A Combined Procedure for Determination of Plutonium Isotopes, 241 Am and 90 Sr in Environmental Samples

Transcription

1 A Combined Procedure for Determintion of Plutonium Isotopes, 41 Am nd 90 in Environmentl Smples

2 FOREWORD Since 004, the IAEA s progrmme relted to the terrestril environment hs included ctivities imed t the development nd testing of set of procedures for the determintion of rdionuclides in environmentl smples. Artificil rdionuclides produced in nucler fission nd ctivtion processes cn be nd hve been relesed to the environment during nucler explosions nd nucler ccidents. Consequently rdiochemists need procedures for nlysis of environmentl smples for those rtificil rdionuclides which re importnt from rdiologicl perspective. In this report, combined procedure bsed on the chemicl seprtion of Pu, Am nd using ion exchnge, extrction chromtogrphy nd precipittion followed by lph spectrometric nd liquid scintilltion spectrometric detection is described in detil. The method ws developed under the supervision of Josue Moreno t the IAEA s Lbortories Seibersdorf t the end of the 1990 s [1,] nd ws tested nd vlidted by the nlysis of stndrd reference mterils nd proficiency test smples in terms of repetbility, nd trueness (reltive bis) in ccordnce with ISO guidelines. Reproducibility tests were performed lter t the IAEA Terrestril Environment Lbortory, Seibersdorf, Austri. This report describes clcultion of the mssic ctivity, the uncertinty budget, the decision threshold nd the detection limit. The procedure is introduced s recommended procedure for the determintion of 39,40 Pu, 38 Pu, 41 Am nd 90 in environmentl smples such s soil, sediment, ir filter nd vegettion smples. The ctivities mentioned bove re ment to be of generl use to wide rnge of lbortories including the lbortories of the IAEA ALMERA (Anlyticl Lbortories for Mesurement of Environmentl RAdioctivity) network. It is expected tht the method for the simultneous determintion of 39,40 Pu, 38 Pu, 41 Am nd 90 in environmentl smples will be useful for routine environmentl monitoring. The IAEA wishes to thnk ll the prticipnts for their vluble contributions to develop the procedure nd review the document. The IAEA officer responsible for this publiction ws C.-K. Kim of the IAEA Environment Lbortories.

3 CONTENTS 1. INTRODUCTION SCOPE NORMATIVE REFERENCES RESPONSIBILITIES TERMS AND DEFINITIONS, SYMBOLS AND ABBREVIATIONS Terms nd definitions, symbols nd bbrevitions used in determintion of α emitting rdionuclides Terms nd definitions, symbols nd bbrevitions used in determintion of Terms nd definitions, symbols nd bbrevitions used for sttisticl evlution of the results PRINCIPLE CHEMICAL EQUIPMENT AND REAGENTS Equipment Chemicls PROCEDURE Smple decomposition Chemicl seprtion Oxidtion stte djustment Anion exchnge seprtion of Pu Plutonium source preprtion by micro co-precipittion technique Preconcentrtion of Am nd by co-precipittion Seprtion of Am by extrction chromtogrphy using TRU resin Seprtion of Am from lnthnides by ion exchnge Americium source preprtion by micro co-precipittion technique Seprtion of strontium with resin Strontium source preprtion by precipittion Counting conditions EXPRESSION OF RESULTS Clcultion of the results of lph spectrometry Clcultion of the mssic ctivity of Pu nd Am nuclides Clcultion of the chemicl recovery of α emitters Determintion of the counting efficiency of the α spectrometer Clcultion of the result of liquid scintilltion counting Clcultion of the mssic ctivity of Clcultion of the chemicl recovery of Clibrtion of the liquid scintilltion counting... 14

4 9.3. Combined uncertinty Clcultion of the combined uncertinty of the mssic ctivity of Pu nd Am nuclides Clcultion of the combined uncertinty of the mssic ctivity of Decision threshold nd detection limit METHOD VALIDATION Selectivity of the sequentil method, possible interferences Linerity, rnge of mesurement Reltive bis of the method (trueness) Repetbility (within -run precision) Chemicl recoveries Reproducibility (between-run precision) TEST REPORT CONCLUSION... 8 REFERENCES... 9 APPENDIXES... 33

5 1. INTRODUCTION Plutonium, 41 Am nd 90 re mong the most hzrdous rdionuclides produced in nucler fission nd ctivtion processes. They hve been relesed into the environment due to the ccidents of nucler power plnts nd reprocessing plnts, nucler wepon production fcilities, the fllout from nucler wepon tests nd the burn up of stellites with SNAP 9A power source. Monitoring their presence in the environment is of mjor importnce tht requires the vilbility of up-to-dte vlidted nlyticl procedures. The present pper discusses combined rdiochemicl procedure tht hs been pplied for the simultneous determintion of plutonium, 41 Am nd 90 in environmentl smples such s soil, sediment, ir filter nd vegettion smples. A gret vriety of methods hve been developed for the determintion of plutonium s well s 41 Am nd 90. Recently three review ppers bout the nlyticl methodologies for these nuclides hve been published [3-5]. Besides the individul determintion of the nuclides mny ttempts hve been mde to develop combined procedures where usully Pu nd other ctinides re seprted first followed by the removl of. These procedures hve the gret dvntge tht the usully tedious smple pre-tretment is performed only once for the determintion of the vrious nlytes. Combined procedures re of gret importnce in reveling correltions between rdionuclides, e.g., Pu, Am nd nuclides in the sme smple. Precipittion, co-precipittion, ion exchnge, solvent extrction re frequently used procedures in the conventionl rdiochemicl methods (ISO : 007 nd ISO : 009) [6-7]. Plutonium cn be retined selectively on nion exchnge resin from concentrted nitric or hydrochloric cid, but for the seprtion of Am nd the conventionl ion exchnge techniques do not hve high selectivity. From the erly 1990 s, new extrction chromtogrphic (EC) mterils becme vilble for the determintion of vrious rdionuclides. The development of the specific crown ether bsed mteril, resin ws mjor brekthrough in the nlysis of rdiostrontium replcing conventionl methods bsed on series of precipittions. Almost prllel to this, vrious trnsurnium element-specific EC mterils, i.e. the UTEVA, TRU, TEVA resins were developed by Horwitz et l. [8-1] t Argonne Ntionl Lbortory, US. These mterils hve become commercilly vilble s the registered products of EiChrom Technologies LLC. For the selective seprtion of Am, TRU resin, supported crbmoylmethyl phosphine oxide derivtive dissolved in tri-butyl phosphte hs been used successfully. EC techniques cn be dvntgeously combined into procedures for the simultneous determintion of ctinides nd rdiostrontium isotopes. Anion exchnge chromtogrphy often forms the bsic prt of combined procedure. Pu nd Th cn be directly seprted by nion exchnge resins from concentrted HNO 3 solution while nd Am together with other smple components re collected in the effluent. After pre-concentrtion e.g. with C oxlte, Am cn be seprted using TRU column nd further purified from lnthnide impurities either with n nion exchnge resin or supported liquid nion exchnger clled TEVA resin. Finlly, is seprted on Resin column. This flowchrt forms the bsis of severl procedures to determine Pu, Am nd isotopes in environmentl smples [1,13-19]. Berlioz et l. [0] combined the ction exchnge seprtion of Am with the seprtion of Pu nd using nion exchnge nd Resin chromtogrphy, respectively. Agyev et l. [1] pplied the clssicl seprtion scheme for the determintion of rdiostrontium ttched to similr combined procedure. Recently, gret vriety of combintions of pure EC procedures hve been reported tht seem to be dequte for the determintion of vrious ctinides nd. Resin is used in ll of 1

