ML20196H572

Final Radiological Survey Performed at General Atomics Bldg 36

ML20196H572
Person / Time
Site:	07000734
Issue date:	02/26/1999
From:	Gonzales L, Maschka P, Joseph Turner GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER
To:
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ML20196H524	List: ML20196H520 ML20196H529 ML20196H544 ML20196H558 ML20196H572
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NUDOCS 9907060384
Download: ML20196H572 (32)

Text

FINAL RADIOLOGICAL SURVEY PERFORMED AT GENERAL ATOMICS' BUILDING 36 Prepared By: John Turner, Paul Maschka, Laura Gonzales, Richard Stowell, Efraim Ramirez, Kevin Busby, Cornelius Stanley & Barbara Lyons.

February 26,1999 O D _. fS7 IS$$k Nob $$34 PDR B_

Table of Contents INTRODUCTION............................................................... 1 SITE DESCRIPTION............................................................ 1 PREVIOUS ACTIVITIES (HISTORY OF USE)....................................... 2 CRITERIA FOR RELEASE TO UNRESTRICTED USE................................ 2 Facilities and Equipment.................................................... 2 Enriched Uranium......................................................... 2 Exposure Rate Guideline.................................................... 2 INSTRUMENTATION.......................................................... 3 B ACKGROUND MEASUREMENTS............................................... 3 Background Measurements for Instruments / Detectors

............................3 Exposure Rate Background.................................................. 4 FINAL S URVEYS PERFORMED.................................................. 4 Objectives and Responsibilities.............................................. 4 Classification of A rea...................................................... 5 Final S urvey Plan......................................................... 5 SURVEY S UMMARY........................................................... 6 RESULTS OF THE FINAL SURVEYS.............................................. 6 Sc ann in g............................................................... 6 Fix ed Measurements....................................................... 6 Removable Contamination Surveys.......................................... 7 Exposure Rate Measurements................................................ 7 Soil / Concrete Samples.................................................... 7 C ON C LU S ION................................................................. 8 List of Tables Table 1:

USNRC's Acceptable Surface Contamination Levels......................... T-1 Table 2:

State of CA Acceptable Surface Contamination Levels........................ T-2 Table 3:

List of Instruments.................................................... T-3 Table 4:

Background Measurements (Obtained from Building 13)...................... T-5 Table 5:

Results of Final Surveys in Building 36.................................... T-6 11

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f l

List of Figures (unpaged)

Figure 1:

Plan View of General Atomics Site l

Figure 2:

Building 36 in Relation to Surrounding Facilities j

Figure 3:

Drawing of Building 36 Figure 4:

Building 36: Masslinn Survey Figure 5:

Floor & Walls: Alpha & Beta Scans & Expsure Rate Measurements Figure 6:

Floor & Walls: Fixed Alpha Measurement Locations Figure 7:

Floor & Walls: Fixed Beta Measurement Locations i

Figure 8:

Horizontal Overheads: Removable Contamination Locations Appendix

" Final Survey Plan for Building 36" dated August 18,1998.

i iii

4 '""""""' menses Building 36 Final Radiological Survey Repo t

}ntroduction General Atomics (GAi is continuing its efforts directed at decontaminating, as appropriate, and obtaining the release to unrestricted use of selected facilities at General Atomics. GA has completed the Final Radiological Survey of Building 36 located at GA's Sorrento Valley Site.

I l

GA is requesting both the Nuclear Regulatory Commission (NRC) and the State ofCalifornia for the P

release of Building 36 to unrestricted use.

This report documents the results of the radiological measurements completed inside Buildin and demonstrates that this area meets the approved criteria for release to unrestricted use. The tota surface area to be released to unrestricted use is ~ 2470 ft (~ 229 m ),

2 2

Site Description A plan view of the GA Site is shown in Figure 1. Building 36 and its location in relation to other facilities at GA's Sorrento Valley Site is shown in Figure 2. A drawing of Building 36 is shown in Figure 3.

Building 36 has external dimensions of~ 55 % ft x 44 % ft (~ 16.9m x 13.6m) and encompasses an 2

2 area of~ 2470 ft (~ 229 m ). The building is composed of a large open area and an office located on the southeast side.

The floor surface is composed of unpainted, reinforced concrete. The floor within the office is composed of reinforced concrete overlaid with linoleum tiles.

