ML20196G507

Vynp Assessment of On-Site Disposal of Contaminated Soil by Land Spreading

ML20196G507
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	06/23/1999
From:	VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20196F406	List: ML20196F401 ML20196G507
References
NUDOCS 9907010178
Download: ML20196G507 (15)

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I Docket No. 50-271 BVY 99-80 Attachment i Vermont Yankee Nuclear Power Station Assessment of On-site Disposal of Contaminated Soil by Land Spreading l

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9901010178 990623 PDR ADOCK 05000271 P POR -;.. .

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BVY 99-80 / Attachment I / Page 1 TABLE OF CONTENTS Page

- LIST OF TABLES ............................................................................ 2 1.0 . INTRODUCTION ................................................................... 3 1.1 Background ..................................................................... 3

- 1.2 Objective ....................................................................... 3 2.0 WASTE DES CRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 3.0 SOIL DISPOSAL AND ADMINISTRATIVE PROCEDURE REQUI REM ENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.0 EVALUATION OF ENVIRONMENTAL IMPACTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1 Site Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2 Radiological Impact. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 s 5.0 RADIOLOGICAL PROTECTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.0 C ON C LU SI ON S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.0 REFEREN C ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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BVY 99-80 / Attachment I / Page 2 LIST OF TABLES Table 1: Radioanalytical Results of Composite Soil Samples..........................10 Table 2: Estimated Total Radioactivity in Soil Volume.................................10 Table 3: Total Activity on South Field After Last Spreading Event................. I1 Table 4: Total Projected Radioactivity Remaining on South Filed at License Expirati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 1 Table 5: All-Pathway Critical Organ /Whole Body Dose Conversion Factors During Vermont Yankee Control o f Disposal Site. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 1 Table 6: All-Pathway Critical Organ /Whole Body Dose Conversion Factors Post Vermont Yankee Control of Disposal Sites (Inadvertent Intruder)............ 12 Table 7: Dose Contribution from Co-60 and Cs-137 in Soil Volume after Land S preading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4 i

Table 8: Present and Future Dose Impact Due to the Soil Spreading for Two Cases . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 I

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1.0 INTRODUCTION

1.1 Background

In 1989, Vermont Yankee Nuclear Power Corporation requested approval from the NRC to routinely dispose of slightly contaminated septic waste in designated on-site areas in accordance with 10CFR20.302(a). Approval from the NRC was granted on August 30, 1989 and the information was permanently incorporated into the Offsite Dose Calculation Manual (ODCM) as Appendix B.

In 1995, Vermont Yankee Nuclear Power Corporation requested that the previous I

authorization for on-site disposal of very low-level radioactive material in septic waste be amended to permit the on-site disposal of slightly contaminated cooling tower silt  ;

material. Approval from the NRC was granted on June 18,1997 and the information was  !

permanently incorporated into the ODCM as Appendix F.

In 1994, approximately 25.5 m' of excess soil was generated during on-site construction activities. Sampling of the soil revealed low levels of radioactivity that were similar in radionuclides and activity to the septic waste and cooling tower silts previously encountened. An evaluation determined that the soil could be managed in similar fashion i as the septic waste and cooling tower silts; however, prior approval from the NRC would  !

be required under 10 CFR 20.2002 (formerly 20.302(a)).

1.2 Objective I

The objective of this assessment is to present the data and radiological evaluation to i demonstrate that the proposed disposition of the soil will meet the existing boundary conditions as approved by the NRC for septic waste and cooling tower silt. The boundary conditions established for disposal of the septic waste and cooling tower silts on the designated plots are:

The dose to the whole body or any organ of a hypothetical maximally exposed individual  ;

must be less than 1.0 mrem /yr.  !

Doses to the whole body and any organ dose of an inadvertent intruder from the probable pathways of exposure are less than 5 mrem /yr.

Disposal operations must be at one of the appraved on-site locations. i 1

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BVY 99-80 / Attachment 1/ Page 4 2.0 WASTE DESCRIPTION -

The soil that is the subject of this evaluation was derived from excavations resulting from activities associated with a new security fence along the plant's Protected Area boundary.

