Aarkrog, A.

Chen, Q.J.

Dahlgaard, H.

Mandrup, K.

Nielsen, Sven Poul

Nies, H.

Yu, Yixuan

The method was successfully used for collecting 239,240Pu from 200 litres seawater by coprecipitation with 16 g FeSO4.7H2O under reducing conditions without filtering. The plutonium is leached by concentrated HNO3 + HCl from the coprecipitate and the solid particles. The precipitate is heated at 400°C and digested in aqua regia. Na2SO3 and NaNO2 have been applied to obtain Pu+4 valence in 0.5-1 N HNO3 for different samples. Plutonium and thorium are coabsorbed on anionic resin from 8 N HNO3. The column is eluated with 8 N HNO3 containing fresh NaNO2 to keep Pu+4 valence for uranium decontamination. The system of the column is changed from 8 N HN03 to concentrated HCl with 50 ml cone. HCl containing a few milligram NaNO2. Further decontamination of thorium was achieved by eluation with concentrated HCl instead of 9 N HCl. The plutonium is successfully stripped by H2O, NaOH, 2 N HNO3 and 0.5 N HNO3 containing 0.01 M NaNO3. The chemical yield of plutonium for a 200 litres-seawater sample is 60-80%. The resolution of theelectroplated thin source is very good

