BVY-92-082, Forwards Response to Request for Addl Info & Revised Application Document Incorporating,As Appropriate Info Given in Response to Questions in Ref to Ltr Re Disposal of Slightly Contaminated Soil

Forwards Response to Request for Addl Info & Revised Application Document Incorporating,As Appropriate Info Given in Response to Questions in Ref to Ltr Re Disposal of Slightly Contaminated Soil

ML20101S115
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	07/10/1992
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20101S119	List: BVY-92-082, Forwards Response to Request for Addl Info & Revised Application Document Incorporating,As Appropriate Info Given in Response to Questions in Ref to Ltr Re Disposal of Slightly Contaminated Soil ML20101S126
References
BVY-92-082, BVY-92-82, NUDOCS 9207160375
Download: ML20101S115 (13)

Text

, _

v w WiVERMONT YANKEE a TNUCLEAR' POWER CORPORATION

, . . Ferry Road, Brattleboro, VT 05301-70o2 ,,,,

ENGlNEERING OFFICE .

k% ~ '

W MAIN STREET -

BOLTON= MA 01740 l608) 7794711 July 10,1932 BW-92-082 W United States Nuclear Regulatory Commission ATTN: Document Control Desk Washir:gton, DC 20555

References:

.(a). License !Jo; DPR 28 (Docket No. 50-271)

(b) Letter, WNPC to USNRC, BW 91 113, dated November 18,1991 (c)  : Letter, USNRC to WNPC, NW 92-23, dated February 18,1992

Subject:

, Response to Request for.Additionalinformation and Resubmittal of Request to

' Dispose of Sil0htly Contaminated Sollin Accordance w!!h 10CFR20.302(a)

Dear Sir:

By Reference (b), Vermont Yankee applied under 10CFR20.302(a) for approval of a proposed alternative disposal method of licensed materials by leaving in place radioactively contaminated SEI

.E and fill materia! located under existing plant structures and buildings.

..NRC requestod additional information via Reference (c). Accordingly, p. ease find Vermont

Yankee's responses to NRC's request of Reference (c). Also, please find attached a revised a . application document incorporating;as appropriate the information given in rerponse to the questions

. in Reference (c). .This application document replaces that submitted by Reference (b) in its entirety.

Should you have additional questions with regard to th!s application, please contact this office.

Very truly yours,-

Vermont Yankee Nuclear Power Corporation W # W Warren P. phy Senior Vice President, O e ons

- Attachment

. cc: USNRC Region i Administrator USNRC Restdent inspector - WNPS lUSNRC Project Manager WNPS 1 fSF'fSS!R 88?fN[ P,DR

'is , , - , . - . . ~. , . . . . - . - . _ - _ . . _ - . . _ . . . . _ _ . . . - - . . . . , - - . , _ - . _ , _ , . . .

7

.o -e RESPONSE TO NRC REOUEST FOR FURTHER INFORMATION ON Vf CHEM SIN 1; 05/15/92

1. -Provide addition information (i.e. calculations) to support the assumption

-that 58,500 cu ft of soil may be contaminated.

ANSVER:. This volume as a worst ca'se scenario, was calculated based on the extremely conservative assumption that the entire 150 ft length of pipa failed and a 120' zone of contamination extended from the pipe down 15 feet to bedrock.

In reality, there may only be s.n approximate 120' conical zone of influence extending down about 15 feet from the failed elbow in the pipeline, and contaninating a volume of about, or less than 10,600 f t 3. The larger, more conservative vclue was selected to emphasize the limited extent of the contamination. It is believed, because of uncertainty about the zone of contamination, a conservative estimate of the total activity can best be msde by assuming that the normal laboratory sample volume of 10 liters of reactor coolant water per week was discharged to the sink over an extended period of 10 years,

- and that all of that water leaked from the pipe into the soil under the Chemistry Laboratory floor.

2. Clarify the basis for reporting the radionuclide concentration on a " wet" basis instead of a " dry" basis. Provide the concentration on a " dry" basis, if available.

ANSVER: The samplas were analyzed in the "as found" moist condition without oven drying, and thus, were reported as " wet", 61ch is standard environmental laboratory practice for "in-situ" sample reporting (other than sediment sc ries) .

- The labe atory has indicated that the moisture content of these samples would not be' expected to exceed 10-20%, by weight. A change in density of thic magnitude would not significantly affect the resulting radiological impact, given the uncertainties in other assumptions.

