ML022970089

Maine Yankee'S License Termination Plan, Section 6, Table of Contents - Attachment 6-19

ML022970089
Person / Time
Site:	Maine Yankee
Issue date:	10/15/2002
From:	Maine Yankee Atomic Power Co
To:	NRC/FSME
References
+sisprbs20060109, -nr, -RFPFR
Download: ML022970089 (302)

Text

MYAPC License Termination PlanRevision 3 October 15, 2002MAINE YANKEELTP SECTION 6COMPLIANCE WITH RADIOLOGICAL DOSE CRITERIA MYAPC License Termination PlanPage 6-iRevision 3 October 15, 2002TABLE OF CONTENTS6.0COMPLIANCE WITH THE RADIOLOGICAL DOSE CRITERIA..............6-16.1Introduction....................................................6-16.2Site Condition After Decommissioning...............................6-16.2.1Site Geology and Hydrology.................................6-26.3Critical Group..................................................6-3 6.4Conceptual Model...............................................6-4 6.5Environmental Media and Dose Pathways............................6-46.5.1Contaminated Materials.....................................6-46.5.2Environmental Media.......................................6-56.5.3Dose Pathways............................................6-56.5.4Radionuclide Concentrations in Environmental Media.............6-56.6Material Specific Dose Assessment Methods and Unitized Dose Factors....6-76.6.1 Contaminated Basement Surfaces.............................6-86.6.2Activated Basement Concrete/Rebar.........................6-206.6.3Embedded Pipe..........................................6-246.6.4Surface Soil.............................................6-276.6.5Deep Soil...............................................6-296.6.6Groundwater............................................6-316.6.7Surface Water............................................6-326.6.8Buried Piping............................................6-336.6.9Forebay and Diffuser......................................6-35l6.6.10Circulating Water Pump House..............................6-426.7Material Specific DCGLs and Total Dose Calculation..................6-446.7.1Conceptual Model for Summing Contaminated Material Dose .....6-466.7.2 Method and Calculations for Summing Contaminated Material Dose.......................................................6-476.8Area Factors...................................................6-536.8.1Basement Contamination...................................6-536.8.2Surface Soil and Deep Soil Area Factors.......................6-54 MYAPC License Termination PlanPage 6-iiRevision 3 October 15, 20026.8.3Embedded Piping Area Factors..............................6-556.8.4Buried Piping Area Factors.................................6-556.8.5Activated Concrete/Rebar Area Factors........................6-566.9Standing Building Dose Assessment and DCGL Determination...........6-566.9.1Dose Assessment Method..................................6-566.9.2 Standing Building DCGLs..................................6-576.9.3Standing Building Area Factors..............................6-586.10References....................................................6-59Attachments -1Fill Direct Dose Microshield Output -2BNL Kd Report for Fill -3BNL Kd Report for Concrete -4Irrigation Memorandum -5 Concrete Density -6Activated Concrete Inventory -7Remaining Embedded Piping -8 Deep Soil Microshield Output -9Deep Soil RESRAD Output MYAPC License Termination PlanPage 6-iiiRevision 3 October 15, 2002 -10Buried Piping List and Projected Concentration Calculation -11Buried Piping RESRAD Output -12Buried Piping Microshield Output -13DCGL/Total Dose Spreadsheets -14Soil Area Factor Microshield Output -15Standing Building Area Factor Microshield Output -16Forebay Sediment Dose Assessment (Has been replaced by Attachment 2H)l -17Unitized Dose Factors for Activated Rebar -18NRC Screening Levels for Contaminated Basement and Special Areasl -19 lSpecial Areas Unitized Dose FactorslList of Tables Table 6-1Environmental Media Affected by Transfer from Contaminated Materials...............6-7 Table 6-2Environmental Media and Dose Pathways for the Resident Farmer Scenario.............6-7 Table 6-3Selected Kd Values (cm 3/g) for Basement Fill Model...............................6-16 MYAPC License Termination PlanPage 6-ivRevision 3 October 15, 2002 Table 6-4Contaminated Basement Surfaces Unitized Dose Factors............................6-21 Table 6-5Activated Concrete Unitized Dose Factors 1.0 pCi/g...............................6-23 Table 6-6A lBOP Embedded Piping Unitized Dose Factors....................................6-25l Table 6-6B lEmbedded Spray Pump Piping Unitized Dose Factors..............................6-26l Table 6-7Surface Soil Unitized Dose Factors 1.0 pCi/g Cs-137...............................6-29 Table 6-8Site Specific Parameters used in RESRAD Deep Soil Analysis.......................6-30 Table 6-9Deep Soil Unitized Dose Factors...............................................6-31 Table 6-10 Buried Piping Unitized Dose Factors............................................6-35 Table 6-10A lEstimated Media Activity....................................................6-37l Table 6-10B lExcavated Soil Direct Dose...................................................6-39l Table 6-11Contaminated Material DCGL.................................................6-45 Table 6-12Area Factors (AF) for Surface Soil and Deep Soil.................................6-54 Table 6-13Gross Beta DCGL For Standing Buildings.......................................6-58 Table 6-14Area Factors (AF) for Standing Buildings........................................6-59 MYAPC License Termination PlanPage 6-1Revision 3 October 15, 20026.0COMPLIANCE WITH THE RADIOLOGICAL DOSE CRITERIA 6.1IntroductionThe goal of the MY decommissioning project is to release the site for unrestricted use incompliance with the NRC's annual dose limit of 25 mrem/y plus ALARA and the enhanced State of Maine clean-up criteria of 10 mrem/y or less for all pathways and 4 mrem/y or less for groundwater sources. Both the State and NRC dose limits apply to residual radioactivity that is distinguishable from background. This section provides the methods for calculating the annual dose from residual radioactivity that may remain when the site is released for unrestricted use.

The dose assessment methods are used to determine Derived Concentration GuidelineLevels (DCGLs) for nine different potentially contaminated materials. The DCGLs are the levels of residual radioactivity that correspond to the enhanced state clean-up criteria of 10 mrem/y or less for all pathways and 4 mrem/y or less for groundwater sources to the average member of the critical group. The DCGLs developed to demonstrate compliance with the enhanced State criteria are intended to also serve to demonstrate compliance with the NRC's 25 mrem/y plus ALARA regulation.Maine Yankee intends to dismantle equipment and systems and remediate structures andland areas (per LTP Sections 3 and 4) to ensure that residual radioactivity levels are at, or below, the DCGLs. After remediation is completed, a final site survey will be performed (per LTP Section 5) to verify compliance with the DCGLs. The final survey report will document that the DCGLs have been met and serve to demonstrate that the Radiological Criteria for License Termination, as codified in 10 CFR 20 Subpart E and Maine State Law LD 2688-SP 1084 have been fully satisfied.A dose assessment will be performed for each of the following materials: 1) contaminatedbuilding basement surfaces; 2) embedded pipe; 3) activated concrete/rebar;

4) groundwater; 5) surface water; 6) surface soils; 7) buried piping; 8) deep soils; and 9)

Forebay sediment. Appropriate dose models and model input parameters were developed and justified for each material. The dose from each material was evaluated and summed with that from other materials as necessary to determine the total dose to the average member of the critical group.

6.2 Site Condition After Decommissioning This section provides a brief overview of the planned site condition afterdecommissioning as well as a summary of site geology and hydrology. Detailed information on the planned final site condition is provided in Section 3.2.4. LTP MYAPC License Termination PlanPage 6-2Revision 3 October 15, 2002Section 8.4 provides a more detailed overview of the geological and hydrologicalcharacteristics of the site.In general, when decommissioning is complete the site will be predominantly a backfilledand graded land area restored with indigenous vegetative cover. The only above grade structures remaining per the current plans include the 345 KV switchyard. The former Low-Level Waste Storage Building (now the ISFSI Security Operations Building) will remain in place until the fuel is removed from the ISFSI. Building basements and foundations greater than three feet below grade will be backfilled and left in place.

Buried piping that is at least three feet below grade will be remediated as necessary, surveyed, and abandoned in place. 6.2.1Site Geology and Hydrology The site geology consists of a series of ridges and valleys striking north-south thatreflect the competency and structural nature of the underlying bedrock. Deep valleys are filled with glaciomarine clay-silt soil and ridges are characterized by exposed bedrock or thin soil cover over rock. Surface drainage moves both to the north and south along the axes of the topographic valleys and also runs east and west down the flanks of the ridges. In the plant area, where the ground surface is relatively flat, manmade underground storm drains and catch basins control the surface runoff. In the area south of Old Ferry Road, drainage from a large area north of Old Ferry Road and the northern half of Bailey Point discharges in underground manmade piping to Bailey Cove. The groundwater regime at the Maine Yankee facility is comprised of twoaquifers: (1) a discontinuous surficial aquifer in the unconsolidated glaciomarine soils and fill material; and (2) a bedrock aquifer. The surficial aquifer is not present continuously across the site, as the overburden soils are thin to non-existent in some portions of the site. This is especially true in the southern portion of Bailey Point. The bedrock aquifer is present below the entire site and vicinity. Groundwater originating near the surface in the northern portion of the sitegenerally moves vertically into the soil except in the wetland areas where groundwater discharge locally occurs. After slow movement through the soil, the groundwater moves into the deeper bedrock and travels toward the bay, discharging upward in the near-shore area. In the southern portion of the site, groundwater originating near ground surface generally stays near the surface, rather than penetrating deep into the bedrock.

MYAPC License Termination PlanPage 6-3Revision 3 October 15, 2002During plant operation, impacts to the groundwater flow regime were limited todraw-down of the groundwater surface caused by foundation drains around the containment structure and, to a lesser extent, draw-down caused by active water supply wells. Following decommissioning of the containment structure, groundwater levels will recover to approximate pre-construction levels.

6.3 Critical

GroupThe regulations in 10 CFR 20 Subpart E require the dose to be calculated for the averagemember of the critical group. The critical group is defined in 10CFR20.1003 as "the group of individuals reasonably expected to receive the greatest exposure to residual radioactivity for any applicable set of circumstances." The average member of the critical group is a conservative approach and is also used for demonstrating compliance with the dose criteria in Maine State Law LD 2688-SP 1084. The critical group selected for the

MY site dose assessment is the resident farmer.

The resident farmer is a person who lives on the site after the site is released forunrestricted use and derives all drinking and irrigation water from an onsite well. In addition, a significant portion of the resident's diet is assumed to be derived from food grown onsite. NRC guidance in NUREG-1727, NUREG-1549, and NUREG-5512 identify the resident farmer as a conservative onsite critical group. The resident farmer critical group applies to existing open land areas and all site areas where standing buildings have been removed to three feet below grade. It is unlikely that other future site uses would result in a dose exceeding that calculatedfor the hypothetical resident farmer. It is more probable that actual future occupants of the site would engage in behaviors that would result in lower doses. For example, it is more likely that a hypothetical future resident would use the municipal water supply, as opposed to well water, since this is the common practice in the vicinity of the site and the yield from onsite test wells has been determined to be low and not suitable for consumption. Further, it is most likely that the site will be limited to industrial use. In

this case the future site occupant would be a worker as opposed to the resident farmer. A third example would be an onsite resident who does not derive a significant fraction of dietary needs from an onsite farm. The important conclusion from these examples is that the dose calculated for the hypothetical resident farmer will likely be a conservative

estimate of the dose that an actual site occupant or site visitor would receive. Maine Yankee has assessed the potential for the filled basements to be excavated andoccupied at some time in the future and does not believe that this scenario meets the "reasonable expectation" threshold required by the definition of a critical group in 10 CFR 20.1003. As stated in NUREG-1727, page C26, compliance with the dose limit does not require an investigation of all possible scenarios and the use of the average MYAPC License Termination PlanPage 6-4Revision 3 October 15, 2002member of the critical group is intended to emphasize the uncertainty and assumptionsneeded in calculating potential future dose, while limiting "boundless speculation" on possible future exposure scenarios. As discussed above, selecting the resident farmer critical group is a sufficiently conservative projection of future land use. Further assuming that an individual excavates filled basements and attempts to renovate and occupy the basements is not considered plausible and results in excessive conservatism.Notwithstanding the very low probability of excavation occurring, Maine Yankee willlimit the potential activity on basement fill to concentrations below the surface soil DCGL level corresponding to 10 mrem/y. In addition, cost studies conducted to date indicate that it is more expensive to remediate soil than basement surface contamination.

As discussed in Section 6.9, the selected Basement Contamination DCGLs are limited in order to maximize soil DCGL levels. The cost optimization process supported selecting Basement Contamination DCGLs that are below the NRC screening values for standing building surfaces. At these levels, the resident farmer dose for contamination onl basement surfaces was shown to be low (per Table 6-11) for any credible future land use.l

6.4 Conceptual

ModelThe Conceptual Model for dose to the resident farmer critical group is different to someextent for each contaminated material due to the different physical characteristics of the

materials and different source term radionuclides. The Conceptual Model for each

material is described in detail in Section 6.6. In general, the overall site Conceptual Model includes a resident farmer who lives on thesite after release for unrestricted use, draws drinking water and irrigation water from the worst-case onsite well location, and derives a substantial percentage of annual food

requirements from the onsite resident farm.The hypothetical dose from each potentially contaminated material is evaluatedindependently. However, the total resident farmer dose results from the summation of the contributions from all materials and all pathways. The method for summing the doses and selecting DCGLs for all contaminated materials is provided in Section 6.7.

6.5Environmental Media and Dose Pathways6.5.1Contaminated Materials

There are nine contaminated materials that could contribute to dose:

a.Embedded pipeb.Buried pipel MYAPC License Termination PlanPage 6-5Revision 3 October 15, 2002c.Activated concrete/rebard.Groundwater e.Surface Water f.Basement surfaces g.Surface soil h.Deep soil i.Forebay Sediment6.5.2Environmental Media After considering radionuclide transfer from the nine contaminated materials, there are five environmental media that could deliver dose to the resident farmer.

These are groundwater, surface soil, deep soil, surface water, and basement fill.

Groundwater concentration may increase through the transfer of radionuclides from contaminated basement surfaces, activated concrete/rebar, deep soil, and embedded pipe. Note that the "groundwater" environmental medium includes contributions from water contained in building basements as well as other sources.

Basement fill may also become slightly contaminated through the transfer of contamination from basement surfaces, embedded piping, and activated

concrete/rebar. Table 6-1 indicates which environmental media are affected by

the transfer of radionuclides from contaminated materials.The residual contamination in the Forebay sediment is not transferred to any ofthe five environmental media and is evaluated independently. Therefore, Forebay

sediment is not included in Table 6-1.6.5.3Dose Pathways

The five environmental media listed in Table 6-1 deliver dose to the residentfarmer through one or more of the following dose pathways: 1) drinking water;

2) direct exposure; 3) ingesting soil, plants, animals, or fish; and 4) inhaling resuspended soil. These pathways are consistent with those listed in NUREG-1549 for the resident farmer. A given environmental medium will not contribute dose through all pathways. Table 6-2 lists the dose pathways applicable to each environmental medium. Notethat groundwater contributes to the plant and animal pathways through irrigation.6.5.4Radionuclide Concentrations in Environmental Media To calculate the dose from each pathway the radionuclide concentrations in each environmental medium must be calculated. The concentrations in the surface soil, MYAPC License Termination PlanPage 6-6Revision 3 October 15, 2002deep soil, and surface water can be used directly in the dose assessment since there is no contribution from other contaminated materials. However, the final concentrations in groundwater and basement fill, and the resulting dose, will depend on the transfer of contamination from other materials. Final concentrations in the five environmental media are calculated by summing

contributions from various materials as listed below. The contaminated materials that contribute to each of the environmental media aresummarized below. The materials in brackets are those requiring transfer

evaluations.*Groundwater Concentration = [basement surface contamination] +[embedded pipe] + [activated concrete/rebar] + [deep soil] + [buried pipe]

+ existing groundwater concentration*Basement Fill Concentration = [basement surface contamination] +[embedded pipe] + [activated concrete/rebar]*Surface Soil Concentration = surface soil concentration*Deep Soil Concentration = [buried pipe] + deep soil concentration l

• Surface Water Concentration = surface water concentration MYAPC License Termination PlanPage 6-7Revision 3 October 15, 2002 Table 6-1Environmental Media Affected by Transfer from Contaminated MaterialsGround WaterSurface Soil Deep Soil Surface WaterBasementFillBasementContamination XXSurface SoilXDeep SoilXX GroundwaterX Embedded pipeXX Surface WaterX

Activatedconcrete/rebar XXBuried Pipel X X Table 6-2Environmental Media and Dose Pathways for the Resident Farmer ScenarioDirect RadiationDrinking Water Plant,Animal, Soil Ingestion InhalationFish IngestionSurface SoilXXXDeep SoilXBasement FillXGroundwaterXX*X*Surface Water XX* These pathways result through irrigation 6.6Material Specific Dose Assessment Methods and Unitized Dose FactorsEach material has unique characteristics that must be considered when developing the conceptual and mathematical model for dose assessment. This section provides the dose assessment methods and results for each material in a unitized format by expressing the

dose as a function of unit concentrations such as 1 dpm/100 cm 2 or 1 pCi/g. The unitizedformat facilitates the summation of doses from all materials and the selection of material specific DCGLs (see Section 6.7).

