ML20004C024
| ML20004C024 | |
| Person / Time | |
|---|---|
| Site: | 07001623 |
| Issue date: | 05/14/1981 |
| From: | Book H, Pang J, Perez G, Thomas R, Zurakowski P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20004C023 | List: |
| References | |
| ETIN-810514, NUDOCS 8106010439 | |
| Download: ML20004C024 (1) | |
Text
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O U. S. ?!UCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGIO!i V Report No. 81-02 License No. SMii-1471 Priority 4 Category H License No. 04-00650-07 Priority 3 Category FIA Licensee:
Regents of the University of California Berkeley, California 94720 Facility Name: Camp Parks, California Inspection at: Building 305 Inspection Conducted: March 11-13 and April 16, 1981
[ ~
M edowu[O I/ b il Inspectors:
P. R. Zu a.kowsk1 a Radia ion Specialist Date Signe'd g
B c-t 71LM If,19f(
H.
E.' Book, Inspector Date gned '
- 7. M k awn, m tt J. F. Pang,Jadiation Specialist Date Signed b [A)
A1n lL,\\%I w-G. P. Perez, Engineering Aid (Co-Op)
Date Signed Approved by:
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) T. 4 0, / 3, / k /
R. D. Thomas, Chief Date S4gned l
Mater al Radi ogical Protection Section
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II% )I k Approved by:
CHM H. E. Book, Chief Date W gned Radiological Safety Branch Summary:
i l
Inspection conducted on March 11-13 and April 16, 1981, Report No. 81-02 l
This report details the third attempt to complete the confimatory radiological survey of the decontamination of Building 305 at Camp Parks. Details of the previous surveys are contained in Inspection Reports 80-1 and 81-1.
Pursuant to a letter dated February 26, 1981 from Mr. Andris Peterson, Radiaticn Safety Officer, University of California-Berkeley, on March 11 and 13,1981, two Region V inspectors and one Engineering Aid returned to Camp Parks to complete the confirmatory survey. 36 inspector hours on site was used in this effort.
On April 16, 1981, two Region V inspectors returned to Camp Parks to followup on the decontamination of an area containing contaminated soil (Details -
paragraphG-4).
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8106010439
Suamary (cont.) Results: As a result of the surveys which involved both alpha and beta-gamma survey instruments, it was determined that the contamination levels within the interior of Building 305, Camp Parks, was within the NRC guidelines for the release of the building for unrestricted use.
Two sump well water samples were collected from the plutonium spiked growth experimental area and sent to the DOE-Radiological and Environmental Sciences Laboratory (RESL) in Idaho for analyses. The results did not indicate any significant alpha contamination (E-11suci/ml, Pu-239).
(Details in paragraphs F-1 and G-2).
Four soil samples which were removed from an area of strontium-90 contamination under Building 305 were also analyzed by the DOE-RESL. The results indicated soil contamination levels ranging from E-5 to E-7 pei/gm (strontium-90) (Details in paragraphs F-2 and G-3).
Subsequent to the decontamination of the soil area by the licensee, a resurvey of the area on April 16, 1981, by NRC inspectors, indicated no detectable activity.
(Detailsinparagraph G-4).
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DETAILS A.
Persons Contacted 1.
Mr. Andris Peterson, University of California, Berkeley, Radiation Safety Officer 2.
Mr. Joseph B. Mackey, Department of the Army, Camp Parks, Facilities Logistics Service Manager 3.
Mr. Michael Schoonover, Health Physicist, University of California, Berkeley B.
Background
On October 13, 1980, the licensee requested NRC to terminate License SUM-1471.
They reported that all special nuclear material had been transferred to the Lawrence Livermore National Laboratory and that all radiation measurements taken at Camp Parks were at background levels.
It should be noted that materials under NRC License 04-00650-07 had also been used at Camp Parks. The Department of the Army requested the NRC to verify that Camp Parks is clear of all radiological contaminants (letter dated August 15,1980).