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Downloaded from orbit.dtu.dk on: Dec 19, 2017Determination of plutonium in environmental samples by controlled valence in anionexchangeChen, Qing Jiang; Aarkrog, A.; Nielsen, Sven Poul; Dahlgaard, H.; Nies, H.; Yu, Yixuan; Mandrup, K.Publication date:1991Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Chen, Q. J., Aarkrog, A., Nielsen, S. P., Dahlgaard, H., Nies, H., Yu, Y., & Mandrup, K. (1991). Determination ofplutonium in environmental samples by controlled valence in anion exchange.  (Risø-M; No. 2856).•DKCM0OO4 2. D RisO-M-2856 Deteimination of Plutonium in Environmental Samples by Controlled Valence in Anion Exchange Qingjiang Chen, Asker Aarkrog, Sven P. Nielsen, Henning Dahl-gaard, H. Nies, Yixuan Yu, K. Mandrup Risø National Laboratory, Roskilde, Denmark February 1991 RISØ-M-2856 DETERMINATION OF PLUTONIUM IN ENVIRONMENTAL SAMPLES BY CONTROLLED VALENCE IN ANION EXCHANGE Qingjiang Chen*, Asker Aarkrog, Sven P. Nielsen, Henning Dahlgaard, H. Nies**, Yixuan Yu*, K. Mandrup •Institute of Atomic Energy, Beijing, China ** Deutsches Hydrographisenes Institut, Hamburg, Germany Abstract. The method was successfully used for collecting 239»240Pu from 200 litres seawater by coprecipitation with 16 g FeS04.7H20 under reducing conditions without filtering. The plutonium is leached by concentrated HN03 + HCl from the coprecipitate and the solid particles. The precipitate is heated at 400*C and digested in aqua regia. Na2S03 and NaN02 have been applied to obtain Pu** valence in 0.5-1 N HN03 for different samples. Plutonium and thorium are coabsorbed on anionic resin from 8 N HNOj. The column is eluated with 8 N HN03 containing fresh NaN02 to keep Pu** valence for uranium decontamination. The system of the column is changed from 8 N HN03 to concentrated HCl with 50 ml cone. HCl containing a few milligram NaN02. Further decontamination of thorium was achieved by eluation with concentrated HCl instead of 9 N HCl. The plutonium is successfully stripped by H20, NaOH, 2 N HN03 and 0.5 N HN03 containing 0.01 M NaN03. The chemical yield of plutonium for a 200 litres-seawater sample is 60-80%. The resolution of the electroplated thin source is very good. February 1991 Risø National Laboratory; DK-4000 Roskilde, Denmark ISBN 87-550-1620-0 ISSN 0418-6435 Grafisk Service, Risø 1991 3/v TABLE OF CONTENTS 1. INTRODUCTION 5 2. FLOW SHEET OF THE PROCEDURE FOR 200 LITRES SEAWATER... 5 3. RESULTS AND DISCUSSION 7 4. CONCLUSION 14 APPENDIX 1 15 REFERENCES 17 5 1. INTRODUCTION Previous works1*2 have demonstrated that an anion exchange separation of plutonium could be used for routine analysis of environmental samples. The procedures based on the absorption of anionic complexes of plutonium froi: nitric and hydrochloric acid media have been reviewed1. The Pu(NO,)fZ and PuCl^are absorbed on the anionic exchange. However, the plutonium valence (Pu*3-4S<) is variable. The Pu*3 is easily oxidized to Pu**with NaNOz and H202 while Pu*5'* are reduced to Pu*4 with NaNOj, but the reaction is slow and incomplete. Especially for large volumes seawater samples with organic material and impurities, we found that it was very difficult to control the plutonium valence with NaN02 and H202. The chemical yield of plutonium was low too. He further observed a thorium contamination in case of large volume seawater eluted by 9 N HC1. Hence it was important to develop a new method to control the plutonium valence and improve the thorium decontamination for large volume seawater and environmental samples. 2. FLOW SHEET OF THE PROCEDURE FOR 200 LITRES SEAWATER On board the ship: 1 1) Acidify 200 litres seawater to pH about 2 with 200 ml concentrated HC1. 