Regulatory Guide 4.5

Measurement of Radionuclides in the Environment Sampling and Analysis of Plutonium in Soil

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Issue date:	05/31/1974
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May 1974 U.S. ATOMIC ENERGY COMMI1ON

REGULATORY GLJIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 4.5 MEASUREMENTS OF RADIONUCLIDES IN THE ENVIRONMENT

SAMPLING AND ANALYSIS OF PLUTONIUM IN SOIL

A. INTRODUCTION

of exposure to humans. Nevertheless, the long half-life

(24,390 years) of the predominant plutonium isotope, Paragraph (e) of § 20.106, "Concentrations in Pu-239, coupled with its high relative radiotoxicity, effluents to unrestricted areas," of 10 CFR Part 20, make it desirable to document and periodically reassess

"Standards for Protection against Radiation," provides its distribution and fate in the environment.

that the Commission may limit the quantities of radioactive materials released in air or water by licensees during a specified period of time if it appears that the A soil sampling and analysis program provides the daily intake of radioactive materials from air, water, or most direct means of determining the concentration and food by a suitable sample of an exposed population distribution of radionuclides in the environs of nuclear group, averaged over a time period not exceeding one facilities. Hence, it would be desirable to include in year, would otherwise exceed specified quantities. environmental monitoring programs, a program for Section 20.201, "Surveys," of 10 CFR Part 20 requires sampling and analyzing soil for plutonium. A soil that a licensee conduct surveys of levels of radiation or analysis program would have the most significance for concentrations of radioactive material as necessary for the preoperational monitoring program since it would compliance with AEC regulations in Part 20. Paragraph serve to establish baseline concentrations of plutonium prior to operation of the facility. Soil analysis, although (c) of § 20.1, "Purpose," of 10 CFR Part 20 states that useful in special cases involving unexpected releases, is a every reasonable effort should be made by AEC licensees to maintain radiation exposures, and releases of poor technique for assessing small incremental releases radioactive materials in effluents to unrestricted areas, as and is therefore not recommended as a method for monitoring routine releases of radioactive material.

far below the limits specified in Part 20 as practicable, Nevertheless, because soil is an integrator and a reservoir i.e., as low as is practicably achievable, taking into of long-lived radionuclides, and serves as an intermediary account the state of technology, and the economics of in several of the plutonium pathways of potential improvements in relation to benefits to the public health importance to humans, for example, resuspension and and safety and in relation to the utilization of atomic plant uptake, knowledge of the buildup of plutonium energy in the public interest. and other long-lived radionuclides in soil is essential. A

soil-monitoring program conducted annually should be This guide describes procedures acceptable to the adequate to assess the cumulative deposit of plutonium Regulatory staff for sampling and analysis of plutoniumn in soil.

in soil with the sensitivity and accuracy needed to adequately monitor plutonium in soil in the environs of fuel reprocessing and fuel fabrication facilitie

B. DISCUSSION

The sampling and analytical procedures described in the appendices to this guide are acceptable to the The Regulatory staff has reviewed and evaluated the Regulatory staff as bases for meeting the performance data on plutonium in environmental and biological standards required to adequately inventory the samples and has concluded that plutonium plutonium deposited in the environs of nuclear facilities.

concentrations in these media are generally low and Other procedures selected for sampling and analyzing often below the detection limit of state.of-the-art plutonium in soil should conform to similar standards of equipment, and should be of little significance in terms performance.

