ML20207N068

Insp Rept 70-0754/86-03 on 861031-1205.Major Areas Inspected:Surveys & Collection of Soil Samples & Analysis of Samples.Confirmatory Survey Conducted on 861031 Indicated That NRC Guidelines Met

ML20207N068
Person / Time
Site:	07000754
Issue date:	01/06/1987
From:	Pang J, Thomas R, Zurakowski P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
Shared Package
ML20207N041	List: ML20207N040 ML20207N068
References
70-0754-86-03, 70-754-86-3, NUDOCS 8701130427
Download: ML20207N068 (8)

Text

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U. S. NUCLEAR REGULATORY COMMISSION REGION V Report No. 70-00754/86-03' Docket No. 07000754 License No. SNM 960 Licensee: General Electric Company Vallecitos Nuclear Center P. O. Box 460 Pleasanton, CA 94566 Facility Name: Vallecitos Nuclear Center Inspection,att Pleasanton, CA' 94566

. Inspection Conducted: October 31, 1986; November 14, 1986; November 21, 1

1986; November 24, 1986; November 25 - December 5,

. 1986 (analysis of samples) 4 Inspector: f ky 'fWJ4*b l ~ l* ' N 7 P. R. (Zurakowski, Radiation Specialist Date Signed 4.F. Gw t - L -47 i

J. F. Pang, Tadiation cialist Date Signed Approved by: _[ CC R. D. Thomas, Chief

_ [d D te' Signed

/

Nuclear Materials Safety Section Summary:  :

Inspection of October 31, November 14, 21, 24, November 25-December 5, 1986

[ Report No. 70-00734/86-03)

Areas _ Inspected: In a letter dated September 24, 1986, the licensee requested  :

NRC Region V to conduct a confirmatory survey of a Radwaste Storage Area

, located in back of Building 400, Vallecitos Nuclear Center, to establish that the area can be released for unrestricted use. A confirmatory survey was conducted on October 31, 1986, by two NRC inspectors. Surveys and collection of soil samples were taken on November 14, 21, and 24 by one NRC inspector.

. Analysis of the soil samples were performed by the NRC Region V Radiation Laboratory Specialist.  ;

Results: The confirmatory survey of October 31, 1986, disclosed that the NRC guidelines showr. in Appendix A were not met. The licensee then conducted

further decontamination efforts. Subsequent confirmatory surveys, conducted with a Micro-H portable gamma scintillation survey instrument, an air proportioned alpha survey instrument, a beta gamma survey instrument and laboratory multichannel analyser, found the contamination levels were within I

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2-the NRC guidelines as shown in Appendix A. The soil contamination levels as shown in Table I were within the release criteria for soil as specified in SECY 81-576, Disposal or Onsite Storage of Residual Thorium or Uranium from Past Operations, dated October 5, 1981. Based on the results of these surveys and soil sample data, it was determined that the Radwaste Storage Area located at the Vallecitos Nuclear Center can be released for unrestricted use.

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DETAILS

1. P_ersons Contacted-Mr. G. E. Cunningham, Senior Licensing Engineer Mr. D. C. Bowden, Senior Engineer Nuclear Safety Ms. L. Kessler, Associate Chemist

2. Background in a letter dated September 24, 1986, the licensee requested NRC Region V to conduct a confirmatory survey of the Radwaste Storage Area located at the rear and adjacent to Building 400 of the Vallecitos Nuclear Center.

The area in question is located adjacent to the High Bay Area of Building 400 (Figure 1) and consisted of a concrete pad approximately 20 feet in length by 8 feet in width. The pad was covered by an I-beam type structure with an aluminum sheet roof. The common wall with the High Bay Area was aluminum siding. The other three sides were enclosed with cyclone fencing with an outer layer of fiberglass siding. (Note: The fencing /iluminum siding walls and concrete pad were completely .emoved prior to the final NRC surveys.)

The pad held a one-thousand gallon steel tank which received liquid waste from the High Bay Area (natural, depleted, and low-enriched uranium). A second steel tank (100 gallons) was located in a concrete vault below ,

grade level. This tank served as an overflow for the waste tank and as a sump for the High Bay Area.

