Quivira Mining Company P.O. Box 218, Grants, NM USA 87020 (505)287-8851

October 19, 1999

Ms. Elaine Brummett Uranium Recovery Branch U.S.N.R-C. 11555 Rockville Pike Rockville, MD 20850

Re: License SUA-1473 Docket Number 40-8905 Information Request - Windblown

Dear Elaine,

Please find enclosed the information that was requested within your September 22, 1999 email to Quivira regarding the windblown clean-up activities at the Ambrosia Lake facility.

Please contact me if you have any questions.

Rrr

Peter Luthiger Supervisor, Radiation Safety And Environmental Affairs

Enclosure

xc: T. Vitkus (ORISE) File

CONTENTS

Tab I .... ... ........ .................... Site H istory

Tab 2 ........................... ERG Procedures

Tab 3 ............................................. Site Map - Background Sample Locations

Tab 4 ........................................ Site Map - Windblown Clean-up Zones

Tab 5 ............................................. Site Map - Backfill Zones

Information pertaining to the site/process history has been collated from documents previously submitted to NRC. The information is contained in the following sections:

1. General geography of the site including a list and map of various industrial activities that have occurred in vicinity of site;

2. Description of mining activities; 3. Description of milling activities; 4. Description and operational history of tailings management system.

) ,O GEOGRAPHY

The Quivira Mining Company milling facility is located in the

Ambrosia Lake mining district in the southeastern part of McKinley

County, New Mexico. The mill restricted area encloses the

following areas: Section 31, Tl4N, R9W; W/2 SW/4 Section 32, TI4N,

R9W; N/2 Section 6, Tl3N, R9W; NE/4 Section I, Tl3N, RlOW; SE/4

SE/4 Section 36, TI4N, RIOW and Section 4, T13N, R9W.

The Ambrosia Lake mining district, named for an almost perpetually

dry lake bed (approximately 20 miles north of the town of Grants,

New Mexico) is roughly limited by the lake bed on the north, Grants

on the south, the villages of San Mateo on the.east and Prewitt on

the west. The district is approximately 22 miles long and 6-10

miles wide situated in an elongated strike valley (approximately

7020 feet elevation MSL) which has been eroded into the lower

Mancos shale formation. The valley strikes ,northwest and is

bounded on the south by the rim formed by the outcrop of the Dakota

sandstone and on the north by the high sandstone cliffs and steep

shale slopes of the Mesaverde outcrop. The surface of the valley

is generally flat or gently rolling, broken only by an occasional

dry wash or outcrop of thin Tres Hermanos sandstone of the Mancos

shale.

I

MUTES, PROCESSNG PLANTS, ANT) POWErl" PLANTS, 1970V

Man t~ustrName Srmbol 17" ~ of Site Locattan company

S1 Coal Ummflan: Ctwbca Coal Plant 4-isn-19W C ba oa ,

Coal VIne Mrv

Coal m-ine. (Strrp)

Coal Mine (Strip)

Coal ,'ine (Strip)

rGas, 1*2eizg Plant

Gas m ocesi Plant

tmdustrial Rocks &

Indusmral Rocks & Minerals, Mine Induatriai Rocks-&Minerals, Umie

IndusriaLJ Rocks & Minerals Mine all P eflnery

Uranium MIJI/Pmlan:

uranium ilrl

Uranium mill/Plant

Uranium NMill/Plant

luanau mMinePln

Uranium Mime

rjraniu M-ine

Uranium mine

Urmniun: Mine

'Uramn:u Mine

U7raniu mMine

Uranlum Mine

"Uranum Mize

Uranium M-ine

Ancoaml No. I

\eutmare

McKinley

Wllac lant

Lybraook I1 Pant

U.S. Gaumm Plant

Red Dog icinderi

Samv .4nteue Pit (1±iestone)

a.&. Gypsum

Ilniza Plamt

M~auc Rock 3"=nt

lxurr-mcc-ee mlant

Azactmda P'lant

So1rO Plant

Tflnted NuclearT3oiestakce Plant

.kmn Lee

Cbsac- Rock No. 1,

The Irlea ~Ocis

Fa73taCk

Johz y M

Mariana L.ake

Marquez Canton9

17-14N- 17W

31-14N-107

Z4 T17N- 11w

13-I SN-17w

1 l-14N-7W

3 3-17Y-N-6 1

21-13N-OZW

13-13N- 1 I

30-13N-qw

7&l8l!3N-O'W

12-I1SN-14W

36- !3N-5w

AmccaA, Inc.