The volume of soil generated was approximately 25.5 m , and is typical of fill material containing light to dark brown poorly sorted soils with some small stones, and includes small incidental pieces of asphalt. The soil was removed from its original location by shovel, backhoe sad front-end loader, and placed into dump trucks for transport to the location between the cooling towers where it was deposited on the ground surface and covered to prevent erosion. This location was selected because it was away from areas routinely occupied by plant staff, and could easily be controlled. The most probable source of the low levels of radioactive contamination is the presence of below detectable removable contamination redistributed by foot traffic from inside the plant to walkways and parking areas. Subsequent surface runoff carries the contamination to nearby exposed soil near the Protected Area boundary where it had accumulated over time to low level detectable concentrations.

In April 1995, a total of 20 composite soil samples were collected to characterize the volume. Composites were obtained by collecting a grab sample from one side, the top and the opposite side at equal distances along the length of the pile, then combining the three into one sample. Soil samples were sent to t'ae Yankee Atomic Environmental Laboratory for analysis and counted to environmental lower limits of detection required of environmental media. Results of the analyses are presented in Table 1. Analytical results are provided for when the samples were collected and decay corrected to the present. The results identified both Cs-137 and Co-60 in most of the composite samples, which verified that plant-related radioactivity was present in th: soil.

For the purpose of estimating the total activity in the soil pile, the actual analytical result was used for those samples that were less than the MDC to calculate the average radioactivity concentration.

3 The mass of soil (dry) was estimated by multiplying the total in-situ volume (25.5 m ) by 3

its wet density,1.47E+03 kg/m , and then dividing by the wet: dry ratio of 1.12, thus yielding a mass of 3.35E+04 kg (dry). The mass of the soil was then multiplied by the average Co-60 and Cs-137 concentrations measured in the soil to obtain the total activity 3

of each radionuclide in the 25.5 m . Table 2 presents the estimated total radioactivity in 3

the 25.5 m of soil at the time of sample collection and analysis, and decay corrected to the present.

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BVY 99-80 / Attachment I / Page 5 .

3.6 SOIL DISPOSAL AND ADMINISTRATIVE PROCEDURE REQUIREMENTS The method of soil disposal will use the technique ofland spreading in a manner consistent with the current commitments for the on-site disposal of septic waste and cooling tower silts as approved by the NRC. The accumulation of radioactivity on the disposal plot for this soil spreading operation will be treated as if cooling tower silt or septic waste was being disposed of since the characteristics of all these residual solids are similar (earthen-type matter). The south field (approximately 1.9 acres in size) designated and approved for septic waste and cocling tower silts disposal has been used for all past

' disposal operations, and will be used for the placement of this soil. Determination of the radiological dose impact has been made based on the same models and pathway assumptions used in the previous submittals.

Dry soil material will be dispersed using typical agricultural dry bulk surface spreading practices in approved disposal areas on-site. Incidental pieces of asphalt and stones that were picked up with the soil from area where paving ran along the fence lina will be 3 screened out before the soil is spread and disposed of as radioactive material at an off-site i licensed facilit,; if. detectable radioactivity is found. )

l Records of the disposal that will be maintained include the following:

(a) The radionuclide concentrations detected in the soil (measured to environmental lower limits of detection).

(b) The total volume of soil disposed of.

(c) The total radioactivity in the disposal operation as well as the toul accumulated on each disposal plot at the time of spreading.

(d) The plot on which the soil was applied.

(e) Dose calculations or maximum allowable accumulated activity determinations required to demonstrate that the dose limits imposed on the land spreading operations have not been exceeded.

To ensure that the addition of the soil containing the radioactivity will not exceed the boundary conditions, the total radioactivity and dose calculation will include all past disposals of septic waste and cooling tower silt containing low-level radioactive material on the designated disposal plots. In addition, concentiation limits applied to the disposal of earthen type materials (dry soil) restrict the placement of small volumes of materials that have rela:ively high radioactivity concentrations.

Any farmer leasing land used for the disposal of soil will be notified of the applicable restrictions placed on the site due to the spreading oflow level contaminated material.

These restrictions are the same as detailed for the previously approved septic waste ,

spreading application.

U BVY 99-80 / Attachment I / Page 6 4.0 EVALUATION OF ENVIRONMENTAL IMPACTS 4.1 Site Characteristics The designated disposal site is located on the Vermont YarAee Nuclear Power Plant site and is within the site boundary security fence. The south field consists of approximately 1.9 acres and is centered approximately 1500 feet south of the Reactor Building. This parcel ofland has been previously approved by the NRC for the land disposal of septic waste and cooling tower silt.

