Add about 100 mg of sodium nitrite and heat to boiling until no more brown fumes are given off. Cool.
Step 27
Pass through a prepared ion exchange column (Procedure E3d). Rinse the beaker with small quantities of 8 M HNC% and add the washings to the column. Wash the column with 10 column volumes of 8 M HNOs. Collect the raffinate and washings for analysis of americium and/or curium if required (Procedure E4).
Step 28
Wash the column with 10 column volumes of concentrated HC1, or until the eluate is colourless. Discard the eluate.
Step 29
Elute the plutonium from the column by passing 10 column volumes of concentrated HC1 containing 2% hydriodic acid into a clean beaker. Evaporate to dryness on a hot plate.
Step 30
Add a few drops of concentrated HC1 to dissolve the residue. Evaporate to dryness.
Sample preparation Procedure E3c, Pg. 5 of 6
Step 31
Add a few drops of concentrated HNOs to dissolve the residue. Evaporate to dryness.
Step 32
Repeat steps 30 and 31 until a white residue is obtained (normally there is no need for this step).
Step 33
Dissolve in plating solution, add to a plating cell (see Figure E3 for an example cell), and electroplate onto a 2.5 cm stainless steel disc at 500 mA for 2-3 hours.
Step 34
Add 1 mL of concentrated ammonia solution and continue the electroplating for one minute.
Turn off the current; quickly empty the plating cell and dismantle.
Step 35
Wash the plate with water and then methanol. Dry and submit for alpha-spectrometry (Procedure E3).
FIGURE E3
EXAMPLE OF AN ELECTROPLATING CELL
H. Electrode
Body
j ! Liner i •
Polished face ! ;
*^ ; — ' Disk :_•, O-ring
[ Bottom L= Electrode
FIGURE E2
AN OVERVIEW FLOW CHART FOR SAMPLE PREPARATION IN CASE OF PLUTONIUM ANALYSIS
Water
, •-,•<. -,.,.,. Ash slowly to Acidify and dilute 450degyc
Add Fe carrier Dissolve in HF Leach with aqua "I f Dissolve in 8 M regia•
Purpose
To prepare an ion exchange column suitable for the separation of plutonium from 8 M HNOs solution.
Discussion
The column removes plutonium from the solution and allows americium and curium to pass through.
Equipment/Supplies
> 1 cm diameter ion exchange columns
Reagents
> Anion exchange resin; Dowex AG 1X8, 100-200 mesh
> Nitric acid; 8 M
Step 1
Slurry anion exchange resin (Dowex AG 1X8, 100-200 mesh or equivalent) with water.
Step 2
Add enough slurry to an empty 1 cm diameter ion exchange column to form a column height of 8 cm. Let the water drain to the surface of the resin.
Step 3
Condition the column by passing 60 mL of 8 M HNOs, and allow to drain to the surface of the resin. The column is now ready for addition of the sample (Step 27, Procedure E3c).
Discussion
241 Am is a gamma-ray emitter and should be able to be detected using gamma ray spectrometry at the concentrations which may pertain after an accident. However, it is possible that radionuclides of curium will also be present, especially if the accident involved nuclear material. The method for americium is the same for curium, although the recovery will not necessarily be the same. Yield determinants for both elements are therefore required.
If the particular radionuclide of curium that is or may be present is known (242Cm or 244Cm), then the other must be used. Early measurement to determine which is present should be carried out with no curium yield determinant; if necessary, the recovery of this first sample can be inferred from future analyses of the same matrix.
This method is generally applicable for a solution of americium or curium arising from virtually any matrix. The starting material is the raffinate from the anion exchange column of the determination of plutonium (Procedure E3). The removal of plutonium by anion exchange must be carried out even if the analysis of plutonium is not required. The americium and curium are separated by extraction chromatography on TRU-resin and TEVA-resin (Eichrom Industries Inc.). Because of the small size of sample required in these situations, matrix effects are almost eliminated. It may not be possible, therefore, to scale up the method for larger samples.
The use of these resins is a recent innovation over more traditional methods; however, their use results in a significant time saving, both operator and real tune, and this is important in the immediate aftermath of a radiological incident.
In Table E3 sample sizes, typical minimum detectable activity concentrations (MDAs), based on the 95% confidence level, and approximate times of analysis are shown [17, 18].