Carbon~ Coal Cornoany

Coal Companv

Homah mining Companv

7l Paws Nattmal Gas Coa.

Southerm Union Co. 7.S.* 07psun: Co.

Mendoza Red Oug

Gaill Sand & Gravel(, o.

UT.S. Grsm= Co.

Shell Oll Co.

United Nuclear ror-4.

Kterr-'-1c~me Nuhclear e-orm. The Anaconda Co.

S5HIO Petroleum Co.

Un~ited Nuclea-omestake P~ar~mers

United Nuclear rCorp.

'?:e.. McGee "Tuclear Corp.

Ranc2hers E.'tloration and D~eVelopmen: Co.

Four Corners Exploatidon Co.

Todilto Exploration and Develamm.ent Corn.

R.anchers Exoloration &c Ovelopoment 'a.

Ranchers :'=!aation 3C Development ro.

GUlf -mineral Resmrces

Baounm Resources o.

Unitred Nuclear on

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U

U

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4

1

z I

31

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Map I-iustrT Name Sym=boi Trpe of Site - L~ocation o an

V 11

V 17

Uranium Mine

UranimMine

Uranium MNale

Uranium Mine

"UranLtim Mine

7-=' *Mine

Uraniuim Mine

Uranium Mine

Uranium Mine

Uranum Mine

'Uranium %fine

Uranium Mine

Uranium %line

Uranium Mine

Uranium Mine

aranium Mine

Uraniu Mine

Uranium Mine

'Uranium %fine

Uranium Mine

Ujranium Mfine

UrzanIum Mine

Uraniu Mine

Uranium Mline

L.7r.num Mine

Uranium Mine

Nose Rack No. I

Poison Cinyon

Rubj no. I

sandstone

Sec-tion 11

Section 1%

Se~ctn 113

Section 15

Section 17*

Section 19

Section Z3

Section 24"

Section 25

Section Z7 East

Section 30

Section 30 West

Section 3Z

Section 3z

Section 35

Section 36

Wester~n Section :I

Tak~ile-Paguate Complex

1. J. No0. I

Mt. Tavlor

PLlo Puercoa'

34-' 4N-OVF

11-144N- I "

1Z-l4N-t0W

13-34N-10W

15-14X-10OW

17 14N..OW

10- 14N--QW

Z3-1414-lOW

Z4-14N-IOW

Z5-7 4N-l0W

3 0-14N-4W

30-14N-zOW

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36-154N-13W

2. 4. 5-loN3 W- Z6. 33, 35-UIN-5SW

13-uN-5W

='derdevelopnzent)

3 0-i11 N-4W

18-1 ZN-3W7 Imdeytievelopment)

N.A. Not krail able.

Since the 1q9" publication, 5-veral of the area's -nines liave closed. ;ndicated above.

M~e~VcGee 'Nuclear C orvoration ziie cllosu-res are

Sourct- NTet Mexico 1=4tmtte of Mdining and Tec~lical Bureau of Mines and Mineral Resources. 100

3

0hilli. Uranium Coro.

Reserve Oil & minerals

Western Nuclear, Tnc.

United Nutclear trorp.

United 'Nuclear-tRomestake Partners

Cobb N4uclear Corn.

United Nuclear-Fomestake Zartners

United Mucletz-Homestske Partners

Kerr-McG-ee Nuclear Cc=n.

"ICarr-Mc~ee N1uclear r~

United Nucilea-Fomestake Paz ners

KMrT-hcG'ee Nucilear Corp,.

United INuclear-5!omestake partners

United Nuclew ýcrt.

Keyr-McGee Nuclear co"n.

Kerr-Mc~eea Nuclear Corn.

Cobb NTuclear Crorz.

UJnite-d Nuclear-'ýomestaike partners Xer-Mcý-ee Nuclear f-c-n.

'Kerr-Mcl~ee Mtuclear (7orn.

Western Nuc-lear, L-tc.

"The Anacczda ro.

Solilo Natural R.esources Co0.

Gulf Mineral P. esources

United N~uclear tCor.

Kerr-Mcc-e-e , uclear I-"n.