4.2 RadiologicalImpact The amount of radioactivity added to the south field soil is procedurally controlled to ensure that doses are maintained within the prior approved limits of the boundary

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To assess the dose received (after spreading the soil) by the maximally exposed individual during the period of plant controls over the property, and to an inadvenent intruder after plants controls of access ends, the same pathway modeling, assumptions and dose calculation methods as approved for septic and cooling tower silt disposal were used. These dose models implement the methods and dose conversion factors as provided in Regulatory Guide !.109.

The following six potential pathways were identified and included in the analysis:

(a) Standing on contaminated ground.

(b) Inhalation of resuspended radioactivity.

(c) Ingestion ofleafy vegetables.

(d) Ingestion of stored vegetables.

(c) Ingestion of meat.

l (f) Ingestion of cow's milk.

boa the maximum individual and inadvertent intruder are assumed to be exposed to l - these pathways; C e difference between them is due to the occupancy time. The basic assumptions used in the radiological analyses include:

(a) Exposure to ground contamination and re-suspended radioactivity is for a period of 104 hours0.0012 days <br />0.0289 hours <br />1.719577e-4 weeks <br />3.9572e-5 months <br /> per year during the Vermont Yankee active control of

, the disposal sites and continuous thereafter. The 104-hour interval is representative of a farmer's time spent c a plot ofland (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> per week for 6 month:).

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BVY 99 80 / Attachment I / Page 7 (b) For the purpose of projecting and illustrating the magnitude of dose impacts over the remaining life of the plant, it is assumed that the concentration levels of activity as of April 1,1999 remain constant. Table 1 indicates the measured radioactivity levels for Co-60 and Cs-137 first noted h, the soil, and decay corrected to April 1,1999.

(b) For the analysis of the radiological impact during the Vermont Yankee active control of the disposal sites until 2013, no plowing is assumed to take place and all dispersed radioactive material remains on the surface forming a source of unshielded direct radiation.

(c) The crop exposure time was changed from 2160 hours0.025 days <br />0.6 hours <br />0.00357 weeks <br />8.2188e-4 months <br /> to 0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> to reflect the condition that no radioactive material is dispersed directly on crops for human or animal consumptiou. Crop contamination is only through root uptake.

(d) The deposition on crops of re-suspended radioactivity is insignificant.

(e) The pathway data and usage factors used in the analysis are the same as those used in the Vermont Yankee's ODCM assessment of off-site radiological impact from routine releases, with the following exceptions.

The fraction of stored vegetables grown on the contaminated land was conservatively increased from 0.76 to 1.0 (at present no vegetable crops for human consumption are grown on any of the approved disposal plots).

Also, the soil exposure time to account for buildup was changed from the standard 15 years to 1 year.

(f) It is conservatively assumed that Vermont Yankee relinquishes control of the disposal sites after the operating license expires in 2012 (i.e., the  ;

source term accumulated on a single disposal plot applies also for the '

inadvertent intruder).

(g) For the analysis of the impact after Vermont Yankee control of the site is relinquished, the radioactive material is plowed under and forms a uniform mix with the top six inches of the soil; but nonetheless, undergoes re-i suspension in the air at the same rate as the unpbwed surface contamination. However, for direct ground plane exp?sure the self-shielding due to the six-inch plow layer reduces the surface dose rate by about a factor of four.  !

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BVY 99-80 / Attachment 1/ Page 8 4

As shown in the previous submittals, in which the concentrations of Co-60 and Cs-137 in septic waste exceed those identified in the soil, the liquid pathway was found to be an insignificant contributor to the dose. Therefore, the liquid pathway is not considered in this analycis.

The dose models and methods used to generate deposition values and accumulated activity over the operating life of the plant are documented the ODCM. Table 3 presents the radioactivity that currently exists on the south field after the last spreading event which occurred on September 28,1998 (total elapsed time from September 28,1998 to April 1,1999 is 184 days). In addition, the total activity on the south field is presented assuming the addition of the 25.5 m' of soil subject of this evaluation.

The total activity that would be present on south field at license termination (i.e., total )

elapsed time of 14 years post April 1,1999, or 2013), assuming no future additions of i material containing radioactivit';after disposal of the proposed soil volume was also I evaluated and is presented in Table 4.