USAEC REGULATORY GUIDES Copies of pubtlshed guides may be obtained by requet indicating the divisions destired to the US. Atomic Enorgy Commsnon, shington, D.C. 20548, Regulatory Gaidto ore Issued to deseorlwe and make avilIible to the public Attenio*n: Director of Reglatory Standesds. Comments and suglestions for nmathods aceptabl to the AEC Regulatory staff of i nplemientine specific parts of improvements in theagude er eorage nd shiould be sent to the Secretary.

the Conmiasaon's reguletions, to delinlete tachnilues used by the staff in of the Commission. U.S.Atomic EneryCommision. Wshington. D.C. 20548.

evalueting specific prbisme or postubeted accidents, or to provide guidance to Attention: Chief, Public Proceedinge Staff.

applicants. Regulatory Guides we riot substitutes for regulations and Copliance with tse is not required. MIthodI and inlutions differeint from thlos set out in The guides eIs bsud in the following ton broed divisions:

the guides will be -cm1t11 If they provide a basis for the findings requIsitO to the isuance or comntinuence of a permit or license by the Comnslion. 1. Power Reactors

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3. Fuels and Materials Facilities 8. Occupotionsil Health Publied guides will be vid periodically. as appropriate, to acpommodate 4. Environmontal and Siting 9. Antitrust Review commantmand to reflect now Information or eoxprionce. 5. Mtrials end Plant Protection 1

0. General

APMENOIX A

SOIL SAMPLING AND SOIL SAMPLE PREPARATION

No single soil-sampling method is adequate to I. HAIL Maldin far SON Sampling and Soil Sample sample all soil types at all locations. For example, a method designed to sample cohesive sandy loam soil A soi sampling and analysis program provides an may not be suitable for sampling the dry loose soil common to some arid areas of the U.S. Rocky sofls

"acceptable method of assessing long-term buildup of present problems for all sampling methods. It is iong-lived radioactive contaminants in the environment.

necessary, therefore, that each situation be handled on a Surface soll analysis can also serve to define case-by-case basis and that the procedure be adjusted contamination contours or distribution patterns soon appropriately in a given situation, Two soil-sampling after a hypothetical acute airborne release of a procedures are described here-the method described in contaminant. The latter would require sampling of only HASL 300, ' which can be used for most soil types, and the top 5 cm of soil, including the vegetation.

a more specialized procedure for sampling dry sandy Experience indicates that attempts to sample a shallower soil.2 The techniques and principles embodied in these depth result in les reproducible samples. In many areas, procedures are generally applicable to most situations a site meeting the desired criteria has a root mat and should be used as guides for sampling soils at extending several centimeters into the ground, and it is specific sites. rarely possible to remove an intact core les than 5 cm in depth.

A. Site Selection

" "Procedure ManuaL," HASL 300, Health and Safety Laboratory, U.S. Atomic Energy Commission, 376 Hudson Street, New York, New York. When soil is sampled as part of a preoperational survey around a plant, it is desirable to select areas that sampling method used by SSoil the Nevada Applied can be resampled at a later time should it become Ecoloay Group at Nevada Test Site, which has been modified by necessary. Figure I shows a suggested distribution of the Regulatory staff.

II VECTOR WIND

PREDOMINANT

Mils 0 1 2 3 4 5 10

Kiloine rs; 0 l.6 3.2 4.8 6.4 8.0 16 Figure 1. PRELIMINARY SOIL SAMFLING SITES NEAR A NUCLEAR FACILITY

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sampling sites covering the area surrounding the plant, The procedure after the selection of an undisturbed with emphasis on the downwind direction. About 13 site that meets the criteria previously discussed is as siles, with the furthest extending 16 km (10 miles) follows: Lay out a straight line transect about 4.6 m (15 downwind, should give an adequate picture of ft) long. Since it may be desirable to resample the site at background levels in the environs of a plant. If a later time, measure the coordinate distances to FrLed necessary, sampling at this same array of sites would landmarks to identify the relative postion of the promide a preliminary picture of the contamination transect.

pattern.following a release. It is also suggested that one or more samples be taken close to the center of the most Press the 5-cm-depth topsoil cuttei into the ground heavily populated area in the vicinity of the plant. without twisting or disturbing the grass cover or surface soil. This may best be accomplished by stepping on the rim of the cutter with both shoe heels. If more force is The procedure described here is designed to obtain required to press the cutter into the ground, a rubber samples that will measure the total amount of an mallet may be used. Gently twist the handle of the initially airborne contaminant that has fallen out in a cutter to cleanly remove the topsoil plug. Take a total of given area. It will not evaluate the unusual case where ten topsoil cores in a straight line, about 30 cm apart, excessive accumulations occur in low spots, at the foot placing the cores in a plastic bag. (The total area sampled of slopes, or in flooded areas. is 620 cm 2 .)