1 l.

t 1

.. .o

3. There is an unt.sually large distance gap between the sample taken at 37.5 inches and the next ons at 85.5 inches compared to the relatively uniform spacing on the other suples. Since the 37.5 inch sample has the highest concentration, it would seem prudent to have taken samples above and below that level to obtain a more detailed profile of the spatial distribution of the contamination.

Provide justification for this gap or provide data on soil boring sample results for depths closer to the 37.5 inch level, and revise the appropriate data tables.

5. The. graph titled " BORING FN-1" presents a misleading representation of the distribution on contamination. The x-axis plots the sample depth in a linear manner, which 1 t is not. Additionally, as discussed in question 3, the large gap of missing data between the highest concentration sample and the next sample skews the data representation. Provide a revised graph (including data from question 3) that appropriately reflects actual scale.

ANSWER: The spacing of sanples taken for analysis in boring FN-1 was as consistent as ': ample recovery allowed. Correct sample depths are r.hown on the graph titled " Boring 'MV-1"". Some of the depths of samples presented in Table 1 are off by 1 fr: a corrected copy of this table is attached. This discrepancy resulted from the use of both the top and the bottom of the lab floor as a dat.un for sampling during the course of the boring operation, and the fact that these reference points were established as exactly 1 ft apart. This ditference was recognized and corrected as part of the original analysis of the data, however, the original values were mistakenly included in Table 1. The graph has been re-plotted using " inches" rather than " feet and fractions" as the abscissa.

4. Provide the basis for assuming that disposal of 10 liters / week of radioactive material is a conservative value. Provide information on sample analysis and routines to support your answer.

AF%T.R: Vermont 'innkee Technical. Specification 4.6.B.1.a. states "a sample of reactor coolant shall be taken at least every 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and annlyzed for 2

i

ao ,.-

radioactive l iodines of I-131 through I-135 during power operation". Section 4.6.B.1.b, states "an isotopic analysis of a reactor coolant sample shall be made at least once per month". Conversation with plant chemistry personnel and review of completed plant chemistry procedures indicates 1 liter samples are collected and _ brought to the laboratory for analysis on a daily basis. The basic assumption is .that these sr.mples were disposed in the laboratory sink, under the assumption the contents was going to the Chemical Drain Tank. One sample per day equates to 7' liters per week. This value was rounded up to 10'11ters per week.

A 100 m'. aliquot of the monthly sample is analyzed for gamcc emitters. A review ,

of several years . .* of data indicated that recent results were somewhat higher than earlier analyses and would represent a conservative basis for determining the total- activity that may have been disposed to the sink over a protracted time period. Therefor the most recent results available were used to estimate the radionuclide concentration of gamma emitters. A sample of rea tor water, taken in the same time frame, was analyzed by the Yankee Atomic Electric Company, Part 61 Laboratory for all radionuclides important to 10CFR61. The results of these analyses provided the basis for the estimate of radionuclide concentratica and distribution.

It is reasonable to assume that the drain leak began as a small corrosion hole in the drain line near the elbow. This allowed small quantities of liquids to

' leak into the soil. As time progressed, the corrosion continued and the leak -

increased in magnitude and an increasing fraction of the material discharged to the drain leaked. It is unlikely that the entire volume of water leaked out of the-pipe. Undoubte Uy a significant percentage of water followed the path of least resistance, down the open pipe.Neither the exact start time, nor magnitude of-leakage is preciaely known, therefore it is conservatively assumed that all of the estimated liquid discharged to the sink for the previous 10 year period resulted-in leakage. It is believed this approach has resultad in a conservative estimation of the total activity that may have been discharged to the sink and the calculated radiological impact represents the upper bound of exposure.

3

. s.

6. Due to methodology errors that -were Cound in the January 1990 draf t of NUREG/CR-5512, use of that methodology is not appropriate. Provide a reanalysis using other available methodology.

ANSWER: Only the on-site intruder drinking water pathway was analyzed using the NUREG/CR-5512 methodology, which is r.aw reanalyzed. A conservative intruder drinking water scenario can be postulated in which a family settles on site 20 years in the future af ter plant closure and digs a shallow well to obtain its drinking water needs. It_ is postulated that the total activity is that presented in the right hand-column of Table 7, i.e. ,10 years of weekly releases followed

by 20 years of decay, forms the activity source term. It is further assumed that none of the activity has migrated nor has any of the activity been retarded in its movement to an "undsrground pool", which is the source of drinking water.