The exterior walls of the building are composed of corrugated (standard stock) sheet metal. All of the exterior walls are attached to a stmetural steel framework and adjoin the edge / footing of the concrete floor. There is a reinforced concrete, structural wall approximately 2 meters in height a the west wall that overlaps onto a portion of the north wall. There is one vertical panel of fiberg g

g inlayed within the south wall that allows light to enter. The large roll-up door and the two entry I

doors are composed of metal. The door to the office is composed of wood.

The roof consists of ribbed steel sheet decking. The ribbed steel sheets span supporting rafters and I-beams to which they are fastened.

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+10 CENNEAL AFCMBCs Building 36 Final Radiological Survey Report Previous Activities (History of Use)

Building 36 is currently being used for non-radioactive work. The building is being occupied by personnel and equipment involved with the Super Critical Water Oxidation Development Project (SCWO). In the past the building was used for various projects, but none of these projects were known to involve the use of radioactive material.

The only history of radioactive material being within the building occurred during 1987-1988 when a properly packaged fission chamber was temporarily stored on the ground floor as shown in Figure

3. The fission chamber was an integral component of an In-core Flux Monitoring Unit (IFMU) device that was to be installed in the Fort St. Vrain, Colorado Project.

The entire fission chamber device was approximately 20 feet long. The fission chamber was located at one end of the device and was 5.5 inches long and 0.41 inches in diameter. The fission chamber was a totally sealed canister with the highly enriched uranium inside. The box, in which the fission chamber device was stored, was approximately 20 feet long x 8 inches wide x 8 inches in height.

The exterior surface of this package was checked for contamination before being moved into the building and it was well below the release criteria. To our knowledge, the package was never opened while it was stored in Building 36.

Criteria for Release to Unrestricted Use Facilittpnd Equioment The U.f,. MRC's criterion for releasing facilities and equipment to unrestricted use is shown in Table 1. The State of California's guidelines, "DHS Criteria for Release of Facilities and Equipment to Unrestricted Use," also known as "DECON-1," is shown in Table 2.

Enriched Uranium The approved guideline values for residual contamination for release to unrestricted use for enriched uranium are provided as follows:

2 2

5,000 dpm/100 cm (averaged over a 1 m area) 15,000 dpm/100 cm (maximum in a 100 cm area if the average over 1 m is met) 2 2

2 1000 dpm/100 cm (removable activity) 2 Exoosure Rate Guidelint The guideline value for exposure rates measured at I m above the surface, is 10 R/hr above background levels.

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Samummuumynames Building 36 Final Radiological Survey Report g

Instrumentation A list ofinstruments used during the radiological surveys is shown in Table 3. The table includes:

(1) a description of the instrument, model number and its serial number, (2) a description of the detector (if applicable) and its serial number, (3) instrument ranges, (4) calibration duc dates, (5) typical background readings and (6) calibration efficiencies (if applicable). All of the instrumems I

used were calibrated semiannually and after repair, except for exposure rate meters which were calibrated quarterly.

I Background Measurements Background Measurements for Instruments / Detectors

~

Building 13 on GA's main site was used for conducting background measurements on instruments used for the final survey because: (1) there is no history involving radioactive materials or storage u

of radioactive materials in Building 13, and (2) the various surfaces found in Building 36 could also be found in Building 13.

For the fixed background measurements (shown in Table 4) the mean and standard deviation, for I

each surface surveyed with the 100 cm gas flow proportional detector, were calculated using 2

equations 8-11 and 8-12 from the draft version of NUREG/CR-5849' as shown below:

k=A[l.', xi Equation (8-11) n, I

I Equation (8-12) 31(A-#M n-1 Minimum detectable activities (MDA's) for each type of surface (see Table 4), were calculated using equation (5-2) from the NUREG/CR-5849 as follows:

I 3 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.

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4mmusummommer Building 36 Final Radiological Survey Report Equation (5-2) 2.71 +4.65/B,xt 2

MDA=

(dpm/100cm )

txEx 100 Where:

Ba = background rate (cpm) t = count time (min)

E = efTiciency 2

A = area of the detector (cm )

Exnosure Rate Background Typical exposure rate background for this site is about 15 R/hr measured at I m from the surface.