6 these procedures for the seprtion of usully with cceptbly high chemicl recoveries (>50%). Horwitz et l.[9] nd Thkkr [] recommended to use UTEVA nd TRU tndem columns for the seprtion of ctinides where U nd Th re retined on the UTEVA column while Am nd Pu re retined on the TRU column from to 3M HNO 3 solution. cn be recovered from the effluent nd cn be seprted on Resin column. This procedure hs been pplied by LRos et l. [3] nd Melldo et l. [4]. For the rpid determintion of ctinides nd rdiostrontium Mxwell et l. [5-6] recommended the use of TEVA, TRU nd Resin columns where Pu nd Th re seprted on TEVA, Am nd U on TRU nd on Resin column. All ctinides cn be seprted on single TRU column nd cn be retined nd seprted from the effluent on Resin column. This procedure ws pplied by Spry et l. [7], Olhov et l. [8]. The recommended procedure described in the present pper is bsed on the method developed by Moreno et l. [1, 13].. SCOPE This document describes method for the simultneous determintion of plutonium isotopes, 41 Am nd 90 in soil, sediment, ir filter nd vegettion smples using lph spectrometry nd liquid scintilltion counting technique following the rdiochemicl seprtion of the nlytes. The method cn be used for the routine environmentl monitoring purposes. The method cn lso be pplied for wter smples. The list of rdionuclides nd their bsic nucler properties re summrized in Appendix I. The mss of the smple required for the nlysis is typiclly up to 10 g in cse of soil, sediment nd 100 g in cse of vegettion before shing, respectively. 3. NORMATIVE REFERENCES ISO 7870, Control chrts Generl guide nd introduction ISO 7966, Acceptnce control chrts ISO 575-1, Accurcy (trueness nd precision) of mesurement methods nd results - Prt 1: Generl principles nd definitions ISO 575-, Accurcy (trueness nd precision) of mesurement methods nd results - Prt : Bsic method for the determintion of repetbility nd reproducibility of stndrd mesurement method ISO 575-4, Accurcy (trueness nd precision) of mesurement methods nd results - Prt 4: Bsic methods for the determintion of the trueness of stndrd mesurement method ISO Guide Guide to the expression of uncertinty in mesurement. ISO/IEC Guide 43-1:1997. Proficiency testing by interlbortory comprisons-prt 1.: Development nd opertion of proficiency testing schemes. QUAM: 00.P1 EURACHEM/CITAC Guide,000. Quntifying Uncertinty in Anlyticl Mesurement ISO/TS 1748, 004. Guidnce for the use of repetbility, reproducibility nd trueness estimtes in mesurement uncertinty estimtion ISO : 007 Mesurement of rdioctivity in the environment Soil Prt 5: Mesurement of Pu isotopes by α-spectrometry

7 ISO : 009. Mesurement of rdioctivity in the environment Soil Prt 5: Mesurement of strontium 90 ISO 1199, 010. Determintion of the chrcteristic limits (decision threshold, detection limit nd limits of the confidence intervl) for mesurements of ionizing rdition Fundmentls nd ppliction. 4. RESPONSIBILITIES It is the responsibility of the nlyst to follow this procedure nd to estblish pproprite sfety nd helth prctices. Complince with ntionl nd/or internl chemicl nd rdiologicl sfety rules is obligtory. Specil cre hs to be pid to hndling dngerous nd toxic chemicls, e.g. concentrted nitric, hydrochloric nd hydrofluoric cids nd rdiotoxic elements. 5. TERMS AND DEFINITIONS, SYMBOLS AND ABBREVIATIONS 5.1. Terms nd definitions, symbols nd bbrevitions used in determintion of α emitting rdionuclides α : mssic ctivity of α emitting nlyte t the reference time or smpling dte [Bq kg -1, s dry mss] A α : ctivity of the α emitting rdionuclide used for efficiency clibrtion of the α spectrometer [Bq] C T : certified concentrtion of the trcer t the reference dte used for α spectrometric nlysis [Bq g -1 ] f 1 : correction for decy of the nlyte during the time intervl between the reference time or smpling dte (t E ) to strting time of α spectrometric mesurement (t S ) f : correction for decy of the nlyte during the α spectrometric counting intervl t G f 3 : correction for decy of the trcer during the time intervl between the reference dte of the trcer (t C ) nd strting time of α spectrometric mesurement (t S ) f 4 : correction for decy of the trcer during α spectrometric counting intervl t G f t : tiling prmeter in α spectrometry f 1cl1 : correction for decy of the trcer used for efficiency clibrtion of the α spectrometer in the time intervl from its clibrtion to the beginning of the 1 st mesurement f 1cl : correction for decy of the trcer used for efficiency clibrtion of the α spectrometer in the time intervl from its clibrtion to the beginning of the nd mesurement f cl1 : correction for decy of the trcer used for efficiency clibrtion of the α spectrometer in the counting intervl of the 1 st mesurement f cl : correction for decy of the trcer used for efficiency clibrtion of the α spectrometer in the counting intervl of the nd mesurement I N1 : net count rte of the 1 st spectrometer [counts s -1 ] I N : net count rte of the nd spectrometer [counts s -1 ] m : net weight of sh used for nlysis [kg] clibrtion source to determine the efficiency of the α clibrtion source to determine the efficiency of the α 3