The site should be nearly level with moderate to Sometimes it may not be possible to remove a good permeability. There should be little or no runoff

5-cm-deep plug cleanly because of a thick root mat. If during heavy rains and no overwash at any time. Such a the topsoil and bottom soil are to be combined, a 10- or site is frequently found on smooth ridge crests, level

15-cm-depth cutter may be used to remove the-topsoil by virgin land, and well-kept lawns and grounds around institutional buildings. The site should not be near pounding it partway into the ground with the rubber enough to buildings or trees to be sheltered during mallet until it is possible to remove the core intact.

blowing rains. Soils having very high earthworm activity Topsoil depth cannot be measured accurately by this should be avoided because of uneven mixing of the soil method.

to considerable depths.

C. Depth Profile B. Core Method An area where there are no rocks and stones and Experience has shown that a total sample area of very few pebbles is suitable for taking soil samples at

460 to 930 cm2 (1/2 to I ft2 ) will provide d reasonably various depths. A sandy loam type soil such as is found good estimate oftotal deposit if the area consists of a on Cape Cod or eastern Long Island can be sampled composite of ten or more individual plugs or cores, A satisfactorily. These conditions, of course, are rarely tool for taking samples may be anything that takes a found in the areas of interest. Consequently,* the core or plug that is of equal area throughout its entire attempted use of the method described below runs the depth. A good pair of sampling tools is an risk that subsoil layers may be contaminated with higher

8.9-cm-diameter (3-1/2-in.-diameter) topsoil cutter that specific activity from upper layer soil.

takes a 5-cm-deep (2-in.-deep) sample and a

8.3-cm-diameter (3-1[4-in.-diameter) barrel auger that 1. Procedure cuts an 8.9-cm-diameter (3-1/2-in.-diameter) sample.

As in the core sampling method, the depth The topsoil cutter is used to remove the sod to a profile samples are taken so that the weight and depth of depth of 5 cm, and the auger takes the remaining sample the material collected can be directly related to the to the depth desired. The soil from ten cores sampled to surface area. To the extent that grass cover and terrain a depth of 30 cm (12 in.) is composited to make a single affect the choice of sampling area, the site selection sample weighing from 18 to 36 kg (40 to 80 pounds). If criteria previously described apply. Lay a tarpaulin desired, the 0 to 5-cm sod samples may be kept separate, (about 2 m square) on the ground near the clipped area.

making a sample of higher concentration. The amount of Dig a trench about 60 cm wide by 90 cm long by 60 cm contaminant found in the upper 5 cm and that found in deep immediately, adjacent to the clipped area, placing the remaining subsurface are added to give the total for the removed dirt on the tarpaulin. Usually, the sod can the 620 cm2 (0.67 ft 2) of surface represented by the be cut out in blocks, making it easy to replace after ten cores. sampling. Smooth the long side of the trench adjacent to the clipped area with a flat blade shovel or mortar Powdery, dry, loose, single-grain soils cannot be trowel, making it perpendicular to the surface. Take the sampled in a simple, satisfactory way by the core first 5-cm increment by pushing a three-sided square pan method. It is best to take sarpples when the soil contains with cutting edges on the open side (' 5 cm x 15 cm x 5 enough moisture to be cohesive, even if this necessitates cm deep) into the side 5 cm below the ground surface.

that, the area to be sampled be wetted by sprinkling. Use a sharp flat-bladed knife to score the edge

s. then

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rcrnmve the first cut and seal in a small plastic bag. Cut e. Crush the entire soil sample, then blend for away the topsoil on either side of the first cut to make a about 30 minutes.

