ML20138G270

Provides Response to NRC Comments Re Proposed Sampling & Survey Plan for Fsv Effluent Pathway.Response Documents Fsv Liquid Effluent Discharge Pathway Areas Are Acceptable for Release for Unrestricted Use IAW Draft NUREG/CR-5849

ML20138G270
Person / Time
Site:	Fort Saint Vrain
Issue date:	04/28/1997
From:	Borst F PUBLIC SERVICE CO. OF COLORADO
To:	Jim Hickey NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
RTR-NUREG-CR-5849 P-97029, NUDOCS 9705060238
Download: ML20138G270 (8)

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. l O rubiic16805 WCRservice-191/2; Platteville, Colorado 80651

= = = .- i April 28,1997 Fort St. Vrain P-97029 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

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Mr. John W. Hickey, Chief Decommissioning and Regulatory Issues Branch Docket No. 50-267

SUBJECT:

Confirmatory Radiation Survey of Liquid Effluent Pathway, Response to NRC Comment

REFERENCES:

1. NRC I2tter, Pittiglio to Fuller, dated April 23,1997 2

(G-97039)

2. PSCo Ixtter, Borst to Weber, dated September 11,1996 (P-96068)

Dear Mr. Hickey:

This letter provides Public Service Company of Colorado's (PSCo) response to NRC comments in Reference 1, regarding the proposed Sampling and Survey Plan for the Fort St. Vrain Effluent Pathway, previously submitted via Reference 2. This response documents that Fort St. Vrain's liquid effluent discharge pathway areas are acceptable

for release for unrestricted use.

As part of the NRC's review of the Reference 2 submittal, the Oak Ridge Institute for Science and Education (ORISE) performed confirmatory surveys of the liquid effluent discharge pathway areas at Fort St. Vrain. As indicated in the referenced letter, ORISE identified one sample with residual activity that exceeds site guideline values. This sample, near location flag number 157, included activity where the sum of the fractions of nuclide concentrations to guideline values was 1.9. In accordance with guidance in Draft NUREG/CR-5849 and in the Reference 2 proposed plan for final radiation survey of the effluent pathway, samples whose sum of fractions exceeds 1.0 require evaluation to determine whether average contamination levels in the 100 m2 area surrounding the elevated sample exceed the guideline values. ,

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P-97029 5 April 28,1997 .

Page 2 As described in the attached report, the weighted /nean sum of fractions for the 100 m 2

. investigation area was determined to be 0.23. This value is much less than 1.0 and demonstrates that levels of residual activity in the areas examined in ORISE's j confirmatory survey are acceptable for unrestricted use.

, Based on the infonnation provided in the attached report, PSCO requests NRC approval j of the proposed Sampling and Survey Plan for the Effluent Pathway as submitted in

Reference 2, and as implemented during the final survey. At this time, PSCo would also i like to re-state our position that the entire Fort St. Vrain facility satisfies the criteria for unrestricted release, and we respectfully request that Facility Operating License (Possession Only), Number DPR-34, be terminated.  ;

If you have any questions regarding this information, please contact Mr. M. H. Holmes at (303) 571-7633.

Sincerely,

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Frederic J. Borst  !

Decommissioning Program Director l FJB/SWC Attachment .

cc: Regional Administrator, Region IV Mr. Robert M. Quillin, Director j Radiation Control Division Colorado Department of Public Health and Environment ,

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l EVALUATION OF AVERAGE ACTIVITY IN 100 M2 AREA AROUND FLAG 157 IN GROUP E EFFLUENT DISCHARGE PATHWAY AREA Attachment to P-97029 l

April 1997 1

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Evaluation of Average Activity In 100 m2 Area Around Rag 157

, In Group E Emuent Discharge Pathway Area l  ;

Introduction This report describes the acceptability of the area surrounding the elevated sample

identified in the ORISE confirmatory survey. The report combines the sample results- i

imm the NRC's independent contractor with the sample results in the adjacent 100 m2 l 1 investigation area obtained by SEG to demonstrate compliance with Fort St. Vrain  ;

! unconditional release criteria. The averaging criteria contained in the final survey plan l

[ and procedures was used and is consistent with the method contained in Draft l l NUREG/CR-5849.  !

