ML20101T407

Forwards Response to NRC Three Addl Questions Re 830714 Request for Approval for Alternative Onsite Disposal of Very Low Level Radioactively Contaminated Secondary Side Cleanup Resins,Per 10CFR20.302

ML20101T407
Person / Time
Site:	Davis Besse
Issue date:	01/29/1985
From:	Crouse R TOLEDO EDISON CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
1118, TAC-60875, NUDOCS 8502060150
Download: ML20101T407 (10)

Text

-

.:..e TOLEDO hm EDISON RCHAAo P. C AOUSE Docket No. 50-346 vc. pr o.nt m.,

License.No. NPF-3 Serial No. 1118 January 29, 1985 Director of Nuclear Reactor Regulation Attention: Mr. John F. Stolz Operating Reactor Branch No. 4 Division of Licensing United States Nuclear Regulatory Commission Washington, D.C. 20555

Dear.Mr. Stolz:

-By letter dated July 14, 1983 (Serial No. 972), Toledo Edison submitted to the NRC a request for approval for the alternative on-site disposal of

'very-low-level radioactively contaminated secondary-side clean up resins for the Davis-Besse Nuclear Power Station Unit No. 1. This request was made pursuant to the regulation of 10 CFR 20.302.

Your letter of May 4, 1984 (Log No. 1509) requested additional information to support our request for approval to dispose on-site certain very-low-level radioactively contaminated wastes. Toledo Edison submitted a response dated July 30, 1984 (Serial No. 1065), for the additional information.

During the month of November 1984, three additional questions were asked by the NRC in a telephone conversation with our Licensing personnel.

Attachments 1 through 3 provide Toledo Edison's response to the questions.

Very truly yours, RPC:DWB:lah cc: DB-1 NRC Resident Inspector 8502060150 850129 PDR ADOCK 05000346'-

X PM ,

TOLEOO, OHlO 43652 noo\

THE TOLEGO EOISON COMPANY EOISON PLAZA 300 MADISON AVENUE ii I l

Pr

' Docket Ns. 50-346

-Lic:nne No. NPF-3 Serial'No. 1118

' January 29, 19851

' Attachment 1 RESPONSES TO NRC QUESTIONS DURING TELEPHONE CONVERSATION IN NOVEMBER 1984 Question 1: Estimate of the dose from ground water for the worst possible disposal site.

Response: The maximally exposed individual dose has been estimated to be less than 0.0002 mrem per year. Justification for this value is given in Attachment No. 2.

. Question 2: Provide the basis for selecting the worst. location and the

j. principle parameters used in the dose estimate.

Response: The selection of the disposal area is not significant since the assumptions used to calculate the dose estimates for a maximum potential individual exposure with a groundwater well were based on the location of the well' being in close proximity to the disposal area. Attachment No. 2.provides details of the calculations used to determine the dose.

Question 3: Provide a map indicating the location of the burial site and the worst location for the nearest well.

Response: Attachment No. 3. indicates the proposed disposal area and the nearest groundwater well to the disposal area. The water from the well is not used for drinking water.

Samples are collected quarterly and analyzed for

. radioactivity as part of the environmenta1' radiological monitoring program.

f L..

,- i Dock 2t No. 50-346 Liczn:2 No. NPF-3

. Serial No. 1118 January 29,-1985 Attachment 2 '

GROUNDWATER MIGRATION ANALYSIS FOR THE ON-SITE DISPOSAL OF LOW-LEVEL RADI0 ACTIVELY CONTAMINATED RESIN AT THE DAVIS-BESSE NUCLEAR POWER STATION Introduction By letter dated July 14, 1983, Toledo Edison Company submitted to the NRC a request for approval for the alternative on-site disposal of very , sw-level radioactively contaminated secondary-side clean-up resin.

The NRC has requested additional information related to the potential off-site doses due to groundwater migration. This report is an analysis of the potential, maximum dose to an individual due to groundwater migration of the very-low-level radioactive material contamination on the resin as per the proposed disposal.

'The model used for evaluating the potential radiation exposures from groundwater migration has been based on the model used by the NRC for development of the regulations on shallow land disposal of radioactive material (10 CFR 61 rulemaking). Additionally, this model is currently being used by.the NRC in their evaluation of de minimis levels of radioactivity for various type waste and disposal methods. The model and application are discussed in detail in NUREG/CR-3585, "De Minimis" Waste Impacts Analysis Methodology, and AIF/NESP-013, Generic Methodology for Assessment of Radiation Doses from Groundwater Migration of Radionuclides in LWR Wastes in Shallow Land Burial Trenches.