Two Region V inspectors conducted a radiological confirmatory survey of Building 305 at Camp Parks on November 13, 1980. That survey is documented in Report 80-01 to the Regents of the University of California.
Based upon the results of the November 13, 1980 survey, it was detemined that additional decontamination would be required in some areas on the interior of Building 305.
For all surveys the criteria were based on the NRC requirements established by the " Guideline for Decontamination of Facilities and Equipment prior to Release for Unrestricted Use or Termination of Licenses for Byproduct, Source, or Special Nuclear Material, November 1976."
On February 2, 1981, two Region V inspectors, expending 10 inspector i
hours, continued the radiological confirmatory survey of Building 305.
It was again determined that additional decontamination would be required in some areas on the interior of Building 305.
(See Report No. 81-01).
On March 11 and 13,1J1 two Region V Inspectors and one Engineering Aid expending 36 inspector hours, continued the confirmatory survey.
The survey which attempted 100% coverage of all floor areas, reachable wall areas and accessible cabinet areas in radiation work places, indicated that the contamination levels within the interior of Building 305 were below release limit guidelines.
However, the building could not be released for unrestricted use until results from the water and soil sample survey were received from The Department of Energy Radiological l
and Environmental Sciences Laboratory.
(These results are summarized in paragraphs F-2 and F-3).
. C.
Field Radiation Detection Instruments The field radiation detection instruments selected to perform this survey were:
1.
Eberline E-520, Serial #1462 due for recalibration en 4/7/81.
2.
Eberline E-520, Serial #1943 due for recalibration on 4/7/81.
3.
Eberline E-520, Serial #1939 due for recalibration on 4/7/81.
4.
Alpha air proportional count rate meter NRC #000375 due for recalibration on 4/7/81.
5.
Alpha air proportional count rate meter NRC #502839 due for recalibration on 4/7/81.
Note: Because it was estaglished during previous surveys that the contamination was of small areas ( 15 cm ) and fixed, wipes for removable contamination with subsequent analysis with Region V's NMC Gas Proportional Counter was not necessary.
D.
Acceotable Contamination Release Levels The acceptable contamination levels established by the guideline for strontium-90 in the absence of more hazardous radionuclides are summarized in Table I.
TABLE I ACCEPTABLE LEVELS Averace Maximum Removable 2
2 2
Contamination 1000 dpm/100 cm 3000 dpm/100 cm 200 dpm/100 cm 2
In order to establish release levels (dpa/100 cm ) in terms of counts p(er minute recorded on the survey meper, certain assumptions were made:
1)thedetectorfacecontainslgcm area; (2) contamination spread over ap area greater than 100 cm will be considereg as averaged over 100 cm withanacceptancelevelofIg00dpm/100cm;(3) contamination contained in an area less than 100 cm oraspotlessthan15cmjwill be considered at the maximum acceptance level of 3000 dpm/100 cm ; (4) the contamination has been determined to be fixed and not removable by wipes; and (5) the E-520 and associated HP-260 pancake probe used during this survey has an established 20% efficiency for strontium-90.
Based upon the aboye assumptions, it is possible to detemine release levels (dpp/100 cm ) in terms of an instrument reading (CPM).
If 1000 dpm/100 cm 21s considered as the releasable level for an area grecter than 100 cm, then the instrument reading is determined to be, 10
= 6.7 (1) 5 cm 2
1000 dom 100 cm x.20 = 29.9 net cpm (30.0 nepm rounded)
(2)
(3) Therefgre: 30 nepm on the instrument is equivalent to a 1000 dpm/
100 cm release level.
. 2 If 3000 dpm/100 cm is cgnsidered as the maximum r3{easable level for an area less than 100 cm or a spot less than 15 cm, tgen an assumption is made that all the activity is contained in the 15 cm area of the detector face; therefore, the instrument reading is detennined to be, 3000 dpm x 0.20 = 600 net cpn (1)
The ingtrument reading of 600 net cpm is equivalent to the 3000 dpm/
100 cm (maximum) as stated in TABLE I.