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Confirmatory surveys were performed by Environmental Survey and Site Assessment i Program (ESSAP) of the Oak Ridge Institute for Science and Education (ORISE) of the l

Fort St. Vrain Effluent Discharge Pathway on March 31 and April 1,1997. One sample  ;

j collected and analyzed by ORISE showed activitics in excess of the guideline value. The j j sum of the nuclide concentration-to-guideline values for the sample collected near flag  !

i 157 along the Goose Quill ditch banks was 1.9. The nuclide activities for the elevated l ORISE sample are shown in Table 1 below. l

! Table 1 l ORISE Reported VC.a l

Sample) Radionuclide Concentrations l(pCi g)j l Concentrationit o-; )

l  ? Guideline' Ratio 1 l Co-60 Cs-137 Section D, Flag 157 8.8 i 0.3 6.3 i 0.3 1.9

! Investigation Sampling l SEG cc1' acted investigation samples from each ORISE sampling location on April 2, l 1997. Tae SEG samples were archived so that if any ORISE sample showed elevated j results the average concentration within the surrounding 100 m2area could be determined j in accords.cc with FSV procedures and protocols. A SEG surface sample was collected from the soil surrounding the ORISE location, effectively widening the hole. A 100 m 2 i grid was established around the ORISE sample location and eight additional surface

! samples were obtained in accordance with Fort St. Vrain final survey procedures. A j SEG subsurface soil sample (6 to 12 inches below the surface) was collected from the

ORISE sample location. SEG samples labeled as Flag #156 correspond to the ORISE 3

sample labeled as Flag #157 (the selection of the nearest flag marker was subjective).

j Figure 1 shows the investigation sample location.

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l Sample Preparation and Counting i Once the sample was identified as elevated by ORISE, the corresponding SEG

investigation samples were prepared for counting by drying, sieving and placing each a

sample in a marinelli container. Each sample was then counted for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> on the 2

Canberra Q gamma spectroscopy system in accordance with SEG procedure REDS-INST-238, Operation of the Canberra Q LLWA Gamma Spectroscopy System with Collimated Counter Array. The analysis library was prepared to include all gamma j emitting nuclides of concern at FSV and verified using DOE-TIC-11026, Radioactive

Decay Data Tables, D. C. Kocher,1981.

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! Based on the sample densities (range of 0.903 to 1.26 g/cm') a calibration efficiency for  !

a 1.15 g.cm 3solid matrix was used to quantify the results.

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A list of approximate, representative MDAs for this sample analysis is as follows:

Nuclidei  !-MDEF f(pCi/g)'

Cs-137 - 0.0311 Co-60 0.0320 l Eu-155 0.130 l Eu-152 0.191 l

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Results l The results are shown in Table 2 along with the original ORISE sample datt.. The " sum 4

of the fractions", SOF was determined for each sample by summing the ratio of the observed nuclide concentration to the nuclide concentration guideline value equating to i

] 10 mrem TEDE. Guideline values were obtained from FSV-FRS-TBD-209, FinalSurwy l i Requirementsfor the Liquid Efluent Pathway. The data were evaluated using procedure ,

l FSV-SC-FRS-I-110, Final Surwy Data Analysis. At flag #156/157 the SEG sample ,

i surrounding the ORISE hole was identified as #2 within the investigation area; the 2

, samples represent the same 11.11 m area. The original ORISE sample result and SEG investigation sample (sample #2) result were compared, and the higher result was used for calculation of the area weighted mean.

] The elew.xi area was determined using the samples whose SOF exceeded 1.0 assuming

] each sample represented 11.11 m 2 area (1/9 of the 100 m2 averaging area). The factor by which any single sample could exceed the guideline value by, F, was calculated using  ;

. the following equation:

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4 F=h A I l j where A is the elevated area of samples exceeding SOF of 1.0.

l The elevated area (area exceeding the guideline value) was determined to be confined to j one grid representing 11.11 m2. The maximum value by which any sample could exceed i

the release criteria is therefore 3.0. The weighted mean SOF from the 100 m2 i investigation area, determined in accordance with the procedure, is 0.23.

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- i, Table 2 Investigation Sample Results at ORISE Sampic Location Sample Density Co-60* Cs-137 - Eu-152 Eu-155 Sample 100 m2 l (g/cm') (pCi/g) (pCilg) (pCilg) _ (pCi/g) SOF Weighted Mean SOF l (surface j l

samples)

Flag #156/157 SEG1 1.045 0.00 ORISE 8.8000 6.3000 1,91 j SEG 2* 0.903 5.7750 4.1850 1.1040 0.5286 1.40 (not used)

SEG 3 0.991 0.7151 0.7655 0.3081 0.17 SEG 4 0.924 0.00 SEG5 1.000 r,.e.)

SEG 6 1.021 0.00 SEG 7 0.899 0.00 SEG8 1.085 0.00 SEG 9 1.181 0.0421 0.00 0.23 sub- SEG 10 1.043 0.4919 0.3702 0.11 surface Concentration Guideline 5.58 18.7 13.2 439 (1) Blank entnes indicate no activity atxwe the MDA.

(2) SEG sample surrounding the ORISE location. The ORISE result was used for weighted mean calculations.

Conclusion The elevated area (area exceeding the guideline value) was determined to be confined to one grid representing 11.11 m2 . No individual sample exceeded the guideline value by a factor of 3.0.

The weighted mean " sum of fractions", SOF for the 100 m2 area surrounding the location identified by ORISE was determined to be less than 1.0. The weighted mean SOF for Flag 156/157 was 0.23 equating to 2.3 mrem Total Effective Dose Equivalent. J 4

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