2) Add 16 g FeS0».7 H20, 2*2Pu and 200 g Na2S205. Stir by air bubbling for 1 h to reduce all Pu valences to Pu*3. 3) Basify the 200 litres seawater to pH * 8.5-9 with diluted NaOH (0.5-1 N) to precipitate Fe(OH)2. The diluted NaOH is added with a shower to reduce formation of Ca(0H)2 and Mg(OH)2. 4) Let stay for 5 h or overnight. Siphon off the super-natant liquid to get about 5 litres of Fe(OH)2 slurry. 5) Acidify the solution to about 0.1 N HC1 with con-centrated HC1 (10 ml HCl/litre). 6) Transfer the sample to laboratory for analysis. 6 In the laboratory: 2. 1) Add Na2S203 (2 g/litre) to the sample solution. Let stay for 1 h. 2) Slowly add diluted NaOH with a small shower to pH = 8.5 to prevent formation of Mg(OH)2 and Ca(OH)2. Let stay for 30 Bin. 3) Siphon off the supernatant liquid. Filter the precipitate with glass filter paper AG/A. Discard the solution. 4) Dissolve the Fe(OH)2 with 100 ml cone. HC1 and 100 •! cone. HN03. 5) Filter the solution through glass filter paper AG/A into a 500 ml beaker. Evaporate to complete dryness. 3. 1) Heat at 400*C for 1 h. Let stay for cooling. Add 120 ml aqua regia to dissolve. Cover the be*»ker with a glass disc, heat for 1 h. 2) Evaporate to dryness. Repeat step 1). Filter the solution. Wash the precipitate with 100 ml 8 N HN03. Discard the precipitate. 3) Evaporate to about 7 lal. Dilute to 150 ml. The acid is about 0.5-1 N HN03. 4) Add 3 g Na2S03. Let stay for 20 min. The plutonium is reduced to Pu*3. 5) Add 3 g NaN02. Let stay for 10 min. The Pu*3 is oxidized to Pu*\ 6) Acidify the solution to 8 N HN03 with 165 ml concentrated HN03 4. 1) Add the solution to a column (10 x 2.1 cm AG 1-X4, 100-200 mesh) which is equilibrated with 50 ml 8 N HNO, + 1 g K2S2Oa and 100 ml 8 N HNO, + 0.5 g NaN02 (fresh). The flow rate is about 3 ml/min. 2) Hash the column with 350 ml 8 N HN03 (10c.v) + 1 g NaN02 (fresh). 3) Hash with 50 ml concentrated HC1 which is saturated with 100 mg NaN02 (fresh). 4) Hash with 300 nl concentrated HC1. 7 5. 1) Strip with: 30 ml H20, 20 ml 0.3 NaOH, 30 ml H2Of 20 ml 2 N HNO,. 200 ml 0.5 N HNO, containing 0.01 M NaNO,. Evaporate to dryness. 2) Dissolve the precipitate with 10 ml 0.7 N HNO,. Add 300 mg Na2SO,. Stir and let stay for 15 min. Add 300 mg NaNO,. Let stay for 10 min. Add 12 ml cone. HNO,. 3) Make a column (7 x 0.8 cm) Ag 1-X4 100-200 mesh. Eluate the column with 20 ml 8 N HNO, containing 3 mg/ml NaNO, (fresh). 4) The solution is passed through the column. The flow rate is about 1 ml/min. 5) Hash the column with 20 ml 8 N HNO, containing 3 mg/ml NaN02. 6) Strip with: 4 ml H20, 4 ml 0.3 N NaOH, 4 ml H20, 4 ml 2 N HNO,, 20 ml 0.5 N HNO, containing 0.3 M NaNO,. 7) Add 0.3 ml cone. H2SO*. Evaporate to dryness. 6. 1) Dissolve the precipitate with 0.5 N H2SO«. Wash the beaker with 9 ml 0.5 N H2S04. Combine these solutions into the electrodeposition cell. 2) Adjust the solution to pH » 2.2 for electrodeposition. 3) The current is 0.6 A/cm2. The time is 6 h. Cool the cell with water. 4) Cover the surface of the source with VYNS thin film (10-15 Mg/cm2). 