ISO 15366:1999 pdf free download.Nuclear energy — Chemical separation and purification of uranium and plutonium in nitric acid solutions for isotopic and dilution analysis by solvent chromatography.
ISO 15366 specifies a procedure to separate and purify uranium and plutonium contained in input solutions of irradiated nuclear fuels and final products handled at spent-fuel reprocessing plants. before their isotopic analysis by a mass spectrometric method as described ISO 8299 or alpha spectrometry as described in ISO 11483. The procedure applies to samples containing 2 ig to 150 tg Pu and 0.1 mg to 2 mg U in up to 2 ml of 3 moVl nitric acid solution. The U/Pu-ratio may range from 0 up to 200.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of ISO 15366. For dated references, subsequent amendments to. or revisions of, any of these publications do not apply. However, parties to agreements based on ISO 15366 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 5725-2:1994, Accuracy (trueness arid precision) cit measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method.
ISO 8299:1993, Determination of isotopic content and concentration of uranium and plutonium in nitric acid solution — Mass spectrometric method.
ISO 11483:1994. Preparation of plutonium sources and determination of 238Pu/239Pu isotope ratio by alpha spa ctrometry.
3 Principle
The chemical separation is performed on a chromatography column of silicagel impregnated with trinoctyiphosphine oxide (TOPO). Plutonium(IV) and uranium(Vl) in 3 mol/l nitric acid are selectively fixed on the column. Americium, the fission products and other interfering elements are not retained. Plutonium is eluted after reduction to the trivalent state with a mixture of hydroiodic and nitric acids; uranium is eluted by an ammonium carbamate solution.
Reagent blanks are treated and measured in parallel with the samples to verify the absence of significant cross- contamination between samples.
4 Apparatus
4.1 Shielded glove box or fume cupboard
4.2 Disposable polypropylene or glass columns, witt, a length of 90mm. a tunnel reservoir of 9,5 ml, a support bed volume of 1.4 ml, a bed height of 26mm. an inner diameter of bed reservoir of 8,4 mm, and titled with trite of polyethylene or glass of 20 pm, respectively 70 pm porosity (see Figure A.1). Suitable polypropylene columns with polyethylene trite are available commercially and well adapted to robollzed operation. The packing and conditioning of the columns are described wi normative annex A. The ctiromatographic columns shall be disposed of in the radioactive waste alter use.
4.3 Three hoiplates, reserved respectively for the treatment of the samples preceding their separation, and the treatment of the separated fractions of plutonium and uranium.
4.4 Standard laboratory equipment. flaslis and beakers. pipettes. glassware. stands and supports for columns, sample vials, traction tubes. etc.
5 Reagents
Use only reagents of recognized analytical grade or better. All aqueous solutions shall be prepared with distilled or deionized waler (con&ictlvity c 70 nScm-l. or resistivity P>15 Mfcm).
5.1 Concentrated nitric acid and nitric acid solutions, ‘(HNO) -6 moLt, 3 mci/I arid 1,7 molIL
5.2 Hydrolodic acid solution, c(Hl) = 0,1 mci/I, In nitric acld c(HNO) = 1.7 moM (5.1). The acid mixture shall be prepared freshly far each working sesson. The acid mixture i stable for about S h. The concentrated hydroiodllc acid (suprapure, mass traction of 56%) is commerc2ally available as suprapure reagent In sealed glass ampouies. It is kept in a refrigerator at about 6 CC. If more than 7 days elapsed since cutting the ampoule. open a new one.
5.3 Animonlum carbamate ICAS No. 1111.78.0] solutIon. c(NH4CO2NH2) = 0.7 moi/1.
5.4 Sllicaget 100, 63 pm — 200 pm (see A,3.1).
5.5 Trl.n-octylphosphlne oxide. c(TOPO) 0,2 mci/I solution in cyclohexane.
WARNING — This reagent Is flammable and should always be handled In a wail ventilated place and never In the vicinity of a flame.