MYAPC License Termination PlanPage 6-8Revision 3 October 15, 20026.6.1 Contaminated Basement Surfacesa.Conceptual Model The Dose Model for contaminated basement surfaces assumes that thebuildings are demolished to three feet below grade. The remaining basements are then decontaminated as necessary, filled with a suitable material (current plans call for fill with Bank Run Sand or flowable fill)l and the area restored to grade, which results in a three-foot cover over the top of the filled basements. After the site is restored, rainwater and groundwater infiltrate into the basements and occupy the void space in the

fill material. The available void space volume is a function of the fill material porosity.The entire inventory of contamination on the basement surfaces, includingthe concrete and steel liner, is assumed to be instantaneously released and mixed with the water that has infiltrated into the basements. In this context, "surface" is intended to include all radioactivity, at all depths (this

does not include activated concrete, which is treated as a separate material). Analyses of Maine Yankee concrete have indicated that, on average, the contamination is about 1 mm deep in the concrete. The liner

contamination should be true surface contamination, i.e., not at any significant depth.Using a mass balance approach, the radionuclides that are released fromthe surfaces are assumed to instantaneously reach equilibrium between the water, fill, and concrete. The relative equilibrium concentrations in the water, fill, and concrete are a function of the material Kd, mass, and porosity.The critical group is the resident farmer who is assumed to drill a domesticwater well into the worst case basement, i.e., that with the highest basement surface area to volume ratio. The amount of activity available for release is assumed to be directly proportional to the surface area of contaminated material. Therefore, the highest surface area/volume ratio results in the maximum radionuclide inventory and maximum concentrations in the water, fill, and concrete. The resident farmer is also assumed to occupy the land immediately above the basement, which maximizes direct exposure through the 3-foot cover. (Since the resident farmer is assumed to receive dose from exposure to surface soil based on 100% stay-time, the additional direct dose from basement fill is a MYAPC License Termination PlanPage 6-9Revision 3 October 15, 2002 conservative addition to dose. Thus, no credit is taken overall for the absence or presence of the 3 foot cover.)The conceptual model results in three dose pathways to the residentfarmer: 1) drinking water from the well; 2) irrigating with water from the

well; and 3) direct radiation from radionuclides in the fill.b.Mathematical Model A mathematical model was developed to calculate the equilibrium radionuclide concentrations in the basement water, fill, and concrete after the infiltration of rainwater and groundwater. Contamination is assumed to diffuse into and re-adsorb on concrete surfaces since concrete is a porous media. The re-adsorption on the steel liner is expected to be less than the concrete and is considered to be bounded by the concrete analysis.

The mathematical model includes calculations to determine the resident farmer dose from drinking water derived from a well drilled directly into the basement fill, irrigating with the water, and being directly exposed to the covered fill. The model is intended to be a simple, conservative, screening approach.The radionuclide inventory, water volume, fill volume, and concretevolume subject to re-adsorption are the quantities required to determine

the equilibrium radionuclide concentrations in the three materials. The

initial condition of the model is that a volume of water has infiltrated into the basement that is equal to the annual volume required for drinking, domestic use, and irrigation by the resident farmer. As stated above, the well is placed directly into the basement fill containing the water. From

this initial condition the volumes and masses of the three materials, and the maximum radionuclide inventory released to the water, can be calculated.The annual resident farmer well-water usage is assumed to be 738 m 3 (justification provided below). This implies that the fill volume is 738 m 3divided by the porosity of the soil, which is assumed to be 0.3(justification provided below). Therefore, the model fill volume is

2460 m 3. This is the minimum fill volume required to contain the annualresident farmer water volume. Depending on the infiltration rate, smaller fill volumes could supply the required 738 m 3/y water volume, but thiswould result in slightly lower average annual concentrations. Assuming a MYAPC License Termination PlanPage 6-10Revision 3 October 15, 2002 model volume of 2460 m 3, and no dilution through infiltration recharge, isthe most conservative approach.The actual basement open volumes of the PAB, Spray, and Fuel buildings are less than 2460 m 3, but the containment basement volume is greater, i.e., 8217 m

3. The larger containment volume has no effect on the resultsince the additional hypothetical water volume does not affect the

radionuclide concentrations in the water, or the assumed annual water use.

In fact, as explained below, using actual containment basement dimensions, including volume and surface area, would reduce water concentrations by a factor of 3.7 since the surface area to volume ratio for

the containment basement is lower than that used in the model. The effect of surface area to volume ratio and the rationale for selecting the value

used in the model are described below.The basement surface area to open volume ratios have a direct effect onthe results and are necessary for determining two parameters. The most important affected parameter is the maximum radionuclide inventory.

Less important, but also related, is the volume of concrete available for re-adsorption of radionuclides. Using the maximum surface area/volume ratio from the four basements maximizes the radionuclide inventory and the resulting water, fill, and concrete concentrations.The maximum ratio of concrete surface area/basement open volume of 1.7 m 2/m 3 is found in the Spray building basement. The surfacearea/volume ratios for the Containment, PAB, and Fuel buildings are

0.46 m 2/m 3 , 1.03 m 2/m 3 , and 0.49 m 2/m 3, respectively. Using themaximum ratio of 1.7 m 2/m 3 results in conservative dose calculations forthe Containment, PAB, and Fuel buildings by factors of 3.7, 1.65, and 3.5 respectively. If necessary, as the project proceeds, Maine Yankee may use building-specific surface area/volume ratios based on the data presented in Section 6.6.1(d)(2) to calculate building-specific DCGLs.Multiplying the 1.7 m 2/m 3 ratio by the fill volume (2460 m

3) results in themaximum contaminated surface area that could contribute to the source term for a given 738 m 3 of water. Accordingly, the maximum surface area in the model would be 4182 m 2, which exceeds the actual surface area of any of the building basements. This occurs because the 1.7 m 2/m 3 ratio isfrom the Spray building and the maximum surface area of 3775 m 2 is inthe Containment building. However, consistent with a conservative screening approach, and to maintain the correct mathematical relationships MYAPC License Termination PlanPage 6-11Revision 3 October 15, 2002between porosity, annual water volume, and surface area, the 4182 m 2surface area will be used in the model. Note that using 3775 m 2 wouldreduce the available source term and thereby reduce water concentrations.Assuming that the water penetrates to a depth of 1 mm in the concrete, the concrete volume available to re-adsorb radionuclides from contaminated

water is 4.2 m

3. The 1 mm depth is based on analyses of contaminatedMaine Yankee concrete. Although the conditions are different, i.e., water saturation after decommissioning versus periodic wet contamination events during operation, the penetration of water into the concrete after the basements are filled with water is also assumed to be 1 mm. This is considered a conservative assumption since increasing the concrete penetration depth will decrease the concentrations in the fill and in the

water.The model uses two approximations related to re-adsorption onto concretethat have a very small effect on the final results. First, the fill volume is calculated assuming all of the 738 m 3 water volume is contained in the fill,not mixed between the fill and concrete. An exact solution would require consideration of both the fill and concrete volumes simultaneously.

However, the affected concrete volume is very low and the corresponding

water volume in the concrete is about 1 m

3. This is less than 1% of the 738 m 3 total and is insignificant. Second, the porosity of 0.3 is assumed to apply to both fill and concrete. The same porosities are used in the

model in order to produce the simplified solution provided in Equation 7.

However, site-specific measurements indicate that the actual concrete porosity is 0.15. Using a porosity of 0.15 would decrease the volume of

water in the concrete to about 0.5 m 3.. An exact solution to these twoapproximations would have a very small effect on the results and is an unnecessary level of detail considering the conservative screening

approach used in the model.The approach assumes uniform mixing among the soil, water, andconcrete. Uniform mixing within the fill is not unreasonable considering

the surface area to volume ratio of 1.7 m 2/m 3. Assuming a planargeometry, this means that the water is required to mix over a distance of 0.6 m in the backfill. Although assuming planar geometry is a simplification, it demonstrates that water mixing over long distances in the fill is not intrinsic to the validity of the screening model.

MYAPC License Termination PlanPage 6-12Revision 3 October 15, 2002The calculations for determining the equilibrium concentrations in thebasement water, fill, and concrete are based on a mass balance approach.

The total mass in the system, M t, is the sum of the mass in the water (M w),the mass sorbed to the fill (M b), and the mass sorbed to the concrete (M c). For these calculations, mass is expressed as activity, A. The total activity, A t, is the total radionuclide inventory in the 4182 m 2 basement concretesurface under consideration. Equations (1) through (7) described below

are solved for each radionuclide in the Maine Yankee Radionuclide Mixture.A t = A w + A f + A c (1)Where:A t is total activity (pCi)

A w is the total activity in water (pCi)

A f is the total activity in the fill (pCi)

A c is the total activity in the concrete (pCi)The activity in the water is defined as:

A w = !C V t (2)Where:! is the porosity of the fill and concrete C is the concentration in solution (pCi/l) and, V t is the total system volume (sum of the volume of fill and concrete, m 3).At equilibrium the activity adsorbed to the fill and concrete is directly proportional to the concentration in the water. The proportionality

constant used in these calculations is the distribution coefficient, Kd, and

has units of cm 3/g. Distribution coefficients are widely accepted measures of sorption onto the solid phase, and the solid/liquid phase ratio, and are accepted for use in risk assessments by national and international regulatory agencies and scientific organizations including the U.S. Nuclear Regulatory Commission and the U.S. Environmental Protection Agency.The activity adsorbed on the fill and the concrete can be represented as:

A f = " f Kd f C V f (3)Where: " f is fill bulk density (g/cm 3)Kd f is fill distribution coefficientC is water concentration(pCi/l)

MYAPC License Termination PlanPage 6-13Revision 3 October 15, 2002 V f is fill volume (m 3)and A c = " c Kd c C V c (4)Where: " c is concrete bulk density (g/cm

3) Kd c is concrete distribution coefficient C is water concentration (pCi/l)

V c is concrete volume (m 3)The bulk density of the fill is assumed to be 1.5 g/cm 3 based on analyses ofpotential fill (reference provided below). For the concrete, a site-specific value of 2.2 g/cm 3 was used (reference provided below). V is the volume of the solid phase; V f is 2460 m 3 and V c is 4.2 m 3. Combining the terms from Equations (2), (3), and (4) gives:

A t = !C V t + " f Kd f C V f + " c Kd c C V c (5)Multiplying the second and third terms by (!V t)/(!V t), i.e., 1, andrearranging gives:

A t = !C V t + (!V t C)( " f Kd f V f) /(!V t ) + (! V t C)(" c Kd c V c)/(! V t) (6)Recognizing from Equation (1) that the term, !C V t is the activity in the water phase, A w, allows Equation 6 to be rewritten as:

A t = A w (1 + " f (Kd f/!)(V f/V t) + " c (Kd c/!)(V c/V t))(7)To calculate the water concentration, drinking water dose, concentration inthe fill, and concentration on the concrete surfaces, Equation (7) is first solved for A

w. All of the terms in Equation (7) are known except A

w. Thewater concentration, C, is then calculated using Equation (2). After solving for C, the backfill and concrete concentrations are calculated using

Equations (3) and (4).c.Dose Calculations The concentrations in the basement water and fill are used to calculatedose. There are three dose pathways to the resident farmer after the fill is MYAPC License Termination PlanPage 6-14Revision 3 October 15, 2002placed in the basements, the three-foot cover is completed, and waterinfiltrates the basements. These are drinking water dose, irrigation dose, and direct dose. The dose calculations are described in Equations (8) through (10). The equations are used to calculate dose for each radionuclide in the Maine Yankee mixture. There will be no ingestion or inhalation associated with the fill because ofthe presence of the cover. Ingestion or inhalation could occur if the fill were excavated at some time in the future. To account for this possibility, the projected basement fill concentration is limited to ensure that the concentration will not exceed the surface soil DCGL and that the dose will not increase over that calculated with the earthen cover in place. In fact, the hypothetical dose would decrease if the fill were excavated at some time in the future.1.Drinking Water Dose Drinking water dose is calculated from the radionuclide concentrations in the basement water. As shown in Table 6-1, the basement water is one of several contributors to drinking water dose. The annual water intake is assumed to be 478 L/y consistent with the default values in the NRC screening code, DandD, Version 1. Dose conversion factors are taken from Federal

Guidance Report No. 11.

Dose dw = ( C pCi/l)(478 L/y)(DCF mrem-y/pCi)(8)Where:C is water concentration in pCi/LDCF is FGR 11 dose conversion factor2. Irrigation Dose Including irrigation dose is conservative because irrigation inMaine is uncommon due to relatively high annual precipitation.

However, consistent with a screening approach it is included. The irrigation rate is assumed to be 0.274 L/m 2/d (justification providedbelow). The source of the water is the resident farmer well placed in the building basement. The annual irrigation volume is mixed in

a 15 cm depth of soil, which is consistent with the NRC DandD

model as described in NUREG-5512, Volume 1. The dose from the resulting soil concentrations were calculated using the NRC MYAPC License Termination PlanPage 6-15Revision 3 October 15, 2002screening values in NUREG-1727, Table C2.3 , converted tolmrem/y per pCi/g.

Doseirrigation

= (Csoil pCi/g)(NUREG-1727 mrem/y per pCi/g) (9)Where:Doseirrigation is the annual dose from irrigation (mrem/y)

Csoil is soil concentration in pCi/g (NUREG-1727) is the soil screening value from NUREG-1727, Table C2.3 converted to mrem/y per

pCi/g Csoil = (pCi/L in water)(0.274 L/m 2/d)(365 d)(1 m

2) (1m 2)(0.15 m)(1E+06 cm 3/m 3)(1.6 g/cm

3) (10)3. Direct Dose The direct dose was calculated using the Microshield codeassuming a three-foot soil cover, 10,000 m 2 area, and 5.8 m depth.

The 5.8 m depth represents the deepest basement, i.e., containment.

The Microshield result for "Deep Dose Equivalent, Rotational Geometry," was used and is generally referred to as "exposure."

The resulting exposure rate was multiplied by the annual outdoor occupancy time of 964 hours0.0112 days <br />0.268 hours <br />0.00159 weeks <br />3.66802e-4 months <br /> (0.1101 x 365 days x 24 hr/day) from the NRC DandD, Version 1, screening code to calculate the annual direct exposure dose. The Microshield output reports are provided

in Attachment 6-1.d.Model Input Parameters The following section describes and justifies the parameters used in the concentration and dose calculations. 1. Distribution Coefficients, Kd Fill Kd values were either derived from literature (mean values) orfrom the results of analyses of site-specific fill materials. The site-specific Kd analyses were performed by Brookhaven National Laboratory (BNL) (results provided in Attachment 6-2). At this time, the most likely fill material is Bank Run Sand or flowablel fill. Therefore, the average Kd's for Bank Run Sand or flowablel MYAPC License Termination PlanPage 6-16Revision 3 October 15, 2002fill from Attachment 6-2 were used in the model. Table 6-3 listsl the fill Kd's, and the reference, for each radionuclide.Concrete Kd values were either derived from literature or from theresults of site-specific Kd analyses. The site-specific Kd analyses were performed by BNL (results provided in Attachment 6-3).

Table 6-3 lists the concrete Kd's, and the reference, for each radionuclide. It is seen that for cement, a few Kd's were left blank.

This indicates data were not available and a value of zero (0) wasl used in the calculations. A Kd of zero (0) maximizes thel concentration in water. In addition, the Krupka reference did not contain Kd information for cobalt or iron. It was assumed that the Kd's for these two metals were the same as nickel. However, the overall effect of the concrete is small, regardless of Kd.