The releasable level for removab}e contamination is to be determined from a wipe of an area of 100 cm. The wipe is counted in a laboratory gas proportional counter. The present counter is a NMC Gas Proportional Counter, Model No. PC-55, which has an efficiency of 71.0% as established by a strontium-90 standard.
The net cpm of the wipe, when corrected for counter efficiency can not exceed 200 dpm.
E.
Padiation Survey Method A 100% survey was attempted of the entire south wing of Building 305 and the growth chamber area by the two NRC Inspectors and the Engineering Aide. This included the entire floor area, all reachable wall areas and all accessible cabinet areas.
Because it was determined by prior surveys that the main contaminant was Sr-90, the E-520 with an HP-260 pancake probe was used by each inspector.
Because experimentation with plutonium was known not to have occurred in the South Wing of Building 305, a 100% survey was not attempted with alpha air proportional count rate meters. A modification of a statistical survey method devised by T. N. Throckmorton, PhD (a statistician for the State of California) was used.
In short, Dr. Throckmorton's method states that if one carefully surveygseveraldozenonesquarefootareasselectedatrandominevery 100 ft of area and finds nothing, then one can be assured at a 90%
confidence level that no significant contamination exists in the entire area of interest. A statement from one of Dr. Throckmorton's publications is included below, "It is assumed that the distribution of hotspots over the surface area is represented by the Poisson distribution. That is, if 4 is the average number of hotspats per unit area, then the probability of finding exactly l
x hotspots in an area of n units is given by P(x)=e-n0(n0)*/x'.
(1)
This distribution is derived from an assumption that any hotspots are randomly and independently distributed over the surface; that is, they l
do not tend to fall in clusters. This assumption would not be appropriate prior to cleanup operations.
However, it seems probable that more extensive cleanup efforts would be conducted in the " dirty" areas and, hence, that those particles remaining are likely to be scattered in a more randon manner. A limited discussion on the possible effect of clustering is given later in the report.
(The effect of clustering is not included in this report.
It was part of Dr. Throckmorton's original paper).
\\
The desired 90% confidence level requires that there be no more than a 10% chance of deciding gn area is clean when it has an overall average of 0 =.1 hotspots/100 ft. The smallest possible sample size which affords this protection is based on a decision rule which accepts the area if and only if no hotspots occur in the sample.
If sections are each 100 square feet, it is easily established fron equation (1) that a minimum sample size of n = 23 sections is necessary."
We modified Dr. Throckmorton's tethod somewhat by taking our sample areas in places where contamination would be more likely to be found (onworkbenches,nearsinks,nearbaseboards,nearventsetc.).
- However, at least 25% of the sample areas were taken completely at random.
Using this method, no alpha contamination was found anywhere in the building (including the North Wing which was used only for office, storage and machine shop space. This survey method was also used in the North Wing in checking for Sr-90 contamination with the E-520 is fitted with HP-260 probes.
F.
Vater and Soil Sampling Method 1.
The sump wells at each end of the concrete pad were found to be covered with wooden planks and almost completely filled with water.
There appeared to be algae and perhaps other solids suspended in the water.
Prior to taking the one liter samples, the water was stirred vigorously for several minutes to have a mixed sample.
A one liter sample was taken from each well and mailed to DOE's Radiological and Environmental Sciences Laboratory.
2.
Soil samples were taken where it appeared that contamination had leaked through the floor.
The flooring had previously been cut away during decontamination efforts. The two sites selected were underneath the south growth chamber and Room 14 where a drain pipe had penetrated the floor. The drain pipe was fomerly used to transport contaminated water to an outside storage tank which was removed many years ago.
