ML20154D645

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Radiological Survey Rept for Release of Torrey Pines West Land Area to Unrestricted Use
ML20154D645
Person / Time
Site: 07000734
Issue date: 09/30/1998
From: Gonzales L, Joseph Turner
GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER
To:
Shared Package
ML20154D618 List:
References
NUDOCS 9810070283
Download: ML20154D645 (12)
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{{#Wiki_filter:.. + - - - Radiological Survey Report for the Release of "Torrey Pines West" Land Area to Unrestricted Use Prepared By: John Turner and Laura Gonzales Septemher 30,1998 pbk 00!! h obb734 C PDR s

TABLE OF CONTENTS i Page INTRODUCTION ..............................................................I S ITE DES CRI PTI ON............................................................ 1 CRITERIA FOR RELEASE TO UNRESTRICTED USE................................ 1 Exposure Rate Guideline.................................................. 1 Soil Criteria .............................................................1 PREVIOUS ACTIVITIES (HISTORY OF USE)....................................... 2 INSTRUMENTATION .........................................................2 B ACKGROUND MEASUREMENTS............................................... 3 Background Soil Concentrations............................................. 3 Exposure Rate Measurements ...............................................3 GM (beta / gamma) Surveying................................................ 3 SURVEY PLAN AND PROCEDURES.............................................. 3 S urv ey P l a n.............................................................. 3 Soil Sam pling............................................................ 3 Exposure Rate Surveys..................................................... 4 GM (beta / gamma) Surveying................................................ 4 RES ULTS O F S U RVEYS......................................................... 4 S oil S am plin g............................................................ 4 Exposure Rate Measuruments................................................ 4 GM (beta / gamma) Surveying................................................ 4 CONCLUSION................................................................4 TABLES - Table 1: Torrey Pines West Site Soil Sample Results.............................. 5 Table 7: Background Soil Sample Results....................................... 6 Table 3: Exposure Rate Measurements - Torrey Pines West ........................7 FIGURES (unpaged) Figure 1: General Atomics Site t Figure 2: GA's Main Site Figure 3: Torrey Pines West Site and Soil Sample Locations i l 11 t I

INTRODUCTION General Atomics (GA) is continuing its efTorts directed at decontaminating, as appropriate, and obtaining the release to unrestricted use of selected facilities and land areas at General Atomics. One small land area, identified as "Torrey Pines West" is located near GA's Building 30/31 complex. GA has recently conducted an exposure rate survey and implemented a soil sampling plan of the "Torrey Pines West" land area to ensure that residual contamination was not present in this land area. This area was categorized as a "non-impacted" area. A "non-impacted area" is an area which has never been used for work involving radioactive materials or for storage of radioactive materials. Therefore, only a limited amoun' of surveying and sampling was required to demonstrate that this area meets the criteria for release to unrestricted use. GA obtained exposure rate measurements and collected and analyzed soil samples by gamma spectroscopy to demonstrate compliance with the release criteria. No radiological contamination was detected. This report summarizes those surveys and demonstrates that the radiation levels and soil concentrations are well below GA's approved release criteria for unrestricted use. SITE DESCRIPTIQM A plan view of the GA site is shown in Figure 1. The location of the "Torrey Pines West" land area in relation to other facilities on GA's main site is shown in Figure 2. The "Torrey Pines West" land area is shmvn in Figure 3. The total land area is approximately 1.85 acres (80,591 ft2), CRITERIA FOR RELEASE TO UNRESTRICTED USE Exoosure Rate Guideline The guideline value for exposure rates measured at I m above the surface, is 10 R/hr above background levels. Soil Criteria The predominant radionuclides found in soil at GA and the soil release criteria in pCi/g is provided below. Cs-137 15 pCi/g Co-60 8 pCi/g Thorium (Th-228 + Th-232) 10 pCi/g Enriched Uranium (U-234 + U-235) 30 pCi/g Depleted Uranium 35 pCi/g I i

if more than one radionuclide exists, the sum of the fractions of the concentrations is calculated a follows: C E L, n.n C, The average soil concentration of radionuclide i. = The maximum soil limit for f(pCi/g). L, = The sum of the fractions must be less than one in order for the soil to meet the release criteria. PREVIOUS ACTIVITIES (HISTORY OF USE) The "Torrey Pines West" acreage is a small land area which was categorized as a "non-impacted" area because it had never been used for work involving radioactive materials or for storage of radioactive mate:ials. The land area includes a small storage yard (" lower storage yard") which have never been used for storage of radioactive material. Equipment in this storage yard was checked for radioactivity and nothing above normal background levels wa; identified. INSTRUMENTATION The instrument used for conducting exposure rate measurements was a Model 19 microR meter manufactu.ed by Ludlum Measurements, Inc. The microR meter used (S/N 87120) contains a 1" x 1" Nal(TI) scintillation detector mounted internally with five ranges that provide readings from 0-5000 pR/hr. The calibration due date was 08/19/98 for the instrument used to conduc+. exposure rate measurements in the "Torrey Pines West" area. The asphalt surface was surveyed with a GM meter / probe prior to removal and subsequent soil sampling at one location (TPW-10). The instrument used to survey the asphalt surface was a Ludlum Model 3 (S/N 99410) with four ranges that provide readings from 0-100,000 cpm. The corresponding detector used with this instrument was a Ludlum Model 44-9, beta / gamma probe (S/N 117842). The 2 detector has an active probe area of 15 cm. The calibration due date was 10/12/93 for the instrument / detector used in this survey and its efficiency was 21.25%. Soil samples were counted on a gamma spectroscopy MCA system using a high purity germanium detector manufactured by Canberra Industries, Inc. located in GA's Health Physics Laboratory. The lower sensitivity depends on the counting time and the type of sample counted. The system is 2