The vault containing the sump tank was free poured concrete. A circular i form was used for the vault cavity, but no forms were used for the outer l surface. As a result, the vault was an irregular concrete mass with a i.oncrete thickness of 1-1/2 to 2 feet. The vault has been removed as a single unit. The vault and both tanks were disposed of as radioactive  !

waste prior to the first NRC survey.

The licensee has stated that they wish to release both Building 400 and the adjacent Radwaste Storage Area for unrestricted use. However, because there is no longer a seat between the Radwaste Storage Area and the High Bay Area due to extensive excavation heavy rains during the '

winter months would cause flooding and impede further work inside the building. Therefore, the licensee's wishes at this time to release the Radwaste Storage Area for unrestricted use so that the excavation may be filled in and capped. '

This report presents the results of the NRC confirmatory surveys on October 31, November 14 November 21, and November 24, 1986. Soil samples taken on November 21 and 24 were analyzed by Region V's Radiation Laboratory Specialist during the weeks of November 24 and December 1, 1986.

The survey criteria were based on NRC requirements established by the

" Guidelines for Decontamination of Facilities and Equipment Prior to

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.. Release for Unrestricted Use or Termination of Licenses for By products,  ;

Source, o'r Special Nuclear Material, July 1982." (Appendix A).

,The criteria for soil release was based upon data from SECY 81-576, .

, ' Disposal or Onite Storage of Residual Thorium or Uranium from Past

- ~ 0perations, dated October 5,1981.

3. Confirmatory Survey of October 31, 1986 A. Instruments The field radiation detection instruments selected for this survey were: (1) an Eberline Model E-520 Geiger Counter with a " pancake" probe, (2) an Eberline Model PRM-7 gamma scintillation survey meter, and (3) LRL alpha survey meter. The specific instruments used and their calibration status were:

Instrument Identification No. Calibration Due Eberline E-520 Geiger NRC 008252 February 10, 1987 Counter '

Eberline PRM-7 Micro-R NRC 008596 January 28, 1987 Meter  :

LRC Alpha Survey Meter NRC 000374 May 10, 1987 B. Areas Surveyed Approximately 2/3 of the concrete pad was still in place during the survey of October 31, 1986. The Inspectors found yellow stains in cracks and under the concrete edge overflow barrier' contained '

activity in excess of the release limits specified in Appendix A.

Readings with the E-520 using a calibrated pancake probe of 1500 to 4000 cpm translated to reading from 20,000 to 53,000 dpe/100 cm2 ,  ;

The licensee stated that the entire concrete pad would be removed and arrangements would be made to obtain core samples from the area where the 100 gallon radwaste tank had been.

4. Confirmatory Survey of November 14, 1986 A. Instruments  !

l The instruments used were the same ones identified in 3A above.

B. A l cas Surveyed L

Prior to this survey it was noted that the concrete pad, alivninum (

roof and support, and the chain link fence had been removed 1 caving  :

a 2\' deep X 9' X 24' trench where the pad had formerly been  ;

located, j

(1) liiero-R Meter Survey The entire 8' X 20' trench area where the concrete pad had been '

and the common wall with the liigh Bay to a height of 6' were i

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3 surveyed. No reading above the 10-12 micro-R per hour background was found.

(2) Alpha and Beta Surveys An approximately 75% survey of the concrete footing next to the common wall with the liigh Bay was made with an Eberline E-520 instrument and a pancake probe. This footing was approximately 2.5' X 20' in size. All readings were less than 50 cpm with four exceptions, two spots read 150 cpm and two others read 100 cpm. Random spot checks with the LRC alpha survey instruments covering approximately 10% of the area indicated all readings were less than 10 cpm. The highest of the above readings, 150 cpm, when translated to dpm indicated a reading of 1350 dpm/100 cm2 for the two elevated spots. This is well within the limits for fixed contamination in a small area.

No. reading above background was found on the common wall with the liigh Bay with any of the three instruments used.

A 25% random spot check of the soil inside the trench with the E-520 instrument and a pancake probe indicated no readings above background. Background was measured to be approximately 50 cpm /per probe area. Soil samples taken in the area are discussed in the next sectica.