This value can be measured south of Building 15 (an office building on the non-impacted eastem portion of the GA site). Measurements taken offsite in 10 different locations over a period of a year also give an average of about 15 R/hr (measured 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 walls, and up to 28 R/hr inside concrete lined trenches or concrete lined pits (background measurements inside a concrete pit near Building 2 confirmed this).

Final Surveys Performed Obiectives and Resoonsibilities The objectives of the final survey plan were (1) to demonstrate that the average surface contamination level for each survey unit was below the approved release criteria, (2) to show that the maximum residual activity did not exceed three times the average value in an area up to 100 cm, (3) 2 that a reasonable effort was made to clean removable contamination and fixed contamination (if necessary) and (4) that the exposure rates in occupiable locations are less than 10 R/hr above background measured at I meter above the surface.

Surveys were taken only by qualified Health Physics Technicians having a minimum of three years Health Physics experience in accordance with approved Survey Plans. Samples (100 cm wipes) 2 were counted in GA's Health Physics Laboratory which maintains an effective QA program.

Every survey conducted was documented on a daily basis to a worksheet or drawing showing the approximate locations surveyed. The documentation included the results of the measurements 4 of 8 l

___m__

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.hmsumurm.arnemes Building 36 Final Radiological Survey Report l

(including units), the technician's signature, date, instrument (s) used (including the model and serial number of both the ratemeter and detector), calibration due date, % efficiency, background readings (if applicable) and any other pertinent information.

1g 5

Classification of Area Unagected Areat Building 36 was classified as an " unaffected" area due to the temporary storage of the fission chamber along the north wall of the building (see Figure 3).

Final Survey Plan A survey plan was developed based on the previous history of the building, the radionuclide(s) of concem, the various types of surfaces, the potential for contamination and the classification of the area (unaffected).

In Building 36, the alpha surveys were sufficient to determine compliance with the release criteria, although beta monitoring was also performed. Alpha measurements are satisfactory for the following reasons:

1.

In " highly" enriched uranium (uranium used in the fission chamber was typically ~ 90%

g enriched); alpha monitoring is the method of choice. At this enrichment, the U-234 activity J

present has increased significantly. The alpha to beta ratio is approximately 116:1.2 Because of this, alpha monitoring was the measurement of choice for enriched uranium.

2.

Alpha surveys are accurate if the surface is clean and free of dust and debris. All surfaces were cleaned before scanning or fixed measurements were performed.

.I The surveys included scanning of the floor and wall surfaces, large area masslinn smear surveys, collection and analyses (by gross alpha / beta counting) of 100 cm wipes, the taking of fixed 2

measurements and exposure rate measurements ( R/hr).

The surveys were completed in accordance with an approved written Final Survey Plan. A copy of the Survey Plan is provided in the Appendix to this report: " Final Survey Plan for Building 36" dated August 18,1998.

I I

2 From Table 54 of"IIcalth Physics Manual of Good Practices for Uranium Facilities" Prepared for DOE by Idaho National Engineethg Laboratory, docurnent EGG-2530, UC-41, dated June 1988.

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h SENBEREAFOREEN Building 36 Final Radiological Survey Report Survey Summary A summary of the number of fixed measurements, smears and exposure rate measurements (pR/hr) taken during the Final Survey is provided as follows:

Building 36 Final Survey Summary Survey

1. ofFixed

1. of Fixed

1. of Smears

1. of Exposure Rate Measurements Measurements Measurements a

p

( R/hr)

Final Survey 16 27 6

13 Results of the Final Surveys The results for the Final Surveys are provided in Tables 5 and locations are shown in Figures 3 through 8.

Scannine 2

Scans with a 434 cm alpha gas-flow proportional detector (floor monitor) were conducted in order to identify elevated areas of activity. Areas with elevated readings would then be further investigated with hand held a instmments/ detectors to determine if the levels were above the release criteria. No areas were discovered that disolaved elevated levels of a activity. The results of these scans are provided in Table 5 and the locations are shown in Figure 5.

2 Scans with a 434 cm beta gas-flow proportional detector (floor monitor) were also conducted in order to identify elevated areas of activity. Areas with elevated readings would then be further investigated with hand-held p instruments / detectors to determine if the levels were above the release criteria. No areas were discovered that disclaved elevated levels of B activity. The results of these scans are provided in Table 5 and the locations are shown in Figure 5.