,he.-f about 45 cm long by 15 cm wide and 5 cm from the

,irface. Lightly brush away any particles that may have f. Spread out the sample, mark off quarters, faLlen on the shelf. Apin, push the open-end cutting pan and take scoopfuls from each quarter consecutively until into the side, cut, and remove the next 5-cm-thick approximately 3 kilograms have been collected.

incremental sample. Continue this procedure until samples have been taken to the desired depth. The actual g. Pass this subsample of soil through a depth of a cut can be determined between cuts by grinder or pulverizer and transfer to a one-gallon placing a two by four on the surface and measuring the wide-mouth polyethylene bottle.

distance from the lower surface of the two by four to the subsurface. 2. Equipment When all of the samples have been taken, fill the Scale-Capacity of -50 kg trench with dirt from the tarpaulin, and replace the sod Crusher -To precrush rocks to more suitable taken from the trench. size for pulverizer Pulverizer-For pulverizing to about 100 mesh A depth profile is useful only for finding the relative Blender-Capacity "-'0.056 m3 (2 ft 3 )

vertical distribution of the radionuclide. Therefore, it is necessary to sample deeply enough that close to 100 E. Reporting of Data percent of the radionuclide is measured. Since only 230

cm2 of surface area at one spot is umpled when depth Results should be expressed in nanocuries per gram increments are taken, the integrated deposit is not of dry soil (total soil): the field bulk density should be necessarily representative of the area. recorded, as well as the area and depth sampled, to provide information necessary to also calculate and

2. Equipment express contaminant activity per unit area.

Three-sided square pan with cutting edges on. II. Method of Nevada Applied Ecology Group for open side (15 cm x 15 cmx 5 cm deep Sampling and Sample Preparation of Nevada Test made of 0.16-cm-thick cold-rolled steel, Site Soil (modified for Regulatory purposes)

welded at the comers).

Plastic bags, 52 x 23 x 0.02 cm The method developed specifically for the Nevada

(20i x 9 x o0o00 in.) Test Site under the auspices of the Nevada Applied Mortar trowel Ecology Group should be applicable to other similar Long flat-bladed knife soils. The "ring" and "trench" methods have been used Meter stick (or 24-in. ruler) by the Nevada Applied Ecology Group for soil sampling One 1.5 m length of two by four on or around the Nevada Test Site. Either method can be Tarpaulin used to obtain surface samples (defined as the upper

5 cm of soil) or profile samples.

D. Soil Sample Preparation A. Ring Method I. Procedure In the ring method, a ring (12.7 cm ID x 2.5cm deep) is, pressed into the soil. Soil inside the ring is a. Spread out sample on a plastic sheet and removed with a disposable plastic spoon to a depth of allow it to air dry. This may take three days or more. 2.5 cm and is bagged. Soil is next removed from outside the ring to the 2.5 cm depth, the ring is pressed into the b. Break up soil aggregates and pull apart the soil another 2.5 cm, and another sample is taken with a topsoil plugs (consisting of vegetation and mot mat). second spoon. In this manner, profile samples can be With a pair of scissors, cut up the vegetation so that it taken to a desired depth; at lower depths where can eventually be distributed homogeneously. radionuclide concentrations may be low, it may be desirable to increase increments to multiples of 2.5 cm.

c. When the sample is completely dry, weigh the entire sample to +/-50 grams. A spmple consists of soil taken from a minimum depth of 5 cm. A minimum of five separate samples d. Remove large rocks (>2.5 cm), weigh should be taken along a straight line transect and separately, and discard. (For gravelly soil, it may be composited for analysis. Since it may be desirable to desirable also to screen out the greater-than.2-mm resample the site at a later time, the coordinate distances fraction after appropriate treatment of the samnle to of the transect should be measured to fixed landmarks break up soil aggregates.) to identify the relative position of the transect.

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i. TreM* MlltsU nks) swd elapse between its appiation a&d sampling to slow for euilibratiom of moisture.