3. RESULTS AND DISCUSSION Seawater samples as large as 200 litres are collected with Fe(0H)2 coprecipitate at pH * 8.5-9 in a reducing system. The Fe(0H)2 is dissolved in cone. HC1 and cone. HN03. The plutonium is dissolved and leached from possible plankton and solid particles present in the solution. The diluted NaOH (0.5-1 N) is added with a shower to reduce the formation of Ca(0H)2 and Mg(OH)2. This is of benefit for the plutonium purification. The sample is heated to 400'C for one hour and digested with aqua 8 regia to destroy the organic material, which say interfere when controlling the valency of plutonium. By the heating, decontamination for polonium is furthermore obained. Na^o, - NaNO, NazSO] and NaNO, are applied in preparation of Pu*4. The plutonium valences (Pu**'5-') are reduced to Pu*3 by Na^O, and then, the Pu*3 is oxidized to Pu*4 by NaNO, in 0.5-1 N HN03. Both reactions are fast and nearly quantitative. A high proportion of Pu*4 is obtained. Table 1 shows the chemical yield of plutonium using redox-systems of NaN0z-NaN02 and Na2S03-NaN02 respectively. Table 1. Comparing the chemical yield of plutonium by redox-systems of NaNOz-NaN02 and Na^SOz-naV02 respectively. No. Seawater Reducing Oxidizing Chemical yield litres agent agent 242Pu, % 165 50 NaN02 NaN02 24.0 197 200 Na2S03 NaN02 88.6 198 200 Na2S0, NaN02 83.6 When NaN02 and H202 are applied in preparation of Pu*4, the Pu*3 is rapidly oxidized by NaN02 and H2Oz; but the Pu*3,6 are rather slowly reduced to Pu*4 by NaN02 and H202. When the H202 is used to prepare Pu*4, the decontamination for uranium is furthermore inefficient. This is shown in Table 2. Table 2. Comparing uranium decontamination in seawater using H202 and NaN02 respectively. No. Seawater Agent 23eU (Bq/m3) "4U (Bg/m3) litres 165 40 5 ml 30% H202 8 . 1 9 . 3 168 50 2 g NaN02 0 . 0 5 9 0 . 6 3 9 The anion exchange column is equilibrated with 8 N HNO, containing K^O, and 8 M HNO, containing fresh NaHO, to clean for any impurity in the anion ion exchange in order to prevent any interference. During washing of the coluwi with 8 N HHO, for uranium decontamination, the ehemu yield of plutonium is often lost by a change of plutonium valency. In order to keep Pu**, the eluate of 8 N HNO, containing fresh NaNQz is used. When the system is changed from HNO, to HCl, the plutonium valence is changed by oxidation of the mixture of HNO, + HCl. Therefore, 50 ml cone. HCl containing a few milligram NaNOz is used as eluate to prevent the change of the plutonium valence. In Table 3 the chemical yields of plutonium samples are compared when the system is changed to HCl with and without the addition of NaN02. Table 3. Comparing the chemical yield of plutonium by changing the system using 50 ml cone. HCl + few milligram NaN02 and 50 ml cone. HCl only. No. Volume Chemical yield litres Agent 2*2Pu, % 197 200 50 ml cone. HCl 88.6 a few milligram NaN02 198 200 " 83.6 200 200 50 nl cone. HCl 57.5 Stripping plutgnimn He think there are two problems in the plutonium stripping with low acid concentration, i.e. micro-absorption of plutonium and low chemical yield of plutonium. In this work, the plutonium is successfully stripped with Hz0, NaOH, 2 N HNO, and 0.5 N HNO, containing 0.03 M NaNO,. When Pu is stripped with NaOH, the plutonium is hydrolyzed to Pu(OH). leaving the anion exchange resin. Then the Pu(OH), is dissolved in 2 N HNO, and further stripped with 0.5 N HNO, containing 0.03 M NaNO, as a scavenger to prevent the micro plutonium absorption. Table 4 shows the stripping efficiency between 500 ml 0.5 N HNO, + 0.03 M NaNO, (low acid concentration) and H20, NaOH, 2 N HNO,, 200 ml 0.5 N KNO, + 0.03 M NaNO,. Table 4. The chemical yield of plutonium at the different stripping condition between 300 ml 0.5 N HNO, + 0.03 M NaNO, (low acid concentration) and H20, NaOH, 2 N HNO,, 200 ml 0.5 N HNO, + 0.03 M NaNO,. No. Seawater Stripping Chemical yield litres condition 2*2Pu, % 175 50 300 ml 0.5 N HNO, + 46.9 0.03 M NaNO, 176 200 300 ml 0.5 N UNO, + 45.0 0.03 M NaNO, 203 200 H20, NaOH, 2 N HNO,, 79.5 200 ml 0.5 N HNO, + 0.03 M NaNO, Before electrodeposition the sample is heated at 400*C and dissolved in aqua regia for destroying the organic material to get a thin source and for polonium decontamination. Table 5 and 6 show a comparison of the results obtained by the previous used method and the present one, and Figs. 1 and 2 show sample spectra from the two tables. 