8 p αa : sum of lph emission probbilities of the individul lines in the ROI of the nlyte p αt : sum of lph emission probbilities of the individul lines in the ROI of the trcer q=m w /m : wet weight per sh weight rtio q I : isotopic impurity rtio of the nlyte in the trcer solution R GA : gross counting rte of the α emitting nlyte in the smple [counts s -1 ] R BA : blnk counting rte in the ROI of the α emitting nlyte [counts s -1 ] R GT : gross counting rte of the α emitting trcer in the smple [counts s -1 ] R BT : blnk counting rte in the ROI of the α emitting trcer [counts s -1 ] t E : reference time or smpling dte for the determintion of α emitting nuclides t S : strting time of α spectrometric mesurement t C : reference dte of the trcer in α spectrometric mesurement t G : cquisition time of the α spectrum of the nlyte [s] t B : cquisition time of the α spectrum of the blnk/bckground [s] V T : mss of the trcer solution used for α spectrometric nlysis [g] y: uxiliry prmeter ε: detection efficiency of the α spectrometer η: chemicl recovery of the α emitting rdionuclides 5.. Terms nd definitions, symbols nd bbrevitions used in determintion of 90 : mssic ctivity of 90 t the reference time or smpling dte [Bq kg -1, s dry mss] o, : known ctivity (from certified stndrd solution) of 90 stndrd solution t the reference dte used for efficiency clibrtion of LSC [Bq] C,sol : concentrtion of the stndrdized crrier solution [mg g -1 solution] C,nt : concentrtion of nturl in the smple [mg g -1, s dry mss] I A : gross count rte of the source in the region A (chnnels 5 to 50) in LSC, [counts min - 1 ] I B : gross count rte of the source in the region B (chnnels 50 to 1000) in LSC, [counts min -1 ] I ABg : gross count rte of blnk in the region A (chnnels 5 to 50) in LSC, [counts min -1 ] I BBg : gross count rte of blnk in the region B (chnnels 50 to 1000) in LSC, [counts min -1 ] I A,CAL : gross count rte in region A in the efficiency clibrtion process of LSC [counts min -1 ] I B,CAL : gross count rte in region B in the efficiency clibrtion process of LSC [counts min -1 ] f Y : tiling prmeter in LSC f 1 : decy correction fctor for the decy of 90 in the time intervl t 1, from the reference dte till the beginning of the mesurement f : decy correction fctor for the decy of 90 during mesurement time t, f g : grvimetric fctor of in strontium oxlte monohydrte (/C O 4 *H O) f 1,CAL : correction fctor for decy of 90 during the time intervl between the clibrtion time nd strting time of the clibrtion mesurement (t 1,CAL ) 4

9 K: uxiliry prmeter [counts min -1 ] K CAL : uxiliry prmeter in the clibrtion process of LSC [counts min -1 ] m ox+pp : mss of strontium oxlte nd filter pper [mg] m pp : mss of filter pper used for filtering strontium oxlte [mg] m sol : mss of the crrier solution dded to the smple [g] r : chemicl recovery of r,cal : grvimetric recovery fctor of in the clibrtion process t S : counting time of the smple in LSC, [min] t 1 : time intervl between the reference dte or smpling dte nd the beginning of the mesurement of 90 [min] t : mesurement time of 90 [min] t 1,CAL : time intervl between the reference dte of the 90 / 90 Y certified stndrd solution nd the beginning of the clibrtion mesurements [min] ε : counting efficiency of 90 in region A in LSC λ : decy constnt of 90 [s -1 ] λ A : decy constnt of α emitting nlyte [s -1 ] if time intervl is expressed in s λ T : decy constnt of α emitting trcer nuclide [s -1 ] if time intervl is expressed in s 5.3. Terms nd definitions, symbols nd bbrevitions used for sttisticl evlution of the results *: decision threshold [Bq kg -1, s dry mss] #: detection limit [Bq kg -1, s dry mss] C: the ssigned/reference vlue of the nlyte in the reference mteril [Bq kg -1, s dry mss] r L : repetbility limit [Bq kg -1, s dry mss] R L : reproducibility limit [Bq kg -1, s dry mss] S r : stndrd devition of repetbility [Bq kg -1, s dry mss] S R : stndrd devition of reproducibility [Bq kg -1, s dry mss] X : mesured men vlue [Bq kg -1, s dry mss] δ: reltive bis of the result [%] In the following u(x) indictes the uncertinty of quntity x. 6. PRINCIPLE A combined procedure for sequentil determintion of 90, 41 Am nd Pu rdionuclides is described. In the rdiochemicl procedure, tetrvlent Pu is retined on n nion exchnge resin column from 8M nitric cid, Th is eluted with 9M HCl nd Pu is stripped from the column s trivlent species with 0.1M NH 4 I/ 9M HCl solution. Americium nd re preconcentrted from the effluent with clcium oxlte, then Am is seprted from the mtrix components using TRU resin column, nd from lnthnides using n nion exchnge resin column, finlly is selectively seprted from the effluent by extrction chromtogrphy 5

10 using resin column. The determintion of α-emitters is performed by isotope dilution lph-spectrometry using 4 Pu or 36 Pu nd 43 Am trcers. 90 is determined by liquidscintilltion counting. According to the procedure, oxidtion stte of Pu is djusted to the tetrvlent stte by reduction using ferrous ion (generted from ferric ion with hydrzinium hydroxide) s reducing gent followed by selective oxidtion to Pu(IV) using NNO s follows: () Reduction of Pu species to Pu 3+ with Fe + Pu 4+ (q) + Fe + (q) Pu 3+ (q) +Fe 3+ (q) PuO + (q) + 3Fe + (q)+4h + Pu 3+ (q) +3Fe 3+ (q)+h O (b) Oxidtion of Pu(III) to Pu(IV) nd formtion of the nionic nitrte complex Pu 3+ (q) + HNO (q) +H + Pu 4+ (q) +NO (g) +H O The bsic equtions describing the extrction equilibri on the nion exchnge resin nd the EC mterils, i.e. TRU nd resins, re the following: () Extrction equilibrium for the seprtion of Pu using nion exchnge resin: Pu 4+ (q) + 6NO - 3(q) + RESIN-NR 3 + (NO 3 ) - (org) (RESIN-NR 3 + ) [ Pu 4+ ( NO - 3) 6 ] - (org) + (NO 3 ) - (q) where RESIN-NR 3 + (NO 3 ) - (org) represents the strong bsic nion exchnge resin in nitrte form. (b) Extrction equilibrium for the seprtion of Am using the TRU resin: Am 3+ (q)+ 3NO 3 - (q) + 3E (org) Am(NO 3 ) 3.E 3 (org) where E is the extrctnt (octylphenyl-n,n-di-isobutylcrbmoylmethylphosphine oxide (CMPO) dissolved in tributylphosphte) on n inert support in the TRU Resin. (c) Extrction equilibrium for the seprtion of using the resin: + (q)+ NO 3 - (q) + CE (org) (NO 3 ) CE (org) Where, CE is the extrctnt (bis-t-butyl-cis-dicyclohexno-18-crown-6) on n inert support in Resin. The bsic chrcteristics of the extrction chromtogrphic mterils re summrized in Appendix II. The flowchrt of the procedure is shown in Appendix III Equipment 7. CHEMICAL EQUIPMENT AND REAGENTS Alph spectrometry systems including pssivted ion implnted plnr silicon detectors (including multiplexer, ADC, spectrl storge, processing fcilities nd vcuum pump) Liquid Scintilltion Counters Gs proportionl counter Polysulfone Filter Funnels, 50 ml cpcity Polytetrfluoroethelene (PTFE) bekers (6.5 cm outer dimeter, 10 cm height with 0.3 cm wll thickness nd volume of bout 50 ml) with PTFE clips nd luminum jckets to ssist the evportion High performnce microwve digestion unit Anlyticl blnce with ccurcy of 0.1 mg 6