A rectangular trench of apr'opiate size is dug IS to

25 cm deeper than the desired samplin depth. Samples D. wmAple Pmreprslo are taken from a trench wall with a three-sided tray. 10

Wfore a weighed portion of the soil is ground in cm wide by 10 cm long by 2.5 cm deep.

preparaton fox analysis, it is desirable to oven-dr%

The procedure for taking a sampl is as follows: The (I 10 C) for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and sieve it. A 0.6-cm.mesh ('4-in.

tray is pushed in from the side of the trench with the mesh) screen removes larger stones and some organic top edges of the tray flush with the surface of the debris such as roots, straws, etc.; the weight basis is. of course, the total soil. The plutonium contribution of ground. After the tray is pushed into position, press stone, larpr than 0.6 cm (34 in.) is generally negligible:

,down with a trowel or a thin, flat piece of metal however, if desired, the larger stoma can be acid-washed approximately 15 cm wide above the open.sdded front and the wathings added to the fraction that passes end of the tray. With the metal or trowel In place, the throvu the O.6-cm (%4n.) screen. If the quantity of soil outside the tray is scraped off down to the depth of organic material is aot negligble (i.e., if it consists of the tray. The separated soil is removed and bagged, and more than a few strands of roots and/or a few leaves), it the process is repeated until blocks of soil have been should be analyzed separately; the result should- be removed to the desired depth. A sample consists of soil weighted for the amount of organic matter relative to taken from a minimum depth of 5 cm. A minimum of the total sample and added to the result for plutonium five samples should be taken along a straight line in the soil.

transect, each from a separate trench, and composited for analysis. Since it may be desirable to resample the The volume or "nature" of soil adhering to roots site at a later time, the coordinate distances of the and other debris may be such as to bias results: such transect should be measured to fixed landmarks to debris may be be washed with a gentle spray from a identify the relative position of the transect.

wash bottle to remove the soil, and the washings may be added to the smaller-thanO.6-cm (N in.) fraction. This The trench method is often used for taking depth fraction, plus additions, should be oven-dried again and profile samples to obtain information on the distribution weighed.

of a contaminant with depth.

C. Factors in Soil Sampling E. Reporting of Deta Results should be expressed in nanocurizs per gram If care is taken, either method works well in of dry soil (total soil). the field bulk density should be fine-textured soils; however, "stony" soils present recorded, as well as the area and depth sampled. to difficulties. In stony soils, larger scoops are recommended. Larger scoops and hence larger soil provide information necessary to also calculate and volume will minify perturbations caused by stones, express contaminant activity per unit area.

which interfere with the progress of the edges of the fIt. Disecuion scoop as it is passes through the soil. A representative depth. however, is more important than a representative Both the HASL and Nevad Test Site procedures are width. intended to provide deposition and/or concentration data that are typical of a given area, and are thus based Areas to be sampled should be undisturbed and on criteria for obtaining samples that are most should be well removed from dusty roads and from sites representative of that area. It is probable, however, that that show evidence of previous construction. A distance at some koitions of nuclear facilities, these guides of no less than 120 m (400 ft) from the outer edge of canot be entirely met due to the special nature of t1e construction is recommended. When it is desirable to terrai. In such instances, each site should be handled on sample soil for the measurement of environmental a cme-by-cse basis.

redistribution of radioactive materials by physical, chemical, and biological factors, a random sampling For example, if the facility site does not have scheme is preferable to a biased selection of sampling suitable sampling areas, i.e., large flat open areas covered sites. A practical method of selecting sampling sites is by with grass, a greater number of soil cores should be locating them randomly by direction from grid points or taken for compositing than from a more suitable area.

other fixed points on an area. Using the HASL criterion of ten cores per sample from a good site as a base, a less suitable site may require Soils should be neither muddy nor dry at the time sampling and compositing of 15 or more cores to obtain of sampling: soils with moisture content near field a reasonably representati* sample.

capacity sample best. A fine spray from a sprayer has been employed with success to provide optimum In areas where the ground is covered with tall grass.

moisture for dry soil: if a spray is used, time (about 30 it may be necessary to separately sample the grass and