Table 6-3Selected Kd Values (cm 3/g) for Basement Fill ModellRadionuclideMeanFlowablelFill KdReference for Mean KdConcrete KdReference for Kd in cement lH-300Fe-5525Baes, Table 2.13100Krupka Table 5.1 Ni-63128lAttachment 6-2100Krupka Table 5.1Mn-5450Sheppard, Table A-1 Co-57128lAttachment 6- 2100Krupka Table 5.1Co-60128lAttachment 6-2100Krupka Table 5.1Cs-13479lAttachment 6-23Attachment 6-3Cs-13779lAttachment 6-23Attachment 6-3Sr-906Attachment 6-21.0Attachment 6-3 Sb-12545Sheppard, Table A-1 Pu-238550Sheppard, Table A-15000Krupka Table 5.1 Pu-239/240550Sheppard, Table A-15000Krupka Table 5.1 Pu-241550Sheppard, Table A-15000Krupka Table 5.1 Am-2411900Sheppard, Table A-15000Krupka Table 5.1 MYAPC License Termination PlanPage 6-17Revision 3 October 15, 2002 Table 6-3Selected Kd Values (cm 3/g) for Basement Fill ModellRadionuclideMeanFlowablelFill KdReference for Mean KdConcrete KdReference for Kd in cement lCm243/2444000Sheppard, Table A-15000Krupka Table 5.1C-145Sheppard, Table A-1 Eu-152400Onishi, Table 8.35 Eu-154400Onishi, Table 8.352.Maximum Surface Area to Volume Ratio The building basements that will remain following demolition ofsite structures include the Containment, PAB, Spray and Fuel Building basements. The open-air volumes of the basements are

8217 m 3 , 1584 m 3 , 1136 m 3 , and 837 m 3 respectively. This represents the volume of fill required in each basement. The wall

and floor surface areas are 3775 m 2 , 1637 m 2 , 1883 m 2 , and 409 m 2respectively. The basement volumes and surface areas were

determined in Maine Yankee calculation EC 01-00(MY). The maximum surface area to volume ratio of 1.7 m 2/m 3 is found in theSpray building basement.

3. Porosity The porosity of the fill material is assumed to be 0.3. The range ofmean porosities for a wide variety of soil types are listed in

NUREG-5512, Volume 3, "Residual Radioactive Contamination From Decommissioning. Parameter Analysis," Page 6-64, Table 6.41. The porosities listed in NUREG-5512 ranged from

0.36 to 0.49.

The projected dose from contaminated concrete in the basement fillmodel decreases with increasing porosity. However, the projected

doses from the embedded pipe and activated concrete increase with increasing porosity. This is because the source term for embedded and buried piping is constant and the source term for contaminated concrete is a function of surface area. All three dose assessment models are conservative. However, the activated concrete and embedded piping source term assumptions are much more MYAPC License Termination PlanPage 6-18Revision 3 October 15, 2002 conservative than those used for the basement concrete and theresulting dose is a small fraction of that from contaminated concrete. Therefore, the porosity effect on the contaminated concrete dose is used to select a porosity at the lower end of the range, e.g., 0.3.4. Annual Drinking Water Volume The annual drinking water volume was assumed to be 478 l/y.

This is the default volume from NRC DandD, Version 1 screening

code.5. Irrigation Rate and Annual Irrigation Volume Annual irrigation volume was based on interviews with representatives of the Maine USDA-NRCS. The individuals

contacted are documented in a memorandum provided in -4. The USDA representatives indicated that irrigation in Maine is uncommon, but that in drought years irrigation may occur. The Maine USDA representatives indicated that the drought irrigation rate for a family garden would not be expected to exceed 4-5 in/y (10 to 12 cm/y). The 10 cm/y rate was

used in the model, which can be converted to 0.274 l/m 2/d. Tocalculate total annual volume, the 10 cm/y rate was multiplied by

the default cultivated area of 2400 m 2 from the DandD screeningmodel (NUREG-1727, Appendix C, Section 2.3.2). This results in the annual irrigation volume of 240,000 l/y.6. Annual Domestic Water Use

Annual domestic water volume is derived from NUREG-5512,Volume 3, Page 6-37, Table 6-19. The per capita consumption rate for the State of Maine is listed as 124,422 l/y. Assuming a family

of four, this corresponds to a total domestic water volume of 497,688 l/y. The assumption of four occupants is based on the land occupancy rate from NUREG-1727, Table D2, of 0.0004

persons/m 2 and an assumption that the resident farm size is 10,000 m 2.

MYAPC License Termination PlanPage 6-19Revision 3 October 15, 20027. Total Resident Farmer Annual Well Water Volume The total annual volume of water from the resident farmer well isthe sum of the domestic use plus irrigation use. Domestic use is 497,688 l/y and irrigation use is 240,000 l/y for a total of 737,688 l/y. A rounded value of 738 m 3/y was used in the model. 8. Concrete Density Concrete density was determined by site-specific analysis to be2.2 g/cm3 (Attachment 6-5). 9. Fill Material Density Density of the possible fill material is 1.5 g/cm 3 (Attachment 6-2). This corresponds to Bank Run Sand.10.Soil Density Density of soil is 1.6 g/cm 3 based on an average of the densities ofBank Run Sand and Bank Run Gravel from Attachment 6-2. This average is assumed to be representative of the site soil, which is comprised primarily of backfill. 11.Dose Conversion Factors (DCFs)

The DCFs are in units of Committed Effective Dose Equivalent(CEDE) and are taken from Federal Guidance Report No. 11, "Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion," Table 2.2, EPA-520/1-88-020.12.Outdoor Occupancy Time The DandD, Version 1, default value of 0.1101 y or 965 hr/y is used.e. Unitized Dose Factors for Contaminated Basement Surfaces Using Equations 1-10 above, the radionuclide concentrations in basementwater, fill, and concrete, and the dose to the resident farmer were calculated using a simple spreadsheet application. The activity of each MYAPC License Termination PlanPage 6-20Revision 3 October 15, 2002radionuclide in the Maine Yankee mixture for contaminated surfaces was set to1 dpm/100 cm 2 of surface area. The surface was assumed to be concrete for the purpose of the calculation to evaluate the potential effect of re-adsorption on concrete. The spreadsheet output and the resulting unitized dose factors are provided in Table 6-4 (see next page). 6.6.2Activated Basement Concrete/Rebara.Conceptual Model Activated concrete and rebar is present in the ICI sump area in thecontainment building. The current plan is to remediate activated concrete exceeding 1 pCi/g total activity (sum of all radionuclides) and any rebar associated with this concrete. The walls and floors consist primarily of concrete with rebar being a small percentage. Characterization results indicate that the total activity concentration in rebar is about 1.9 times higher than the concrete surrounding the rebar. In addition, the radionuclide mixtures for concrete and rebar differ as indicated in

Table 2-9. However, as shown in Attachment 6-17, the calculated dose from the rebar is less than the dose from the surrounding concrete (see Table 6-11 for activated concrete dose), accounting for both the higher relative concentration and the rebar radionuclide mixture. The concrete dose was 4.07 E-2 mrem/y and the rebar dose was 3.54 E-3 mrem/y.l Therefore, the walls and floors are conservatively assumed to be comprised entirely of activated concrete in the dose calculation.

MYAPC License Termination PlanPage 6-21Revision 3 October 15, 2002Porosity0.30Fill Volume2460.0 m 3Annual Total Well Water Vol738.0 m 3Bulk Density1.50 g/cm 3Surface Area/Open Vol1.70 m 2/m 3Irrigation Rate0.274 L/m 2-dYearly Drinking Water478.0L/yrConcrete Volume4.18 m 3Surface Soil Depth0.15mWall Surface Area4182.0 m 2Concrete Density2.20 g/cm 3NUREG-1727FGR 11 MicroshieldKdKdDrinkingIrrigationDirectTotal Nuclidemrem/y permrem permrem/y perInventoryInventoryFillConcreteAdsorptionWaterFillConcreteNuclideWater DoseDoseDose DosepCi/gpCipCi/gdpm/100 cm2pCicm3/gmcm3/gmFactorpCi/LpCi/gpCi/gmrem/ymrem/ymrem/ymrem/ySr-901.47E+011.42E-040.00E+001.00E+001.88E+056.02E+011.00E+003.02E+028.45E-045.09E-058.45E-07Sr-905.74E-055.52E-060.00E+006.29E-05Cs-1344.39E+007.33E-056.09E-051.00E+001.88E+057.91E+013.00E+003.96E+026.44E-045.09E-051.93E-06Cs-1342.26E-051.26E-063.10E-092.38E-05Cs-1372.27E+005.00E-051.20E-051.00E+001.88E+057.91E+013.00E+003.96E+026.44E-045.09E-051.93E-06Cs-1371.54E-056.49E-076.11E-101.60E-05Co-606.58E+002.69E-056.30E-041.00E+001.88E+051.28E+021.00E+026.40E+023.98E-045.09E-053.98E-05Co-605.12E-061.16E-063.20E-086.32E-06Co-571.67E-011.18E-062.80E-081.00E+001.88E+051.28E+021.00E+026.40E+023.98E-045.09E-053.98E-05Co-572.25E-072.96E-081.42E-122.54E-07Fe-552.50E-036.07E-070.00E+001.00E+001.88E+052.50E+011.00E+021.27E+022.01E-035.01E-052.01E-04Fe-555.82E-072.23E-090.00E+005.84E-07H-32.27E-016.40E-080.00E+001.00E+001.88E+050.00E+000.00E+001.00E+002.55E-010.00E+000.00E+00H-37.80E-062.57E-050.00E+003.35E-05Ni-631.19E-025.77E-070.00E+001.00E+001.88E+051.28E+021.00E+026.40E+023.98E-045.09E-053.98E-05Ni-631.10E-072.11E-090.00E+001.12E-07Key ParametersContaminated Basement Surfaces Unitized Dose FactorsTable 6-4DOSE CALCULATION FACTORSCONTAMINATED CONCRETE ANNUAL DOSESource TermKdWATER, FILL, CONCRETE CONCENTRATION MYAPC License Termination PlanPage 6-22Revision 3 October 15, 2002With the exception of the source term calculation, the conceptual model foractivated concrete is identical to the conceptual model for contaminated basement surfaces described above. A conservative screening approach was used to account for the activated concrete source term by assuming that the entire inventory of the residual activity in the activated concrete, at all depths, is immediately released into the 738 m 3 of water in the basement fill. A morerealistic model would account for the fact that the activated inventory would be released very slowly over time and that the concentration would decrease with depth. Concentration decreases with depth since the most highly activated concrete will have been removed during remediation. In addition, the concrete concentration at all depths is assumed to be equal to the surface concentration of 1 pCi/g. This is conservative since the concentration will actually decrease with depth. However, since the dose using the screening approach was very low, the detailed analyses required to justify release rates and actual concentrations with depth were not necessary. b.Unitized Dose Factors for Activated Concrete Although activated concrete is present at depth beneath the surface, the unit dose calculation for activated concrete is based on a concentration of 1 pCi/g total activity (sum of all radionuclides) at the surface of the floors and walls of the ICI sump. The surface activity (measured volumetrically) is the measurable quantity that will be used to demonstrate compliance during the final status survey. However, the total inventory, i.e., source term, includes the radionuclides in the entire volume of activated concrete, including surface and subsurface. The total inventory was determined to be 3.30E+08 pCi asl described in Attachment 6-6. This inventory may change if the remediation level (i.e., DCGL) for activated concrete is changed. The final dose assessment will be based on the actual remediation level selected. To determine the inventory of each radionuclide, the total 3.30E+08 pCilinventory must be multiplied by the radionuclide fraction in the activated concrete mixture. The resulting radionuclide specific inventories are input to the "inventory" column in the spreadsheet developed for the contaminated basement surfaces. All of the resulting water, fill, and concrete

concentrations and dose calculations are identical to those described for the contaminated basement surfaces in Section 6.6.1.

The "Activated Concrete/Rebar"spreadsheet is provided in Table 6-5, whichlists the unitized dose factors for all radionuclides in the activated concrete mixture assuming a unit inventory of 1 pCi/g total activity at the surface of activated concrete.

MYAPC License Termination PlanPage 6-23Revision 3 October 15, 2002Porosity0.30Fill Volume2460.0 m 3Annual Total Well Water Vol738.0 m 3Bulk Density1.50g/cm 3Surface Area/Open Volume1.70 m 2/m 3Irrigation Rate0.274 L/m 2-dYearly Drinking Water478.0L/yrConcrete Volume4.18 m 3Surface Soil Depth0.15mWall Surface Area4182.0 m 2Concrete Density2.20g/cm 3Activated Concrete Total Inventory3.30E+08Total pCi per pCi/gActivated Concrete Total Conc.1.00pCi/gNUREG-1727FGR 11 MicroshieldKdKdDrinkingIrrigationDirect Total Nuclidemrem/y permrem/pCimrem/y perNuclideInventoryInventoryFillConcreteAdsorptionWaterFillConcreteNuclideWater DoseDoseDoseDos epCi/gpCi/gFractionpCi/gpCicm3/gmcm3/gmFactorpCi/LpCi/gpCi/gmrem/ymrem/ymrem/ymrem/yCs-1344.39E+007.33E-056.09E-058.40E-038.40E-032.77E+067.91E+013.00E+003.96E+029.74E-037.49E-042.84E-05Cs-1343.32E-041.85E-054.56E-083.50E-04Co-606.58E+002.69E-056.30E-044.00E-024.00E-021.32E+071.28E+021.00E+026.40E+022.79E-023.56E-032.79E-03Co-603.59E-048.16E-052.25E-064.43E-04C-142.08E+002.09E-060.00E+005.80E-025.80E-021.91E+075.00E+001.00E+022.72E+019.52E-014.76E-039.52E-02C-149.51E-048.80E-040.00E+001.83E-03Eu-1543.13E+009.55E-063.10E-049.00E-039.00E-032.97E+064.00E+025.00E+032.06E+031.95E-037.80E-049.75E-03Eu-1548.90E-062.71E-062.42E-071.19E-05Fe-552.50E-036.07E-070.00E+001.24E-011.24E-014.09E+072.50E+011.00E+021.27E+024.36E-011.09E-024.36E-02Fe-551.26E-044.84E-070.00E+001.27E-04H-32.27E-016.40E-080.00E+006.47E-016.47E-012.14E+080.00E+000.00E+001.00E+002.89E+020.00E+000.00E+00H-38.84E-032.91E-020.00E+003.80E-02Eu-1522.87E+006.48E-062.09E-041.11E-011.11E-013.66E+074.00E+025.00E+032.06E+032.41E-029.62E-031.20E-01Eu-1527.45E-053.07E-052.01E-061.07E-04Ni-631.19E-025.77E-070.00E+007.00E-037.00E-032.31E+061.28E+021.00E+026.40E+024.88E-036.24E-044.88E-04Ni-631.35E-062.58E-080.00E+001.37E-06Activated Concrete Unitized Dose Factors 1.0 pCi/gTable 6-5Key ParametersDOSE CALCULATION FACTORSACTIVATED CONCRETE ANNUAL DOSEWATER, FILL, CONCRETE CONCENTRATION KdSOURCE TERM MYAPC License Termination PlanPage 6-24Revision 3 October 15, 20026.6.3Embedded Pipea.Conceptual Model

Embedded pipe includes pipes that are encased in the basement concrete walls or floors that will remain after demolition and remediation. The

conceptual dose model is identical to that described for contaminated basement surfaces. However, analogous to activated concrete, the source term calculation includes the entire radionuclide inventory contained in all embedded piping, regardless of location. The entire inventory is assumed to be instantaneously released into the worst case 738 m 3 of basement water. b.Unitized Dose Factors for Embedded Pipe The total embedded pipe inventory is calculated assuming a unit contamination level of 1 dpm/100 cm 2 over the entire internal surface areaof all embedded pipe remaining after decommissioning. A list of the embedded piping planned to remain after decommissioning is provided in -7. The internal surface area of the embedded piping is

154 m 2. Assuming a unit inventory of 1 dpm/100 cm 2 the total inventorylwas determined to be 6.95E+03 pCi.. The 6.95E+03 pCi inventory appliesl

to each radionuclide at a "unit" concentration of 1 dpm/100 cm

2. Based onthis value, an inventory was calculated and input into the spreadsheet developed for the contaminated basement surfaces. The spreadsheet inventory" column input was calculated by multiplying the pipe surface contamination level, in this case a unitized level of 1 dpm/100 cm 2, by the6.95E+03 pCi unit inventory. Because two distinct areas (Embedded Sprayl Pump Piping and BOP Embedded Piping) were created to addressl embedded piping, two different DCGL calculations (and spreadsheets) werel created. Each spreadsheet addresses separate unit inventories that sum tol the above total inventory (Spray Pump and BOP embedded inventories arel 1.19E+03 and 5.75E+03 respectively). These forms facilitate the use of thel spreadsheets in the total dose and DCGL calculations provided in Section 6.7. All of the resulting water, fill, and concrete concentrations, and dose calculations are identical to those described for the contaminated basement surfaces in Section 6.6.1. The BOP Embedded Piping and Embedded Spray Pump Pipinglspreadsheets are provided in Tables 6-6A and 6-6B. The results representl the unit dose factors for embedded piping assuming a source term of