11 Hot plte with mgnetic stirrer Drying oven Electric muffle furnce Micropipettes LS glss vils Stndrd lbortory equipment Acid resistnt, ventilted fume hood 7.. Chemicls Trcer solution of 43 Am, useful rnge 0.05 to 1.0 Bq g -1 Trcer solutions of 4 Pu or 36 Pu, useful rnge 0.05 to 1 Bq g -1 Strontium crrier solution, useful rnge 10 to 50 mg g -1 Anion exchnge resin (AG 1-X8 or Dowex 1-X8 ( mesh)) Anion exchnge resin (AG 1-X4 ( mesh) or corresponding resin) TRU resin ( µm) resin ( µm) TEVA resin ( µm) Clcium crrier s C(NO 3 ) in 0.1M HNO 3 solution (100 mg C + ml -1 ) Iron crrier s Fe(NO 3 ) 3 in 1M HNO 3 solution (100 mg Fe 3+ ml -1 ) Hydrzinium hydroxide, N H 5 OH (100%) Sodium nitrite, NNO 1M HNO 3 M HNO 3 3M HNO 3 8M HNO M HNO 3 (65%) 9M HCl 10M HCl (3%) 0.1M NH 4 I/9M HCl freshly prepred NHSO 4 (5%) Liquid scintilltion cocktil which is gel type or is suitble for lph/bet seprtion Oxlic cid, H C O 4.H O Boric cid, H 3 BO 3 Mohr s slt (NH 4 ) Fe(II)(SO 4 ) 6H O Ethnol (80%) Nd O 3 M HF (40%) Nd crrier s Nd(NO 3 ) 3 in 1M HNO 3 solution, 5 nd 0.5 mg ml -1 of Nd 3+ NNO (5%) 7

12 Membrne filter (5 mm-dimeter, 0.1 nd 0. µm pore-size) 1M NH 4 SCN,'-bipyridine in ethnol (0.1 mg ml -1 ) 1M HNO 3-93% CH 3 OH 0.1M HCl-0.5M NH 4 SCN-80% methnol 1.5M HCl-86% methnol bromocresol green-0.1% wt/vol in ethnol The preprtion of chemicl regents is described in Appendix IV. All the chemicl regents needed to crry out this procedure must be of nlyticl grde Smple decomposition 8. PROCEDURE 1) Ash the smple t 600 o C in progrmmble electric muffle furnce. ) Determine wter content of the smple with smll smple liquots tht re dried t the desired temperture nd durtion. 3) Add 10 g of shed soil, sediment or vegettion smples to PTFE (Polytetrfluoroethelene) beker (bout 50 ml cpcity, 0.3 cm wll thickness) contining PTFE coted mgnetic stirring br. 4) Add 10 mg strontium crrier, 43 Am nd either 36 Pu or 4 Pu trcers. Typiclly, trcers of Bq ctivity re dded to low level environmentl smples. The selection of the type nd mount of plutonium trcer depends on the expected mssic ctivity of α emitting plutonium rdionuclides. 5) Cutiously dd 40 ml of 40% HF in the smple, nd then boil covered for bout hours followed by evportion with PTFE cover rised on PTFE clips to thick slurry. 6) Repet the step 5) nd digest three times the smple with 50 ml of 65% HNO 3. 7) Add 50 ml 3% HCl nd -3 g of boric cid to the wet residue nd then boil for hours. 8) Trnsfer the solution into glss beker with few milliliters of 65% HNO 3 nd evporte to ner dryness. 9) Add 50 ml of 65% HNO 3 then evporte to moist residue without bking the smple. 10) If the destruction is not complete wht is indicted by the evolution of brownish vpor t the end of the evportion, evporte gin the residue with 10 ml of 65% HNO 3. 11) Add 70 ml of 1M HNO 3 to the solution then boil for 30 minutes to dissolve s much of the smple s possible. 1) After cooling, trnsfer the solution into centrifuge tube nd then centrifuge for 10 minutes t 3000 rpm. 13) Evporte the cler superntnt solution to bout 90 ml if it is necessry. 14) Filter the solution through 0. µm pore size polypropylene membrne to remove smll mounts of insoluble mteril. Filtrtion my be postponed until lter (8... step3). 15) Wsh the filter with to 3 ml 80% ethnol nd dry it for 5 minutes t 80 o C in n oven followed by 1 hour in vcuum desicctor. 16) Mesure gross α nd β ctivity of the filter using proportionl counter. If significnt α 8

13 nd β ctivities remin on the filter, the residue is further processed s described bove (the steps 5 15). Activity my be due to U nd Th progeny tht re locked in resistnt minerls like zircon tht re extremely difficult to dissolve with minerl cids. 8.. Chemicl seprtion Oxidtion stte djustment 1) Add ml of 5% NH 3 nd 1 ml hydrzinium hydroxide drop-wise, slowly with vigorous stirring to the solution obtined from 8.1. step. 14) to llow trnsient precipittion (e.g. iron hydroxide) to re-dissolve. Thus, the oxidtion stte of Pu is djusted to Pu(III). ) Tke drop of the smple in smll weighing bot nd dd drop of 1M NH 4 SCN solution, then check the color of the solution. The reduction of Fe(III) to Fe(II) is usully controlled by thiocynte test: The purple color indictes the presence of Fe(III). Becuse the Fe(III)-SCN test is so sensitive, it is difficult to ssess the degree of Fe(III) reduction, since even very smll concentrtion of Fe(III) will give positive signl. A test to exmine the production of Fe(II) in the presence of Fe(III) is bsed on,'- bipyridine. A drop of the smple solution dded to severl drops of 0.1 mg ml -1 of,'- bipyridine in ethnol will give red-pink color if Fe(II) is present in significnt concentrtion; there is no color (or perhps very light yellow) for this regent in the presence of Fe(III). (If the smple does not contin Fe, 1 ml of the Fe crrier solution is dded). 3) If the reduction of Fe is not complete, dditionlly dd hydrzinium hydroxide s long s the thiocynte or bipyridine tests indicte the presence of significnt mount of Fe (II). Most often complete reduction of Fe(III) to Fe(II) is not ccomplished. This my be due to the presence of phosphte, which strongly complexes Fe(III) nd hinders its reduction. However, the reduction of Pu to Pu(III) will be controlled by the Fe(II)-Fe(III) couple nd Pu reduction will be obtined if significnt frction of the Fe(III) hs been reduced. 4) Cool the solution, then dd 30 ml of 65% HNO 3 to bring it to bout 4 M HNO 3. 5) Het the solution to boil for bout 0 minutes to destroy the excess of hydrzinium hydroxide nd oxidize Fe (II) to Fe (III). 6) Cool the solution to room temperture nd then dd 5 g of sodium nitrite to stbilize the tetrvlent oxidtion stte of Pu. 7) Boil gin the solution to decompose ccess HNO, then cool it 8) Add 70 ml of cold 65% HNO 3 to the solution to produce finl 00 ml solution of 7-8M HNO Anion exchnge seprtion of Pu 1) Fill the strong bsic nion exchnge resin in the chloride form (AG 1X8 or Dowex 1-X8, mesh) into glss column (1 cm inner dimeter nd 14 cm resin length) nd cover the top of resin with 1 cm lyer of corse-grin qurtz grnules. ) Wsh the column with 100 ml of M HNO 3 to convert from chloride to nitrte form, nd then condition the resin with 50 ml of 8M HNO 3. 3) Lod the smple solution obtined from 8..1 step 8) on the column under grvity flow. Just before loding the smple solution onto the column, it is recommended to filter it through fst filter pper (e.g., Whtmn #41 or equivlent) to remove geltinous silic 9