TABLE E3. CHARACTERISTIC PARAMETERS OF AMERICIUM/CURIUM ANALYSES
airboume particulates 1m3 0.003 Bq/m3 48
water 1L 0.1 Bq/L 24
soil 0.3 Bq/kg 26
grass 50 g 0.1 Bq/kg 29
milk 50 mL 0.1 Bq/L 26
vegetables 50 g 0.1 Bq/kg 29
Americium/curium analysis Procedure E4, Pg. 2 of 3
Equipment/Supplies
> Alpha spectrometer system
> Worksheet E3
Stepl
Evaporate raffinate from plutonium separation (Step 27, Procedure E3c).
Step 2
Prepare the sample using Procedure E4a.
Step 3
Measure prepared sample in alpha spectrometer until appropriate counting statistic is achieved.
Step 4
Calculate the americium and curium activity using the following expression:
A _ As p l k e- ( Rx- Rb) -P x
A,, — —
Where
Ax = activity of americium or curium [Bq]
Aspike = activity of spike radionuclide, e.g.2 3Am or 242Cm [Bq]
Rspike = Rb = px =
count rate in the spike peak [cps]
background count rate [cps]
transition probability for americium or curium transition probability for spike radionuclide.
Am-241 Cm-242 Cm-244
5.487 6.113 5.805
0.852 0.738 0.764
StepS
Record and keep all relevant data and results in spectrometer logbook. Complete Worksheet E3.
Purpose
To convert the various matrices into suitable solution for analysis.
Discussion
This analysis can be performed together with plutonium.
Equipment/Supplies
^ Electrodeposition cell
r> Power supply for electrodeposition r1 Stainless steel discs
> Glassware, beakers, volumetric flasks, glass rods, PTFE beakers etc.
> Hotplate
r> pH meter, single probe
Reagents
> Hydrogen peroxide; concentrated
> Ascorbic acid; 0.8 M in water; make fresh as required
> Nitric acid; concentrated, 8 M and 2 M
> Formic acid; 0.1 M
> Ammonium thiocyanate; 2 M in 0.1 M formic acid, 1 M in 0.1 M formic acid
> Hydrochloric acid; concentrated; 4 M and 9 M
> Ammonium hydroxide solution; concentrated
> Sulphuric acid; concentrated
> Plating solution; buffered ammonium sulphate. Carefully add 60 mL of concentrated sulphuric acid to about 700 mL of water with constant stirring. Adjust the pH to 5.3 with ammonium hydroxide solution when cool. Dilute to 1 L with water; check pH and readjust immediately before use
> Methanol
Step 1
Evaporate the raffmate from the plutonium separation (step 2, Procedure E3c) to dryness.
Dissolve in 5 mL of 8M HNOs, cover with a watch glass and warm gently on a hot plate. If the solids do not dissolve add a few drops of hydrogen peroxide and boil gently for a few minutes.
Step 2
Add 15 mL of water and 1 mL of freshly made 0.8 M ascorbic acid solution, if a blue colour is formed continue adding ascorbic acid solution until it disappears and then add
approximately ImL in excess.
Add the sample solution to a prepared TRU-resin column (Procedure E4b). Drain to the top of the resin. Wash the beaker and column with 10 mL of 2 M nitric acid.
Step 4
Wash the column with 4 mL of 9 M hydrochloric acid to convert the resin to a chloride form, combine this eluate with that from Step 5.
StepS
Elute the americium and curium with 15 mL of 4 M hydrochloric acid. Combine the eluate with the wash solution from Step 4 and evaporate to dryness on a low heat hot plate.
Step 6
Dissolve the residue in 10 mL of 2 M ammonium thiocyanate in 0.1 M formic acid and pass through a prepared TEVA-resin column (Procedure E4c). Wash the beaker and column with several small portions of 1 M ammonium thiocyanate in 0.1 M formic acid using 10 mL in all.
Step?
Elute the americium and curium with 15 mL of 2 M hydrochloric acid into a 50 mL beaker containing 10 mL of concentrated nitric acid.
StepS
Evaporate the eluate to near dryness on a hot plate, add 2 mL of nitric acid and re-evaporate, repeat two times. A small amount of sulphuric acid formed by decomposition of the
thiocyanate will remain.
Step 9
Dissolve in plating solution, add to a plating cell (see Figure E3), and electroplate onto a 2.5 cm stainless steel disc at 500 mA for 2-3 hours.
Step 10
Add 1 mL of concentrated ammonia solution and continue the electroplating for one minute.
Step 11
Turn off the current; quickly empty the plating cell and dismantle.
Step 12
Wash the plate with water and then methanol. Dry and submit for alpha-spectrometry (Step 3, Procedure E4).