IV 13

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V2 2

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T 29

T 30

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T 34

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Z-0 MINING ACTIVITIES

Mines owned by Quivira supplying ore to the mill at Ambrosia Lake

are located in a northwest to southeast trending zone of the

Westwater Canyon formation commencing with Section 22, T14N, RIOW,

and terminating with Section 36, TI4N, R9W. An additional mine

known as Church Rock I located in the Navajo Reservation in Section

35, TI7N, Rl6W, also supplies ore to the mill on an intermittent

basis. Additional mines are in some stage of development in the

area. Additional sources of mill feed are discussed in section 3.4.

Of the nine mine shafts located in the Ambrosia Lake valley, in

one, Section-22, physical mining has been terminated and the future

development will depend upon chemical removal of the residual ore

values. Sections 17, 24, and 33, are currently in a standby state

due to the depressed condition of the uranium market.

The ore in all of these mines is located in the Westwater Canyon

units of the Morrison formation which is an active aquifer. The

ore mined is a grayish colored sandstone averaging approximately

0.15 percent U308 with occasional high values to 0.5 percent

and low values to 0.05 percent. Varying amounts of contaminating

substances are present in the ores as mined. Only molybdenum

exists in sufficient quantity to make recovery a necessary activity

as an additional step in the milling. The ore contains a

significant amount (2 to 5 percent) of limestone.

SO MILL PROCESSING AND CONTROL

General

Quivira began processing uranium ore at the Ambrosia Lake, New

Mexico mill in November 1958. The initial rated capacity was 3630

tons per day, but this has since been expanded to 7000 tons per

day. Approximately 31 million tons of ore have been processed

through this facility from start-up through August 1983. (Figure

3-1 provides a pictorial of the operation from mine to product.)

The ore is leached with sulfuric acid, and pregnant solution is

separated from the spent solids in a countercurrent decantation

circuit utilizing cyclones, classifiers and thickeners. Uranium

and a molybdenum byproduct are recovered from solution by solvent

extraction. The organic solvent is stripped with salt brine and

the yellowcake is precipitated from strip solutions with ammonia.

The recovery of U308 exceeds 96 percent. See Figure 3-2 for

process flow and Table 3-2 for material balance.

Ore Handling

Ore is hauled from the mines to the mill in bottom dump trucks with

approximately 28 ton capacity. Each truckload is weighed, sampled

for moisture content, and dumped into one of sixteen (1000 ton)

below grade ore pockets. A front end loader is used to move ore

SUFRCACID PMANT

SAMPLING

FINE ORE STORAGE AND

GRINDING

MINES

CRUSHING -.

SODIUM CHLORATE

LEACHING

SWASHING CLASSIFIERS%PACKAGING

~SHIPPING

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from the below grade ore storage pockets to the primary crusher at

the feed end of the mill. Ores from different sources are kept in

separate ore pockets and handled separately through the crushing

and sampling section for accountability purposes and securing the

proper blend for uranium content and mineral components.

Crushing and Sampling

Ore lots usually of about 1000 ton size are crushed to minus 1 inch

using an open circuit jaw crusher and impact crushers in closed

circuit with two screens. The crushed ore is sampled in four

stages with additional intermediate sample crushing and with the

amount of the fourth cut varied to obtain approximately 200 pounds

of minus 1/8 inch sample. The entire sample is dried in a gas

-ffred drum dryer before final sample preparation.

Crushed ore is stored in a 5000 ton capacity bunker which is

divided at the bottom into six. separate 60 degree cones which

discharge through vertical transition sectidns to special 60 inch

wide, slow speed belt feeders. This particular design has proven

effective in handling wet ore without the need for drying. The

belt feeders supply the rod mill circuit.

Grinding

Beginning with the grinding operation, the ore processing is

divided into two parallel but identical lines. The ore feeds at a

rate of about 150 tons per hour to each of the two open circuit rod

mills. Feed rate is monitored by conveyor scales and is controlled

remotely by the grinding operators. The rod mills operate at a

q

density of 70 percent solids using heated water for dilution, and

produce a 28 mesh product normally containing from two to five

percent plus 28 mesh and about 70 percent plus 150 mesh. Trash is

removed from the mill discharge by stationary screens. Rod milled

ore slurry is pumped to the leaching tanks on a continuous basis.

Leaching

Each leaching circuit consists of 14 rubber lined steel tanks, 13

feet in diameter by 14 feet high, equipped with turbine type

agitators and arranged for gravity flow of slurry through the tanks

in series to obtain a residence time of about three hours.