calibrated using NIST traceable standards and performance checked daily. BACKGROUND MEASUREMENTS Background Soil Concentrations Natural background concentrations measured by gamma spectroscopy in soil near the GA site have been established (at the 95% confidence level) and are provioed in Table 2. The locations from which these samples were taken are also provided in Table 2. Soil samp!es were counted for a minimum of 30 minutes each. A 30 minute count is sufficient to detect the radionuclides ofinterest (Cs-137, Co-60, U-235, U-238 and thorium daughters) at levels well below GA's approved soil release criteria. Exposure Rate Background Typical exposure rate background for this site is about 15 pR/hr at I m from the surface; measured south of Building 15 (an office building). Measurements taken offsite in 10 different locations over a period of a year also give an average of about 15 pR/hr (at I m from the surface). Normal background exposure rates increase to about 22 R/hr at I m from the surface in small rooms with concrete floors and.vah. GM (beta / gamma) Surveying The typical background range for an asphalt surface is 40-;20 epm. SURVEY PLAN AND PROCEDURES Survey Plan Since the "Torrey Pines West" area was "non-impacted"(i.e., an area which has never been used for work involving radioactive materials or for storage of radioactive materials), only a limited amount of surveying and sampling was performed. A total of ten (10) locations were selected for soil sampling and exposure rate measurements. The locations selected took into consideration the p,roximity of the area to GA's site property boundary, potential drainage from other sites, availability of soil and accessibility. l Spil Samnling Ten " surface" soil samples were collected from 10 individual locations each with a sample size of approximately I kilogram. These shallow samples were collected to a depth of 15 cm (0-6") using manual equipment (i.e., long handled spade). Nine samples were collected from the surface of the i 3 1 I

_ _. _ ~ 9 soil (TPW-1 through TPW-9) and one of the samples (TPW-10) was obtained beneath a layer of asphalt as shown in Figure 3. These samples were properly logged, labeled, packaged and tracked. All debris (i.e., grass, rocks, sticks, asphalt and foreign objects) were removed from each sample. Samples were dried, weighed and counted in the GA Health Physics Counting Laboratory by gamma spectroscopy. Exoosure Rate Surveys i xposure rate measurements (in R/hr) were taken at the surface and at I meter from the surface at each of the ten (10) sampling locations. GM (beta /gammal Surveying Soil sample TPW-10 was obtained beneath an asphalted surface. The asphalt surface was surveyed with a GM counter prior to its removal and subsequent soil sampling underneath the asphalt. RESULTS OF THE SURVEYS Soil Samoling j The results are reported in Table 1 in pCi/g for each radionuclide ofinterest. The results indicate that values are r it or near background levels and well below the soil release criteria. Exoosure Rate Survey Exposure rate measurements were all less than 10 R/hr above background at 1 m from the surface (background = ~15 R/hr). See Table 3 for results of each measurement. GM (beta /gammal Surysy2DE The asphalt surface surveyed with a GM counter read < 120 cpm (typical background levels for this type of surface area range from 120 cpm). (. CONC,LUSION Exposure rate surveys and soil sample results provided in this report, demonstrate that the land, designated as "Torrey Pines West", meet the NRC-and State-approved r;uidelines for release to unrestricted use. ~ 4

.. ~ 4 .......L4', >..-{- ~,W' Table 1. - - Gamana Spectroscopy Results of Soil Saunples Collected frons"the Tvrey Pines West M,, - 1 3.-- ? :. s e ] ,...,.u .T 1 (N Fiannaw 1 &in A-- -tm el -- - i - b - 1* nano N t .s c ~ : E

w;

^ 2)*U; 723g

2jzegg 7 2 22s Rai Total Thorium *

4"' Cst ~' "Co:s 92.77 ke' pert ? -186 (144) kev peaki . ' Averageof. I (228n) 7. imgg+2 nth) [ 661.6 kev peak kAverage of}. V 1173/1332 kev peaks 3 Sab5hbIN-: ^

583/238 kev peaks s.