14 tht often forms slowly from soil/sediment solutions. Otherwise, the column could esily become blocked. 4) Wsh the column with 50 ml of 8M HNO 3 to rinse out the feed solution. 5) Combine the effluent nd wsh solution for the nlysis of Am nd nuclides. 6) Remove Th from the column with 100 ml of 10M HCl. 7) Strip Pu from the column with 100 ml of freshly prepred 0.1M NH 4 I-9M HCl solution. The iodide reduces Pu(IV) to Pu (III) which does not form n nionic chloride complex. 8) Neptunium nd U if present re retined by the resin column since they re not reduced by iodide to trivlent form Plutonium source preprtion by micro co-precipittion technique 1) Add 1ml of 5% NHSO 4 to the Pu strip solution nd evporte 3 to 4 times to dryness with.5 ml of 65% HNO 3 to voltilize iodine, convert the chloride to the nitrte nd oxidize Pu (III) to Pu (IV). ) Dissolve the residue in few ml of hot 1 M HNO 3, trnsfer it into plstic tube with up to 0 ml of 1M HNO 3 nd then dd 50 µg of Nd (III) to the solution. 3) Add 100 mg of Mohr s slt, (NH 4 ) Fe(II)(SO 4 ) 6H O to reduce Pu to the trivlent stte. Under these conditions some of the U is possibly reduced to the tetrvlent stte by Fe(II). By the ddition of 1 ml of 5% NNO solution Pu(III) nd ny U(IV) re probbly oxidized to Pu(IV) nd U(VI). The presence of HNO elimintes excess Fe(II) preventing possible U reduction nd upon ddition of HF co-precipittion with NdF 3. (In presence of HF, Fe(II) becomes n even stronger reductnt for U.) 4) Add 5 ml of 40% HF to the solution to form neodymium fluoride suspension tht dsorbs the tri- nd tetrvlent ctinides. 5) After minutes, filter the solution through membrne filter (dimeter 5 mm, pore size 0.1 µm). 6) Wsh twice the filter with to 3 ml of 4% HF nd once with to 3 ml of 80% ethnol, then dry it in n oven t 60 0 C for 0 to 30 minutes nd store in vcuum desicctor for 0 minutes. 7) Mount the filter on stinless-steel disc nd plce it in n α spectrometer. Plutonium sources cn lso be prepred by electrodeposition Preconcentrtion of Am nd by co-precipittion 1) Evporte the combined effluent (see 8.. step 5)) from the nion exchnge column to moist residue. ) Dissolve the residue in 150 ml of double distilled wter, then dd 10 g of oxlic cid to the solution. 3) Adjust the ph of the solution while stirring nd heting to 5.5 to 6.0 with smll portions of 5% mmoni in the presence of 1 ml of 0.1% bromocresol green indictor to precipitte clcium-mgnesium-strontium oxltes. Under these conditions in mny cses, most of the Fe remins in solution in the form of soluble oxlte complexes. If the mount of C in the smple solution is less thn pproximtely 500 mg, bout 3 to 5 ml of clcium nitrte solution contining 100 mg ml -1 C is dded. 10

15 4) Centrifuge the oxlte precipitte nd wsh three times with 5 ml double distilled wter. 5) Dissolve the precipitte in 5 to 30 ml of 65% HNO 3 nd evporte to moist residue. 6) Repet the evportion with dditionl 5 to 30 ml of 65% HNO 3 until the fuming of brown gses ceses. The mount of nitric cid needed to destroy nd dissolve the C oxlte depends on the C content in the smple solution Seprtion of Am by extrction chromtogrphy using TRU resin 1) Dissolve the residue from 8..4 step 6) in 0 to 30 ml of M HNO 3. If the residue is not dissolved in the solution, the centrifuging or the filtrtion with 0.45µm membrne filter is recommended. ) After filtering, Fe(III) content in the smple solution is checked by the thiocynte test. If the test is positive (red color), scorbic cid is dded up to 300 mg to the solution to reduce Fe(III). 3) TRU resin column (bed volume of 1.3 ml, column length 6 mm) is prepred nd conditioned with 5 ml of M HNO 3. 4) The smple solution is loded onto the column tht is wshed with 10 ml of M HNO 3 under grvity flow. 5) The combined effluent is used for the nlysis of 90. 6) Column is wshed with 4 ml of 9M HCl nd Am is stripped together with the lnthnides with 15 ml of 4M HCl solution. Any trces of Th nd U tht might be present remin on the column providing further purifiction of the Am frction Seprtion of Am from lnthnides by ion exchnge 1) Evporte three times the stripped solution to dryness with 1 ml of 65% HNO 3. to convert it to nitrte. ) Dissolve the residue in 10 ml 1M HNO 3-93% CH 3 OH. 3) Fill nion exchnge resin, e.g. AG 1x4 (mesh ) or corresponding resin in glss column (inner dimeter 10 mm, column length 10 mm). 4) Precondition the column with 100 ml 1M HNO 3-93% methnol. 5) Lod the smple solution on the column under grvity flow then wsh it with 0 ml 1M HNO 3 93% methnol to rinse out the feed solution. 6) Elute lnthnides with 80 ml 0.1M HCl-0.5M NH 4 SCN-80% methnol followed by 0 ml of 1M HNO 3-93% methnol. 7) Strip Am from the column with 70 ml 1.5M HCl-86% methnol solution Americium source preprtion by micro co-precipittion technique 1) Evporte three times the Am frction with ml of 65% HNO 3 to dryness fter dding 1 ml of 5% NHSO 4 to destroy the thiocynte ions. ) Dissolve the residue in 0 ml 1M HNO 3. 3) Prepre the mericium source in similr wy s Pu sources but Mohr s slt nd NNO re not dded (see in 8..3.). (Am sources cn lso be prepred by electrodeposition). 11