11 Table 5. Plutonium analyses of seawater samples from the North Sea using the old radiochemical procedure, (nd * not detected). Sample no. Volume ^Pu-yield 22*Tn (•') (%) 0»Bq) *"Pu (mBq m') »•pu (mBq •"') 870075 870076 870077 870078 870079 870080 870081 870082 870083 0.2 0.2 0.2 0.2 0.2 1.0 1.8 1.8 1.8 7.6 12.6 9.4 7.6 7.3 41.4 3.7 24.8 7.2 nd 20±43% nd 15+33% 76±15% 228± 9% nd nd 149115% 17.1±19% 13.0116% 16.4±19% 7.5130% nd 12.51 7% 12.0122% 15.01 7% 15.3113% nd nd nd nd nd 0.5125% nd 0.7116% nd Table 6. Plutonium analyses of seawater samples from the Danish Waters (Hessel«) using the new radiochemical procedure. Sample Volume 242Pu-Yield ""Th no. (m3) (%) (*iBq) 2W. M*Pu "*Pu (mBq m3) (mBq m3) 890197 890198 890201 890202 890203 890205 0.2 0.2 0.2 0.2 0.2 0.2 88.6 83.6 72.5 76.1 81.9 72.2 nd nd nd ---7.41 8% 7.21 8% 9.01 8% ---0.7135% 1.7117% 2.0117% ---1 •> TYPE - - ! MCA • 01 SEMSKT # 01 SEQUENCE # REALTIME - 5 K 7 0 5 . 0 0 SEC0N3S. LIVETINS -D t U COiXECTES AT 09: » OK 13-MAS-83 SMOG. OOF • 38269900 SECONDS 1000.00I 100.00* O o o T"t X en b-z D O u c ^ io.oor E » i i.oo|-k r o.ici-c * I 1 0.011 242 Pu r 239,240 Pu Bf IBW!1 )tt JJ I ri V Li ni n i i 128 256 363 511 C H A N N E L NUM3ER : p - SEAKATER. POLARSTE*;. '.4-MH-B7. SAMPLE 87-614. 1000 LITRES • " >-<-• DETECTOR 4? COUNTING NO. 87008C Fig. 1. Sample spectrum (no. 870080) showing thorium contaaination (2MTh and daughters). 13 TYPE - - 1 MCA # 01 SEGMENT * 01 SEQUENCE # 0 REALTIME - 580186 .00 SECONDS. LIVETIME - 5B01B6.00 SECONDS DATA COLLECTED AT 08. 21: ON 05-FEB-9C 10000.OOF 1000.00 100 00 O O O io.oof X en i -z D O u l.oor o.ior o.oi L 242 Pu 2 3 9 , 2 4 0 Pu h \iÉi\dåÉ\k\åh} u 111! i LiA. H 17729.™ 126 256 363 CHANNEL NUMBER Q A M P ! P ' SEAWATER. HESSELOE. AUGUST 1969. 200 LITRES O H I IF L L . DETECTOR 33. COUNTING NO. 890198 511 Fig. 2. Sample spectrum (No. 890198) showing no thorium contamination. 14 4. CONCLUSION 1. Na2S03 and NaN02 are successfully applied to prepare Pu+4. 2. The plutonium is stripped fiorc anion ion exchange by H20, NaOH, 2 N HN03 and 0.5 N HN03 + 0.01 M NaN03. 3. With the new procedure we have obtained high decontamination factors for uranium and thorium, high chemical yields (60-80%) for plutonium and high alpha energy resolutions. 15 APPENDIX 1 Purification of Plutonium from disc 1. Put the disc in a 50 ml beaker. Add about 0.5 ml 8 M HN03. Let stand for 1 hour to dissolve. Wash the disc with cone. HC1 several times. 2. Wash the disc with 1 *. HN03 until clean. Discard the disc. 3. Add 1 nil 1 H NaN03. Evaporate to dryness. Add 3 ml cone. HN03 and 3 ml HC1. Heat to dryness. 4. Dissolve with 10 ml 0.7 N HN03. Heat for a few min. 5. Add 300 mg Na2S03. Stir to dissolve. Let stand for 15 min. The plutonium is reduced to Pu+3 valence. (30 mg/ml Na2S03). 6. Add 3C0 mg NaN02 (30 mg/ml). Stir to uniformity. The plutonium is oxidized to Pu+*. Let stand for 10 min. 7. Add 12 ml cone. HNO, to get about 8 N HN03. 8. Make a column (7x0.8 cm) AG 1-X* 100-200 mesh. Eluate the column with 20 ml 8 N HN03 containing 3 mg/ml NaN03 (fresh). 9. Add solution to column (0.5 ml/min). 10. Wash the column with 20 ml 8 N HN03 containing 3 mg/ml NaN02. 11. Strip with 4 ml H20, 4 ml 0.3 N NaOH, 4 ml H20, 4 ml 2 N HN03 and 20 ml 0.5 N HN03 + 0.01 M NaN03. 12. Add 0.3 ml cone. H2S04. Evaporate to dryness. Add 3 ml cone. HN03 and 3 ml cone. HC1. Evaporate to dryness. 