-- Ansage of ; V;- .~ - unmii 1.v h ~ w ~ ' ~ ~ l ? Ra6enacude Concentadok (pCVg)J '.:;Notei Backgromed am sakrected - Resakski$i i TPW t - 1.93 0.65 0.15

  • 0.06 0.59 0.10 0.81
  • 032 1.40 ND ND

[ i r TPW 2 1.81

  • 0.58 0.20
  • 0.06 0.85
  • 0.10 1.29* 032 2.14 0.07 0.06 ND TPW 3 2.16
  • 0.61 0.13
  • 0.05 0.66 0.10 134
  • 0.27 2.00 ND ND

[ TPW 4 1.92 0.59 (0.22 0.23) 0.65

  • 0.14 1.20 + 037

.1.85 ND ND L TPW 5 2.05

  • 0.61 0.20
  • 0.08 0.92
  • 0.13 1.54 033 2.46 ND ND i

1 TPW 6 2.60

  • 0.76 0.18
  • 0.06 0.89
  • 0.10 133*032 2.22 ND ND i

TPW 7

  • 2.83
  • 036 0.22
  • 0.05 130* 0.07 2.07 0.19 337 0.11
  • 0.04 ND

~ TPW 8 1.77 0.61 0.13

  • 0.07 0.78
  • 0.10 1.13 030 1.91 ND ND TPW 9 1.84 0.64 0.17 0.07 0.82
  • 0.10 134
  • 034 2.16 0.12
  • 0.07 ND

[ t l TPW IO 0.92 + 038 0.07

  • 0.05 0.40 0.08 0.76 0.20 1.I6 ND ND l
  • Sample counted for 2 hours. All other samples counted for 30 minutes.

[ i i f 5 l 1 t i i m ..m m

Table 2i Typical Ba'ckground Radionuclide Concentrations (pCi/g) in Soil '

i E Sample : Cs-137 .Th.228 Ra-228 . Total. U-238 ' U-235 a go Dh-232). -Thorium Th 228 + - Th-232 AJ ND 1.28 :0.07 1.47

  • 0.14 2.75 1.98
  • 0.31 0.15
  • 0.03 G2 0.12 0.03 0.92
  • 0.07 1.01
0. I 2 1.93 1.86
  • 0.29 0.12 0.02 AC ND 1.29
  • 0.07 1.34 0.14 2.63 2.27 0.27 0.20
  • 0.03 BKG-1 ND 1.40
  • 0.16 1.44 0.28 2.84 2.06 0.43 0.19
  • 0.06 BKG-2 ND 1.54
  • 0.15 1.57 0.27 3.11 2.30
  • 0.45 0.17 0.05 BKG-3 ND 1.40
  • 0.14 1.62 t 0.26 3 02 ND 0.19 0.05 BKG-4 ND 0.67 0.09 0.84 0.17 1.51 1.15
  • 0.37 0.09 0.04 BKG-5 ND 1.51
  • 0.16 1.79 0.31 3.30 2.77 i 0.67 0.12
  • 0.06 BKG-6 ND 0.68 0.09 0.76
  • 0.16 1.44 ND 0.08
  • 0.03 BKG1 ND 1.17
  • 0.12 1.28 t 0.22 2.45 1.83
  • 0.43 0.11 0.04 Mean
  • 2 o 1.19 A 0.64 1.31
  • 0.68 2.5
  • 1.32 2.03
  • 0.93 0.14 0.09 Samples gamma scanned for I hour.

2 ND= < 0.1 pCi/g for Cs-137, < l.0 pCi/g for U-238 8 Samples collected in June and August 1993, typically about 1-2 miles from the Building 37 site at the following locations: AJ Collected on a hillside west of Building 39 & northwest of building 37, ~3' from GA's fence. l G2 Collected about 1200 feet wea of Bldg 1 (near T.P. RD.), and ~7/8 of a mile southwest of Building 37. AC Collected 1. bout I mile southeast of the main site & aboat 2 miles southeast of Building 37. BKG.1 Collected about I mile from Building 37 at the Scripps llospital Entrance, east of Genesse Ave. BKG-2 Collected about 1.2 miles from Building 37 at Sorrento Court Rd. by North ctrance tc Post Office. BKG 3 Collected about 1.5 miles from Building 37 r.t Sorrento Vista Parkway near Lusk Blvd. South. BKG-4 Collected about I mile west from Building 37, west off Genesee corner of North Torrey Pines Road l and Torrey Pines Scenic Drive BKG 5 Collected about 2 miles west of GA off of La Jolla Shores Drive. BKG-6 Collected about 2 miles northwest of Building 37 on North Torrey Pines Road BKG-7 Collected about 2 miles near V.A. Ilospital on La Jolla Village Drive (soutt. west) a 6 l i

Table 3: . Exposure Rate Measurements - Torrey Pines WM - .g ! LOCAT10NE pR/hr ; on surface ' at I m - TPW-1 13 12 TPW-2 15 14 TPW-3 15 14 TPW-4 12 11 TPW-5 15 14 TPW-6 15 14 TPW-7 17 15 TPW-8 14 13 TPW-9 14 13 TPW-10 14

13 Background

15 Survey completed July 30,1998 using a Ludlum Measurements Model 19 microR meter # 87120, calibration due date August 19,1998. 7

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