5. Soil Contamination Survey of. November 21, 1986 On November 21,1986,' the licensee arranged to have a contractor to take soil (core) samples in the area where the 100 gallon waste tank had formerly been buried. See Figure 1 for details on where the core samples were taken. 'The twelve samples taken (2 samples per core) were placed in a drying oven over the weekend of November 22-23. Upon removal from the oven on November 24, the samples were randomized and split with the licensee for analysis. The twelve samples taken by Region V were analyzed by gamma spectroscopy utilizing a Nuclear Data 6600 System fitted with an 18% Relative Germanium Detector. The analyses were performed by Region V's Radiation Laboratory Specialist during the weeks ending November 28 and December 5, 1986. The results are shown in Table 1.

6. Conclusion The radiological surveys and soil contamination IcVels of the Radwaste Storage Area located adjacent to the liigh Bay Area of Building 400, Vallecitos Nuclear Center, Pleasanton, California, Indicated that this area is well within the NRC release limits for unrestricted use. Since I it has been found that the NRC guidelines for release to unrestricted use have been met, it is the recommendation of Region V that this area be released for unrestricted use.

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l TABLE 1 GE Vallecitos Soil U Th Sample No. pCi7gm pCI7gm Top-1 0.9 1 Top-2 0.8 0.9 Top-3 0.9 1 Top-4 0.8 1 Top-5 0.8 1 Top-6 0.7 0.9 Bot-1 0.9 1 Bot-2 1 0.9 Bot-3 0.8 1 Bot-4 0.8 1 Bot-5 0.9 1 Bot-6 0.9 1 A 100 gram fraction of each of the 12 soil samples was analyzed by gamma spectroscopy with a minimum counting time of about 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The U and Th values were inferred from daughter product activities on the assumption that equilibrium was present at least through Ac-228 for the Th-232 chain and through Bi-214 for the U-238 chain. Within the statistical uncertainty of the measurements, U-235 concentrations are consistent with the U-235/U-238 ratio for natural uranium.

Appendix A ACCEPTABE SITdFACE CONTAMINATION LEVEIS NUCLIDES* AVERAGE

• ' MAXINIM df *'

REMOVARE U-mat. U-235, U-238, and associated 5,000 dpa a/100 ca z 15,000 dre a/100 ce 1,000 den a/100 ca 8 decay products Transuranics, Ra-226. Ra-228. Tk-230, 100 dre/100 cm 2 300 dpe/100 cm 2 20 dpa/100 cm2 Th-228, Pa-231, Ac-227. I-125, I-129 Ta-mat. Th-232 Sr-90, Ra-223, Ra-224, 1000 dys/100 ce t 3000 dpe/100 cat 200 dpe/100 ce t U-232, 1-126, 1-131, 1-133 Reta gamma emitters (seclides with 5000 dye 37/100 cat 15,000 dpm pT/100 cm2 1000 dpa $7/300 caz decay modes other than alpha emiccios or spontaaeous fission) '

except Sr-90 and others noted above.

• henere surface contamination by both alpha- and beta gamma-emitting nuclides exists, th limits established for alpha- and beta-gamma-esitting anclides should apply independently.

As used in this table, dpa (disintegrations per minute) means the rate of emission by radioactive material as determined by correcting the comets per siaste observed by as appropriate detector for background, efficiency, and geometric factors associated with the instrumentation.

Neasurenests of average contaminant should not be averaged over more than I square meter. For objects of less surface area, the average shoald be derived for each such object.

d The easiamo contanamation level applies to an area of not more than 100 cut ,

% amoest of removable radioactive material per 100 cet of surface area should be determined by wiping that area with dry filter or sof t absorbent paper, applying moderate pressure, and assessing the amount of radioactive material on the wipe with an appropriate instrument of kaous efficiency. nihen removable contamination on objects of less surface area is determined, the pertiment levels should be reduced proportionally and the entire surface should be wiped.

'The average and maximum radiation levels associated with surface contamination resulting from beta-gamma emitters should not exceed 0.2 stad/hr at I cm and 1.0 stad/hr at I cm, respectively, measured threugh not more than 7 milligrams per square centimeter of total absorber.

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