Etud Measurements A total of 16 fixed alpha measurements were performed during the final survey in the unaffected areas (i.e., floors and walls). The final measurements were taken using a 50 cm alpha scintillator 2

ZnS(Ag) detector. The applicable background for the 50 cm alpha detector was subtracted from 2

the survey readings and these readings were converted from cpm to dpm/100 cm using the 2

appropriate count time, the efficiency of the detector and the geometry of the detector. The results are provided in Table 5 and their approximate locations are shown in Figure 6. All the fixed alpha 2

measurements were < 140 dpm/100 cm,

6cf8

4 -=" momers Building 36 Final Radiological Survey Report A total of 27 fixed beta measurements were performed during the final survey in the unaffected areas (i.e., floors and walls). The final measurements were taken using a 100 cm Eas-proportional beta 2

detector. The applicable background for the 100 cm beta detector was subtracted from the survey 2

readings and these readings were converted from cpm to dpm/100 cm using the appropriate count 2

time, the efficiency of the detector and the geometry of the detector. The results are provided in Table 5 and their approximate locations are shown in Figure 7. All the fixed beta measurements were less than the MDA for the respective surfaces surveyed (see Table 4 for MDA results in 2

dpm/100 cm for each surface surveyed).

Removable Contamination Surveys A total of 6 smears were taken during the final survey. These removable contamination smears were taken from horizontal overhead surfaces.

Smears consisted of using a Whatman Filter Paper (4.7 cm diameter) and wiping an area of~ 100 2

2 cm. The smears were counted in GA's Health Physics Laboratory using a Canberra 2404 low level alpha / beta counting system. The maximum smear results are provided in Table 5 and their approximate locations are shown in Figure 8. The maximum smear results were < 10 dpm/100 cm2 2

for a and 10 dpm/100 cm for p.

Masslinn surveys were also conducted on all floors by wiping the surfaces with masslinn cloths and measuring the activity on the masslinn cloths with a hand-held 15 cm GM pancake detector and a 2

2 hand-held 50 cm alpha detector. The masslinn survey results are provided in Table 5 and approximate locations are shown in Figure 4. All readings were less than or equal to natural background levels. No decontamination was required.

Exoosure Rate Measurements A total of 13 direct radiation exposure rate measurements were taken at various locations inside the building. The measurements were taken at ~1 meter above the surface using a microR meter. The exposure rate measurement results are provided in Table 5 and in Figure 5. Measurements taken throughout the building were all equal to 10 R/hr.

Soil / Concrete Samoles No sampling of the concrete or soil beneath the concrete was required in any areas of Building 36, since they were classified as " unaffected" and no radioactive contamination was detected on any of the floor surfaces or walls.

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4 '""""" msnmar Building 36 Final Radiological Survey Report Conclusion Final contamination and radiation surveys provided in this report for Building 36, demonstrate that the building meets the approved guidelines for release to unrestricted use.

+

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Table 1: USNRC'S ACCEPTABLE SURFACE CONTAMINATION LEVELS

. Nuclides*

AverageW MaximumW :

RemovablsW (dpm/100cm ) '

(dpm/100 cm )

(dpm/100cm )

8 2

r U-nat, 235U,23sU, & associated decay products 5,000 a 15,000 a 1,000 a Transuranics,226Ra,228Ra, 23*Th, 22:Th, 23 ipa, 100 300 20 227Ac,1251, i29; Th-nat, 232Th, "Sr, 223Ra, 224Ra, 232U, i261, 33,

1,000 3,000 200 I

13g Beta / gamma emitters (nuclides with decay modes other than alpha emission or 5,000 15,000 1,000 spontaneous fission) except "Sr and other noted above.

Where surface contamination by both alpha-and beta / gamma-emitting nuclides exists, the limits a

established for alpha-and beta / gamma-emitting nuclides should apply independently.

b As used in this table dpm (disintegrations per minute) means the rate of emission by radioactive material as determined by conecting the counts per minute observed by an appropriate detector for background, efficiency and geometric factors associated with the instmmentation.