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soil. One method for doing this is to measure off a that the vegetation growing on the soil, which usually minimum of one meter square of Vpound and to collect Ihc hrao within this area by cropphng it to about a contains some of the deposited Material, also be Ow,-cm hei*ht. The soil within this area could then he included in the analysis. When the grass fraction is sampled by taking five plugs and core (one taken at analyzed separately, the data should be normalized to etnch vitinor and one taken in the center) using the HASI. the area of soil sampled and the result added to the soil

",'remethod described In this apWrnx. Two of these data.

one-meter.quare plots which are spaced at least ten feet apart should provide the recessary number of plugs and Interference from rocks is a common problem. It uores needed for compodting. The $rats could be may be necemsry in some instances to sample in a analyzed separately or added to the soil and analyzed different area if the rock problem is severe in a given together with the soil. If the latter technique is used, it area. If moving to another area is not feasible, the would he necessary to process the grass first by grinding sampling procedure should be modified to minimize the and/or ashing and then adding a proportionate aliquot of effect of the rocks. This may be done by sampling larger the rass to the soil. Since the primary objective of soil diameter cores to deeper depths. All rocks should be included in the sample. Rocks may be removed by analysis is to obtain representative measurements of deving after the soil sample has been appropriately dried c')ntanminants deposited on the ground, it is essential and weighed.

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APPENDIX B

RADIOCHEMICAL ANALYSIS OF PLUTONIUM IN SOIL

The radiochemical analytical procedure described Stainless steel disc (I.9-cm - 2.2-cm diam. polished helow is based on the procedure currently in use at Los on one side)

Alamos Scientific Laboratory. Testing by a number of PTFE beakers (250,400, 600 ml, etc.)

laboratories (Pacific Northwest Laboratory, Battelle PTFE stirring rods (-0.3 cm x - 12 cm)

Memorial Institute, Los.Alamos Scientific Laboratory, Reynolds Electrical and Engineering Company) has shown the procedure described in this guide to be D. Extraction generally applicable for analyzing plutonium in soil, including Nevada Test Site soils. The main features of I. Weigh a l0-g soil aliquot into a 250-ml PTFE

this procedure include the use of an acid-extraction beaker. Add an appropriate quantity of Pu-236 mixture containing HF, HCI, and HNO 3 , Pu-236 or tracer. (Note I at the end of this section.)

Pu.242 tracer, electrodeposition of the plutonium, and counting by alpha spectrometry. Samples consisting of 2. Add 60 ml of HNO 3(70%) and 30 ml of HF (48%).

10 to 50g of soil can be,readily analyzed by this Digest on a hotplate with frequent stirring for about procedure, Using normally available laboratory an hour. (Notes 2 and 3)

equipment and materials. Soil samples much larger than this tend to be unwieldy because special equipment and

3. Remove from the hotplate and cool somewhat materials such as large centrifuges, large PTFE beakers, before adding 30 ml each of HNO 3 and HF. Digest etc., are usually required. The analysis of large soil with some stirring for about an hour.

aliquots is desirable, however, because larger aliquots usually provide a more representative sample. In general, it would be poor practice to use aliquot sizes containing 4. Remove from the hotplate and cool. Carefully add less than 10 g of soil unless smaller than 10 g samples are 20 ml of HCI (38%) and stir. Heat on a hotplate for replicated. 45 minutes with occasional stirring.

A. Principle 5. Add about 5 g of powdered boric acid, and digest for an additional 1. min. Stir occasionally.

Plutonium is extracted from soil with a combination of nitric, hydrofluoric, and hydrochloric acids in the 6. Add about 200 ing of sodium bisulfite and digest on presence of Pu-236 (or Pu-242) tracer. Plutonium is a hotplate. Continue heating and evaporate to a isolated by anion exchange and electrodeposited onto a liquid volume of-10 ml.

stainless steel disc for determination by alpha spect romet ry. 7. Add -50 ml of water and digest on a hotplate with stirring for -10 min to dissolve soluble salts.