This model has been simplified for the evaluation of the groundwater migration for disposal of very-low-level radioactively contaminated resin at Davis-Besse by the following assumptions:

-- in general, conservative application of default values for model parameters as discussed in NUREG/CR-3585; modeling of an intruder well, thereby maximizing the potential dose calculation; and no consideration of migration retention due to soil characterists.

In general, conservative assumptions have been used throughout in order to provide very conservative dose estimates for a maximum potential individual exposure with a groundwater well located in close proximity to the disposal area. By this approval, the final selection of the actual disposal area at the time of the, dredging of the basin bottoms'will not be limited by this analysis.

Conclusion By the conkervative application of the groundwater migration model, the maximum 1y exposed individual dose'has been estinted to be less than 0.0002 mrem per~ year. Individual radionuclide dose calculations are summarized in Table 1.

e

.~ G:sL , . - .

, ,< ' t ' Dock:t N3.^ 50-346

!Licin3a No. NPF-3

' Serial.No. 1118:

(January 29,:1985-

' Attachment 2.

m Model Discussion

'The'model as used for the analysis is represented by the equation:

I ,

Di=.I f,

• fd

• Iw

• I s

• C g

• m g where:

D = does or dose commitment f = time delay-factor

.f" = site design and operation factor f '= waste form and package factor (m8 /yr)

.f"* = site selection factor (also called confinement or reduction 1 factor, corresponding to the groundwater analogy of X/Q) (yr/M )8 C~ = concentration of radionuclide i in the disposed resins PbCFg = radionuclide specific pathway' dose conversion factor (arem/yr per uCi/ml)

'For: conservatism and consistency with the. guidance of NUREG/CR-3585, the

values of f, and fg have been set equal to unity, meaning that the L groundwater migration =is assumed to be initiated at the time of burial.

-This, approach is consistent with the fact that no exterior containers will

.be used for the packaging of the bottoms prior to burial.

.The[wasteformandpackagefactorf-isrepresentativeofthesourceters denoting the' annual volume of contalinated water that enters the aquifier ibeneath'the disposal' area. This value is calculated by the equation:

I fw,= f1

• V

- w- *'f c where: ' '

f1 = fraction of the total-disposed waste volume that is comprised oflthe waste stream'-(unitiess)

V" = annual volume of 8water that percolates through the-disposal

' facility cover (m /yr) f* = fraction of waste radionuclide concentration transferred to the

'leachate (unitiess)

For.the Davis-Besse proposed disposal, the'value of fl has been set equal ~

"to 1:(i.e.,iall materials placed.in the' disposal-area will be-comprised of-ithe very-low-level radioactively contaminated basis bottoms).

The parameter V is' simply the percolating infiltration multiplied.by.the Leffective dispola1' site surface area.-.For conservatism,.it has been- '

assumed'that the dredged basin bottoms are disposed of in'a manner that-2

,yleids an effective surface area of 3.2E+03 m .(i.e.,8-an effective ~ depth sof 1~ foot for,the total estimated volume of 34,000.ft of bottoms to be

! disposed). . Based on the guidance of NUREG/CR-3585,'the percolating.

F Linfiltration has been set equal to'two' times the percolation component VI of 74 mm of water per year that is representative of the northeast. '(The 2

• VI approach.for establishing the value of the infiltration is

' conservative,' characteristic of an unattended open dump.with pot holes and L-

.o

. Dock 2t Ns. 50-346-LicInsa N2. NIF s Serial'No. 1118

' January 29, 1985 Attachment 2 subsidence depressions that result in concentrated sources of rain water infiltration') .

The value of-f can be calculated by the equation:

c f

• N i *t c

• 10 M c

where:

M g'= fraction of the specific radionuclide transferred from the

' disposed waste to the teachate due to contact of water at continuous . full saturation (unitless)  !

t' = fraction of the year that the infiltrating volume of water is in contact with the waste (tnitiess) 10(3,y)=. accessibility multiplier Values for M -have g been taken from NUREG/CR-3585, Table 6-5. The 3

parameter'10(1-IA) is a multiplier due to the inaccessibilities of activated metals waste. For this evaluation, this parameter has been set

.' equal to unity.