I In order to demonstrate compliance with the boundary conditions, the critical organ and whole body dose from all pathways to a maximally exposed individual during Vermont Yankee control, and to the inadvertent intruder were calculated. The dose calculations were performed using the dose conversion factors presented in Table 5 and 6 below which were obtained from the ODCM. The contribution to dose from Co-60 and Cs-137 to the whole body and organ at the present and at license expiration is presented in Table

7. The present and future total dose impact from the south field with and without spreading of the soil is presented in Table 8.

These results demonstrate that disposal of the approximately 25.5 m3 of accumulated soil will be wel' within the accepted dose limit criteria of 1 mrem /yr to any organ or whole body during the control period, and 5 mrem /yr to an inadvertent intruder after control of the site is assumed to be relinquished. This analysis shows that significant dose margin still exists on the approved disposal plots to accommodate potential future spreading operations.

5.0 RADIOLOGICAL PROTECTION The disposal operation of soil piles will follow the applicable Wrmont Yankee procedures to maintain doses as low as reasonably achievable and within the specific dose criteria as previously approved for septic waste and cooling tower silt disposal.

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6.0 CONCLUSION

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Soil generated from on-site construction activi. ties reflects an earthen type material similar in characteristics to septic waste residual solids and cooling tower silt with respect to the radiological pathway behavior and modeling. Based on the similarity in characteristics between the proposed soil volume and waste streams that have already

' been approved for disposal, and the evaluation of the incremental dose impact, it is concluded that disposal of the approximately 25.5 m' of existing soil through on-site land spreading will meet the boundary conditions specified in the ODCM. That is, with respect to the addition of the approximately 25.5 m' soil pile to the existing radioactivity already spread on the south field:

1. Total doses to the whole body and critical organ to the hypothetically maximally exposed individual were estimated as 3.00E-02 mrem /yr and 1.04E-01, respectively, which are less than the prescribed 1.0 mrem /yr.

2. Total doses to the whole body and critical organ of an inadvertent intruder from the probable pathways of exposure were estimated as 1.13E-01 mrem /yr and 2.21E-01 mrem /yr, respectively, which are less than 5 mrem /yr.

3. The disposal is assumed to take place on the south field that is the same site approved for disposal of septic waste and cooling tower silts.

If the soil were spread on an approved plot which had not yet been used for disposal, the dose impact from the approximately 25.5 m' of soil alone would at present be 4.17E-03 mrem /yr whole body and a maximum organ dose of 1.46E-02 mrem /yr. In addition, l'o r the inadvertent intruder, the whole body dose would be 1.60E-02 mrem /yr, and a maximum organ dose of 3.11E-02 mrem /yr. Each of these doses also meet the boundary conditions specified in the ODCM.

7.0 REFERENCES

(1). Vermont Yankee ODCM,'Rev 23, Appendix B, " Approval of Criteria for Disposal of Slightly Contaminated Septic Waste On-Site at Vermont Yankee".  !

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(2) Vermont Yankee ODCM, Rev 23, Appendix F," Approval Pursuant to 10CFR20.2002 for On-Site Disposal of Cooling Tower Silt".

(3) USNRC Regulatory Gaide 1.109, Rev 1, " Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 19CFR Part 40, Appendix I", dated October 1997. j j

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, l BVY 99 80 / Attachment I / Page 10 Table 1 Radionnalytical Results of Composite Soil Samples Cs-137 Co-60 (pCi/kg) (pClikg)

Sampie ID April,1995 April,1999 April,1995 April,1999 G22716 234 213 49 " 29 G22717 522 476 143 84 G22718 337 307 37 " 22 G22719 291 265 'l11 66 G22720 348 317 47 " 28 G22721 135 123 73 43 G22722 107 98 82 48 G22723 222 203 140 83 G22724 180 164 92 54 )'

G22725 269 245 118 70 G22726 810 739 114 67 G22727 378 345 106 63 G22728 810 739 124 73 G22729 376 343 62 37 G22730 331 302 87 51 G22731 253 231 5** 3 G22732 150 137 58 34 G22733 247 225 105 62 G22734 326 297 54** 32 G22735 1 235 214 100 59 Average 328 299 85 50 Maximum Value 810 73 9 143 84 l Minimum Value 107 98 5 3 StandardDeviation 191 1 74 37 22

• Average wet to dry sample weight ratio equal to 1.12. Average wet density equal to 1.47 gm/cc.