16 8..8. Seprtion of strontium with resin 1) Add 3 ml 65% HNO 3 to the combined effluent (from step 5) of the TRU resin column to djust the cidity to bout 3M HNO 3. ) Precondition resin column (inner dimeter 10 mm, column length bout 100 mm) with 100 ml of 3M HNO 3. 3) Lod the smple solution on the column under grvity flow (pproximtely 1 drop s -1 ). 4) Wsh the column with 100 ml of 3M HNO 3 to remove most of the lkline erth metl interferences. 5) Elute strontium from the column with 30 ml de-ionized wter Strontium source preprtion by precipittion 1) Add 300 mg of oxlic cid to the strip solution. ) After dding bout 3 ml 5% NH 3 (ph=9 to 10), het the solution to form strontium oxlte precipitte. 3) Cool the solution to room temperture. 4) Filter the precipitte through pre-weighed filter pper then determine the chemicl recovery of strontium by grvimetric method. 5) Plce the filter with the oxlte precipitte into liquid scintilltion vil then dd exctly 1 ml 1M HNO 3 to the vil to dissolve the precipitte. 6) Add 15 ml scintilltion cocktil to the vil nd mix it Counting conditions 1) Count α source in the α spectrometers typiclly for 1 to 5 dys. ) Count source in the liquid scintilltion counter for 0 to 1000 minutes depending on the ctul ctivity of the smple. 9. EXPRESSION OF RESULTS 9.1. Clcultion of the results of lph spectrometry Clcultion of the mssic ctivity of Pu nd Am nuclides The method used for clcultion of the mssic ctivity of lph emitting rdionuclides is described in detil in the pper of Knisch in IAEA-TECDOC-1401 [9]. The principl ide of clcultion is isotope dilution where the ctivity of the nlyte is clculted on the bsis of the known trcer ctivity (C T.V T ) dded to the smple. Gross pek res in selected regions in the lph spectr re determined by the pproprite lph softwre. The rtio of the net pek res (or count rtes) of the nlyte (R GA - R BA ) nd the trcer (R GT - R BT ) re tken to be equl to the rtio of the disintegrtion rtes. In cse of overlpping peks, tiling correcetion hs to be performed to clculte the net count rtes. Typicl α spectr of Pu nd Am sources with the pproprite region settings re shown in Fig. V. 1. nd Fig. V.. in Appendix V. The mssic ctivity of the nlyte ( α ), i.e. 39,40 Pu, 38 Pu or 41 Am t the reference time is clculted ccording to the generl formul below: α CT VT = f f m q. f f p R ( R R q αt GA BA I pαa GT RBT ) (1) 1

17 where the decy correction fctors re defined s follows: f f f f A ( t 1 = e λ 3 4 S t λ t = 1 e = e E ) A G λa t G λt ( ts tc ) λ t = 1 e T G λt t G () (3) (4) (5) In eqution (1) m is the mss of sh smple, q is the dry smple mss to sh rtio while p αa, p αt nd q I re corrections ccording to α emission probbilities in the pproprite ROIs nd the impurity of the trcer, respectively Clcultion of the chemicl recovery of α emitters The chemicl recovery cn be clculted from the trcer net count rte (R GT - R BT ) in the sme spectr if the counting efficiency (ε) is known ccording to the following eqution: RGT RBT η = ε * C * V * f T T 3 (6) Determintion of the counting efficiency of the α spectrometer In order to determine the counting efficiency of the α spectrometer, clibrtion sources of known ctivities were prepred from certified stndrd reference solutions (e.g. 4 Pu, 43 Am) by micro-coprecipittion using NdF 3, s described in nd The filtrte of the 1 st NdF 3 source ws collected nd nd NdF 3 source ws prepred from the solution by dding nd portion of the Nd solution (50 µg Nd 3+ ) nd repeting the filtrtion. Both sources were mesured in the α spectrometer nd the sum of the net count rtes ws relted to the totl ctivity of the stndrd solution to void possible filtrtion losses. The efficiency of the α spectrometer ws clculted s follows: I ε = 1 f1 cl1 fcl1 + I N f1 cl f A N cl α (7) 9.. Clcultion of the result of liquid scintilltion counting Clcultion of the mssic ctivity of 90 The determintion of the mssic ctivity of 90 is performed using the double energetic windows method. The method is described in detil by Moreno [13] nd Moreno et l. []. This method permits the 90 determintion without witing until rdiochemicl equilibrium between 90 nd 90 Y hs been reched. The first energetic window, ROI A includes the totl 90 spectrum nd the low energy region of 90 Y spectrum. The second window, ROI B includes the high energy region of the 90 Y spectrum. A typicl LSC spectrum of 90 source with the region setting is shown in Appendix V. The 90 ctivity in the source is determined 13

18 by subtrcting the contribution of 90 Y (f Y (I B - I BBg ) to the net count rte in ROI A, (I A - I ABg ). The 90 Y contribution is clculted from the net count rte of 90 Y recorded in ROI B, (I B - I BBg) nd the mesured rtio of net count rtes of 90 Y in ROI A to ROI B (f Y tiling prmeter). The mssic ctivity of 90 ( ) cn be clculted ccording to eqution (8) or to the modified eqution (9): ( I I ) f ( I I A ABg Y B BBg = f1 f m r ε q 60 where f Y K f1 f = m r ε q 60 = I I A, CAL B, CAL I I ABg BBg ( A ABg Y B BBg ) K = I I ) f ( I I ) (11) λt1 f e 1 f = (1) λ t = (13) 1 e, λt, In eqution (8) the chemicl recovery of (r ) nd the counting efficiency of 90 in ROI A hve to be determined from independent mesurements (see in 9... nd 9..3.). The tiling prmeter (f Y ) is determined by the mesurement of pure 90 Y source (see in 9..3.), f 1 nd f re decy correction fctors, for the decy of 90 in the time intervl t 1, from the reference dte till the beginning of the mesurement nd for the decy of 90 during mesurement time t,, respectively. (8) (9) (10) 9... Clcultion of the chemicl recovery of The chemicl recovery fctors of strontium in the smple experiment nd lso in the clibrtion experiment re determined by grvimetry using the formul below: r f = C g, sol ( m m ox+ pp sol + C m, nt pp ) m (14) Clibrtion of the liquid scintilltion counting Both the efficiency (ε ) nd the shpe/tiling prmeter (f y ) re obtined from n independent clibrtion experiment where strontium nd yttrium re seprted from certified stndrd solution of known ctivity. The trcer solution in 3M nitric cid solution is pssed through resin column nd wshed with 3M nitric cid. Strontium source is prepred from the strip solution s oxlte nd counted in the LSC to determine counting efficiency. Yttrium source is prepred from the combined effluent nd wsh solution of the resin column tht is evported to dryness nd tken up in 1 ml 1M HNO 3. The solution is mixed with 15 ml scintilltion cocktil nd counted immeditely to determine f y. The chemicl procedure is described in nd The following equtions re used for clcultion of the efficiency: 14