Using r.he assumption presented in the Final EIS for 10CFR61 (Ref,1) for natural percolation of precipi*ation into a groundwater system, the measured annual precipitation for the site, and assuming a small area of recharge, a conservative value of total dilution water voltene (and hence specific activity) can be postulated for the drinking water scenario. The methodology presented in Regulatory Guide 1.109 can then be app?.ied to calculate the radiological impacts.

l The_averaga precipitation for Vermont Yankee for the period 1981-1990 was 40" per year. Reference 1 documents an annual precipitation rate of 41" and a percolation rate of-2.9", for a NE. site. We have assumed an area of recharge consisting of a circle of 500 f t. radius (7.85E+05 sq. ft.), which represents a small fraction of the plant site upgradient from the Chemistry 1.aboratory. The assumption _is made that a percolation rate of 2,9" per year occurs for the next 20 years. Converting this volume to milliliters, results in an " underground pool" containing 1.075+11 ml. Table A, presents the specific activities of the i radionuclides of concern.

Using the data from Ts.ble A, and the methodology of Reg. Guide 1.109, (Ref.2;

- - results in a maximum whole body dose of 6.4E-02 mrt 1/yr to an adult and a maximum L organ dose of 1.9E-01 mrem /yr to the infant liver.

l' i 4 l

m e m  :

~

'i Table A*

Radionuclide Activity and Concentration v

Nuclide Total Concentration Activity l pCi/ml pCi

, H-3 ,

2.6E+04 2.4E-07 Mn-54 4'9E 06 4.6E-17 Fe-55 2.6E+00 2.4E-ll Co-60 3.0E+01 2.8E-10 Cs-134 4.8E-02 4.5E-13 Cs-137- 8.7E+01 8.lE-10 Sr-9G 2.0E-01 1.9E-12 1

Activity from previous submf*tal, Table 7, 10 years of releases 'followed by 20 yea:.; of decay.

Appears as. Tabic _8 in the revised analysis An alternate evaluation was made using the RESRAD code (Ref. 3) . Assumptions for input for this program included: 1) a zone of contamination consisting of a cube whose side was ' equal- to the depth to bedrock, 4.7 meters; 2) the activity consisted of that present s,fter ten years of discharges (Table 5, right column) dispersed within a' calculated l'.6E+05 kg of reil; 3) distribution coefficients s

and a hydraulic conductivity value from NUREC/CR-3332 (Ref. 4). At timo equals 20 years, .the total wholebody- dose was calculated to be 4.6E-02 mrem /yr;

^ essentially all from Tritium.

A third calculation was made using the methodology presented in Reference 4.

' This model provides a -relatively simple approach to ground water transport of radionuclides. lactors considered, and values assigned, in this model are presented in the following Table B.

l' 5 i

t l'

I l

v. ..

Table B q ^'l Groundwater Factors Spill source model point source Ground'watar velocity 0.026 meters /dsy Dispersion coefficienta 2 (long), 1 (trans)

Aquifer thickness 1.47 meters Retardation Coefficients Co-60 860 H-3 1 Fe-55 1290 Mn-54 1290 Sr-90 18 y Cs-134, 137 173 Time since spill (years) 20 Relative well lo ation. Highest nuclide concentration (most conservative)

The results are expressed as a radionuclide concentration in the aquifer at. the

. well location. The radionuclide values from Table 5 as noted above, were used

' as-initial values. The methodology of Regulatory Guide 1.109 (Ref.2) was then applied to determine the dose. A result of 3.76E-01 mrem /yr, whole body served L

to bound and confirm the previous two calculations.

It. should be noted that the major contributor to the radiological impact of the on site drinking water pathway is Tritium. The other radionuclides, due to their

. low concentration, and half-life, do not add any significant contribution to dcse calculated 20 years af ter . release. The well location is critical wh.n retardation effects are considered, and unless the well is in close proximity to

- a - postulated plume , no significant exposure is calculated.

For purpose of evaluation, it is assumed the well is located at the maximum concentration for 6

m u.; . . , -.L each nuclidefidentitied. The results of the' dose analysis indicctes that even

=_with'this assumption,.there is no significant dose. Tritium is assumed to have

the highest' concentration and no retardation, which results in the only .

radionuclide with the most significant radiological impact of any of the nuclides assumed;in the release'.