1 dpm/100 cm 2, for each radionuclide, on the internal surfaces of thelassociated pipe. l MYAPC License Termination PlanPage 6-25Revision 3 October 15, 2002Porosity0.30Fill Volume2460.0 m 3Surface Soil Depth0.15mBulk Density1.50g/cm 3Surface Area/Open Vol1.70 m 2/m 3Irrigation Rate0.274L/m 2-dYearly Drinking Water478.0l/yrConcrete Volume4.18 m 3Annual Total Well Water Vol738 m 3Wall Surface Area4182.0 m 2Concrete Density2.20g/cm 3Embedded Pipe Conversion Factor5754.5pCi per dpm/100 cm 2Total Inventory1.00E+00dpm/100 cm 2NUREG-1727FGR 11 MicroshieldKdKd DrinkingIrrigationDirectTotalNuclidemrem/y permrem/pCimrem/y perInventoryInventoryFillConcreteAdsorptionWaterFillConcreteNuclideWater DoseDoseDoseDosepCi/gpCi/gdpm/100 cm2pCicm3/gmcm3/gmFactorpCi/LpCi/gpCi/gmrem/ymrem/ymrem/ymrem/ySr-901.47E+011.42E-040.00E+001.00E+005.75E+036.02E+011.00E+003.01E+022.58E-051.55E-062.58E-08Sr-901.75E-061.69E-070.00E+001.92E-06Cs-1344.39E+007.33E-056.09E-051.00E+005.75E+037.91E+013.00E+003.96E+021.97E-051.56E-065.90E-08Cs-1346.89E-073.84E-089.47E-117.27E-07Cs-1372.27E+005.00E-051.20E-051.00E+005.75E+037.91E+013.00E+003.96E+021.97E-051.56E-065.90E-08Cs-1374.70E-071.98E-081.87E-114.90E-07Co-606.58E+002.69E-056.30E-041.00E+005.75E+031.28E+021.00E+026.40E+021.22E-051.55E-061.22E-06Co-601.56E-073.56E-089.79E-101.93E-07Co-571.67E-011.18E-062.80E-081.00E+005.75E+031.28E+021.00E+026.40E+021.22E-051.55E-061.22E-06Co-576.86E-099.03E-104.35E-147.76E-09Fe-552.50E-036.07E-070.00E+001.00E+005.75E+032.50E+011.00E+021.27E+026.13E-051.53E-066.13E-06Fe-551.78E-086.81E-110.00E+001.78E-08H-32.27E-016.40E-080.00E+001.00E+005.75E+030.00E+000.00E+001.00E+007.78E-030.00E+000.00E+00H-32.38E-077.85E-070.00E+001.02E-06Ni-631.19E-025.77E-070.00E+001.00E+005.75E+031.28E+021.00E+026.40E+021.22E-051.55E-061.22E-06Ni-633.35E-096.43E-110.00E+003.42E-09Table 6-6ABOP Embedded Piping Unitized Dose FactorsKey ParametersEMBEDDED PIPE ANNUAL DOSEDOSE CALCULATION FACTORSSource TermKdWATER, FILL, CONCRETE CONCENTRATION MYAPC License Termination PlanPage 6-26Revision 3 October 15, 2002Porosity0.30Fill Volume2460.0 m 3Surface Soil Depth0.15mBulk Density1.50g/cm 3Surface Area/Open Vol1.70 m 2/m 3Irrigation Rate0.274L/m 2-dYearly Drinking Water478.0l/yrConcrete Volume4.18 m 3Annual Total Well Water Vol738 m 3Wall Surface Area4182.0 m 2Concrete Density2.20g/cm 3Embedded Pipe Conversion Factor1191.7pCi per dpm/100 cm 2Total Inventory1.00E+00dpm/100 cm 2NUREG-1727FGR 11 MicroshieldKdKd DrinkingIrrigationDirectTotalNuclidemrem/y permrem/pCimrem/y perInventoryInventoryFillConcreteAdsorptionWaterFillConcreteNuclideWater DoseDoseDoseDosepCi/gpCi/gdpm/100 cm2pCicm3/gmcm3/gmFactorpCi/LpCi/gpCi/gmrem/ymrem/ymrem/ymrem/ySr-901.47E+011.42E-040.00E+001.00E+001.19E+036.02E+011.00E+003.01E+025.35E-063.22E-075.35E-09Sr-903.63E-073.50E-080.00E+003.98E-07Cs-1344.39E+007.33E-056.09E-051.00E+001.19E+037.91E+013.00E+003.96E+024.07E-063.22E-071.22E-08Cs-1341.43E-077.95E-091.96E-111.51E-07Cs-1372.27E+005.00E-051.20E-051.00E+001.19E+037.91E+013.00E+003.96E+024.07E-063.22E-071.22E-08Cs-1379.73E-084.11E-093.87E-121.01E-07Co-606.58E+002.69E-056.30E-041.00E+001.19E+031.28E+021.00E+026.40E+022.52E-063.22E-072.52E-07Co-603.24E-087.37E-092.03E-104.00E-08Co-571.67E-011.18E-062.80E-081.00E+001.19E+031.28E+021.00E+026.40E+022.52E-063.22E-072.52E-07Co-571.42E-091.87E-109.01E-151.61E-09Fe-552.50E-036.07E-070.00E+001.00E+001.19E+032.50E+011.00E+021.27E+021.27E-053.17E-071.27E-06Fe-553.68E-091.41E-110.00E+003.70E-09H-32.27E-016.40E-080.00E+001.00E+001.19E+030.00E+000.00E+001.00E+001.61E-030.00E+000.00E+00H-34.93E-081.63E-070.00E+002.12E-07Ni-631.19E-025.77E-070.00E+001.00E+001.19E+031.28E+021.00E+026.40E+022.52E-063.22E-072.52E-07Ni-636.95E-101.33E-110.00E+007.08E-10Table 6-6BEmbedded Spray Pump Piping Unitized Dose FactorsKey ParametersEMBEDDED PIPE ANNUAL DOSEDOSE CALCULATION FACTORSSOURCE TERMKdWATER, FILL, CONCRETE CONCENTRATION MYAPC License Termination PlanPage 6-27Revision 3 October 15, 20026.6.4Surface Soila.Conceptual Model Surface soil includes all soil within the first 15 cm of the ground surface. TheNRC screening values for soil from NUREG-1727, Table C2.3, are used for the unitized dose calculations Therefore, the conceptual model is identical to that described in NUREG-1727. The screening values include the dose from all pathways. The groundwater contribution to the screening value dose is negligible and is entered as zero. The screening values are used because they were specifically generated by NRC to be conservative calculations of the

resident farmer dose and are recommended for use in NUREG-1727.Verification Conditions (for Surface Soil Screening Values).

NUREG-1727,NMSS Decommissioning Standard Review Plan, Appendix C, describes the justification necessary to allow direct use of these screening. Per the NUREG, the following conditions must be satisfied:1.The initial residual radioactivity (after decommissioning) iscontained in the top layer of the surface soil [that is, approximately 6 inches (15cm)].2.The unsaturated zone and the groundwater are initially free of contamination.3.The vertical saturated hydraulic conductivity at the specificsite is greater than the infiltration rate.

The above conditions are satisfied for the Maine Yankee site.

Condition One. The direct use of these screening values is only for surfacesoil (approx. 6 inches). Section 6.6.5 calculated a dose from deep soil (that is, greater than 6 inches) separate from the use of the surface soil screening

values. (See Section 6.6.5)

Condition Two. Maine Yankee does not use the surface soil screening valuesto address potential site groundwater contamination from H-3. H-3 presence in the groundwater and surface water is assumed based upon the highest measured readings and is covered by separate dose assessments. (See

Sections 6.6.6 and 6.6.7)

Condition Three. The soils at Maine Yankee that are in areas currentlycontaining nuclides elevated above background, and those soils that are MYAPC License Termination PlanPage 6-28Revision 3 October 15, 2002planned to be used to fill the foundations are bank run sand and gravel. TheAdams or Hinckley USDA Soil Series would provide the closest approximation. The minimum saturated vertical hydraulic conductivity of these soils is 0.001 cm/sec or 1.417 inches per hour. Average saturated hydraulic conductivity rates would be about 10 times this, or 14 inches per hour. Infiltration capacity is based on land cover type, antecedent moisture

condition prior to a rainfall or snowmelt event, and the rate of water supply

available for infiltration. The permanent water table at the Maine Yankee site in the area of interest is approximately elevation 10 to 15 feet above Mean Sea Level, indicating a distance of 6 to 11 feet from the existing ground surface to the average water table position. Therefore, this much of the sand fill will be unsaturated. Infiltration capacity is limited by the unsaturated hydraulic conductivity of the soil. The unsaturated hydraulic conductivity of the sand fill is typically from 1/10 to 1/100 of the saturated hydraulic conductivity. Precipitation rates rarely exceed one inch per hour in Maine.

Therefore, because the typically expected maximum precipitation rate is less than the minimum saturated hydraulic conductivity, and because the fill is unsaturated for 6 or more feet down and unable to transmit water downward at a rate exceeding the saturated vertical hydraulic conductivity, infiltration rates in the fill must be less than the saturated vertical hydraulic conductivity.Soil types on the Maine Yankee site are representative of those assumed inthe soil screening model. These soil types include: silt loams derived from glaciomarine sediments, fine sandy loams derived from glacial till, and fill that has a wide textural variation. However, the primary fill in the immediate plant area is a sand or loamy sand. The silt loams are most typical over the undisturbed portions of the site. The exceptions are in the knoll and ridge areas where bedrock is exposed or shallow where the fine sandy loams predominate. Fill areas surrounding the plant buildings are sand or loamy sand. Fill areas north of the 345 KV yard tend to have a silt loam surface covering. The most likely foundation fill material will be bank run sand.

(See Section 6.6.1d.)b.Unitized Dose Factors for Surface Soil The unitized dose factors are generated for each radionuclide directly fromthe NUREG-1727 screening values by converting the values to mrem/y per pCi/g. Table 6-7 provides the "Surface Soil" unitized dose spreadsheet. The results represent the dose from a unit source term if 1 pCi/g for each radionuclide in the soil mixture.

MYAPC License Termination PlanPage 6-29Revision 3 October 15, 2002 Table 6-7Surface Soil Unitized Dose Factors 1.0 pCi/g Cs-137Key Parameters:Soil Depth0.15 mDOSE CALCULATION FACTORSSOURCE TERMSURFACE SOIL ANNUAL DOSENuclideNUREG-1727mrem/y perpCi/g SoilpCi/gTotal Dose mrem/yrCs-1372.27E+001.00E+002.27E+00Co-606.58E+001.00E+006.58E+00H-32.27E-011.00E+002.27E-01Ni-631.19E-021.00E+001.19E-026.6.5Deep Soila.Conceptual Model Deep soil is defined as soil at depths greater than 15 cm. A separatecalculation is required for deep soil because the NRC soil screening values apply to the top 15 cm of soil only. The resident farmer is exposed to deep soil through the direct exposure pathway and groundwater. The deep soil could be brought to the surface at some time in the future through the activities of the resident farmer. Therefore, the deep soil concentration will be limited to the surface soil DCGL. The conceptual model for deep soil assumes a 15 cm layer of uncontaminatedsoil for the purpose of calculating the additional direct radiation exposure.

The 15 cm cover represents the layer of surface soil. The direct radiation from residual contamination in the top 15 cm soil layer was accounted for in the surface soil screening values. A very large volumetric source term was

assumed, i.e., 28,500 m 3, for the purpose of conservatively determining thelpotential for groundwater contamination from deep soil. This is considered a bounding source term volume and essentially represents the entire volume of

soil within the restricted area down to bedrock. After remediation and backfill, the actual remaining volume of deep soil with any significant contamination will be a very small fraction of 28,500 m 3.l MYAPC License Termination PlanPage 6-30Revision 3 October 15, 2002 b.Unitized Dose Factors for Deep SoilUnitized dose factors were calculated using unit concentrations of each of theradionuclides in the soil mixture. The contribution from direct radiation was calculated using the Microshield code assuming a 15 cm cover and default values from DandD for indoor occupancy time (0.6571 y), outdoor occupancy time (0.1101 y), and external radiation shielding factor (0.5512). The

Microshield output reports, deep dose direct radiation calculations, and resulting dose factors are provided in Attachment 6-8. The maximum groundwater concentrations were calculated using RESRADand unit concentrations of each radionuclide in the mixture. The RESRAD groundwater parameters used in the analysis are listed in Table 6-8. Only the parameters pertaining to groundwater transport are listed since the groundwater concentration is the only RESRAD output used. The RESRAD parameters affecting groundwater transport were reviewed by a local hydrologist who is very familiar with the site hydrogeological characteristics (Mr. Robert Gerber, P.E. and Certified Geologist). The parameters in Table 6-

3 are recommended site-specific values. The Kd's were derived from Maine Yankee analyses of Bank Run Sand and Bank Run Gravel. The average of these two materials was assumed to represent the material used to backfill the site during plant construction. Finally, site-specific effective porosity was identified as variable at the site. To account for this variability, a sensitivity analysis was conducted over a range of 0.01 to 0.001. The highest groundwater concentration resulted from a value of 0.01, which was used in the analysis.

Table 6-8Site Specific Parameters used in RESRAD Deep Soil AnalysisParameterValueUnitsContaminated Zone site specific hydraulic conductivity32m/y Contaminated Zone site specific b factor 4.05 Site Specific Effective Porosity0.01 Unsaturated. Zone Site Specific Hydraulic Conductivity1000m/ySite Specific Soil Kds:Co335.0lcm3/glSr152.0lcm3/glCs1200.0lcm3/glNi274.0lcm3/gl MYAPC License Termination PlanPage 6-31Revision 3 October 15, 2002Porosity0.3Yearly Drinking Water478L/ySurface Soil Depth0.15mBulk Density1.6g/cm 3Irrigation Rate0.274L/m 2-dNUREG-1727FGR 11 MicroshieldDeep SoilDerived Water Water DrinkingIrrigationDirectTotalNuclidemrem/y permrem/pCimrem/y perInventoryConversion UnitsInventoryWater DoseDoseDose Dose pCi/gpCi/g pCi/gpCi/L per pCi/gpCi/L mrem/y mrem/ymrem/ymrem/yCs-1372.27E+005.00E-054.00E-011.00E+009.02E-039.02E-032.16E-048.53E-064.00E-014.00E-01Co-606.58E+002.69E-052.40E+001.00E+002.24E-022.24E-022.88E-046.15E-052.40E+002.40E+00H-32.27E-016.40E-080.00E+001.00E+006.69E+036.69E+032.05E-016.33E-010.00E+008.37E-01Ni-631.19E-025.77E-070.00E+001.00E+006.01E-016.01E-011.66E-042.98E-060.00E+001.69E-04Table 6-9Key ParametersDOSE CALCULATION FACTORSDEEP SOIL ANNUAL DOSESource TermDeep Soil Unitized Dose Factors -9 provides the RESRAD output report. The attachmentprovides the results for the radionuclides that were projected to migrate to groundwater over a 1000 year period. The RESRAD code was used only to estimate maximum groundwater concentrations, not calculate dose. The dose from the groundwater concentrations listed in Attachment 6-9 were calculated using the same parameters as in the water dose calculations performed for contaminated basement surfaces, activated concrete/rebar, and embedded piping, i.e, 478 l/y annual water intake and FGR 11 Dose Factors. The spreadsheet output and the unitized dose factors for deep soil are provided in

Table 6-9.6.6.6GroundwaterThis calculation applies to existing groundwater only. As described above, there areadditional contributions to the projected total groundwater dose from other contaminated materials. Groundwater dose is calculated directly from the highest individual groundwatersample result from site monitoring well locations. As reported in Section 2, Attachment B, the only radionuclide identified in site groundwater is H-3 and the maximum concentration was identified in the containment foundation sump at a concentration of 6812 pCi/l. The range of H-3 concentrations identified during characterization sampling of site wells was 441 pCi/l to 6812 pCi/l, for the most part consistent with background levels. The containment sump was re-sampled during continued characterization with 900 pCi/l H-3 identified. In addition, routine containment sump water samples have been collected since February 2000. None of MYAPC License Termination PlanPage 6-32Revision 3 October 15, 2002these samples have exceeded the MDC level of about 2500 pCi/l. (Additionallsampling and analyses of site groundwater conducted in 2002, including thel containment foundation sump, are discussed in Section 2.5.3.d and reported to thel NRC in references noted in that section. The additional sampling confirmed thel nuclide fraction and conservatism of the H-3 activity level assumed in the dosel assessment.)lIn general, it appears that current containment sump H-3 water concentrations arewithin the range expected in area water background. However, to ensure that a conservative water concentration is applied and to avoid the potentially extensive sampling and analyses necessary to demonstrate that the concentrations are at background levels, the 6812 pCi/l H-3 concentration is used in the dose assessment.