5.6 Ferrous sulfat, solution. c’fFeSO4) — 0,1 mcI/i. To be prepared freshly for each working session.
5.7 Sodium nItrite solution. c(NaNO2) — 1 moth. To be prepared freshly for each working session.
6 Procedure (see Figure 1)
LI The sample should contain 2 pg to 150 pg of plutonium and 0,1 mg to 2mg of uranium in a volume of 0,5 ml of 3 mcI/I nitric acid solution (5.1). When starting with dried nitrate samples. apply the tollowing dissolution procedure
a) Add 0,5 ml of 6 moM nitric acid solution (5.1) to the dry samples and evaporate siowly on the first holpiate, keeping the temperature slightly below the boiling point to avoid any splashing and bubbling until nitrate salts crystallize.
b) Remove the sample vessels from the hotplate and redessolve the salts by adding 0.5 ml of 3 maul nitric acid solution (5.1) while still warm (40 “C to 60 ). Shake the vessels for a few seconds.
6.2 Perform a redox valency cycle to ensure that all plutonium 1501 opes are in the tetravalent state before starling the separation, as follows;
a) Add 50 p101 ferrous sulfate solution (5.6) to the sample.
b) Mix and wail for 5 men for a complete reduction of plulonium(Vl) or plutoneum(IV) to pluton,m(tll).
C) Add 50 iI of sodium nitrite solution (5.7) to reoxidize plutonium to the tetravalent state and add a further 100 Ml of 6 mol/1 nitric acid solutIon (5.1 to reach an acid concentration of 3 mol4. Mix again and wait for at least 5 mm,
6.3 Transfer hail of the pretreated sample onto the column, wail proxima1ety 1 mm. add the rest of the sample and let it flow through. This favours the retention of plutonium and uranium In the very upper layers ci the column.
6.4 Wash out the (issian products, together with americlum, from the column using 3 mclii nitric acid solution (5.1) in 3 successive aluoIs 0(2 ml, 3 ml and 4 ml.
6.5 ConditIon the column lot the plutonium elution by adding 2 ml of 1.7 moI?1 nitric acid SolutiOn (5.1). Discard all the wastes colecled until now.
6.6 Ehte the plutonium from the column with the hydroiodic acid solution in nitric acid solution (5.2) with three successive aliquots at 2 ml. Place the vials containing the collected plutonium Iractions on the second hoiplate.
6.7 Wash out the tair of the plutonium with 5 ml of the hy&oeodic acid soluti in nitric acid solution (5.2) in one aluot and discard the plutonium 1ail’ washings to the waste,
6.5 Condition the column for the eluton of the urarwum fraction by adding successively two al.quols of 1 ml distilled water. Discard the water washings to the waste.
6.9 Ekita the uranium with 4 ml of ammonium carbamate solution (5.3). Place the vials containing the collected uranium fractions on the third hotplate
6.10 Let the plutonium and uranium fractions evaporate gently to dryness on the hoiplates at 90 ‘C.
6.11 Remove the fractions from the holpiates. add 0,25 ml of concentrated nitflc acid (5.1) and evaporate again to dryness. Repeat this step once again.
6.12 Pedessotve the plutonium fraction, while the vial Is still warm (40 ‘C to 60 ‘C). with a volume V(Pu) of 3 mol nitric acid solution (5.1) to obtain a plutonium concentration of about 5ong4il. V(Pu).0,Ol8nr(Pu) in mllib.tres. where m(Pu) Is the mass 01 plutonium en micrograms, in the initial sample. SwIrl the vial to facilitate the dissolution,
6.13 Redissolve the uranRim fraction, while the vial is still warm (40 ‘C to 60 ‘C). with a volume V(U) of 1.7 mol)l nitnc acid solution (5.1) tO obtain a uranium concentration of about 1mg/mi. V(U) .0.9 m(U) in milblltres, where m(tJ) is the mass of uranium, in micrograms. Simrt the vial to facilitate the dissolution.
6.14 Stopper the vials containing the plutonium and uranium fractions and transfer them (or measurement by mass spectrometry and by alpha spectronietry.