19 ( I A, CAL I ABg ) fy ( I B, CAL I BBg ) ε = f1, CAL (15) r 60 0, CAL 0, r, CAL 60, CAL K ε = f1, CAL (16) where K CAL = I I ) f ( I I ) (17) ( A, CAL ABg Y B, CAL BBg t1, CAL f = e λ 1, CAL The tiling fctor f Y is clculted ccording to eqution (10) by mesuring the seprted 90 Y source. (18) 9.3. Combined uncertinty The combined uncertinties of the mssic ctivities of the α emitting rdionuclides ( α ) nd 90 ( ) t the time of smpling cn be clculted ccording to the lw of uncertinty propgtion using the mthemticl pproch. In Appendix VI the lgorithms to clculte the combined uncertinty nd the sensitivity fctors re given. Stndrd uncertinties cn be clculted by the spredsheet method, s well [] Clcultion of the combined uncertinty of the mssic ctivity of Pu nd Am nuclides The method used to clculte the combined uncertinties of the mssic ctivities of the α emitting rdionuclides ( α ) is described in detil by Knisch in IAEA-TECDOC-1401 [9]. The combined uncertinty of the concentrtion of the α emitting nlyte (e.g. 39,40 Pu, 38 Pu nd 41 Am) on the smpling/reference dte u( α ) is clculted s follows: u + + = u C + u V α α α α ( α ) ( ) ( T ) ( ) ( T ) ( ) ( ) ( ) u( m CT VT q m + u α α α1 α α α ( ) u( pα T ) + ( ) u( pα A) + ( ) u( f1) + ( ) u( f) + ( ) u( f3) + ( ) u( f4 pα T pα A f1 f f3 f4 1 1 α α α GA BA ( ) u( RGA ) + ( ) u( RBA) + ( ) u( R ) (19) GT yt RGT RBT yt RGT RBT yt ( RGT RBT ) q + R R ) ) The individul uncertinty components cn be obtined from vrious sources, e.g. the producer specifies the uncertinty of the trcer u(c T ), uncertinties of nucler prmeters cn be obtined from relevnt tbles, e.g., u(λ), u(p α ), uncertinties of msses re determined from the properties of the blnce, uncertinties of nucler mesurements re clculted bsed on the decy sttistics (Poisson), e.g. u(r GA ) nd u(r GT ) re clculted similrly: u = R GA ( RGA ), tg u = R GT ( RGT ) (0) tg The uncertinties of the bckground counts should be determined s the stndrd devition of repeted bckground counting. 15

20 Uncertinties of the correction fctors re derived by derivtion of the pproprite equtions: u u u u f ) = f ( t t ) u( λ ) (1) ( 1 1 S E A λ λ t u( A) A G ( f) = f (1 f e ) λa ) = f ( t t ) u( λ ) (3) ( f3 3 S C T λ λ t u( T ) T G ( f4) = f4 (1 f4 e ) λt Exmples for the clcultion of the combined uncertinty of the mssic ctivity of 38 Pu in the certified stndrd reference mteril IAEA-135 is given in Tble VIII. 1. in Appendix VIII. Uncertinty of the mssic ctivity of 39,40 Pu nd 41 Am cn be clculted in similr wy. The spredsheet method ws used to clculte the uncertinty s described in the ppers of Krgten [30] nd Holmes [31] Clcultion of the combined uncertinty of the mssic ctivity of 90 () (4) The method used to clculte the combined uncertinty of the mssic ctivity of 90 ( ) is described in detil by Moreno et l. []. The combined uncertinty of the mssic ctivity on the smpling/reference dte u( α ) is clculted s follows: ( fy ) ( fy ) u ( ) = u( I ) + (, ) + ( ) + ( A u I A Bg u I B u I B, Bg ) K K K K ( I q B I B, Bg ) u( f ) + ( ) + ( ) + ( ) + Y u ε u r u m K ε r m u ( q) + t1 u( λ ) (5) Clcultion of the prtil derivtives is shown in Appendix VII. + The individul uncertinty components cn be obtined from vrious sources, e.g. the producer specifies the uncertinty of the trcer used for clibrtion, uncertinties of nucler prmeters cn be obtined from relevnt tbles (u(λ)), uncertinties of msses (m, q) re determined from the properties of the blnce, uncertinties of nucler mesurements re clculted bsed on the decy sttistics (Poisson), e.g. u(i A ) nd u(i B ) re clculted similrly: u I I A ( A) =, t u I B ( I B) = (6) t The uncertinties of the bckground counts should be determined s the stndrd devition of repeted bckground counting. Uncertinties of the tiling fctor (f Y ) nd the counting efficiency (ε ) re determined from the clibrtion experiments using the lw of uncertinty propgtion in ech cse. The uncertinty of the chemicl recovery (r ) hs to be determined from the grvimetric nd the elementl nlyticl techniques. An exmple for the clcultion of the combined uncertinty of the mssic ctivity of 90 in the certified stndrd reference mteril IAEA-135 is given in Tble VIII.. in Appendix VIII. The spredsheet method ws 16

21 used to clculte the uncertinty s described in the ppers of Krgten [30] nd Moreno [] Decision threshold nd detection limit In ccordnce with ISO 1199:010, the decision threshold, * is obtined from the following eqution : * = k1 α u(0) (7) where k 1-α = is chosen referring to probbility not greter thn 5% tht the error of the first kind (wrongly rejecting the hypothesis tht the nlyte is present) occurs. For the true vlue of the mssic ctivity of the α emitting rdionuclide =0 Bq kg -1, one usully expects R GA =R GB nd therefore u = R GB ( RGA ) (8) tg In the eqution (7), u(0) is clculted ccording to the given method of uncertinty clcultion by replcing R GA with R GB nd u(r GA ) with eqution (8) into the bsic eqution of uncertinty clcultion tht cn be either the mthemticl or the numericl/spredsheet pproch. As result of the clcultion one gets for the vlue of =0 Bq kg -1 nd the clculted uncertinty equls u(0). The decision threshold of 39,40 Pu, 41 Am nd 90 cn be clculted by this method. If 0 Bq/kg t the end of the clcultions thn R GA should not be replced simply by the blnk vlue, R GB, but modified vlue hs to be used wht expresses the rel bckground of the nlyte. This is the sitution when peks re prtilly or completely overlpping. In this cse the tiling of one pek represents the bckground for the nlyte, nd this vlue hs to replce the originl R GA vlue in clculting u(0). This is the sitution, e.g., when the mssic ctivity of 38 Pu is to be determined in the presence of 36 Pu trcer. The tiling of the ltter isotope represents n incresed bckground for the nlyte. In this cse the sum of the clculted tiling nd the bckground hs to replce the vlue of R GA in the clcultion of u(0). Uncertinty(0) is clculted for ech nlyte using the generl expression of the stndrd uncertinty. E.g., the sme spredsheet cn be used to determine the decision threshold tht is used to clculte the mssic ctivity. In ccordnce with ISO 1199:010, the detection limit, # is clculted by the following eqution: Assuming α = β then k 1-α = k 1-β = k, # = k 1 k1 β α u(0) + ( u ( ) u (0)) (9) where refers to or in cse of α emitting rdionuclides nd 90, respectively nd u() is the mesurement uncertinty of the mssic ctivity of the relevnt rdionuclide. Results of clcultions of uncertinties nd determintion of decision threshold nd detection limit re shown on the exmple of the nlysis of 38 Pu, 41 Am nd 90 in the certified stndrd reference mteril (SRM) IAEA-135 in the Tbles IX in Appendix IX. 17