Feed slurry entering the circuit from the rod mills at about 62

percent solids is diluted with recycle solutions .from the

subsequent clarification circuit to obtain an operating density of

about 50 percent solids.

Sulfuric acid, sodium chlorate (oxidant) and steam are added at

several points in the circuit to maintain the proper pH, oxidation

potential (emf.), and temperature. Typical conditions at various

monitored points in the circuit are as follows:

Tank Number Measurement 1 2 5 13

Temperature, *F 110-130 120-140 110-130

pH 0.5-0.7 0.8-0.8 0.9-1.2

emf, millivolts(-) ----- 470-510 410-430

1O

Acid and chlorate consumptions average about 110-130 and 2.5 to 3.5

pounds per ton of ore, respectively.

Liquid-Solid Separation

The recovery of pregnant solutions from the leached slurry is

accomplished with an initial cyclone separation followed by

countercurrent washing of coarse and fine fractions In separate

rake classifier and thickener circuits.

Leached slurry is diluted with recycled No. 2 thickener overflow

solution and fed to two 20 inch cyclones in each circuit operated

at pressures of from eight to ten psi to separate the solids at

about 150 mesh size. The coarser underflow fraction is then washed

countercurrently in a series of five 6 foot x 33 foot rake

classifiers to recover solutions bearing uranium containing fines.

This solution then joins the cyclone overflow fines as feed to

parallel, seven-stage countercurrent decantation circuits

consisting of 120 foot diameter thickeners for six stages and 28

foot diameter high capacity thickeners for the seventh stage. Wash

solution added to both the classifier and thickener circuits is

made up of raffinate from the solvent extraction circuit, 80 to 90

percent of which is recycled, plus makeup tailings solution as

required. The recycle of raffinate returns acid to the washing

circuits to maintain a pH of 1.5 or less in the system and

decreases the total quantity of solution to be disposed of in the

tailings. Wash ratios are between 2.5 and 3.0 in the classifier

circuit and between 1.8 and 2.2 in the thickener circuit.

11

The thickener circuit handles approximately 1/3 of the total feed

solids, with underflow slurries containing about 30 percent solids.

Flocculant in the amount of 0.05 pounds per ton of ore is delivered

to the thickener circuit through a loop line to maintain turbidity

of less than 150 to 200 ppm in the pregnant solution overflowing

the first thickener and also to control the slime level in each

thickener. Soluble losses in the final thickener underflow (slime

tails) represent about 0.5 percent of the total U308, with an

additional 0.15 percent contained in the final classifier sand

product (sand tails) at a density of 75 percent solids.

Solution Cl ari fication

Pregnant solution from the CCD circuits is further clarified to 50

to 75 ppm suspended solids using small additions of flocculant, as

needed, in 60 feet diameter by 20 feet deep reactor-clarifiers.

Underflow from these units, containing some fine slimes, is

recycled as dilution to the leach circuit feed.

Solution overflowing the two reactor clarifiers rejoins to form a

single stream and is further clarified by passing through eight 54

inch (600 square feet) U.S. pressure filters which are operated in

parallel at a feed rate of 300 to 500 gallons per minute each. The

pressure filters are precoated with about 0.1 pound of precoat per

ton of ore, and 0.35 pound of filter aid per ton of ore is added to

the feed solutions.

12-

..........

The pressure filter cycle varies from 4 to 24 hours depending on

the clarity of the reactor clarifier overflow solution. Final

clarified solution passes through storage tanks to solvent

extraction while filter cakes are returned by pumping to the second

or third thickener in the CCD circuit. Filter screens are cleaned

periodically with five percent caustic solution at 140'F.

A 12 foot diameter Baker sand filter, installed several years ago,

supplements the pressure filters for clarification.

Solvent Extraction

Extraction. Two parallel solvent extraction circuits are each

equipped with four stages of integrated mixer settler units

consisting of eight feet diameter by nine- and- a-half feet high

stainless steel, agitated mixing tanks mounted in the center of 40

feet diameter by nine feet high circular wooden settling tanks.

The aqueous phase flows by gravity through each circuit at a rate

of from 1000 to 1200 gallons per minute and is withdrawn from each

settler tank through four jacklegs which- overflow to gathering

pipes connected to a manifold and to the bottom of the next mixer.

The organic phase, normally containing about three percent tertiary

amine (Alamine 336), three percent isodecanol, and the balance a

high flash point kerosene, overflows each settler tank and is

pumped countercurrently to the aqueous phase at a flow rate of from

300 to 400 gallons per minute to the top of the next mixer. The

mixers are operated organic continuous by recycling part of the

organic.

