 0.12 0.79 i 0.17 1.28 i 0.22 1.83 i 0.43 0.1110.04 uean

• 2 o 1.1910.64 0.91 i 0.30 1.3110.68 2.03 t 0.93 0.14 20.09 Samples gamma scanned for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

2 ND=

< 0.1 pClig for Cs-137, < 0.1 pCi/g for Co.60, < 1.0 pCi/g for U-238 Samples collected in June and August 1993, typicaUy about 1-2 miles from the Building 37 site. See Attachment 2 for locations.

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SOIL SAMPLING PLAN FOR PHASE ll OF THE SVA DECOMMISSIONING PROJECT PAGE 13 OF 14 October 21,1993 ATTACHMENT 1: RESULTS OF SVA SOIL SAMPLE ANALYSIS BYIT CORPORATION l

6 16-Jun-92 10:32 AN IT ANALYTICAL EERVICES 2000 GEORGE WASHINCTON WAY. RICHLATID. WA RAD 10 CHEMICAL ANA YSIS REPORT GA Accountis* Listed 3

Results reportee en 920616 3en Fe0M 5vA CDUNTING DV ~R ALL ANALYSIS PERCENT BAMPLE SAMPLE TYPE CUSTN ISDTOPE RESULT ERROR E1ROR SIZE MOIST DATE TIME'

• • Reported => 920616 SOIL UrQ643 U-234 183 2.20E+03 PCI/C 1.26E+01 2.012+02t25) 1.00E-01 0 920422 U-234 RESULT INCLUDES U-233. U-233 RESULT INCLUDES U-236 1

50!L UIC643 U-235 184 5.25E+01 PCI/O 2.44E+00 7.93E+008253 1.00E-01 0 920422 0-234 RESULT INCLUDES U-233. U-233 8tESULT INCLUDES U-236 SDIL UK0643 U-23BDA 185 S.97E+00 PCI/G 8.14E-01 1.17E+00(253 1.00E-01 0 920422 U-234 RESULT INCLUDES U-233. U-235 RESULT INCLUDES U-236 CDIL UIO643 U-234 183 2.39E+03 PCI/G

1. 48E+01 2. 66E42(2S 3 1.00E-01 0 920422 DUPLICATE SAMPLE ANALYSIS. U-234 INCLUDES U-233/U-233 INCLUDES U-236-SDIL-UXO643 U-233 184 1.14E+02 PCI/O 2.94E+00 1.09E+01125) 1.00E-01 0 920422 DUPLICATE SAMPLE ANALYSIS. U-234 INCLUDES U-233/u-235 INCLUDEB U-236 SDIL UXO643 U-23BDA 185 1.21E+01 PCI/O 9.62E-01 1.48E+00425) 1.00E-01 0 920422 DUPLICATE SAF'.PLE ANALYSIS.'U-234 INCLUDES U-233/U-233 INCLUDES U-236 6 Recores listed l

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SOIL SAMPLING PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT PAGE 14 OF 14 October 21,1993 ATTACHMENT 2: LOCATIONS OF BACKGROUND SOIL SAMPLES S AMPLE ID LOCATION AJ Collected on a hillside west of Building 39 and northwest of building 37, three feet from GNs fence.

G2 Collected about 1200 feet and about 7/8 of a mile southwest of Building 37.

AC Collected about one mile southeast of the main site and about two miles southeast of Building 37.

B KG-1 Collected about 1 mile from Building 37 at the Scripps Hospital Entrance, east of Genesse Avenue.

B KG-2 Collected about 1.2 miles from Building 37 at Sorrento Court Rd. by the Post Office entrance (North Side).

BKG-3 Collected about 1.5 miles from Building 37 at Sorrent'., Vista Parkway near Lusk Blvd. South.

B KG-4 Collected about 1 mile west from Building 37, west off Genesee corner of North Torrey Pines Road and Torrey Pines Scenic Drive BKG-5 Collected about 2 miles west of GA off of La Jolla Shores Drive.

B KG-6 Collected about 2 miles nodhwest of Building 37 on North Torrey Pines Road B KG-7 2 miles near V.A. Hospital on La Jolla Village Drive South West

,