7.- ' Provide a discussion on' the correlation between the actual sample concentration and the estimated concentrations to demonstrate that using the

-actual-concentrations would'not result in higher doses. Include the data on- '

sampics tak + at the point immediately below where the pipo penetrates the floor, which had a peak Co-60 concentration of 1.1E+05 pCi/kg.

ANSVER: The: original; intent of the' soil boring sample was to determine if the zone of contamination vas_ local.in-nature, and could be readily-quantified, or

-did-ic_' extend down to: bedrock,-in which case, a more detailed evaluation would be. required. : Asithe 'results show, contamination of Co-60 did extend to bedrock.

'The highest - concentration scoop sample was the material directly beneath the floor' and _ adj acent to the pipe. This volume of contamination was approximately, 1 cu.-ft., and it was entirely removed in the sampling process, so the activity

-at that concentration no longer exists.

Due to = an electrical duct directly below the area- of concern, the core boring

= could not be made directly adjacent' to the pipe and was displaced laterally by approximately four feet. The boring represents a vertical profile taken through a' cone of.ccontamination whose true dimensions are not exactly known. It is n

> speculated: that the high concentration of 1131 pC1/kg from the sample taken at '

labout 4 f t . depth represented. the leading edge of ' the - Co-60 activity at that

' location, e

, Ifz. additional data were available it would likely show elevated activity from-that area upward as distance from the pipe decreased, reaching a maximum adjacent o

?

. ,:.-,- . . . --._.. _. - , . . , ~ . , . _ .__ _ _ _

_, .~ .

i >

j q.

<s.  ;<<.

- to the pipe at- the floor interface, possibly approaching the values measured in .

theiscoor sample material previously removed. We do not believe the sample data -

are sufficient to form the bases of an estimate of total activity. The lateral extent of tho ' contamination is not-known~and can not be . determined without extensive corings under essential plant ~ structures, llowever the data does

represent . a. very satisfactory basis for making a conservative estimate of concentration distribution.

Alternatively, an estimate of. total 3ctivity can be made from an~ estimate of total volume of contamination and an avarage concentration of activity. The total volume .under the full 150 foot length of pipe has been previously estimated in the original submittal as 58,000 ft 3. (Assuming a density of 100 lb/ft*, this is equivalent to 2.65E+06 Kg. ) The average Co-60 concentration (from Table 1 of.the original submittal) is 425 pCi/Kg. This results in an estimate of totali activity - of 1.1E+09 pC1, or, 1.1' mC1. Using the same assumptions,. if the contaminated volume: is 10,000 ft3 , the total activity-estimate:is-1.9E-01 mci. The 10 liter per week discharge over a 10 year period results in a total Co-60 activity at the end of 10 years of 4.lE-01 mci (original submittal, Tabic 5). Thus, the estimates of total activity made from estimates

' of contaminated volumes hoend the estimate used in the analysis. It should be pointed out, that the calculated- radiological . impact comes from Tritium, which vas. estimated from the concentration measured.in reactor water, I

8. . Provide a legible map of the disposal site with compass direction and scale,

[ that includes local land use (e.g. , buildings , nearby residences, wells, etc. ) .

u L

ANSWER:. The Vermont Yankee FSAR contains site maps. We have included a copy of Figure 2.2.4, Station Plan that shows the information you request. In general the residences ' located on the west of the site on Cov. Hunt road have individual shallow-wells.as potable water' supplies. As mentioned previously, the ground water flov is from-west to east to the Connecticut River, and away from the j.- 8

residences. The Chemistry 1mboratory, the source of the leakage is located in the lower lovel of the " Office Bldg", adjacent to the " Turbine Bldg". The grid scale of the plan is $00'. The main potable water supply for the site is provided by the " West Well", whose location is shown uear the 345 KV switchyard.

9. Describe any physical or administrative barriers to prevent present and/or future intrusion into the disposal site (i.e. during building modification, repair of drain line, and decommissioning activities).

ANSWER:. An appropriate note will be placed on the building prints warning of the material beneath the floor and referencing the file number where doewnentation of these activities are kept.

10. What controls are in place to prevent the use of the failed drain line?

ANSWER:. The affected drain lines have been capped. The area around the failed pipe has been backfilled with concrete to the original floor line, and is now inaccessible.

11. What plans, if any, are being considered to repair or replace the failed I drain line?

ANSWER: As noted in the response to question 10, the original line has been capped and is inaccessible. New piping has been run above the floor to the collection tank. This work has already been completed and is currently in use and is capable of periodic inspection to preclude a repeat of this event.