B. Reagents

8. Cool. Using a wash bottle, transfer approximately Ammonium hydroxide (28%) equal parts of the total sample into two 220-mI

Ammonium iodide centrifuge bottles. (Note 4)

Boric acid Dowex I x 4 (100-200 mesh, nitrate form) anion 9. Add I ml of iron carrier solution (10 mg Fe/ml) to resin each centrifuge bottle and stir.

Hydrochloric acid (38%)

Hydrofluoric acid (48%) 10. Add NaOH (50% solution) with stirring to each Iron carrier (10 mg/ml) bottle to a pH of -9. Add 5-10 ml excess of NaOH

Nitric acid (70%) and stir for I min.

Nitric acid (8N)

Oclyt alcohol (Reagent grade) I1. Centrifuge for -5 min, decant, and discard the Pu-236 tracer (or Pu-242) supernate.

Sodium bisulfite Sodium hydroxide (50% solution) 12. Dissolve the precipitate with about 30 ml of 8N

Sodium nitrite HNO 3 saturated with boric acid. Digest in a hot water bath for 10 min.

C. Special Equipment

13. Cool and centrifuge for -5 mrin. Decant the Elect rodeposition apparatus supernate into the original 250 ml PTFE beaker and Ion exchange column (-l1.3 cm ID x~ 15 .cm) save.

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4. Wash the residue with 8N HNO3 saturated with Pu-236 tracer than the expected activity level of boric acid, centrifuge for S min. and combine Pu-238 in the sample.

supernates. Discard the residue.

2. For larger soil aliquots. larger amounts of the acids S. Heat the supernate on a hotplate and evaporate to (in about the same proportions) should be used. Fmi near drynes. example, for a 50 suample, use 200 ml of HNO.

and 100 mi of HF, etc.

6. Add -30 ml of water and heat to disolve the salts.

Cool, and tramfer equal portions into centrifuge 3. For organic soils, first add HNO 3 only, in small tubes. portions with stirring. If the solution threatens to overflow as a result of froth generation, add a few

17. Add NH4FOH, dropwise with stirring, to a pH of -9. drops of octyl alcohol and stir. Digest on a hotplate until the evolution of heavy reddish-brown fumes is

18. Centrifuge and discard the supemate. rodued to a barely visible level. Cool to room temperature before carefully adding HF.

19. Dissolve the precipitate with a minimum of concentrated !1NO3 (70%) and transfer using 8N 4. If large centrifuge tubes are not available, it might HNO 3 solution into a 250-ml beaker. Add 8N be expeditious to perform the precipitation in a HNOs to a vowume of approximately 75 ml. (Note beaker fkti, to allow the precipitate to settle

5) somewhat, to decant the supernate, and then to complete the separation by aentriftsion.

20. Add -200 mg of sodium nitrite (NaNO 2 ) crystals and stu with a stirring rod, bring to a quick gentle 5. If the volume of the hydroxide precipitate i, boil on a hotplate, and cool. Avoid prolonged considerably greater than should be expected from heating. the 10 mg of Fe added, the final volume should be brought up to -100 nd with 8N HNOI or.

21. Passr through an anion-exchange resin column alternatively, the dissolved hydroxides ahould be previously pretrested with SN WO3. WsA with six evaporated to salts first before addition of the 8N

column volures of RN HMOs. Let the Yl'O, just HNO3 solution. The final normality of the HNO0

pass through the column before continuing the wash solution is not extremely critical, but should be ip with six column volumes of 12N HW. (MtM 6) the range of 7-9.

22. Mute with four column volumes of NltI-HO 6. In the absence of an excessive amount of salts (And solution (I ml IM NHMI solution to 20 ml 12N this should be the case with l0g soil samples), a HCO), and collect in a I 50-ml beaker. resin column with dimensions of approximately 1.3 cm ID by 10 cm of wet. settled resin should be

23. Evaporate on a hotplate to 5 ml and add HMNO adequate.

(70%) dropwise. PAN down the sides of the beaker dropwise with HNO9 ad add six drope of HO E. Ekletrmdeposition

(38%). Evaporate to near dryness.