13

Pregnant solution enters the extraction circuit with a U308

content of about one gram per liter. The loaded organic contains

about three grams per liter. Barren solution or raffinate

containing an average of 0.001 gram of U3 08 per liter is

recycled for wash in the CCD thickener and classifier circuits with

a small part (10 to 20 percent) being used, along with recycle

solution from the tailings dam, to repulp tailings for pumping to

disposal.

The extraction circuit operation is monitored by hourly

colorimetric analyses of the No. 2 settler aqueous solutions.

Organic flow is regulated to hold the U308 content of the

aqueous solutions at 0.04 to 0.09 grams per liter at this point.

Stripping. The stripping circuit consists of four stages of

separate eight feet diameter by nine feet high mixers and 22 feet

diameter by eight feet deep settler tanks. Loaded organic enters

the first mixer and flows by gravity through the circuit

countercurrently to a chloride stripping solution which is pumped

through the circuit at a rate varying between 20 and 40 gallons per

minute. The strip solution at a concentration of 1.5 normal

chloride is a mixture of saturated brine, water, recycled

yellowcake filtrate, and barren filtrate from the molybdenum

recovery circuit. After passing through the circuit, the pregnant

strip solution contains 30 to 45 grams of U3 08 per liter.

Molybdenum is not stripped from the organic phase by chloride

solution and, if not controlled, builds up in concentration to the

..............

point that a molyamine sludge layer forms at the interface between

the aqueous and, organic phases. This effect is minimized by

treatment of part of the organic phase in a separate molybdenum

stripping circuit where it is scrubbed with an ammonia solution

before returning to the extraction ci-rcuit. Air lances mounted in

each quadrant of the settling tanks are also used to provide

sufficient agitation to break- up the sludge layer and to keep it

moving with the organic phase for subsequent removal in the

molybdenum strip circuit. Under unusual circumstances, when the

molybdenum content of the feed is particularly high, other measures

such as increasing the organic to aqueous ratio, or raising the

amine content of the organic phase, are employed.

Precipitation, Filtering, Drying- and Packaging. Pregnant strip

solutions from both solvent extraction circuits are combined as )

feed to a series of three eight feet. diameter by 12 feet high

agitated precipitation tanks. Steam is added to the first and 0

second tanks to obtain a temperature of 140 F. A mixture of two

to four parts air and one part ammonia is added to the three tanks

to precipitate the uranium.

Control of pH in precipitation to 6.3 to 6.4 in the second tank is

most important in achieving good product purity and filterability

and the formation of only small amounts of hydrated uranyl

sulfate. The pH is raised to 7.0 in the third tank to insure

complete precipitation. Total ammonia consumption (precipitation

plus molybdenum stripping) is 1.1 to 1.5 pounds per ton of ore.

Is

1,O EXISTING TAILINGS MANAGEMENT SYSTEM

DESCRIPTION

The milling process produces waste solids and liquids called

tailings. The solid tails derive from the host rock from which the

uranium is dissolved and the liquid tails result from the

utilization of water for the various chemical operations required

to concentrate the uranium as "yellowcake". The Quivira mill

normally produces approximately 6200 tons of solid tails and 8,700

tons of liquid tails per day. The tailings disposal method used at

the mill has as its objective the stable retention of all solid

materials and disposal of liquids by evaporation.

The slime tails from the thickener underflow and the sand tails

from the classifiers are repulped with liquid tails to. produce a

slurry of about 40% solids for transport by pipeline for disposal.

The solid tailings from the milling operations are stored in

tailings ponds No. 1 and No. 2, located mostly on Section 31 TI4N,

R9W, McKinley County, New Mexico (Map 2, Sheet 1).

The No. 1 pond covers approximately 263 acres and normally contains

a liquid area of approximately 90 acres. The height of the crest

from the original ground level varies from 25 to 90 feet.