Measurements of average contaminant should not be averaged over more than I square meter.

c For objects ofless surface area, the average should be derived for each such object.

d The maximum contamination level applies to an area of not more than 100 cm,

2 The amount of removable radioactive material per 100 cm of surface area should be determined e

2 by wiping that area with dry filter or soft absorbent paper, applying moderate pressure, and assessing the amount of radioactive material on the wipe with an appropriate instrument of known efficiency. When removable contamination on objects ofless surface area is determined, then pertinent levels should be reduced proportionally and the entire surface should be wiped, f

The average and maximum radiation levels associated with surface contamination resulting from beta-gamma emitters should not exceed 0.2 mrad /hr at I cm and 1.0 mrad /hr at I cm,

2 2

respectively, measured through not more than 7 milligrams per square centimeter of total absorber.

T-1

~

Table 2: STATE OF CA ACCEPTABLE SURFACE CONTAMINATION LEVELS 1 Nuclides" Average *

Maximum 'd' -

Removable ^'

b b

b 2

2 2

(dpm/100cm )

(dpm/100cm )

(dpm/100cm )

U-nat,235g,23sU, & associated decay products 5,000 15,000 1,000 Transuranics,226Ra, 22sRa, 230Th,22sTh,23:Pa, 100 300 20 227Ac,125y,1291 Th-nat, 232Th, "Sr, 223Ra, 224Ra, 232U,126,133,

1,000 3,000 200 1

I 131j Beta / gamma emitters (nuclides with decay modes other than alpha emission or 5,000 15,000 1,000 spontaneous fission) except "Sr and other f

noted above.

Where surface contamination by both alpha-and beta / gamma-emitting nuclides exists, the limits established for a

alpha-and beta / gamma-emitting nuclides should apply independently.

b As used in this table dpm (disintegrations per minute) means the rate of emission by radioactive material as determined by correcting the counts per minute observed by an appropriate detector for background, etliciency and geometric factors associated with the instmmentation.

Measurements of average contaminant should not be averaged over more than I square meter. For objects of c

less surface area, the average should be derived for each such object.

d The maximum contamination level applies to an area of not more than 100 cm,

2 The amount of removable radioactive material per 100 cm of surface area should be determined by wiping that 2

e area with dry filter or soft absorbent paper, applying moderate pressure, and assessing the amount of radioactive material on the wipe with an appropriate instm nent of known eff;ciency. When removable contamination on objects ofless surface area is determined, then pertinent levels should be reduced proportionally and the entire surface should be wiped.

f The average and maximum radiation levels associated with surface contamination resulting from beta-gamma emitters should not exceed 0.2 mrad /hr at I cm and 1.0 mrad /hr at I cm, respectively, measured through not 2

2 more than 7 milligrams per square centimeter of total absorber.

Guidelines For Decontamination of Facilities and Equipment Prior to Release for Unrestricted Use or Termination of Licenses for Byproduct, Source, or Special Nuclear Material, also known as "Decon-1" incorporated into GA's State of CA Radioactive Materials License.

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1 Tcble 4: Backgr und Me:surements'(Obtained frsm Building 13)

I Ludlum Model 2221 Ratemeter S/N 97817.With Model 43-37 Probe S/N 147965 Alpha Floor Monitor Background Scan Resultsi 434 cm Detector (Efficiency = 22.37%)

2

. Background Material-

' Alpha Scan' Range (cpm)

Concrete 6-26 Metal 2-16 Wood 4 16

. Ludlum Model 2221 Ratemeter s/n 84459 With.Model 43-37 Probe s/n 083293

- Beta Floor Monitor Background Scan Results: 434 cm Detector (EfHelency = 22.14%)

2 Background Material Beta / Gamma Scan Range (enm)

Concrete 1400-1570 I

Metal 816-1047 Wood 1061-1262 Ludlum Model 2221 Ratemeter s/n 86332 With Model 43-68 Probe s/n 142540 2

100 cm Beta Detector (Efficiency = 28.80%)

I Background Material Average of10 Measurements.

MDA 1 Minute each (cpm

• 20):

(dpm/100 cm )

2 Concrete 531 56 381 Metal 281 44 '

280 I

Drywall / Sheetrock 287 44 283 Linoleum over Concrete 324 40 300 Fiberglass 304

• 30 280

@ 29.89% Efficiency Ludlum Model 3 Ratemeter s/n 138880 With Model 44-9 Probe s/n 145936 ~

2 15 cm Beta Detector (Efficiency = 22.05%)

Background Material Beta / Gamma Scan Range (cpm)

I Concrete 100-140 Metal 80-100 Drywall / Sheetrock 60-100 I

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gp 777m Figure 1: Plan iew of General Atomics Site c

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l Figure 2: Building 36 in Relation to Surrounding Facilities

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Figure 4: Building 36: Masslinn Survey.