22 The SRM IAEA-135 is sediment smple from the Irish se tht hs elevted ctivities of nthropogenic rdionuclides due to contmintion of vrious sources. About 1 g of the mteril is enough to perform the mesurements. Mesurement uncertinties of the high mssic ctivities of 39,40 Pu, 41 Am re 1 to 3 % nd those of lower ctivities of 38 Pu nd 90 re lso round 10%. The decision threshold for the α emitting nuclides is smll, round 0,3 to 3 Bq kg -1 due to the low bckground of the α spectrometers. The decision threshold of 90 determintion is bout n order of mgnitude higher becuse the bckground of the LSC is higher. Detection limits re bout the double of the relevnt decision threshold vlues. 10. METHOD VALIDATION The procedure ws vlidted in terms of trueness (reltive bis), repetbility, reproducibility, linerity nd chemicl recovery using seven IAEA reference mterils. Tble 1 lists IAEA reference mterils used for the vlidtion of the procedure. TABLE 1: LIST OF SAMPLES ANALYZED FOR TEST METHOD REPEATABILITY Nr. SRM Code 1 IAEA-367, Bikini corl IAEA-368, Mururo corl 3 IAEA-135, se sediment from Sellfield 4 IAEA-36, soil 5 IAEA-37, soil 6 Soil-6, soil 7 IAEA-375, soil Smples represent gret vriety of soil nd sediment mtrices nd different ctivity levels. The results were evluted in terms of reltive bis nd repetbility. Repetbility tests were performed by the stff of the IAEA s Lbortories Seibersdorf t the end of the nineties under the supervision of Josue Moreno. Results of repeted mesurements of the smples re shown in Tble 3 nd 5, chpter The mjor performnce prmeters (reltive bis, repetbility limits,) were clculted nd re shown in the Tble X. 1. in Annex X. Reproducibility tests were performed lso t the IAEA s Lbortories Seibersdorf by new stff using new instruments nd equipment. The lbortory regulrly prticipted in the Mixed Anlyte Performnce Evlution Progrm (MAPEP) orgnized by the Deprtment of Energy (DOE), US. TABLE : LIST OF SAMPLES ANALYZED FOR TEST METHOD REPRODUCIBILITY Nr. Originl Code Mtrix 1 MAPEP-05-RdF13 Air filter MAPEP-05-RdV13 Vegettion 3 MAPEP-05-MW13 Wter 18

23 4 MAPEP-05-MS13 Soil 5 MAPEP-06-RdF15 Air filter 6 MAPEP-06-RdV15 Vegettion 7 MAPEP-06-MW15 Wter 8 MAPEP-06-MS15 Soil 9 MAPEP-07-RdF17 Air filter 10 MAPEP-07-RdV17 Vegettion 11 MAPEP-07-MW17 Wter 1 MAPEP-07-MS17 Soil 13 MAPEP-08-RdF18 Air filter 14 MAPEP-08-RdV18 Vegettion 15 MAPEP-08-MW18 Wter 16 MAPEP-08-MS18 Soil 17 MAPEP-09-RdF1 Air filter 18 MAPEP-09-RdV1 Vegettion 19 MAPEP-09-MW1 Wter 0 MAPEP-09-MS1 Soil Results of reproducibility tests re shown in Tble 6-10, in chpter Selectivity of the sequentil method, possible interferences High selectivity of the method is provided by the specificity of the chemicl seprtions bsed on ion exchnge, extrction chromtogrphy nd precipittions s well s the nucler mesurement techniques. Especilly α spectrometry is known for isotope selectivity. In cse of LSC, the repeted counting of the smples cn confirm the presence of 90 bsed on the shpe of the β spectr nd the hlf-life mesurement. Possible interferences in the determintion of α emitter Pu nd Am nuclides: Pu nd Am cn contminte ech other if the seprtion fils. Pu sources my contin trces of Th or U tht cn deteriorte the source qulity. The resolution of Am sources cn be poor if smples hve high lnthnide content nd the nion exchnge seprtion is not working properly. An dditionl purifiction procedure cn eliminte these problems. Possible interferences in the determintion of 90 : Becuse chemicl seprtion is generlly not ble to seprte isotopes the presence of other rdiostrontium nuclides (e.g. tht of 89 ) in the source cnnot be eliminted, but the shpe of the β spectr gives good indiction for 89 contmintion. Trces of led nd brium isotopes my contminte the mesurement sources if the chemicl seprtion fils Linerity, rnge of mesurement The method ws tested in wide rnge of mssic ctivities of different mtrices in order to represent the suitbility of the method for vrious purposes. The mssic ctivities of 41 Am, 38 Pu, 39,40 Pu nd 90 vried in the rnges of 1 to 300 Bq kg -1, 0.1 to 50 Bq kg -1, 0.5 to 00 Bq kg -1 nd 10 to 100 Bq kg -1, respectively. Linerity of the mesurements under the 19

24 experimentl conditions ws proved by the good greement between the mesured dt nd the reference vlues. It is likely tht the linerity of the method is vlid in much broder rnge thn the one under study strting from the detection limit up to high ctivities where ded time becomes high nd ded time corrections re necessry (below 1% ded time level) Reltive bis of the method (trueness) Severl replictes were nlyzed in order to evlute the trueness. The reltive bis of the method is clculted by the following formul: X C δ ( %) = 100 (30) C Reltive bises re clculted either from the verge vlues of repeted mesurements or from individul mesurement. Reltive bises of repetbility nd reproducibility mesurements re summrized in Tble 3-4 nd Tble 6-9, respectively Repetbility (within -run precision) The repetbility limit is estimted by nlyzing the replictes of the smples of known mssic ctivities in repetbility conditions: (sme instrument, nlyst, etc.). The repetbility limit is clculted by the following formul: r L = S r.8 Acceptnce criteri: The method cn be ccepted if δ <.8 S r. Results of repetbility mesurements re summrized in Tble 4 nd 5. Results of performnce tests re summrized in Appendix X. Performnce tests for the α emitting rdionuclides were performed by the repeted mesurement of the certified SRMs IAEA-367, IAEA-368 nd IAEA-135. Becuse of the lck of enough dt on 90 mesurements were performed nd evluted using other SRMs, i.e. IAEA-375 nd Soil-6. Those smples were selected for intercomprison where the ctivities of the nlytes were high enough to meet the requirements of sttisticl evlution. According to the results shown in Tble X. 1., ll mesurements met the multiple demnds (trueness, repetbility limit) of method performnce criteri. (31) 0