The No. 2 pond covers about 65 acres, and its dam is formed by the

west portion of the No. 1 tail pond. Recent storage has been

16

mainly in pond No. 1, with a relatively small amount going into

pond No. 2.,

The tailings slurry is pumped from the mill repulp tank to a

distributor box located at the north end of the solids disposal

area (Pond 1). From this distributor box tailings can be directed

by electrically operated valves to either side of the disposal area

through 14 inch diameter wood stave pipelines. Replacement of the

wood stave pipe with 16" O.D. polyethylene pipe was started in

1982. A short alternate line is provided for direct discharge into

the, pond in case of any problems with the normal distribution

system. The 14 inch wood stave pipe is fitted with 4 inch rubber

hose spigots on about 30 foot centers. By means of spigoting

hoses, the tailings slurry is conveyed over the top of a

spigotting-dike formed from tailings solids around the top of the

disposal area. The major portion of the solid tailings deposit

just inside the spigotting-dike and the remaining portion of the

finer solids (slimes) and the liquid flow toward a central

impoundment. This method (called upstream spigoting) allows the

major deposition of tails near the spigotting-dike where, after

partial drying, a portion of the solids are dozed up into another

spigotting-dike. The central impoundment retains the liquids and

allows the fines to settle so that clear liquid can be removed to

the evaporation ponds. The central impoundment is equipped with a

siphon decant system which allows removal of the clear tailings

liquid to pond 3 where a portion is recycled to the mill for reuse

and the excess is pumped to evaporation ponds.

OPERATION HISTORY

The tailings disposal area constructed in 1958 consisted of six

ponding areas. Ponds I and 2 were used for solids disposal. Pond

3 is'a decant and seepage collection pond and ponds 4, 5 and 6 were

used for liquid evaporation. All starter dike and retention dikes

were constructed from the clayey natural soils on the site. Early

operations consisted of solids disposal in both pond I and pond 2

utilizing the upstream spigoting method.

A later change in operations temporarily discontinued the use of

pond 2 for solid disposal and the pond 2 dam became the west dam

for pond 1. Utilization of pond 2 for liquid evaporation continued.

The original construction included a decant system on the east side

of pond 1 which was abandoned due to high solid levels. A new

decant system was constructed to the south side which was used

until 1983 when a siphon system was installed.

The continued expansion of the milling capacity required additional

evaporation ponds. Ponds 7 and 8 were built in the early 1960's, 9

through 15 constructed in 1976, and the most recent ponds, 16-21,

went in service in 1979 and 1980.

The upstream spigoting of solids continued on all sides of the pond

1 area with lesser amounts going to pond 2. As the level of the

solids rose to heights inconvenient for spigoting, the wooden

)

area or company property.

tailings line was relocated to a new height. This procedure of

building solids and raising the tailings line has continued to the

present time.

The spigotting of tailings. slurry has been done in virtually the

same manner for in excess of twenty three years. The crest is

designed to allow the slurry to run down, so that the sands are

deposited first, then the finer fractions are deposited as the

solution is decanted off. The crest is pushed up from the beach

material, which consists of the coarser grain size sand. The crest

is compacted first by the equipment used in pushing it up. The

sand is then compacted by the slurry as it makes its way down the

slope. From experience, the spigotted sand (which contains some

fine material) is more stable and is more readily compacted than

sand that is more completely classified. The relative density as

reported in Sergent, Hauskins & Beckwith stability analysis dated

March 5, 1981, indicates a medium dense soil. Normally, seven

spigots are releasing a normal flow of about 2000 gal./min., or a

flow of about 270 gal./min. for each spigot. Since the flow is

directed down slope, the crest acts as a ramp to guide the solution

toward the middle. In the event that the sand should be allowed to

pile up and the slurry breaches the crest, the roadway below the

crest will catch the slurry. A breach of this nature would cause

no major. structural damage and no slurry would leave the tailing

If the spigots were moved in significantly from the crest, a

serious problem could be created. As a mound of sand builds up

below the discharge of the spigot and connects with other mounds

nearby, part of the slimes would be trapped by this newly formed

dam. A pocket of slimes could be formed in the outer perimeter of

the dam large enough to affect the stability of the overall

structure. Also, having the finer fractions near the face of the

dam tends to decrease the permeability and raise the phreatic

surface in that area.

By the end of 1982 nearly 31 million tons of tailing solids had

been deposited at the site since startup and no failures allowing

discharge of radioactive material outside the restricted area have

occurred.

Standard Operating Procedure 2.09

Correlation Between Gamma-Ray Measurements and Ra-226 in Soil

1. Purpose

To describe the procedure for developing a correlation between hand-held gamma-ray measurement instruments and the Ra-226 concentration in the top 6-inch layer of soil.