13. Dissolve with 5 ml 0.5 N H2S0*. Wash the beaker three times with 0.5 N H2S04. Each time with 3 ml (transfer to electrodeposition cell). Adjust the pH = 2.2 for electrode-position. 14. The current is 0.6 A/cm2. The time is 6 h. Cool the cell with water. 15. Cover the surface of source with VYNS thin film (10-15 pg/cm2) 16 The results of the purification are shown in table 7. Table 7. After purification, the plutonium chemical yield. 2*2T Sample Volume ""Pu-Yield ""rh no . (m3) (%) (/xBq) 2 3 9Pu (mBq m"3) 2 3 ePu (mBq m"3) 890197 890198 890200 8900K1 890k2 0.2 0.2 0.2 0.2 0.2 64.5 65.0 53.9 58.5 66.5 nd 21+37% 19+32% nd 17±43% 7.0±10% 7.3+8.9% 7.2+9.6% 6.4±12.1% 8.1±8.8% 0.88±48% 1.4±23% 0.8±38% nd 0.7±36% nd = not detected 17 References 1. G.H. Coleman. "Radiochemistry of plutonium" National Academy of Sciences, Nuclear Science Series. NAS-NS (1965). 2. N.A. Talvitie, Radiochemical Determination of Plutonium in Environmental and Biological Samples by Ion Exchange. Analytical Chemistry. Vol. 43, No. 13 November 1971. Riso National Laboratory RisO - M - 2856 Titlt and author(s) DETERMINATION OF PLUTONIUM IN ENVIRON-MENTAL SAMPLES BY CONTROLLED VALENCE IN ANION EXCHANGE Qingjiang Chen*, Asker Aaarkrog, Sven P. Nielsen, Henning Dahlgaard, H.Nies**, Yixuan Yu*, K. Mandrup * Institute of Atomic Energy, Beijing, China ** Deutsches Hydrographisches Institut, Hamburg, Germany Date February 1991 Department or group Section of Ecology Groups own resist ration number (a) Project/contract no. Pag«* 17 Tables Illustration* References ISBN 87-550-1620-0 Abstract (Max. 2000 char.) Abstract. The method was successfully used for collecting 239.240^  from 200 litres seawater by coprecipitation with 16 g FeSO4.7H20 under reducing conditions without filtering. The plutonium is leached by concentrated HN03 + HCl from the coprecipitate and the solid particles. The precipitate is heated at 400*C and digested in aqua regia. Na2S03 and NaN02 have been applied to obtain Pu** valence in 0.5-1 N HN03 for different samples. Plutonium and thorium are coabsorbed on anionic resin from 8 N HNOj. The column is eluated with 8 N HN03 containing fresh NaN02 to keep Pu*4 valence for uranium decontamination. The system of the column is changed from 8 N HN03 to concentrated HCl with 50 ml cone. HCl containing a few milligram NaN02. Further decontamination of thorium was achieved by eluation with concentrated KC1 insteed of 9 N HCl. The plutonium is successfully stripped by H20, NaOH, 2 N HN03 and 0.5 N HN03 containing 0.01 M NaN03. The chemical yield of plutonium for a 200 litres-seawater sample is 60-80%. The resolution of the Descriptors - I N I S ANIONS; CHEMICAL REACTION YIELD; COPRECIPITATION; DECONTAMINATION; HYDROCHLORIC ACID; ION EXCHANGE; IRON SULFATES; LEACHING; NITRIC ACID; PLUTONIUM 239; PLUTONIUM 240; PLUTONIUM IONS; SAMPLING; SEAWATER; SODIUM HYDROXIDES; SODIUM NITRATES; SODIUM SULFATES; THORIUM, URANIUM; VALENCE Available on request from Rise Library, Rise National Laboratory, (Rit* Bibliotek, Forskningscenter Riso), P.O. Boa 4«, DK-4000 Roskilde, Denmark. Telephone + 45 42 371212. ext. 2268/2260. Tele«: 43116, Telefax: +46467S6627 AMfSOOOOOMS Available on exchange from: Risø Library Risø National Laboratory, P.O. Box 49, DK-4000 Roskilde, Denmark Phone +45 42 37 12 12, ext. 2268/2269 ISBN 87-550-1620-0 Telex 43116, Telefax + 45 46 75 56 27 ISSN 0418-6435 

Determination of plutonium in environmental samples by controlled valence in anion exchange

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Determination of plutonium in environmental samples by controlled valence in anion exchange

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