If, prior to unrestricted release of the site, additional groundwater monitoring data are collected that indicate higher H-3 concentration, or identify other radionuclides, the higher concentrations will be used in the final dose assessment for demonstrating compliance with the 10/4 mrem/yr dose limit. As discussed in Section 2.5.3.d, additional routine sampling of the containmentlfoundation sump and PAB test pit will be conducted routinely until final status surveyl has commenced in these two plant areas. The samples will be taken on anl approximate monthly basis and will be analyzed by gamma spectroscopy and for H-3. l Sample analysis results will be evaluated regarding: (1) the need for additionall assessment (such as, additional sampling or "hard to detect" analyses) and (2) anyl impact to the dose assessment.lThere are no unit dose factors or DCGLs for groundwater. The actual dose from thehighest measured concentration will be used in the total dose calculation. The groundwater dose is calculated using the FGR 11 DCF for H-3 and a 478 l/y intake.

The resulting dose is 0.21 mrem/y. The method for factoring the groundwater dose into the total dose calculation and the DCGL determination for other contaminated

materials is described in Section 6.7.The dose calculation for existing groundwater is provided below.

Dose GW = (6812 pCi/l H-3)(478 l/y)(6.4E-08 mrem/y/pCi) = 0.21 mrem/y(12)6.6.7Surface Water Site surface water from the Fire Pond and Reflecting Pond was sampled duringcharacterization. The results indicated no plant derived radionuclides in the Fire Pond and a low potential in the Reflecting Pond. Therefore, only the Reflecting Pond was considered in the dose assessment. Tritium was detected in the Reflecting Pond at a maximum concentration of 960pCi/l. This activity is not believed to be attributable to Maine Yankee operations.

MYAPC License Termination PlanPage 6-33Revision 3 October 15, 2002 However, a review of available literature on H-3 concentrations in surface water couldnot conservatively demonstrate that the H-3 concentrations identified were consistent with background levels in the region. Additional characterization and literature review may provide the information needed to demonstrate that the H-3 was not plant derived. However, given the very low dose from these H-3 concentrations, it was not considered cost effective to perform more analyses.As for groundwater, the dose from surface water was calculated using existing data. The maximum H-3 concentration of 960 pCi/l was used. As with groundwater, if higher concentrations or additional radionuclides are identified at any time prior to unrestricted release of the facility, the higher concentrations will be used in the final dose assessment for demonstrating compliance. The surface water dose results from drinking water and ingesting fish from the pond. The water dose is calculated using the parameters described above assuming that the resident farmer drinks directly from the surface water source. The dose from fish ingestion is calculated using a water to fish transfer factor of 1 for H-3 (NUREG-5512, Vol. 3, Table 6.30), 20.6 kg fish consumption per year (DandD default value),

and using DCFs from FGR No.11.The calculations for water and fish consumption from onsite surface water with a H-3 concentration of 960 pCi/l is provided below.

Dose SW = (960 pCi/l H-3)(478 l/y)(6.4E-08 mrem/y/pCi) = 2.9E-02 mrem/y(13)

DoseFish = (960 pCi/l)(1.0 pCi/kg per pCi/l)(20.6 kg/y))(6.4E-08 mrem/y/pCi) = 1.3E-03 mrem/y(14)6.6.8Buried Pipinga.Conceptual Model After decommissioning is completed, some piping and conduit will remainunderground at depths greater than three feet below grade. This contaminated material category includes the piping buried in open land, not pipe embedded

in concrete basements, which were described in Section 6.6.3. A list of the buried piping that current plans call to remain after decommissioning is provided in Attachment 6-10. The buried piping is expected to contain very limited levels of contamination, if any. The radionuclide mixture is assumed to be the same as for contaminated materials.

MYAPC License Termination PlanPage 6-34Revision 3 October 15, 2002The conceptual dose model for the buried piping is very simple andconservative. The piping/conduit is assumed to be uniformly contaminated over the entire internal surface area. The piping is further assumed to eventually disintegrate resulting in the total inventory in the pipe mixing with a volume of soil equal to the pipe volume. Without the assumption of the pipe disintegrating, there is essentially no dose pathway from buried piping. The resulting calculated soil concentrations are treated as deep soil and the dose was calculated using the same methods as described above for deep soil.

However, the direct exposure is calculated assuming a three foot cover as opposed to a 15 cm cover. Although not required by the conceptual model, the buried piping DCGLs will be limited to ensure that the projected soil concentrations are below the surface soil DCGLs. This additional measure of conservatism was also applied to deep soil to account for hypothetical future excavation of the buried contamination.b.Unitized Dose Factors for Buried Piping The total surface area and total volume were calculated for all of the buriedpiping planned to remain after decommissioning. Assuming a unit inventory

of 1 dpm/100 cm 2 on the internal surfaces, the total inventory of eachradionuclide was determined. This total inventory was divided by the total volume and converted to grams of soil assuming a density of 1.6 g/cm 3 tocalculate the projected pCi/g soil concentration of each radionuclide. The list of Buried Piping and the calculation of projected pCi/g soil concentration are provided in Attachment 6-10. The resulting concentration is 2.59E-04 pCi/g.The resulting projected pCi/g soil concentration was entered as the source termin RESRAD for each applicable radionuclide. The RESRAD analysis was performed using the same parameters used for deep soil (Table 6-8) with the exception of the source term geometry. For the buried piping, the source term geometry was assumed to be a 142 m 2 area 1 m deep. This corresponds to thetotal volume of all buried piping of 142 m

3. This is a conservative assumptionsince, in reality, the piping is distributed over a fairly large surface area which would result in dilution through groundwater transport compared to the maximum concentration assuming all the pipe is contiguous. The RESRAD

output report is provided in Attachment 6-11. Microshield runs were performed on the unit source term assuming the same 142 m 2 x 1m deep source. The source is assumed to be covered by three feetof soil. The resulting exposure rate was multiplied by the default outdoor occupancy time (0.1101 y) from DandD, Version 1. The Microshield reports MYAPC License Termination PlanPage 6-35Revision 3 October 15, 2002Porosity0.3Yearly Drinking Water478L/yBulk Density1.6g/cm 3Irrigation Rate0.274 L/m 2-dBuried Pipe Conversion Factor2.59E-04pCi/g per dpm/100 cm 2Surface Soil Depth0.15mFGR 11 NUREG-1727MicroshieldWater Pipe SurfaceSoilDrinkingIrrigationDirectTotalNuclidemrem/pCimrem/y permrem/y perInventoryInventoryInventoryWater DoseDose Dose DosepCi/gpCi/gpCi/L per pCi/gdpm/100cm2pCi/g mrem/y mrem/ymrem/ymrem/ySr-901.42E-041.47E+010.00E+002.15E-021.00E+002.59E-043.77E-073.41E-080.00E+004.12E-07Cs-1347.33E-054.39E+002.21E-052.25E-051.00E+002.59E-042.04E-101.07E-115.72E-095.94E-09Cs-1375.00E-052.27E+003.97E-063.27E-041.00E+002.59E-042.02E-098.01E-111.03E-093.13E-09Co-602.69E-056.58E+002.53E-048.14E-041.00E+002.59E-042.71E-095.78E-106.55E-086.88E-08 Co-571.18E-061.67E-019.44E-091.15E-041.00E+002.59E-041.68E-112.07E-122.45E-122.13E-11Fe-556.07E-072.50E-030.00E+004.30E-051.00E+002.59E-043.23E-121.16E-140.00E+003.24E-12H-36.40E-082.27E-010.00E+001.98E+021.00E+002.59E-041.57E-064.85E-060.00E+006.42E-06Ni-635.77E-071.19E-020.00E+002.09E-021.00E+002.59E-041.49E-092.68E-110.00E+001.52E-09Table 6-10Buried Piping Unitized Dose FactorsKey ParametersBuried Piping Annual DoseSource TermDose Calculation Factorsand Buried Piping Direct Radiation Dose Factors are provided in Attachment6-12. The spreadsheet output and resulting unitized dose factors

(1 dpm/100 cm

2) for buried piping are provided in Table 6-10.

6.6.9Forebay and Diffuserla.Forebay Source Terml lForebay Physical Description l

lThe forebay is a basin approximately 400 feet long by 160 feet wide at thel top with a granite (ledge) floor, rock/soil walls on two sides, and smalll concrete walls at each end. The depth is approximately 20 feet. The volumel

is (64,000 ft 2 bottom + 10,150 ft 2 top incline area) x (20 feet deep) = 1.48E6l ft 3 or 42,000 m

3. The surface area of the bottom plus sides (assuming flatl sides) is 7435 m

2. If the rip-rap surface is calculated, the surface area isl 2337 m 2. (This assumes the number of circles of 2 foot diameter containedlwithin the forebay wall area then converting those to a half sphere area of 1l MYAPC License Termination PlanPage 6-36Revision 3 October 15, 2002 foot radius.) The rip-rap volume is estimated at 478 m

3. The total surfacelarea when the forebay is backfilled is 7435 m

2. llThere are four potentially contaminated media associated with the forebay:l ledge, rip-rap, sediment, and soil. Each of these will be examined separatelyl to determine the dose contribution of each medium. It should be noted thatl pre-remediation studies conducted to date indicate that the activity in thel forebay sediment is very insoluble (i.e., no activity is given up to water norl is there detectable activity in a water filtrate). Most of the activity isl contained within the organic layer of sediment or the organic film depositedl on the rip-rap of the forebay. Based on solubility, pH, and water chemistry,l the conditions for the maximum release of activity from sediment or surfacel film are occurring now. In spite of these ideal release conditions, nol detectable activity is found in the standing water of the forebay. l Furthermore, the infiltration water that enters the forebay through pathwaysl in the dikes is brackish which makes the drinking or irrigation pathwaysl doubtful. None the less, drinking and irrigation were evaluated.l lCharacterization Data l

lA detailed discussion of forebay / diffuser characterization is provided inl H. Table 6-10A (below) provides estimated total activity,l where appropriate, for each principal contaminated media. No currentl contamination data are available for the forebay granite ledge floor; butl given its low permeability, the ledge is expected to be clean followingl remediation. This will be verified. The rip-rap activity is based on thel average surface activity of the rip-rap times the entire rip-rap surface area. l l

MYAPC License Termination PlanPage 6-37Revision 3 October 15, 2002 lTable 6-10A lEstimated Media Activity llMedialTotal ActivitylLedgelTo be remediated. (See also Table 2H-5 inlAttachment 2H.)lRip-Rapl10.5 uCi Co-60lMarine SedimentlTo be remediated. (See also Table 2H-5 inlAttachment 2H.)lSoill1.85E4 uCi Co-60l1.52E3 uCi Cs-137l lDrinking Water and Irrigation Dose l

lThe drinking water and irrigation water dose was modeled using the samel approach as that used for the basement fill model. The forebay surface areal

to volume ratio was calculated as 0.177 m 2/m 3, or using the rip-rap surface,l as 0.06 m 2 /m 3. The surface area of 435 m 2 for the source term waslcalculated by multiplying the surface area to volume ratio by the volumel associated with the annual water usage (738m

3) for the soil porosity 0.3. lThe source term for the drinking water was then calculated assuming al contamination level equal to the concrete structure DCGL of 18,000l

dpm/100cm 2. Thus, the dose contribution from the forebay surface arealsource term was calculated as 0.002 mrem from drinking water and 0.0004l mrem from irrigation water. These dose contributions are well below andl are bounded by the dose contributions from the drinking water and irrigationl water sources to the resident farmer from the building basements. l Therefore, these dose contributions are considered separate from the residentl farmer dose modeling scenario. Furthermore, since this dose is sol insignificant and the probability is so low that an individual would be able tol successfully place a viable well within the forebay, survey measurements ofl the forebay surfaces including rip-rap will be limited.l lRock (Rip-Rap) Dose l

lThe exposed surface area of the rip-rap is 2337 m

2. The surface activity islspread over the exposed surface area at 0.1 pCi/g (based on diffuser surfacel

sample and rip-rap sample levels) or 45 pCi/100 cm 2 Co-60. Whenldeposited over the exposed surface area, this level of Co-60 contaminationl results in a total activity from rip-rap of 10.5 uCi. This activity is assumedl MYAPC License Termination PlanPage 6-38Revision 3 October 15, 2002to be instantaneously released and mixed within the forebay soil backfilllvolume. This results in a soil concentration of 1.56E-4 pCi/g Co-60.l lSediment Dose l

lSeveral large pockets of sediment were identified on the floor of the forebayl during diving inspections. There are also small deposits lying between thel rip-rap and also behind the weir (in the seal pit). The activity of thel underwater marine sediment averages 19 pCi/g Co-60 and 2 pCi/g Cs-137. l (One small area of very high activity was discovered which had Co-60 levelsl as high as 445 pCi/g.) The sediment within the forebay is all slated forl removal by washing, settling, filtering and dewatering. The dewateredl sediment will be disposed of as radwaste and will not contributel significantly to dose. Any residual activity remaining following sedimentl removal would be included in the ledge dose for 18,000 dpm/100 cm 2lsurface contamination and the shallow pockets of contaminated sedimentl which might remain have previously been analyzed and found not tol contribute a significant dose (EC 004-01).l lDirect Dose Excavated Forebay Soil l

lCoastal zoning or land use restrictions may prohibit or severely limitl excavation or construction activities in the area of the former forebay givenl its closeness to the shoreline. None the less, the dose from these activitiesl has been evaluated as discussed in this section. Contaminated soil has beenl detected in approximately a two foot deep band behind the rip-rap. Thel nuclide fraction is assumed to be the same as the sediment since it originatesl from the same effluent releases. (See Section 2.5.3 and Attachment 2H forl additional discussion of the nuclide fraction and supporting characterizationl data.) The average activity levels detected were 7.3 pCi/g Co-60 and 0.6l pCi/g Cs-137; maximum levels were 21.3 pCi/g Co-60 and 1.35 pCi/g Cs-l 137. No Sb-125 was detected in the soil samples. A two foot thick band ofl contaminated soil 35 feet high by 400 feet long (the forebay walll

dimensions) for two dike walls is 1586 m 3 of contaminated soil. l lThe excavation of two different sized homes are evaluated to determine thel volume of soil which must be excavated assuming the worst case volumetricl capture of contaminated soil within the excavation volume. An excavationl for a 2000 square foot house results in a factor of 11 associated with thel worst case capture of contaminated soil with clean soil. An excavation of al 1000 square foot house results in a factor of 7.9 associated with the worstl case capture of contaminated soil with clean soil. In neither case, is creditl taken for any additional clean soil which would be generated if thel MYAPC License Termination PlanPage 6-39Revision 3 October 15, 2002excavation was sloped for safety concerns. In both cases, the contaminatedlsoil is assumed to begin at the surface with no cover material, even thoughl the as-left elevation of the forebay will be a few feet above the contaminatedl zone which exists in the inter tidal zone of the forebay. Therefore, al conservative dilution factor of 7 may be applied to determine acceptablel levels of radioactive materials of forebay soil in the two feet immediatelyl behind the rip rap.l lThe dose to a person from the excavation of the contaminated soil is shownl in Table 6-10B below, assuming the dilution factors described above and thel annual outdoor exposure time for soil at the average activity values and forl soil at the 3 pCi/g equivalent activity. The dose reduction due to shieldingl by a 6" concrete basement floor for the average soil activity is also shown inl Table 6-10B. l l Table 6-10B lExcavated Soil Direct Dose lllInitial Dose Rate (mrem/h) llDose at Average lSoil Concentration l(mrem/y)lDose atl3 pCi/g Equivalent l(mrem/y)llAveragelConcentration l3 pCi/glHrs/ylDilutionlFactorlllLarge House l1.30E-02 l3.0E-03l964l11l1.14l0.26lSmall House l7.90E-03l1.80E-03l964l7.88l0.97l0.22lBasementl6.70E-04l---l5756l---l3.9l---llThe excavation scenario dose rates are less than the soil dose rate to thel resident farmer, therefore, this scenario is presented as a separate and dose-l bounded scenario to the resident farmer. l lb.Diffuser Source Terml lThe source term for the diffuser is the sediment entrained within the diffuserl pipes. The sediment activity initially came from plant liquid effluentl releases via the forebay and later via the movement of benthic silt back intol the diffuser pipes by tidal action. These liquid effluent releases were madel in accordance with licensed effluent controls and were routinely reported tol the NRC. The effluent reports contained dose assessments whichl demonstrated compliance with 10 CFR 20 limits. The diffuser consists of 2l pipes 9 feet in diameter and 516 feet long. These two pipes are fed by trunkl lines originating at the forebay. The portions of the trunks that arel submerged and can contain sediment are 1421.5 feet in length. The volumel MYAPC License Termination PlanPage 6-40Revision 3 October 15, 2002occupied by the diffusers is 1860 m 3 and the volume of the trunk lines isl 2562 m 3. This conservatively results in a potential sediment-filled source ofl 4422 m 3. For a circumference of 28.3 ft. and a length of 2543.5 ft, the pipel interior would have a surface area of 71,981 ft