The soil was scooped up with a hoe into a one quart ice cream carton after first scraping away the top layer of saw dust. The cartons were approximately half full. Three samples were taken from the growth chamber area and one from underneath Room 14.
All samples were sent to the DOE-RESL.
u.
Survey Results 1.
The results of the instrument survey are summarized in Table II.
Because the entire building was surveyed on March 11, 1981 by the NRC Inspectors and only 5 spots above the releasable limit were found, the licensee was given the opportunity to decontaminate these spots. A resurvey of the 5 spots on March 13, 1981 indicated that the areas were within the release limits.
. TABLE II March 11, 1981 March 13, 1981
_1st Floor (South Wing)
Survey Survey Room 8
Background
Room 9 Room 10 koom 11 Room 12 Room 13 3 spots 200-1900 cpm
Background
Janitor's Room
Background
Men's Room & Shower Room 14 i spot 1900 cpm
Background
Growth Chamber Room 3 spots 200-900 com Prep Room 4 sinks 200-900 cpm contaminated Prep Room floor 1 spot 300 cpm 2nd Floor (South Wing)
All areas are Background 1st & 2nd Floor (North Wing)_
All areas are Background 2.
The results of water sampling for plutonium are summarized in Table III.
TABLE III NC)
Samole Description Ouantity (ml)_ Results (uci/ml)
A Souti sump well water sample 500 2 + 2 E - 11 B
North sump well water sample 500 6][2E-11 3.
The results of the soil sampling for Strontium-90 are sunmarized l
in Table IV.
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6-i TABLE IV NC)
Samole Description Quantity (g)
Results (uci/g) 1.
Soil sample taken under 10 6.1 + 0.5 E-7 growth chamber 2.
10 3.7 + 0.4 E-7 3.
10 9.9 7 0.6 E-7 4.
Soil sample taken under 10 1.107 0.05 E-5 former drain pipe - Room 14 4.
Resurvey of Contaminated Soil Underneath Building 305 As can be seen from Table IV, soil samples taken underneath the growth chamber room and Room 14 showed slight contamination by Sr-90. On April 16, 1981 H. E. Book and P. R. Zurakowski returned to the building to examine the soil contamination in more detail.
It was found that the contamination was very superficial with penetration into the soil only an inch or so. The contamination under Room 14 was also quite limited in area of only a few hundred square centimeters.
The maximum contanination detected was 1000 cpm. A licensee representative who was present at the time was given the opportunity to scrape up the contaminated soil and place it in 5 gallon cans. A resurvey with a Technical Associates PUG-1AB fitted with a P-11 (due for recalibration on 7/13/81) pancake probe showed no significant contamination above background.
Because of the above considerations and the slight extent of the contamination it was determined that resubmittal of confirmatory soil samples to DOE's RESL was unnecessary.
H.
Conclusions and Recommendations In reviewing the results of the surveys it can be seen that:
1.
No alpha ectivity was found on the concrete pad formally covered with a green house where plutonium spiked growth experiments had been cor.Jucted.
2.
No significant plutonium activity was found in water taken from sump wells at each end of the pad.
l 3.
The final survey of the south wing of Building 305 disclosed no activity greater than background.
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Using a sampling plan similar to one devised by T. N. Throckmorton, PhD, a State of California statistician, no alpha, beta or gamma activity above background was found in the north wing of Building 305.
5.
No activity greater than background was found in the growth chamber area where growth experiments utilizing Sr-90 were conducted over a period of many years.
6.
Although the soil underneath the growth chamber area remains slightly contaminated, the contamination is close to Part 20 drinking water standards.
7.
The soil contamination underneath Room 14 was largely if not completely removed on April 16, 1981.
Any remaining would be near drinking I
water standards.
Leaching of contamination from under the building I
appeared to be nonexistent.
With the above conclusions in mind, it is the recommendation of the inspectors that Building 305 and the adjoining concrete pad located at Camp Parks, California be releosed for uncontrolled use.
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