1. Add 1-1/2 to 2 ml of 4N HCI into the beaker and.

24. Add 50 ml of 8N HNOs solution aso epeat steps wuing a "disposable pipette" (2-m gltass eye-dropper

20 through 23. using a fresh aion-exnmge resin type, with 2-ml bulb), rise down the sides of the column. (A smaller ion-exchange column may be beaker with the sample solution. Transfer the used this time.) solution into a plating cell.

25. Continue heating the sample just to dryness. Rinse 2. Add another 1-1/2 to 2 ml of 4N .C1 solution into down the sides of the Weaker with concentrated the beaker, rinse as above, and add to the plating HC', and evaporate on a hoeplate to appmxlmately call.

I/2 ml. The sample is now ready for electrodeposition. 3. Repeat the above step with -I ml of H2 0.

4. Add a drop of thymol blue indicator solution uiid Notes: add concentrated NH4OH dropwise until the color changes to yellow.

An appropriate quantity of Pu-236 tracer is an activity level which is within an order of magnitude 5. Add 2N HCI solution dropwise to a salmon-pink end of the expected activity level of Pu-239 and Pu-240 point.

in the sample. If Pu-238 determination. is also required, it would be desirable to add no more 6. Electroplate at 1.5 A for 20 min.

4.5-N

7. At the end of 20 min, add 2.3 ml of coomtrated sample mad the ingrowth period, Am-241 activity could NIl 4 OH (two shots with 2.rd disposable pipette). add sipdcantly to the Pu.238 peak. It is desirable, and leave the current on for another 20 sec. therefore, that the plutonium be counted as early as possible after its isolation.

24. Turn the current off, rinse out the solution into a beaker with H2 0, and dismantle the cell, Rinme the Traces of Pu-238 may be present in some Pu-236 disc with H20, and dry it on a hotplate at medium sources; because of the relatively short half-life of heat for 5 min. The sample is ready for counting. Pu-236 (1,041 days), this problem worsens with age.

Each Pu-236 source should be checked for potential F. Counting contamination by other plutonium isotopes. Each plutonium isotope should be accurately determined as a A properly electrodeposited sample should be free fraction of the Pu-236 activity and should be corrected of residue. Normally, three plutonium peaks are for in the analysis. Older Pu-236 sources also contain distinguishable, the Pu-239/Pu-240 peak at 5.11.5.17 U-232 and Th.228 daughters with alpha energies in the MeV. the Pu-238 peak at 5.46-5.50 MeV, and the Pu-236 5.3 - 5.4 MeV range. Therefore, the plutonium fraction peak at 5.72.5.77 MeV (or Pu-242 peak at 4.86-4.90 should be chemically isolated before a check is made for MeV). Since Pu-238 is readily resolved from the other other plutonium isotopes in the Pu-236 source.

plutonium isotopes, it is often advantqaous to use the Plutonium-236 should be corrected for decay if the Pu-238 to Pu-239/Pu-240 ratio as a possible tag for decay period exceeds IS days.

identifying the various sources from which the plutonium may have been released. In those cam where PFutonium-242 tracer, if available, could he used Pu-238 activity is very low, it is well to remember that instead of Pu-236. There are several advantages to using Ani-241 has essentially the same alpha energy (5.44-5.49 Pu-242. First, its half-life is long (3.87 x 10 yr),

MeV) as Pu-238 and will therefore add to the Pu-238 obviating the nocesity for decay corrections. Second, count if present. Although Am-241 is chemically since its alpha energy (- 4.9 MeV) is below the energy removed from the plutonium fraction by this procedure, of either Pu.238 or Pu.239/Pu-240, the potential fresh Am-241 continues to grow in from the Pu.241 problem of "tailing" of a tracer peak into a lower-energy present. Depending on the amount of Pu-241 in the peak region in the detection system is eliminated.

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