2. Converting this area in ft 2lto 100 cm 2 areas results in a value of 6.68E5 100 cm 2 areas. llCoupons of the diffuser pipe were removed and analyzed for surfacel contamination. The nuclides detected were Co-60 and Cs-137 at nearlyl equal activity. The combined activities of both nuclides were approximatelyl 0.28 pCi/g. This specific activity multiplied by the sample mass of 125gl results in approximately 35 pCi per sample. The samples represent aboutl

100 cm 2. The activity was present as a tightly-adhered, thin film of organiclmaterial. Based on the total interior surface area of the diffuser, if all of thel activity on the interior surface of the pipes is relocated to the sediment, thel additional activity would be 30 uCi.l lSediment samples taken from inside the diffuser and analyzed by gammal spectroscopy gave the following average activity values.l lCo-60 1.1 pCi/gl Cs-137 0.15 pCi/gl lThe sediment nuclide activity was determined by multiplying the activityl values by the sediment volumes as shown for Co-60 and Cs-137 for a totall activity of 8315 uCi.l lWater Activity l

lThe sediment activity is assumed to be instantaneously released non-l mechanistically into the waters of Montsweag Bay. (It is likely that thel sediment will remain in the diffuser pipes for years to come and thel radioactivity slowly be reduced by decay.) Since the Bay is an estuary, thel water is considered non-drinkable. The volume of water into which thel activity is released was determined by consulting MYC-2035 whichl discussed the former condenser cooling water "mixing zone". The mixingl zone was established for thermal mixing assuming cooling water is releasedl at a rate of 950 cfs. With the cooling water pumps no longer operable, suchl flow rates are not feasible. However, using the area in which forced mixingl of the diffuser water occurred would result in a reasonable estimate for almixing area for the potential sediment activity released at a much lower flowl rate. (Churchill (1980) stated that the same flow model applies to bothl radionuclide dispersion and hot water dispersion from the plant.)l l

MYAPC License Termination PlanPage 6-41Revision 3 October 15, 2002Using this "mixing zone" and the activities given above for sediment withlHTDs included, the water concentrations for each nuclide were calculated. l This activity level is assumed to exist for a year, when in fact, it would bel dissipated within 56 hours6.481481e-4 days <br />0.0156 hours <br />9.259259e-5 weeks <br />2.1308e-5 months <br /> by tidal flushing of the bay. Assuming dilution,l the water concentration would be reduced by 6.4E-3 (56 h dilutionl time/8760 h per year) and the total annual dose would be on the order ofl 0.005 mrem/y for fish and 0.002 mrem/y for shell fish.l lThe annual dose rate to the individual who consumes seafood from thisl contaminated water source was derived by multiplying the water activity byl the seafood bioaccumulation factors given in NUREG-5512 by the FGR-11l dose conversion factor for each nuclide times the consumption rate takenl from NUREG-5512. Based on a comparison to local marine organisml nuclide levels, the NUREG-5512 values are considered to be conservative.l lThe total dose from eating seafood (fish plus shell fish) grown in thel contaminated water is 0.007 mrem/y. The consumption of this food sourcel would actually replace other food sources included in the dose model. If thel dose from eating this seafood were simply added to the annual dose to thel resident farmer, it would represent a negligible increase compared to thel farmer's total annual dose. Therefore, since the dose increase is negligible,l this dose has not been added to Table 6-11. Furthermore, since the dose isl negligible and the activity would likely be contained in the diffuser forl sufficient time for substantial decay of dose significant nuclides, any furtherl survey measurements of the diffuser will be limited. l lSediment Dose l

lA person could be exposed from direct radiation originating from thel contaminated sediment if it were deposited upon a shoreline or mud flat. l This portion of the calculation assumes that the total sediment activity isl suspended within the area outlined by the "mixing zone" and is then non-l mechanistically dewatered to the condition of a mud flat. The area isl approximately 52,500 m 2 compared to the entire mud flat of Bailey Covel (130,000 m 2). An area ratio of 0.404 describes that portion of the entirelBailey Cove mud flat that could be covered intact by the postulated release.l lThe NRC (RG 1.109) adjusts the annual dose from shoreline deposits for thel amount of time spent on the shore and for the geometry of the shorelinel (shoreline width factor). For tidal basins like Montsweag Bay, the widthl factor is 1. For river shorelines, like the Back River, the factor is 0.2. Forl conservatism, a factor of 1 was used. The NRC time for shoreline recreationl is 47 hours5.439815e-4 days <br />0.0131 hours <br />7.771164e-5 weeks <br />1.78835e-5 months <br /> per year, however, Maine Yankee recognizes (ODCM) thel MYAPC License Termination PlanPage 6-42Revision 3 October 15, 2002presence of the commercial worm digger on the mud flats for 325 hours0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br /> perlyear.llThe sediment dose rate (mrem/hr) is the product of the sediment activityl divided by the mud flat area factor times the dose rate at 1 m from thel resulting activity deposited (from RG 1.109). For Co-60 the dose rate wouldl

be: 7315 uCi/5.25E4 m 2 x width factor of 1 x 1E6 pCi/uCi x 1.7E-8lmrem/hr/pCi/m 2 x 0.404 = 9.6E-4 mrem/hr. (Note that Reg. Guide 1.109 doeslnot provide values for Sb-125. The dose rate was estimated at half the Cs-137l value based on the dose rate for soil.)l lThe total whole body dose rate is 1.01E-3 mrem/h from contaminated mudl flats. Using the worm digger exposure time of 325 hr/y x 1.01E-3 mrem/hr =l 0.327 mrem/y. If the DandD outdoor time fraction (964 hr/y) is used, thel annual dose would be 0.97 mrem/y.l6.6.10Circulating Water Pump House The circulating water pump house (CWPH) was the intake for the plant circulatingwater (CW) system. The water intake was directly from the Back River at high volumes (about 400,000 gpm). The CWPH will be demolished to three feet below grade, backfilled, and stabilized on the river side with rock rip-rap. The intake structure which is below water level will remain in communication with the river.

The contamination potential in this structure is very low. There are three, albeit low potential, exposure pathways from the material that willremain in the demolished and backfilled CWPH: (1) exposure to radionuclides that have leached to the tidal water that saturates the remaining backfilled structure, (2) exposure from the excavation of the limited amount of silt currently on the bottom of the pump house bays, and (3) exposure from contamination that leaches from the structure surfaces, is adsorbed onto fill material, and is excavated at some time in the

future. Exposure to the excavated silt is limited to the same pathways as surface soil.Therefore, the DCGL for the silt will be the same as calculated for surface soil. In addition, the radionuclide mixture is assumed to be the same as that identified for surface soil. This assumption has essentially no effect since the samples will be counted by gamma spectroscopy, which will specifically identify the radionuclides of concern. Limiting the silt DCGL to the surface soil DCGL ensures that there will be no additional dose to the resident farmer, above that already accounted for through the surface soil DCGL, from the hypothetically excavated silt.

MYAPC License Termination PlanPage 6-43Revision 3 October 15, 2002The potential for radionuclide leaching from the surfaces of the CWPH is very remoteconsidering the extremely low potential of contamination being present as a result of

past operations and the fact that if contamination were present from past operations, the constant tidal flushing of the pump house bays would have already removed any leachable material. Notwithstanding this low potential, one water sample will be collected from each of the four pump house bays prior to draining the bays for final survey. The analytical detection sensitivity will be at the environmental LLD level. If no activity is detected, the water leaching pathway will be eliminated from consideration. Potential leaching to water will be evaluated by direct water sampling only. If activity above the environmental LLD is detected in the water samples, the positiveresults will be used to evaluate exposure from fish ingestion using the bioaccumulation factors from NUREG-5512, Vol. 3, Table 6.30, i.e., 20.6 kg fish consumption per year (DandD default value), and DCFs from FGR No.11. If a dose calculation is necessary, the dose will be added to the total dose from the other

contaminated materials listed in Table 6-11. Adjustments will be made to the DCGL's for other contaminated materials, if necessary, to ensure compliance with the 10/4 mrem/yr unrestricted use criteria. Since potential leaching into water is accounted for by direct water sampling, the onlyremaining exposure pathway to consider is the excavation of fill material hypothetically contaminated by radionuclide transfer from structure surfaces to the

fill. The conceptual model developed for the contaminated basement surfaces is adequate to apply to this very low potential pathway. As shown in Attachment 6-13, the DCGL for building basements in Table 6-11 resulted in very low radionuclide concentrations on the basement fill, with all concentrations being less than 1 pCi/g.

Note that one of the criteria applied to the selection of the basement fill DCGL is that the calculated fill concentration be less than the surface soil DCGL. In addition, the Kd's used for the basement fill model (Bank Run Sand) are generally higher than the Kd's for Bank Run Gravel which is being considered for backfill. This indicates that the CWPH fill would have lower concentrations than those calculated for basement fill. However, regardless of the fill material used, it is unlikely that the fill concentration would exceed the surface soil DCGL.Considering all of the arguments presented above, the DCGL calculated for thebuilding basements is appropriate and conservative for application to CWPH surfaces for the purpose of limiting hypothetical dose from the excavated fill pathway (as stated above, the potential leaching to water is addressed by direct sampling of the water). Compliance with the basement fill DCGL will ensure that the fill concentration will not exceed the surface soil DCGLs. Since the concentration of the hypothetically excavated fill would be below the surface soil DCGLs, there will be no MYAPC License Termination PlanPage 6-44Revision 3 October 15, 2002additional dose to the resident farmer beyond that already accounted for through thesurface soil and no addition to the total dose calculated in Table 6-11 is necessary.

6.7Material Specific DCGLs and Total Dose Calculation As described above, calculations were performed to develop conservative dose assessmentmodels and generate unitized dose factors for all contaminated materials at the Maine Yankee site and all radionuclides in the Maine Yankee mixture applicable to each material. When the dose pathways for the resident farmer were evaluated, it was evident that the resident farmer could receive dose from more than one contaminated material. A detailed discussion of the various contaminated materials and dose pathways was provided above. The total dose results from the summation of the contributions from each of contaminated materials.

Therefore, the final DCGLs for each of the contaminated materials are inter-dependent.

This section describes the method used to account for the dose from all materials and selectthe final DCGLs for all materials. The method ensures that the summation of doses from all pathways, at the selected DCGL concentrations for all materials, does not exceed 4 mrem/y drinking water dose and 10 mrem/y total dose. Table 6-11 provides the DCGLs that were selected for the Maine Yankee Site and the resulting total dose for all contaminated materials.

-13 contains the dose calculations for all contaminated materials listed in Table 6-11. The radionuclide mixture for "special areas" differs from the rest of thel basement surfaces. Therefore, a separate DCGL was selected and a separate dose calculation was performed for the "special areas". (See Attachment 2F for a discussion of "speciall

areas".)lThe DCGLs listed in Table 6-11 are target project DCGLs. The formal unrestricted usecriteria are the enhanced State dose criteria of 10 mrem/y or less from all pathways and 4 mrem/y or less from groundwater drinking sources. The DCGL values in Table 6-11 may be adjusted as the project proceeds using the methods and limitations described in this section as long as the dose criteria are satisfied.

MYAPC License Termination PlanPage 6-45Revision 3 October 15, 2002Table 6-11Contaminated Material DCGLBasement Contaminated Concrete (gross beta dpm/100 cm 2):18,000Special Area Contaminated Concrete (gross beta dpm/100 cm

2) 9,500 lBasement Activated Concrete (pCi/g):1.00Surface Soil (Cs-137 pCi/g):3.20 lDeep Soil (Cs-137 pCi/g):3.20 lBOP Embedded Piping [Limit: 100K], (gross beta dpm/100 cm 2):100,000lSpray Building Pump Piping [Limit: 800K], (gross beta dpm/100 cm 2):800,000lGround Water (H-3, pCi/L):6,812 Surface Water (H-3, pCi/L):960 Buried Piping, Conduit and Cable, (gross beta dpm/100 cm 2):9,800Contaminated Material Annual DoseMaterial DrinkingWater(mrem/y)Direct, Inhalation & Ingestion(mrem/y)TotalAnnual Dose(mrem/y)Contaminated Concrete2.70E-01 l3.08E-02l3.01E-01lActivated Concrete1.05E-02 l3.02E-02l4.08E-02lSurface Soil0.00E+00 l7.52E+00l7.52E+00lDeep Soil3.97E-02 l1.48E+00l1.52E+00lBOP Embedded Piping4.59E-02 l5.23E-03l5.11E-02lSpray Building Pump Embedded Piping7.60E-02 l8.67E-03l8.47E-02lGround Water2.08E-010.00E+002.08E-01Surface Water2.94E-021.27E-033.06E-02 Buried Piping, Conduit & Cable6.33E-04 l1.89E-03l2.52E-03lTotal0.68 mrem/y l9.08 mrem/y l9.76 mrem/y llllThe dose summation method is a conservative screening approach. For example, theenvironmental pathway analysis for deep soil indicated that a low concentration of tritium would reach groundwater three years after the site is released for unrestricted use. The location of the deep soil and corresponding groundwater contamination are obviously different from the location of building basements where the hypothetical resident farmer well was placed. In addition, the peak time for H-3 water concentration from deep soil is different

from the peak time for the basement water concentration. Nonetheless, consistent with a screening approach, the peak H-3 concentration in groundwater from deep soil is fully added

to the peak basement water concentration and the sum is used in the dose assessment. There was no reduction in concentration due to the differences in peak dose time or dilution through groundwater transport. A more realistic and less conservative environmental pathway analysis would consider these effects.

MYAPC License Termination PlanPage 6-46Revision 3 October 15, 2002The Maine Yankee commitment to a conservative screening approach is also seen in themethods for adding the dose contributions from embedded piping, activated concrete/rebar, and contaminated surfaces in the building basements, as well the other contaminated materials. It is important to recognize that the conservative results from the dose summation are in addition to the conservatism already built into the unitized dose factor calculations for

the individual contaminated materials.Soil areas outside of the RA boundary will not require consideration of dose from any othermaterials. The area of the RA is approximately 10,000 m 2, which represents the size of theresident farmer survey unit and contains the other contaminated materials considered. The other contaminated materials have essentially no effect outside of the RA and the dose is assumed to result from the contaminated soil only. In this case, the DCGLs will be based on the NUREG-1727 screening values corrected to represent 10 mrem/y. The soil radionuclide mixture applied to areas outside the RA boundary are assumed to be the same as the mixture listed in Table 2-11 The DCGL for areas outside the RA is 4.2 pCi/g. This DCGL can bel calculated most directly by the ratio to the 3.2 pCi/g Cs-137 DCGL provided in LTP Table l 6-11, recognizing that the dose from 3.2 pCi/g is 7.52 mrem/yr. This calculation is providedl

below:ll4.2 pCi/g = (3.2 pCi/g) (10.00 mrem/yr) l (7.52 mrem/yr)l6.7.1Conceptual Model for Summing Contaminated Material Dose The conceptual model for summing doses to the resident farmer essentially combinesthe dose from surface soil and deep soil with the dose from water derived from a well drilled directly into the worst case building basement. The well water is used for irrigation and drinking.

The source term for the well water concentrations includes contributions frombasement contamination, activated concrete/rebar, and embedded piping. The model assumes that the residual contamination in all three materials is instantaneously released and mixed with water that has infiltrated the building basement.