-The value of t eis calculated by the equation: '

te :Pt (N

• V) where:

p = precipitation that infiltrates and comes in contact with the waste (m/yr)

N = waste effective porosity (unitiess)

V = speed of the percolating water (m/yr)'

The porosity has been conservatively assumed to be 25%; the speed of'the percolating water has been set equal to IE-04 cm/sec. '(For Davis-Besse, the actual soil character 1sts yield soil permeabilities in the 10 5% to 10.s en/s'ec range.) As. assumed above, the percolating infiltration p has

~

been set equal to (2

• V1) or 148 mm per year.

The site selection factor f is the' groundwater migration analogy of the L

X/Q meteorological dispersi5n factor. This parameter is calculated by the equation:

f ,= (r ,+ Q) I r tj

.where:

r = geometric reduction factor (unitiess) 8 = dilution factor (m s/yr)

-Q r reduction factor due to migration and radioactive decay L

g3 =(unitiess) i L

o

.. z .-

-Dockit N3. 50-346 I.icznn No. NPF-3

'. Serial No.-1118 ,

January 29, 1985.

Attachment 2 For _ conservatism, the geometric reduction factor r has been set equal to unity, its maximum value. 8 The. dilution factor Q is representative of pumping rate of the groundwater

'well. A value of 3.84 gpm (7700 M3 /yr) has been selected, representative of a lower bound of the dilution volumes for an intruder well as discussed

.in the NUREG/CR-3585.

The migration reduction factor r is a function of the retardation capabilitiesofthesoils,thedNposedwastecharacteristicsandthe distance to the. location of exposure (i.e., distance from the disposal area to the well). Since, in general, the groundwater migration is not a controlling pathway, an indepth evaluation of the site / soil reduction is not'necessary for demonstrating the resulting radiation exposures are inconsequential. Therefore, for conservatism, no credit has been taken for the migration reduction factor (i.e. , rg ) = 1).

. Incorporation of-the assumed value for the parameters as described above within_the dose assessment model yields the following simplified _ equation:

D = 1.1E-03 I M g

• C g

• PDCF g i

.The radionuclide specific pathway dose conversion factor PDCFg for the groundwater pathway is simply the radionuclide ingestion' dose factor

'(aren/uci, ingested) multiplied by the volume of water consumed (al/yr).

' Conservatively assuming an individual obtains all daily water intake (2 liters per day) from the well, the parameter PDCF g simplifies to:

PDCFi = 2 1/d

• 365 d/y

• 1000 ml/1

• DFg

=' 7.3E+05 DF g where:- '

DF radionuclide specific ingestion dose: factor as presented in g = Table A-1 of the July.14, 1983 Toledo Edison submittal (ares /uci, ingested - effective total body)

Incorporating this dose factor conversion with the above equations yields:-

D = 8.0E+02 I M g *C g *DFj i

where:

M fraction of the specific radionuclide transferred from the g = disposed basin bottoms to the -leachate due to contact of water at continuous full saturation (unitiess, adapted from Table 6-5, NUREG/CR-3585)

O

--Docket N3. 50-346 Lic:n:2 No. NPF-3

-Serial No. 1118 R -January 29, 1985 Attachment 2-C average concentration of radionuclide i in the disposed basin f = bottoms (uCi/cm ,3from Toledo Edison Company response to NRC questions)

DFf'= effective total body dose factor for radionuclide i (mr em/uci, ingested; from the July 14, 1983 Toledo Edison Company submittal)

For the principal radionuclides of concern, these values of M , Cg and DF g as respectively adapted from NUREG/CR-3585 and the previous Toledo Edison Company submittals to NRC, are presented in Table 1.

By substituting the radionuclide specific factors in the equation, the maximum potential dose to an individual from the groundwater pathway can be determined. For the worst case, the dose is calculated to less than 0.0002 arem per year. In essence, there is more than a factor of 5000 leeway in the calculation for inaccuracies (or non-conservatism) before I the groundwater pathway becomes imp *ortant.

1 I

. Dock;t N2. 50-346 LicIn:2 No.-NPF-3

-Serial No. 1118

' January 29, 1985 Attachment S.

Table 1

. Partition Ratio Between Ingestion Maximum Waste. Average Dose Potential and Concentration Factor DF Individual Leachate C (arem/ucif Dose Radionuclide Mg (ubi/ml) ingested) (arem/yr)

Mn-54 1.3E-03 1.5E-07 2.5 3.9E-07 Co-58 1.5E-02 3.0E-06 5.0 1.8E-04 Co-60 1.5E-02 7.9E-08 2.5E+01 2.4E-05 Cs-134 1.6E-04 2.4E-06 7.1E+01 2.2E-05 Cs-137 1.6E-04 3.2E-06 5.0E+01 2.0E-05 cj d/22 s

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