2. Discussion

The cleanup of surface soils contaminated with Ra-226 normally is done using in-situ gamma-ray measurements to guide the cleanup activities. Such factors as emanation fraction, Ra-226 concentration vertical profile, gamma shine from nearby sources, and topography all have an influence on the gamma-ray measurements and the technician has to be aware of these possible influences when interpreting measurements. With these precautions, the use of this technique for most situations has been demonstrated to provide sufficient accuracy to assure that an area has been successfully decontaminated.

The procedure that follows results in a correlation between Ra-226 concentration in the top 6inches of soil and the gamma-ray count rate from hand-held radiation detectors. It is appropriate for use in areas where there are no strong gamma-ray sources, no buried radioactive material, and where the topography is relatively flat.

3. Procedure

3.1 Field Equipment

Radiation detectors and associated rate meters, scalers, and collimators

Post-hole digger or other tools used for obtaining 6-inch deep soil samples

MicroR-meter capable of measuring exposure rates ranging from background levels to 100 microRih

Soil Sample labels and bags

Copies of Form 2,09A and Form 2.09B (one for each instrument)

Ink pen

Measuring tape (6 feet minimum)

3.2 Field Data Collection

3.2.1 Point Studies

A. Using the microR meter, locate study areas generally contaminated at levels that provide exposure rate readings taken at 1 meter height of background, 18, 20, 25, 30, 35, 40, and 50 microR/h. Areas should not be in shine areas and should be on relatively flat terrain. Each study area should be large enough that a few steps in any direction should not affect the reading. Record the data for each location on ERG Form 2.09A.

B. At each study area, strike a 36-inch diameter circle on the ground surface. Give each area a unique identifier (e.g. SPI, SP2, etc). All gamma measurements should be made at the center of the circle and at a height specified on the data sheet. The height should be determined by the height that the detector is placed during actual use (e.g., microR meter @ 1 m, bare NaI probe at 12-18 inches, collimated NaI probe at 6 inches). Assure that this height is maintained during all measurements.

C. Prior to disturbing the surface soils, make all gamma-ray measurements and record the results on the ERG Form 2.09B data form. For rate meters, put the response switch on slow and wait for 10 seconds with the detector in place. Look at the meter 10 times and record the readings. When using a rate meter/scaler, integrate the counts over a one minute counting time. A single measurement is sufficient when using the instrument in the scaler mode. Record the data on the ERG Form 2.09B data form for that study area.

D. After all gamma-ray data are reviewed for completeness, draw perpendicular lines through the center of the circle. Take five soil samples from each circle to a depth of six inches. The first sample should be taken from the center of the circle. The other four samples should be centered at a distance of nine inches from the center and on the perpendicular lines. Label the five samples using the study area unique identifier followed by the sample number (e.g. SPI-1, SP1-2, SP1-3, etc.). Record the sample numbers on Appendix A data form.

E. Repeat the above steps for above for each study area.

3.2.2 Plot Studies

A. Select 100 in' grid blocks that have as uniform gamma emission as possible. Choose a minimum of 20 grid blocks where the average gamma levels span the range of interest. Normally, this is from background levels to levels slightly above the cleanup limit. While data may not be available to anticipate the gamma range, a preliminary study with a few data points might be advisable. Data from similar sites may also be used.

B. With the radiation detector placed at the appropriate height above the surface, walk a regular pattern for one minute and allow the scaler to integrate the counts for one minute. Be sure to walk at a pace so that uniform coverage is attained. If a ratemeter is used,

carefully observe the reading while walking over the plot and estimate the average count rate. Record the average count rate on ERG Form 2.09B.

C. If a GPS-based radiological survey has been completed, determine the average count rate for the grid block using a computer software program.

D. Prepare a composite soil sample using a minimum of nine regularly spaced surface soil samples taken to a depth of six inches. Bag each sample individually unless care is taken to take the same mass or volume of soil from each location.

3.3 Laboratory

A. Dry each sample using standard operating procedures

B. Make a composite sample using the samples taken from each point or plot Grind and blend the composite sample until a homogeneous mixture has been obtained. Label this sample with a unique identifier that can be traced to the specific study point or plot.

C. Select aliquots from the composite samples of appropriate size for analysis and QA checks.

D. Perform the Ra-226 assays using standard operating procedures.

3.4 Data Analysis

A. Enter the Ra-226 concentration-gamma count rate data pairs for each instrument in a spreadsheet (e.g. Lotus 123) having the capability to do a linear regression.