The instantaneous release of all contamination is conservative for several reasons.Concrete contamination will be released at a rate associated with the diffusion coefficient for the various radionuclides. Activated concrete/rebar will actually be released to the water at a relatively slow rate more closely linked to physical dissolution of concrete, which is expected be very slow. For embedded piping, the actual contamination release rate is expected to be close to zero because any open pipe end that could be a point of release into a basement will be sealed. Another conservatism is the assumption that all of these sources are mixed in the same worst

case 2460 m 3 of basement volume. In actuality, the various sources are in different MYAPC License Termination PlanPage 6-47Revision 3 October 15, 2002areas and different buildings. Finally, the source term contributions fromgroundwater, surface water, and deep soil were added directly to the basement well

concentrations without consideration of transport or dilution. 6.7.2 Method and Calculations for Summing Contaminated Material Dose The primary inputs to the dose summation are the unitized dose factor calculationsdeveloped for each contaminated material. The unitized dose spreadsheets were used

for the dose calculations without modification. However, the input concentrations and inventories required modification to represent the selected DCGLs as opposed to unit concentrations. The additional calculations required to convert the DCGL values

into radionuclide concentrations and inventories are described in the sections below. To perform the summation and to provide a method to efficiently adjust the DCGLsfor various materials, each of the individual material unitized dose spreadsheets was copied and linked in a single spreadsheet entitled DCGL/Total Dose. The spreadsheet output for the DCGL dose calculation for each material is provided in Attachment 6-

13. These spreadsheets provide the calculations for the dose values reported in Table

6-11.Contaminated Basement SurfacesThe DCGL for contaminated concrete is expressed as dpm/100 cm 2 detectable grossbeta. This form was required because the final survey will be performed using gross beta measurements. The primary criteria for selecting the gross beta DCGL for basement surfaces was to ensure that the total dose, from all contaminated materials, was less than the 10/4 mrem/yr dose limit. There were two secondary criteria applied to the selection of the DCGL; 1) the DCGL would result in calculated basement fill concentrations below the surface soil DCGL, and 2) the DCGL was less than the NRC surface screening values from NUREG-1727, Table C2.2 (see Attachment 6-18).To calculate the dose from a given gross beta DCGL, the gross beta concentration is converted to individual radionuclide concentrations based on their respective fractions in the radionuclide mixture. The individual concentrations are then input to the dose calculation spreadsheet for contaminated basement concrete. Characterization data indicated that the radionuclide mixtures for "special areas" differs from the other thel basement surfaces (see Table 2-8). Therefore, a separate mixture is applied to the dose assessment for the "special areas", resulting in a different DCGL for the "speciall areas". The DCGL selected for the "special areas" resulted in a lower dose than thatl calculated for the rest of the basement surfaces (see Attachment 6-13). Therefore, the total dose shown in Table 6-11 is based on the higher dose calculated for the general radionuclide mixture and DCGL, not the "special areas" mixture. l MYAPC License Termination PlanPage 6-48Revision 3 October 15, 2002 The individual radionuclide concentrations are calculated as follows:Convert the detectable gross beta concentration to total radionuclide concentration:

Total dpm/100 cm 2 = (gross beta dpm/100 cm 2)/(!gross beta radionuclidefractions)(15)Where:Total dpm/100 cm 2 is the summation of activity from all radionuclidesGross beta is the detectable gross beta concentration

!gross beta radionuclide fractions is the sum of the fractions of eachradionuclide in the Maine Yankee mixture with detectable beta Calculate each individual radionuclide concentration as follows:

C R dpm/100 cm 2 = (NF R)(Total dpm/100 cm 2)(16)Where: C R is the concentration of a given radionuclide NF R is the nuclide fraction of a given radionuclideSurface SoilThe DCGL for surface soil is expressed in pCi/g Cs-137. The surface soil dose iscalculated by first determining the individual radionuclide concentrations by ratio to Cs-137 using the relative fractions in the Maine Yankee mixture and then entering the individual concentrations into the "inventory" column in the dose calculation spreadsheet for surface soil. During final survey, and in the final site dose assessment, the non-gamma emittingradionuclides (HTD nuclides) will be accounted for using Cs-137 as a surrogate asl described in Equation 17 (from NUREG-1505, Page 11-2, Equation 11-4). Thel contribution from soil HTD radionuclides will be calculated using the radionuclidel fractions listed in Table 2-11. Cs-137 was selected as the surrogate since it is thel predominant radionuclide in soil (i.e., 89%) and since many of the soil samples willl not result in positively detected Co-60. As seen of page 5 of Attachment 6-13, thel dose contribution from the HTD radionuclides in soil (Ni-63 and H-3) is less than 1%l of the Cs-137 dose. Therefore, the effect of the surrogate calculation on the Cs-137 DCGL w value will be minimal. To calculate the surrogate Cs-137 DCGL, the following equation is used: l MYAPC License Termination PlanPage 6-49Revision 3 October 15, 2002 (17)lCSs D R D R D R D n n137 1 1 1 2 2 3 3...Where:Cs-137 s is the surrogate Cs-137 DCGL w;lD 1 is the DCGL for Cs-137;l R n is the ratio of the HTD radionuclide mixture fraction to the Cs-l137 mixture fraction; andl

D n is the DCGL w of the HTD radionuclide corresponding to 10lmrem/yr. The DCGL's are calculated by inverting the Unitizedl Dose Factors Listed in the LTP, Table 6-7, and multiplying by 10. lThe unitized dose factors were used in the total dose and DCGL calculations. This allowed the dose contribution of each radionuclide to be calculated and reviewed to understand the relative significance of the nuclides in the mixture. The dose

calculated from the Cs-137 concentration shown in Table 6-11 will be the same regardless of whether a "surrogate" Cs-137 DCGL w is used or the unitized dose factors for all radionuclides are used. The Cs-137 to Co-60 ratio will vary in the final survey soil samples and this will beaccounted for using a "unity rule" approach as described in NUREG-1505, Chapterl

11. lBefore applying the unity rule, the DCGLs, for areas inside the RA, will be adjustedlto represent the Table 6-11 total surface soil dose, as opposed to 10 mrem/yr. As seenl in Table 6-11, the dose from surface soil is limited because of the additional dosel from the other contaminated materials on the site. The unity rule calculation will limitl the surface soil dose by multiplying the Cs-137 S and Co-60 DCGL's corresponding tol10 mrem/yr by a factor equal to the Table 6-11 total surface soil dose value divided byl 10 mrem/yr. If the dose contribution from surface soil changes in the future, thel multiplication factor will change accordingly. l lIn order to demonstrate compliance with the surface soil DCGL, the gammal spectroscopy results for each soil sample will be converted to a unity rule equivalentl using the Table 6-11 surface soil DCGL's in the following equation. After thisl conversion, the DCGL becomes a unitless value of 1.0 that is equivalent to the totall surface soil dose shown in Table 6-11. If the dose contribution from surface soill changes in the future, the dose corresponding to a unity rule equivalent of 1.0 willl change accordingly. The unity rule equivalent is calculated per the followingl equation:l MYAPC License Termination PlanPage 6-50Revision 3 October 15, 2002Unity Rule Equivalent 1 = Cs-137 DCGLCo60 DCGL...R DCGL(Cs-137)(Co60)

N(N)SAAWhere: Cs-137 and Co-60 are the gamma spec results,lis the surrogate Cs-137 S DCGL,lDCGL(Cs137)S adjusted to represent the Table 6-11 total surfacelsoil dose, as applicable (inside RA)l is the Co-60 DCGL adjusted tolDCGL(Co60)A represent the Table 6-11 total surface soil dose, aslapplicable (inside RA)l l R N is any other identified gamma emitting radionuclides, and l is the adjusted DCGL for radionuclide N.lDCGL(N)AlAbsent sample-specific information from the final survey, using the radionuclidel mixture fractions to represent the final Cs-137/Co-60 ratios is the best method available to estimate dose and determine target soil concentrations for remediation planning. Activated Concrete/RebarThe DCGL for activated concrete/rebar is in units of pCi/g total activity at the walland floor surfaces. Total activity includes all radionuclides in the Maine Yankee mixture. The target remediation concentration is 1 pCi/g of activated concrete.

Therefore, no modification of the unit dose factor spreadsheet for activated concrete was required to account for the DCGL concentration.

Deep SoilThe DCGL for deep soil, as for surface soil, is expressed in pCi/g Cs-137. The deep soil dose is calculated by first determining the individual radionuclide concentrations by ratio to Cs-137 using the relative fractions in the Maine Yankee surface soil mixture and then entering the individual concentrations into the "inventory" column

in the dose calculation spreadsheet for deep soil. The surface soil radionuclide mixture is assumed to be representative of the deep soil mixture.The issues related to compliance using final survey results for gamma emitters and theuse of Cs-137 as a surrogate for the HTD radionuclides that were described for surface soil also apply to deep soil.

MYAPC License Termination PlanPage 6-51Revision 3 October 15, 2002 GroundwaterThe existing groundwater concentrations are entered directly into the DCGL/TotalDose spreadsheet. This allows the dose from current groundwater contamination to be accounted for. The entered concentration is not intended to be a DCGL. If Maine Yankee's estimate of existing groundwater concentration changes, the value(s) input to the final dose calculation for compliance with the 10/4 dose criteria will use the most applicable concentrations.Surface WaterThe maximum concentration identified was used in the dose assessment. As with thegroundwater concentration, the entered concentration is not a DCGL. If new sample data, if collected, indicates higher concentrations in site surface water, the new data will be used in the final dose assessment to demonstrate compliance with the 10/4 dose criteria.Buried PipingThe buried piping DCGL is expressed as dpm/100 cm 2 gross beta. The DCGL/TotalDose spreadsheet converts gross beta concentration to individual radionuclide concentrations analogous to contaminated basement surfaces. The resulting

concentrations are entered in the dpm/100 cm 2 inventory column in the dosecalculation spreadsheet.

Embedded Piping llThe embedded piping planned to remain after decommissioning has a total internall

surface area of 154.3 m

2. The Spray Building contains 26.5 m 2 of embeddedlcontainment spray pump piping surface area with the remaining 127.8 m 2 located inlthe Containment, Spray Building PAB, and Fuel buildings. l lRemediation performed to date on the Spray Building embedded piping has beenl extensive. Numerous sections of Ric-Wil piping (pipes within a pipe), most less that 5l feet long, that were contained in the concrete walls of the Spray building have beenl removed. Additionally, two Containment Spray Supply lines were removed byl cutting 24- inch diameter cores through five feet of concrete. The cost wasl approximately $30,000.l lThe longest run of Spray building piping that remains is approximately 70 linear feetl of 16 inch diameter, stainless steel Containment Spray Pump lines (CS-M-91, 92).l The two pipes, which are 15 feet apart and cross- connected, extend from the lowerl MYAPC License Termination PlanPage 6-52Revision 3 October 15, 2002level of the Spray building (at El.-14'9") to the safeguards sump (El.-4') inlcontainment and are embedded in over 10 vertical feet and 16 horizontal feet ofl concrete. l lAn extensive effort to chemically decontaminate the containment spray pump pipingl occurred in June 2002. A caustic chemical, which has been successfully used in otherl facilities, was applied to the piping in four separate applications over a total of 74l hours. Although several sections of the vertical piping were decontaminated tol relatively low levels, the majority of piping still contains residual contamination at anl average level of ranging from 1E+04 dpm/100 cm 2 to about 1.5E+05 dpm/100 cm

2. lThe maximum level encountered based on remediation surveys to date is about 4E+05l

dpm/100 cm

2. The cost of this project was on the order of $200,000.l lThe decontamination factors (ratio of before and after contamination levels) werel high initially (up to 104). However, the decontamination factors were low for thel fourth chemical decontamination effort (as low as 1). Further chemicall decontamination is not expected to be effective. The only remaining alternative isl removal and disposal as LLRW waste. Estimates to remove the spray buildingl embedded piping range from about $200,00 to $285,000, excluding disposal costsl which, for the large volume of concrete required to be removed, are approximatelyl

$150,000-175,000. l lAssuming that residual contamination were present at an average level of 8E+05l

dpm/100 cm 2 in the 26.5 m 2 of spray pump piping, the resident farmer doselcontribution would be approximately 0.085 mrem/yr. The 8E+05 dpm/100 cm 2 valuelwas selected to represent the upper range of the average contamination level. l lBased on the total projected costs for removal and disposal of the spray pump pipingl of at least $350,000, the cost per person-rem would be over $4,000,000 per person-l rem. This is far in excess of the NRC ALARA criteria of $2000 per person-rem listedl in NUREG-1727. Therefore, additional decontamination is not justified. l lMaine Yankee has evaluated the contamination potential of the embedded piping inl the Containment, PAB, and Fuel building and does not believe the levels ofl contamination found in the spray pump piping will be encountered in these buildings. l Therefore, two different DCGL's will be used for embedded piping. The DCGL forl the spray pump piping will be 800,000 dpm/100 cm 2 and the DCGL for the rest of thelembedded piping in the Spray Building, Containment, PAB, and Fuel buildings willl

be 100,000 dpm/100 cm

2. llThe inventory for the dose assessment was calculated assuming that the spray pumpl piping (26.5 m

2) is contaminated at 800,000 dpm/100 cm 2 and that the remainingl MYAPC License Termination PlanPage 6-53Revision 3 October 15, 2002embedded piping (127.8 m

2) is contaminated at 100,000 dpm/100 cm

2. The entirelinventory of embedded piping from all buildings was summed and assumed to bel instantaneously released. The dose under these assumptions was calculated to bel 0.136 mrem/yr. l lThe assumption of instantaneous release is conservative since the spray pumpl embedded piping will be filled with cement grout.l l6.8Area Factors6.8.1Basement Contamination The basement contamination conceptual model described in Section 6.6.1 was based on a worst case surface area of 4182 m

2. The model assumes uniform mixing within a0.6 m layer of fill in direct contact with the 4182 m 2 surface area. The conceptualmodel assumes that the activity released from the wall is mixed with the 738 m 3volume of water contained in the 0.6 m fill layer, but does not require the contamination to be uniformly distributed over the entire 4182 m 2 surface area. Themodel source term is the total inventory over the surface and is not dependent on the distribution of the contamination on the surface. Therefore, consistent with the

conceptual model, the area factor could be a simple linear relationship between total activity and area. The area factor formula would then be described using the following equation:AF = 4182 m 2/(elevated area)(18)where: AF is the area factor (elevated area) is the size of the area exceeding the DCGL W Maine Yankee evaluated this potential approach and believes that it is consistent with NUREG-1575 and NUREG-1727 guidance which acknowledges that the area factors should be based on the dose model used to calculate the DCGL. However, it appears that substantially better remediation performance can be achieved than is reflected in Equation (18) and that leaving elevated areas at the levels allowed by the equation is not sufficiently conservative. Accordingly, the area factors for contaminated basement concrete will be calculated using Equation (19), which represents a considerably more conservative approach.

MYAPC License Termination PlanPage 6-54Revision 3 October 15, 2002AF = 50 m 2/(elevated area)(19)where: AF is the area factor (elevated area) is the size of the area exceeding the DCGL W The 50 m 2 area was selected after qualitative consideration of the potential residualcontamination that could remain in elevated areas after a comprehensive remediation effort. Areas greater than 50 m 2 are required to be at or below the DCGL

w. Areafactors can apply to elevated areas on any surface, but are expected to be applied primarily to contamination in cracks and crevices, or other geometries, that are not efficiently remediated. It is not expected that a large number of elevated areas will remain. The number of elevated areas allowed to remain is limited by the formula

presented in Section 5.6.3. 6.8.2Surface Soil and Deep Soil Area Factors The NRC screening values were used to calculate the surface soil DCGLs. Thisapproach does not provide a direct method of linking the area factor calculation to the dose model. The surface soil area factors were determined based on the change in direct radiation as a function of area. The relative exposure was determined using

Microshield. The output reports are provided in Attachment 6-14.Using direct radiation only is a conservative approach since area factors based on theingestion and inhalation dose pathways increase at a faster rate than those based on the direct radiation pathway. This is evident from inspection of Table 5.6 in NUREG-1575 which shows, for example, the higher area factors for Am-241 as compared to

Cs-137 and Co-60. The area factors for surface and deep soil are listed in Table 6-12.