" The apparent response of the gamma isotopic analysis which was less than Minimum Detectable Concentration.

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l Table 2 Estimated Total Radioactivity in Soil Volume Volume Average Concentration Total Activity ofSoil Mass (pCi/kg-dry) ( Ci) 3 Radionuclide (m ) (kg-dry) April,1995 April,1999 April,1995 April,1999 Cs-137 25.5 ;335E+04 328 299 11.0 10.0 Co-60 25.5 l 3.35E+04 85 50 2.8 1.7

BVY 99 80 / Attachment I / Page 11 Table 3 Total Activity on South Field After Last Spreading Event i Total activity after Total activity decay Total activity after I

. last spreading event corrected to April 1, proposed soil Radionuclide ( Ci/ acre) -1999 ( Ci/ acre) disposal (pCi/ acre)

Mn-54 0.17 0.11 0.11 Co-60 5.93 5.55 6.44 Zn-65 0.074 0.044 0.044 Cs-137 32.27 31.90 37.16 Table 4 Total Projected Radioactivity on South Field Remaining at License Expiration Total Activity as of License Expiration Radionuclide ( Ci/ acre)

Mn-54 8.9E-07 Co-60 0.89 Zn-65 7.6E-09 Cs-137 26.33 Table 5 All Pathway Critical Organ /Whole Body Dose Conversion Factors During Vermont Yankee Control of Disposrl Sites Critical Organ Whole Body Dose Factor Dose Factor Radionuclide Individual / Organ (mremlyr per pct /scre) (mrem /yr per pci/scre)

Mn-54 Adult /GI-LLI 3.75E-04 1.93E-04 Co-60 Teen / Lung 7.17E-04 5.31E-04 Zn-65 Child / Liver 1.64E-02 1.03E-02 Cs-137 Child / Bone 2.66E-03 7.02E-04

BVY 99-80 / Attachment 1/ Page 12 Table 6 All Pathway Critical Organ /Whole Body Dose Conversion Factors Post Vermont Yankee Control of Disposal Sites (Inadvertent Intruder)

Critical Organ Whole Body Dose Factor Dose Factor Radionuclide Individual / Organ (mrem /yr per pCUncre) (mrem /yr per pCUncre)

Mn-54 Teen / Lung 1.02E-02 3.12E-03 Co-60 Teen / Lung 3.19E-02 9.09E-03 Zn-65 Child / Liver 1.89E-02 1.25E-02

~Cs-137 Child / Bone 6.98E-03 3.85E-03 Table 7 Dose Contribution from Co-60 and Cs-137 in 25.5 m3 Soil Volume after Land Spreading Present Dose Impact' Future Dose Impact' (Maximally exposed (Inadvertent Intruder)

Case individual)

Dose Individual / Dose Individual /

(mrem /yr) Organ (mrem /yr) Organ Cobalt-60 4.75E-04 Whole body 1.29E-03 Whole body 6.42E-04 Max. Organ 4.51 E-03 Max. Organ Cesium-137 3.69E-03 Whole body 1.47E-02 Whole body 1.40E-02 Max. Organ 2.66E-02 Max. Organ

' Based on inventory of Co-60 of 0.895.pCi/ acre and Cs-137 of 5.26 Ci/ acre in April 1, 1999.

2 Based on inventory of Co-60 of 0.141 pCi/ acre and Cs-137 of 3.82 pCi/ acre in April 1, 2013.

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BVY 99-80 / Attachment I / Page 13 Table 8 Present and Future Dose Impact Due to the Soil Spreading for Two Cases Present Dose Impact Future Dose Impact (Maximally exposed (Inadvertent Intruder)

Case individual)

Dose Individual / Dose Individual /

(mrem /yr) Organ (mrem /yr) Organ Case One South Field as it currently 2.58E-02 Whole body 9.70E-02 Whole body exists 8.96E-02 Max. Organ 1.89E-01 Max. Organ Case Two South Field if disposal of 3.00E-02 Whole body 1.13E-01 Whole body soil volume is approved 1.04E-02 Max. Organ 2.21E-01 Child / Bone Increase in dose impact 4.17E-03 Whole body 1.60E-02 Whole body from disposal of soil 1.46E-02 Max. Organ 3.11E-02 Max. Organ I