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2. a / p scans in cross hatched area.

3. Exposure Rate Measurements were taken. General area pR/hr results were 10 pR/hr.

Figure 6: Floor & Walls: Fixed cx Measurement Locations.

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2. The squares with cross hatches provided are the approximate locations of fixed a measurements taken.

3. All concrete floor surfaces unless noted. (M) = Matal-Wall (FG) = Fiberglass-Wall (C) = Concrete-Wall.

Figure 7: Floor & Walls: Fixed p Measurement Locations.

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2. The squares with cross hatches provided are the approximate locations of fixed p measurements taken.

l

3. All concrote floor surfaces. (SR) = Sheetrock-Wall (M) = Metal-Wall (FG) = Fiberglass-Wall (C) = Concrete-Wall.

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I Figure 8: Horizontal Overheads: Removable Contamination Locations.

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a4

Appendix to Final Radiological Survey Performed at General Atomics' Building 36 Unaffected Area dated February 26,1999 i

l l

" Final Survey Plan for Building 36" i

dated August 18,1998 4

1

~,

4sumsmm.aranmes INTERNAL CORRESPONDENCE W

From:

L. Gonza(s / J. Turner In Reply Refer To:

LQG:98:137 To:

Distribution Date:

August 18,1998 l

Subject:

Issuance of the Final Survey Plan for Building 36 I

The Final Survey Plan for Building 36 has been completed. The Plan was reviewed and discussed with the following HP Technicians: Dane McKay, Cornelius Stanley and Barbara Lyons.

g cc:

K. Asmussen l

F. Dahms P. Maschka

~

B. LaBonte D. Keesling D. McKay C. Stanley B. Lyons B. Noren 1

r L

--_a

(]

August 18,1998 Page 1 of 4

[

Date: August 18,1998 g

Prepared by: John Turner Approved:

Laura Gonzales im I[MMLO Date lE v

- y Final Survey Plan for Building 36 Purpose "Ihe purpose of this survey is to demonstrate that the radiological conditions in Building 36 satisfy the NRC and State of CA guidelines for release to unrestricted use, and to ensure that the radiological conditions are below the approved release criteria specifiod in GA's Site Decommissioning Plan. This final survey will encompass the internal surfaces of the building structure only.

Basksutnad Building 36 is currently being used for non-radioactive work. Presently it is being occupied by personnel and equipment involved in the " Super Critical Water Oxidation Development Project"(SCWO). In the past the building was used for various projects, but none of these projects were known to involve the usage of radioactive material. During the years 1987-1988 it was used for storage of a properly packaged (radioactive) fission chamber, but no residual radioactivity is expected to be encountered in this facility.

C'-

'"- =F = of B mine 36 (see Finure n

~)

"UnmKected Area" - Although Building 36 was used in the past to store radioactive material (i.e., fission chamber), it was properly packaged and stored only after surveys were conducted to demonstrate that contamination levels on the container's exterior were below the release criteria. Therefore, the building is classified as " unaffected"; no contamination is expected to be present.

Descrintion (see Finure for detailc)

The total" unaffected" floor space is ~ 225 m (-16.7m x ~13.5m). Presently this floor space is somewhat 2

restricted (inaccessible) due to the equipment contained in this area by the ongoing SCWO project.

Fia=I Surveys Reauired (oer GA's Site Decommissionine Plan)- see Table for d**=ile 1.

Gridding is not required.

2.

Scan 10% of the accessible floors and 10% of the accessible walls (below 2 meters in height). If readings > 75% of release limits are encountered, the area will be reclassified.

3.

Minimum number of total measurements (removable and fixed) is 30 (unit area < 1500 m ).

2 4.

Minimum number of exposure rate measurements (microR) is 1 per 10 m or 1 every ~ 3 meters 2

(floor area only).