Purpose
To prepare an ion exchange column suitable for initial purification of Americium and Curium.
Discussion
After removal of Plutonium the purification of Americium and Curium is in two stages; this is the first stage.
Equipment/Supplies
r" 0.7 cm diameter ion exchange columns
^ Glass fibre filter papers; Whatman GF/A cut to 0.7 cm diameter
Reagents
> Pre-filter material; Eichrom Industries Inc.
> TRU-resin; Eichrom Industries Inc.
> Nitric acid; 2 M
Step 1
To a column of 0.7 cm diameter add slurried pre-filter material until a 0.6 cm settled bed is formed.
Step 2
Add slurried TRU-resin to form a 2.6 cm settled bed and allow the liquid to drain to the top of the resin.
Step 3
Plug the top of the resin bed with a small disk of glass fibre filter paper (GF/A) to prevent flotation of the resin.
Step 4
Condition the column by passing 3 mL of 2 M nitric acid through it. The column is now ready for the addition of the sample (Step 3, Procedure E4a).
Americium and Curium are further purified using this procedure.
Equipment/Supplies
^ 0.7 cm diameter ion exchange columns
^ Glass fibre filter papers; Whatman GF/A cut to 0.7 cm diameter
Reagents
> TEVA-resin; Eichrom Industries Inc.
> Formic acid; 0.1 M
> Ammonium thiocyanate; 2 M in 0.1 M formic acid
Stepl
To a column of 0.7 cm diameter, add slurried TEVA-resin until a 2.6 cm settled bed is formed.
Step 2
Plug the top of the resin bed with a small disk of glass fibre filter paper (GF/A) to prevent flotation of the resin.
Step3
Condition the column by passing 4 mL of 2 M ammonium thiocyanate in 0.1 M formic acid through it and allow to drain to the top of the resin. The column is now ready for the addition of the sample (Step 6, Procedure E4a).
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Discussion
In most cases several measurements of quantity D will be performed at a given site. Set of independently measured values Dj (/ = 1, m) has statistical nature if it is assumed that D does not change significantly during measurement campaign. The frequency distribution of such set of measured values usually follows log-normal distribution and the best estimate D is the geometrical mean of this distribution (see Procedure F2). However taking into account all possible uncertainties simple arithmetic mean can be used for the representative value D .
Stepl
Calculate arithmetic mean for quantity D for a given site in a given time period:
Where
D = best estimate value for quantity D m = number of measurements.
Step 2
Calculate the uncertainty a of D value, using the expression:
Step 3
Record the result in the appropriate worksheet in the form D + a.
Purpose
To calculate the best estimate of the radionuclide concentration from a set of measurement values.
Discussion
In most cases several samples are analysed to get representative values of the concentration of radionuclides in the environment.
Set of independently measured activities Aj (/ = 1, rri) has statistical nature if it is assumed that A does not change significantly during sampling campaign. The frequency distribution of such set of measured values usually follows log-normal distribution and the best estimate for concentrations is the geometrical mean of this distribution.
However taking into account all possible uncertainties simple arithmetic mean (see Procedure Fl) can be also used for the representative value.
Step 1
Calculate radionuclide concentration (Q) for all m samples collected in the same side within a short period of time using the following expressions.
Air filters
q -V j
Where
Q = radionuclide concentration ofy-th filter [Bq/m3] Aj = activity on they'-th filter [Bq]
Vj = air volume sampled [m3] q = filter collection efficiency.
Water
V, Where
Q = radionuclide concentration in water sample [Bq/L]
Aj = activity on they'-th water sample [Bq]
Vj = volume of water sample [L].
Where
Q = radionuclide surface concentration [Bq/m2] AJ = activity on they-th field soil sample [Bq]
Sj = the area of they'-th sample [m2]; e.g. the area of the sampler multiplied by the number of core samples taken.
Other
Where
Q = radionuclide concentration in sample [Bq/unit]
AJ = activity on they-th sample [Bq]
Qj = quantity of sample [unit].
Step 2
Determine the best estimate (C ) of the concentration for the sampling location in given time by calculating the geometric mean of the data set by the following formula:
Where
C = best estimate for radionuclide concentration m = number of samples.
Step 3
Calculate the uncertainty a of C value, using the expression:
Step 4
Record the result in the appropriate worksheet in the form C ± cr.
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Ill
Response team:
Check at the end of the mission
D Expired — Consult with the EA!
D Instrument returned DFlat
D Batteries changed D Not O.K.
D Adjusted to correct value D Not O.K.