Table 6-12Area Factors (AF) for Surface Soil and Deep Soil lSurvey Unit = 10,000 m 2Area m 2124681625501005001,00010,000Co-137 (AF) l11.9l6.7l4.1l3.2l2.8l2.0l1.7l1.5l1.3l1.2l1.1l1.0lCs-60 (AF) l12.7l7.2l4.4l3.1l2.9l2.1l1.8l1.5l1.2l1.2l1.1l1.0lMY Mix (AF)*

l12.06.84.13.22.82.01.81.51.31.21.11.0 l* Where MY mix is the surface and deep soil radionuclide mixture.

l MYAPC License Termination PlanPage 6-55Revision 3 October 15, 20026.8.3Embedded Piping Area Factorsl lSince the dose model for embedded piping is the same as the basement fill model, thel same area factor equation would apply.l l lAF melevatedarea50 2lAn evaluation of contamination potential and remediation effectiveness in embeddedl piping concluded that area factors can be limited to 2.0. Area factors larger than 2.0l can readily be justified on a dose basis using the above equation. However, al conservative application of ALARA was applied to limit the embedded piping areal factor to 2.0l lThe number of elevated areas in embedded piping will be limited to ensure that thel source term inventory (and annual dose) relative to the selected DCGL(s) is notl exceeded. l l6.8.4Buried Piping Area Factorsl lBuried piping contributes less than one-tenth of one percent of the total dose to thel resident farmer. The volume of piping expected to remain on site is 142.0 m

3. Thelradioactive contaminants associated with buried pipe are considered to be excavatedl to the soil surface uniformly mixed in the top 0.15 m of soil. Under these conditionsl area factors for soil would apply.l lThe following equation calculates an area factor that is ALARA and conserves thel survey unit total inventory. As a measure of conservatism, a limit of 10 is placed onl area factors for buried piping. The DCGLEMC (the DCGL used for the elevatedlmeasurement criteria) is calculated using the same equation.l llAreaFactorBuriedPipingSurveyUnitSizemBuriedPipingElevatedAream()()2 2lFor example, a 20 m 2 survey unit containing a 1.0 m 2 elevated area and using thelDCGL of 9.50E+03 dpm/100 cm 2 would result in an area factor (AF) of 20:l llAreaFactor m m20 20 10 2 2.

MYAPC License Termination PlanPage 6-56Revision 3 October 15, 2002The AF would be limited to 10 as stated above so the allowable activity in thel elevated area would be 9.50E+04 dpm/100 cm

2. The DCGLEMC calculated by thelequation would be 20 times the DCGL or 1.90E+05 dpm/100 cm 2.llIf the maximum concentration of the elevated area (i.e., 9.50E+04 dpm/100 cm

2) werelthe only activity in the survey unit, the unity rule application would be as follows:l llUnityRule Edpm cm Edpm cmwhichis95004100190051000510 2 2....l6.8.5Activated Concrete/Rebar Area Factorsl lThe activated concrete/rebar conceptual model is conservatively treated in the samel manner as the basement contamination model. Activated concrete includes the sourcel term in the entire volume of activated concrete (surface and subsurface). As in thel basement fill model the activated radionuclide inventory is assumed to bel instantaneously released; however, the release of radionuclides for the activatedl concrete is expected to be significantly slower (more conservative) than the release ofl radionuclides from structure's surface contamination. Since the dose models arel identical, the area factor for the Basement Fill Model (Section 6.8.1, equation 19 ofl the LTP) will be used for activated concrete. l l6.9Standing Building Dose Assessment and DCGL Determination6.9.1Dose Assessment MethodThis dose assessment applies to the occupancy of a standing building and does notapply to the filled building basement. Current plans call for only one building to remain standing after decommissioning, i.e., the switchyard relay house. The NRC screening values from NUREG-1727, Table C2.2 were used for building occupancy dose assessment and DCGL determination. The screening values were adjusted to correspond to 10 mrem/y.NUREG-1727, NMSS Decommissioning Standard Review Plan, Appendix C,describes the justification necessary to allow direct use of these screening values.

When using the screening approach licensees need to demonstrate that the particular site conditions (e.g., physical and source term conditions) are compatible and

consistent with the DandD model assumptions.

MYAPC License Termination PlanPage 6-57Revision 3 October 15, 2002The following site conditions are specified for use of the Standing Building screening values:1.The contamination on building surfaces (e.g., walls, floors, ceilings) should be surficial and non-volumetric (e.e., less than 0.4 in (10 mm)).2.Contamination on surfaces is mostly fixed (not loose), with the fractionof loose contamination not to exceed 10 percent of the total surface activity.3.The screening criteria are not applied to surfaces such as buriedstructures (e.g., drainage or sewer pipes) or mobile equipment within the building; such structures and buried surfaces will be treated on a case-by-case basis.

The above conditions are satisfied for the Maine Yankee site.

6.9.2 Standing

Building DCGLs The standing building DCGL was calculated as shown in Table 6-13. The DCGLswere calculated using Equation 4-4 in NUREG-1727 as adjusted for gross beta by multiplying the results by the gross beta radionuclide fraction in the mixture. The DCGL was expressed as gross beta since the final survey of a standing building, if necessary, will be performed using gross beta measurements.

MYAPC License Termination PlanPage 6-58Revision 3 October 15, 2002 Table 6-13Gross Beta DCGL For Standing Buildings(Not Applicable to Basements to be Filled)NuclideNuclide Fraction (n f)ScreeningLevel dpm/100 cm 2 Beta Fraction n f/Screening LevelH-32.36E-024.96E+074.75E-10Fe-554.81E-031.80E+062.67E-09Co-573.06E-048.44E+043.63E-09 Co-605.84E-022.82E+035.84E-022.07E-05Ni-633.55E-017.28E+054.88E-07Sr-902.80E-033.48E+032.80E-038.04E-07Cs-1344.55E-035.08E+034.55E-038.95E-07 Cs-1375.50E-011.12E+045.50E-014.91E-05Sum 6.16E-017.20E-5 DCGL 8.554E+03"#"dpm/100 cm 2(10 mrem/y)6.9.3Standing Building Area FactorsAs discussed above for soil, using the NRC screening values for DCGL determination does not allow for direct determination of area factors. Consistent with the method used for soil, Microshield runs were used to generate the area factors by starting with

an area of 100 m 2 and calculating the relative exposure rate as the area is decreased.

The ratio of the 100 m 2 exposure rate to the respective smaller area exposure raterepresents the area factor for the given elevated area size. Attachment 6-15 contains the Microshield runs and Table 6-14 provides the resulting area factors MYAPC License Termination PlanPage 6-59Revision 3 October 15, 2002 Table 6-14Area Factors (AF) for Standing Buildingsl(Does Not Apply to Building Basements To Be Filled)

Survey Unit Size = 100 m 2Area m 20.51248162550100 Cs-137 (AF) l23.5l12.6l7.1l4.3l2.8l1.9l1.6l1.2l1.0lCo-60 (AF) l23.5l12.6l7.1l4.3l2.8l1.9l1.6l1.2l1.0lMY Mix (AF) l23.512.67.14.32.81.91.61.21.0 l* Where MY mix is the Contaminated Concrete radionuclide mixture.

l6.10References6.10.1Baes, C.F., R.D. Sharp, A.L. Sjorren, and R.W. Shor, 1984. "A Review andAnalysis of Parameters for Assessing Transport of Environmentally Released Radionuclides through Agriculture," ORNL-5786, Oak Ridge National Laboratory.6.10.2U.S. Environmental Protection Agency, 1988. "External Exposure toRadionuclides in Air Water and Soil, Federal Guidance Report No. 11,"

EPA 520/1-88-020, U. S. EPA Office of Radiation and Indoor Air.6.10.3Krupka, K.M., and R.J. Serne, 1998. "Effects on RadionuclideConcentrations by Cement/Ground-Water Interactions in Support of Performance Assessment of Low-Level Radioactive Waste Disposal Facilities," NUREG/CR-6377, PNNL-14408.6.10.4Onishi, Y., R.J. Serne, R.M. Arnold, C.E. Cowan, and F.L. Thompson, 1981. "Critical Review: Radionuclide Transport, Sediment Transport, and Water Quality Mathematical Modeling; and Radionuclide Adsorption/Desorption Mechanisms," NUREG/CR-1322, PNL-2901.6.10.5Sheppard, M.I. and D.H. Thibault, 1990. "Default Soil Solid/LiquidPartition Coefficients."6.10.6Maine Yankee Engineering Calculation, Diffuser and Forebay DoselAssessment, EC-041-01 (MY), Revision 0.l

MYAPC License Termination Plan Revision 3

October 15, 2002 -2 BNL Kd Report for Fill

MYAPC License Termination Plan Revision 3

October 15, 2002 -6 Activated Concrete Inventory

MYAPC License Termination Plan Revision 3

October 15, 2002 -8 Deep Soil Microshield Output

MYAPC License Termination Plan Revision 3

October 15, 2002 -9 Deep Soil RESRAD Output

MYAPC License Termination Plan Revision 3

October 15, 2002 -10 Buried Piping List and Projected Concentration Calculation

MYAPC License Termination Plan Revision 3

October 15, 2002 -11 Buried Piping RESRAD Output

MYAPC License Termination Plan Revision 3

October 15, 2002 -12 Buried Piping Microshield Output

Table 6-11 Contaminated Material DCGL Refer to Section 6 for Table 6-11

ACTIVATED CONCRETE Key Parameters:

Porosity 0.30 Concrete Density 2.20 g/cm 3 Bulk Density 1.50 g/cm 3 Annual Total Well Water Vol 738.0 m 3 Yearly Drinking Water 478.0 L/yr Irrigation Rate 0.274 L/m 2-d W all Surface Area 4182.0 m 2 Surface Soil Depth 0.15 m Fill Volume 2460.0 m 3 Activated Concrete Total Inventory 3.30E+08 Total pCi per pCi/g Surface Area/Open Volume 1.70 m 2/m 3 Activated Concrete Total Conc.

1.00 pCi/g Concrete Volume 4.18 m 3 NUREG-1727 FGR 11 Microshield Kd Kd Drinking Irrigation Direct Total Nuclide mrem/y per mrem/pCi mrem/y per Nuclide Inventory Inventory Fill Concrete Adsorption Water Fill Concrete Nuclide Water Dose Dose Dose Dose pCi/g pCi/g Fraction pCi/g pCi cm 3/gm cm 3/gm Factor pCi/L pCi/g pCi/g mrem/y mrem/y mrem/y mrem/y Cs-134 4.39E+00 7.33E-05 6.09E-05 8.40E-03 8.40E-03 2.77E+06 7.91E+01 3.00E+00 3.96E+02 9.47E-03 7.49E-04 2.84E-05 Cs-134 3.32E-04 1.85E-05 4.56E-08 3.50E-04 Co-60 6.58E+00 2.69E-05 6.30E-04 4.00E-02 4.00E-02 1.32E+07 1.28E+02 1.00E+02 6.40E+02 2.79E-02 3.56E-03 2.79E-03 Co-60 3.59E-04 8.16E-05 2.25E-06 4.43E-04 C-14 2.08E+00 2.09E-06 0.00E+00 5.80E-02 5.80E-02 1.91E+07 5.00E+00 1.00E+02 2.72E+01 9.52E-01 4.76E-03 9.52E-02 C-14 9.51E-04 8.80E-04 0.00E+00 1.83E-03 Eu-154 3.13E+00 9.55E-06 3.10E-04 9.00E-03 9.00E-03 2.97E+06 4.00E+02 5.00E+03 2.06E+03 1.95E-03 7.80E-04 9.75E-03 Eu-154 8.90E-06 2.71E-06 2.42E-07 1.19E-05 Fe-55 2.50E-03 6.07E-07 0.00E+00 1.24E-01 1.24E-01 4.09E+07 2.50E+01 1.00E+02 1.27E+02 4.36E-01 1.09E-02 4.36E-02 Fe-55 1.26E-04 4.84E-07 0.00E+00 1.27E-04 H-3 2.27E-01 6.40E-08 0.00E+00 6.47E-01 6.47E-01 2.14E+08 0.00E+00 0.00E+00 1.00E+00 2.89E+02 0.00E+00 0.00E+00 H-3 8.84E-03 2.91E-02 0.00E+00 3.80E-02 Eu-152 2.87E+00 6.48E-06 2.09E-04 1.11E-01 1.11E-01 3.66E+07 4.00E+02 5.00E+03 2.06E+03 2.41E-02 9.62E-03 1.20E-01 Eu-152 7.45E-05 3.07E-05 2.01E-06 1.07E-04 Ni-63 1.19E-02 5.77E-07 0.00E+00 7.00E-03 7.00E-03 2.31E+06 1.28E+02 1.00E+02 6.40E+02 4.88E-03 6.24E-04 4.88E-04 Ni-63 1.35E-06 2.58E-08 0.00E+00 1.37E-06 SUM 1.07E-02 3.02E-02 4.54E-06 4.08E-02 DOSE CALCULATION FACTORS ACTIVATED CONCRETE ANNUAL DOSE WATER, FILL, CONCRETE CONCENTRATION Kd SOURCE TERM

BOP EMBEDDED PIPE Key Parameters:

Porosity 0.30 Concrete Density 2.20 g/cm 3 Bulk Density 1.50 g/cm 3 Surface Soil Depth 0.15 m Yearly Drinking Water 478.0 l/yr Irrigation Rate 0.274 L/m 2-d W all Surface Area 4182.0 m 2 Annual Total Well Water Vol 738 m 3 Fill Volume 2460.0 m 3 Embedded Pipe Conversion Factor 5754.5 pCi per dpm/100 cm 2 Surface Area/Open Volume 1.70 m 2/m 3 Gross Beta DCGL 1.00E+05 dpm/100 cm 2 Concrete Volume 4.18 m 3 Gross Beta Nuclide Fraction 0.616 Total Inventory 1.62E+05 dpm/100 cm 2 NUREG-1727 FGR 11 Microshield Kd Kd Drinking Irrigation Direct Total Nuclide mrem/y per mrem/pCi mrem/y per Inventory Inventory Fill Concrete Adsorption Water Fill Concrete Nuclide Water Dose Dose Dose Dose pCi/g pCi/g Fraction dpm/100 cm 2 pCi cm 3/gm cm 3/gm Factor pCi/L pCi/g pCi/g mrem/y mrem/y mrem/y mrem/y Sr-90 1.47E+01 1.42E-04 0.00E+00 2.80E-03 4.55E+02 2.62E+06 6.02E+01 1.00E+00 3.01E+02 1.18E-02 7.07E-04 1.18E-05 Sr-90 7.98E-04 7.68E-05 0.00E+00 8.75E-04 Cs-134 4.39E+00 7.33E-05 6.09E-05 4.55E-03 7.38E+02 4.25E+06 7.91E+01 3.00E+00 3.96E+02 1.45E-02 1.15E-03 4.36E-05 Cs-134 5.09E-04 2.83E-05 6.99E-08 5.37E-04 Cs-137 2.27E+00 5.00E-05 1.20E-05 5.50E-01 8.93E+04 5.14E+08 7.91E+01 3.00E+00 3.96E+02 1.76E+00 1.39E-01 5.27E-03 Cs-137 4.20E-02 1.77E-03 1.67E-06 4.38E-02 Co-60 6.58E+00 2.69E-05 6.30E-04 5.84E-02 9.48E+03 5.46E+07 1.28E+02 1.00E+02 6.40E+02 1.15E-01 1.47E-02 1.15E-02 Co-60 1.48E-03 3.37E-04 9.29E-06 1.83E-03 Co-57 1.67E-01 1.18E-06 2.80E-08 3.06E-04 4.97E+01 2.86E+05 1.28E+02 1.00E+02 6.40E+02 6.05E-04 7.73E-05 6.05E-05 Co-57 3.41E-07 4.49E-08 2.16E-12 3.86E-07 Fe-55 2.50E-03 6.07E-07 0.00E+00 4.81E-03 7.82E+02 4.50E+06 2.50E+01 1.00E+02 1.27E+02 4.79E-02 1.20E-03 4.79E-03 Fe-55 1.39E-05 5.32E-08 0.00E+00 1.39E-05 H-3 2.27E-01 6.40E-08 0.00E+00 2.36E-02 3.82E+03 2.20E+07 0.00E+00 0.00E+00 1.00E+00 2.98E+01 0.00E+00 0.00E+00 H-3 9.10E-04 3.00E-03 0.00E+00 3.91E-03 Ni-63 1.19E-02 5.77E-07 0.00E+00 3.55E-01 5.77E+04 3.32E+08 1.28E+02 1.00E+02 6.40E+02 7.01E-01 8.96E-02 7.01E-02 Ni-63 1.93E-04 3.71E-06 0.00E+00 1.97E-04 SUM 4.59E-02 5.22E-03 1.10E-05 5.11E-02 EMBEDDED PIPE ANNUAL DOSE DOSE CALCULATION FACTORS SOURCE TERM Kd WATER, FILL, CONCRETE CONCENTRATION

MYAPC License Termination Plan Revision 3

October 15, 2002 -14 Soil Area Factor Microshield Output