BLD%SUY.WPD I

L l

lI

>)

August 18,1998 Page 2 of 4 l

Release Limits (per GA Site Decommissinnin Plan for Unaffected Areas)

Facility Structure Criteria I

The primary contaminant of concern for this site is enriched uranium. The applicable guidelines for residual contamination on building surfaces for enriched uranium are:

Enriched Uranium 2

2 5,000 dpm W100cm, total, averaged over a 1 m area 15,000 dpm d100cm, total, maximum in a 100 cm area 2

2 1,000 dpm d100cm, removable activity 2

In Building 36, the alpha surveys are sufficient to determine compliance with the release criteria, eithough l

I some beta monitoring will also be performed. Alpha measurements are satisfactory for the following reasons:

I In " highly" enriched uranium (uranium used in the fission chamber was typically ~ 90% enriched);

1.

alpha monitoring is the method of choice. At this enrichment, the U-234 activity present has increased significantly. The alpha to beta ratio is approximately 116:1.' Because of this, alpha l

monitoring is the measurement of choice for enriched uranium, c

2.

Alpha surveys are accurate if the surface is clean, free of paint or other coverings and free ofdust and debris. All surfaces will be clean before scanning or fixed measurements are performed.

)

3.

It is GA's goal to decontaminate the building structure to levels < 2000 dpm d100cm,2 Alpha Alert Levels I

i. de following " alert levels" are exceeded, notify IIP Management so an evaluation can be performed to determine ifincreased survey coverage is required or to evaluate if decontamination is required.

2

> 200 cpm alpha using the large area (434 cm ) probe I

2

> 150 cpm using a hand-held alpha probe (~ 1500 dpm/100cm )

Beta Alert Levels If the following " alert levels" are exceeded, notify HP Management so an evaluation can be performed to determine ifincreased survey coverage is required or to evaluate if decontamination is required.

2

> ~ 300 cpm beta above backcround using the large area (434 cm ) probe 2

> ~ 200 cpm above backcround using the 100 cm probe i

I

' From Table 5-4 of" Health Physics Manual of Good Practices for Uranium Facilities" Prepared for DOE by Idaho National Engineering Laboratory, document EGG-2530, UC-41, dated June 1988.

i

)

stausuvxro

+

August 18,1998 Page 3 of 4 Exposure Rate Level ne guideline value for exposure rates measured at I m above the surface is 10 pR/hr above background.

Exposure Rate Alert Background is typically ~15 pR/hr (but may vary with type of facility & location). Alert Level is 20 pR/hr, Documentation Every radiological survey conducted must be documented on a daily basis to a worksheet/ log book and on a drawing showing the appropriate locations surveyed. The documentation must include the resu!ts of the measurements (including units), the technician's printed name and signature, date, instrument (s) used (including the model and serial number of both the ratemeter and % detector), calibration due date, %

efficiency, background readings (if applicable) and any other pertinent information.

I BLDMSUV.WPD l

8 q

Planned Final Surveys for Building 36 - August 18,1998 Type of Survey

""'I I

I '"

Masslin Surveys Yes Concrete Floor N(Scan w/ 434 cm probe) 10% a,10% p (2) 2 P

Lower Walls Scan (bottom 2 m) 10% a,10% p 8

(Scan w/434 cm probes) 1 Walls Scan (above 2 m)

Not Required i

Number of Planned 30 Total as follows Measurements WW Alpha fixed on Floor 8

Beta fixed on Floor 4

I Alpha fixed on Walls 8 (2/ wall)

Beta fixed on Walls 4 (1/ wall)

Removable (wipe) 6 (overheads) pR/hr Readings I every ~ 3 m

@ l m from surface Floor Surface Concrete I

Clean all surfaces to remove debris or dirt (wash, mop and/or vacuum, as needed).

m m

If contamination above background is detected on any of the floor surfaces, IIealth Physics will evaluate the need for additional survey coverage. Survey coverage will be increased if contamination levels above 75% are detected (the Site Plan requires reclassification if levels >75%

are detected).

m For the fixed measurements:

For a measurements; use the hand held alpha counter (~5-10 second count). Document all readings in epm.

For p measurements; take a 1 minute count using the 100 cm gas flow proportional 2

detector (beta) with the Model 2221 ratemeter. Document all readings (md mark on a j

drawing where the readings were taken.

Take fixed measurements on wall ~1 meter from floor surface.

]

[

Fixed measurements should be taken as evenly distributed in the room as possible

=

l (accessible locations).

M 2

'l For removable measurements, take a 100 cm wipe at select locations; count using a low level olp l

counter.

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