B. Do a least-squares linear regression and plot the results. Evaluate the suitability of the results for use in predicting the Ra-226 concentrations in soils.

C. Develop cut-off gamma count-rates and/or exposure rates that correspond to Ra-226 concentrations of interest, considering errors in predicting the concentrations and desired safety factors. Confidence limit lines may be calculated and displayed with the correlation using methods described in Walpole, R. E. & Meyers, R. H., 1978. Probability and Statistics for Engineers and Scientists. New York, New York: Macmillan Publishing Company.

ERG Form 2.09B

Ratemeter/Scaler Model Detector Serial Number Serial No.

Count Time (if applicable) Reading units Technician

J Location I. D. Reading

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Location I. D. Reading

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ERG Form 2.09A

Location ID. lExposure Rate JSoil Sample Numbers ILocation I.D.I...... . .a Soil Sample Numbers

t I I ___________

STANDARD OPERATING PROCEDURE 1.52

GPS - WADIOLOGICAL SURVEYS USING VEHICLE

1. PROCEDURE

To describe the daily task for the radiological surveying with and operation of the site survey vehicle.

2. DISCUSSION

For the operation of the site survey vehicle there are task that must be performed before, during and after surveying. This SOP must be used in conjunction with other SOPs for the daily survey and operation of the site survey vehicle.

3. PROCEDURE

3.1 Equipment

NOTE: 3.1.1 - 3.1.5 is for each individual GPS-Rad unit being used.

3.1.1 Ludlum Model 2221 Ratemeter with RS232 capability (2221)

3.1.2 Ludlum Model 44-10 Gamma-Scintillation Probes (probe)

3.1.3 12' C-C Cable

3.1.4 RS232 Cable

3.1.5 GPS ROVER Unit (ROVER)

3.1.6 GPS BASE Unit (BASE)

3.1.7 site vehicle with probe harness

3.1.8 Check source

3.1.9 Function check sheet

3.2 Instrument / Detector Assembly and Electronics Set-Up

NOTE: It is very important to perform the fuinction check in the same location everyday. Radiological readings can vary from spot to spot even if only a few feet away.

3.2.1 Attach probes to vehicle harness at 18 inches above ground and place ROVER units in secure position.

3.2.2 Attach GPS unit to Ludlum 2221 RS232 port and attach Ludlum 44-10 to 2221 using C-C cable.

SOP 1-52

3.2.3 Turn on instruments and function check (See ERG SOP 1-04) with source at 6 inches below probe. Record all results and applicable data on a daily function check sheet (ERG Form 1.01).

3.2-4 Set up and begin logging data with BASE station (ERG SOP 1.50) and ROVER (ERG SOP 1.51).

NOTE: It is important to choose a background check location where the gamma readings will not be influenced by site operations.

3.2.5 Proceed to daily background check location and perform a one minute count of background and record data on daily function check sheet.

3.2.6 While at background check location take at least 30 point location "shots" with GPS unit. This helps in mapping process.

3.2.7 Surveying

NOTE: It is important to achieve proper coverage. Proper coverage consist of at least five gamma readings per 10 meter by 10 meter grid. Excess readings are desired, but too dense of data will result in not being able to visually read results on map.

3.2.7.1 To achieve proper data coverage drive vehicle at a speed similar to a fast paced walk. This is can be accomplished by allowing vehicle to idle along in 4WD-Low or "granny gear".

3.2.7.2 Have someone walk at 9 feet to side of vehicle and place pin flags or spray paint on ground at intervals easily seen by driver. When vehicle makes next pass by, driver should attempt to pass probe over marked line. This allows data to be taken in consistent pattern.

3.2.7.3 Proper planning will allow for an area to be completely surveyed in a given time. It is not desirable to start a large section on one day and finish on another.

3.2.8 At the end of surveying day proceed to background check location and perform a one minute background count and the 30 point location "shots" with GPS unit again. Record data on daily function check sheet. Perform function check as in section 3.2.3.

3.2.9 When all field operations are finished, shut down both the BASE and ROVER units and download data (See ERG SOP 1.50 and 1.51).

4. ATTACHMENTS

4.1 ERG Form 1.01 (Daily Function Check Sheet)

SOP 1-52

OVERSIZE

NOT INTO IMAGE

PAGE (S)

CONVERTED ELECTRONIC FORM.

PAPER COPY AVAILABLE IN FILE CENTER.

IS NRC