9

4 References

1. NUREG-0945, Vol.1 Final Environmental Impact Statement on 10CFR61 " Licensing

]

Requirements for Land Disposal of Radioactive Waste", U.S. Nuclear Regulatory Commission, November,1982.

2. Regulatory Guido 1.109, " Calculation of Annual Dose to Man from Routino Releases of Reactor Fffluents for the Purpose of Evaluation Compliance with 10CFR50, Appendix I", rev.1, October, 1977.

3. RESRAD, ver. 4.3, USDOE, " Methodology Description for Compliance with DOE Order 54005, Chap. IV", in press.

4. NUREC/CR-3332, " Radiological Assessment", Chapter 4, U.S. Nuclear Regulatory Commission, September, 1983.

l 10

TABLE 1 (Revised)

SOIL BORING SAMPLE RESULTS 'Soring MW-1)

DEPTH BEIDW TOP OF FLDOR Co-60 MN-54 (inches) (PCi/Kg, wet) 25.5 308 5 37.5 383 339 49.5 1131 914 73.5 296 12 l

104.5 351 1 109.5 21 7 133.5 166 <MDA 160.5 90 5

, ~ .

184.5 879 <MDA

- __ x~

AVERAGE 425 183 CONCENTRATION g 11

- - - - - - - - ~ . _ . ~* - - , _ ,

~ - ~ ~ -  %

~ -

I.

.,7.

% ,,,, % e4

.,m

. ~,

~~'~~%si... A-

" '. U,*,hh

,,,;r

~ s Y,*,'?) % s m

/

• s..

b.,e.

f f

fr o *

..Mtuit.*'*h*aAW%,, '- %,

',, *apa g

"""* e vsq w f Wr.f

~

4 s

N ~

I * '~

</fEW . ,-. + ~Gr 1 , ,,

1-

.. \.

f.y,.

,m

• w

..c I 7,*]' -

S

.c .

• 5,,,' /c"f ' ,

., j 't l*,J f

p j ' i'. \

• J N , e r s

+

h, ,

-- ' 3 5. /.< ,/

• J

• ~~.*c:

4

, a,--

% .' 'c-6.s.g I e=~

d m.

s.,_a .

' ,d\

q ,

%4, A .

~=%i._m R ~~

3,5 7441 # h.. :. -@=

o =Li .[M ~;Y-l

~W-a

+ _ _ - . ,

~~ -[.l ~"

Qa !, ~ A=J -

==._

-J

~.

g----- q i

%.. / ---

.p" m l

/ .  ;

"~~

Y, p/ .

f'//

' f }

ww -

• g.,

,l i

\ ,

.r . -H, *1 __ .,a.- agg t #

[

l '-

. . . , _ , ~ . -

e

/_g,. * ' - - -

S w rri.m L- e

. /

/

P.:.7,0-

- Ai3i g ,

l l

y

.~~~.'.i '6 l- t i

4

_ r_

& .-/

I c.,.,.

s, 5Y.

• _ p..3 -o $' ,

?,g Ca'~3

/

/

. . + . ,

s Le r.n wo

, = ~ g ,...

u .,.

-l.

'J ;

o sic J

t V  : a

, ..e

• m~~ c

~

d

~

r.

\.m-.

~ "

W 7h-WA' 2 - -

-s

. . . . ~ -

1. -.\tm, w .mp. :gm s.:

g n .

5

. }_

i ,i

n. .

k !b W '

. . . . . . - ,~

Si yd ,- AEijjg -

N _

f. NG"' <

APERTURE I i

T s:p.K_' -hf...((/-$kk i

-*"'[ :[]{ #

CARD g f Also Available Ogg

[ * ~

\' Aperture Card

@ & C Tff f  %'4 I.

I5J

. V\ ' ~ = -

1+ N){ z. . . . . .

l

• • • I,?

• p $. 'a .a.

&7 / t%. .

m

==: m=

.m % moma .

• • , .i

• • ""*"*"*"'2,

.. {

\

id ,~I .. q I

M.. . , \ \ ~ 0""..#\ Q(L . - . i

\

-e ymi j~ ~

1 - /1 AV Q gf y .Q g,  :

rf s

.6,. - . . . , . . . - . . . . ,

-[

j i .; $ .

f~ 4 um

- /l 9 VERMONT YANKEE NUCLEAR POWER STATION i

Q N

Y Station Plan L > N

. . . . . . .. . ,