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Journal ArticleDOI

A comparative study using liquid scintillation counting to determine 63Ni in low and intermediate level radioactive waste

01 Apr 2016-Journal of Radioanalytical and Nuclear Chemistry (Springer Netherlands)-Vol. 308, Iss: 1, pp 261-270

AbstractA comparative study using liquid scintillation counting was performed to measure 63Ni in low and intermediate level radioactive waste. Three dimethylglyoxime (DMG)-based radiochemical procedures (solvent extraction, precipitation, extraction chromatography) were investigated, the solvent extraction method being considered as the reference method. Theoretical speciation calculations enabled to better understand the chemical reactions involved in the three protocols and to optimize them. In comparison to the method based on DMG precipitation, the method based on extraction chromatography allowed to achieve the best results in one single step in term of recovery yield and accuracy for various samples.

Summary (3 min read)

Introduction

  • In France, the National Radioactive Waste Management Agency is in charge of the long-term management of all radioactive waste.
  • Several repository sites have been built in order to accommodate nuclear waste packages.
  • Elimination of the interfering elements is mainly achieved with ammonium citrate during the rinsing step.

Reagents and equipments

  • All chemicals (nitric acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, ammonium hydroxide, hydrogen peroxide, citrate ammonium, sodium citrate, tartaric acid, 2-nitroso-1-naphthol, dimethylglyoxime) were of analytical grade.
  • Ultra-pure water (resistivity 18.2 M cm) was obtained from a Milli-Q purification system (Millipore, France).
  • Anion-exchange resin AG1-X4 (50-100 mesh) was supplied by Bio-Rad Laboratories .
  • All measurements of gamma emitting radionuclides were completed using a high purity germanium detector (Canberra, ) which was calibrated with a multi gamma standard (9ML01ELME20) supplied by CERCA LEA .
  • The uncertainties of the 63 Ni activities concentrations were calculated according to the standard NF M60-317 [21] by combining the uncertainties associated with the quantities of digested samples, the standards, the recovery yields and the LSC measurements.

Sample preparation and digestion

  • The different radioactive samples were collected in several French nuclear facilities and laboratories.
  • They consisted of the following types of materials: evaporate concentrates, steels, muds embedded in concretes, effluents, ion exchange resins embedded or not in polymers and graphites (denoted from S1 to S8 in this work).
  • All samples were digested using a microwave acid digestion system (Speed Wave, Berghof, Germany), except graphites.
  • The resulting solutions were transferred to 100 mL volumetric flasks and diluted with ultra-pure water.
  • As examples, the chemical and radiochemical compositions of two studied samples (S1 and S2) are detailed in Table 1 .

Method 1 based on the organic extraction of the Ni(DMG) 2 complex

  • Aliquots of the digested samples were first weighed in a beaker.
  • As the reaction between Co and 2-nitroso-1-naphthol proceeds rather slowly [34] , the solutions were allowed to stand for about 30 min.
  • 3x10 mL of chloroform were then added to extract the Co-nitrosonaphtol complex in the organic phases whereas Ni remained in the aqueous phases.

Method 2 based on the precipitation of the Ni(DMG) 2 complex

  • As the total activity concentrations of the other radionuclides are not 10 times higher in comparison to 63 Ni in the studied samples, only one precipitation step was implemented from the specifications of this standard [21] .
  • Aliquots of the digested samples were first weighed in a beaker.
  • The precipitates were collected by filtration and washed with water.
  • Afterwards, the solutions were evaporated near to dryness (otherwise insoluble black residues were obtained as indicated in Ref. [26] ).
  • DMG was then decomposed with hydrogen peroxide.

Method 3 based on the precipitation of the Ni(DMG) 2 complex on Ni resin

  • Eichrom Technologies recommend to eliminate Given the Fe compositions of the studied samples, an additional purification step was introduced only for the steel sample.
  • From the works of Hou et al. and Rajkovich et al. [6, 23] , it was decided to implement a separation on the anion exchange AG1-X4 resin before the purification step on the Ni resin.
  • The AG1-X4 resin has indeed a higher loading capacity towards Fe (around 15 mg/g resin) in comparison to TRU resin (5 mg/g resin).
  • The resulting solutions were then evaporated to dryness and the residues were treated as described above in the protocol dedicated to the Ni columns.

Speciation studies

  • A previous work of their group demonstrated the importance of speciation studies in order to achieve a better understanding of the behaviours of the analytes during the different separation steps and to optimize the radiochemical procedures [25] .
  • This approach was also investigated by Rosskopfova et al.
  • Ni which was not complexed by 2-nitroso-1-naphthol remained in the aqueous phase.
  • From the speciation studies, it can be inferred that the behaviours of Ni, Co and Fe strongly depend on the considered purification methods.

Applications of the three DMG-based radiochemical methods to real nuclear waste samples

  • From the literature, it is not obvious to choose the best selective radiochemical procedure based on DMG (solvent extraction, precipitation and extraction chromatography) and to determine if a single separation step can be implemented for nuclear waste samples.
  • To answer this question, the three radiochemical methods based on the use of DMG complexing agent were applied to different types of radioactive waste samples (evaporate concentrates, steels, muds embedded in concretes, effluents, ion exchange resins embedded or not in polymers and graphites).
  • The Ni recovery yields were satisfactory whatever the analysed samples and the radiochemical methods.

Where

  • For method 2 based on DMG precipitation, the E n values were higher than 1 for the majority of the studied samples (up to 17), which indicated that the performances of method 2 were unsatisfactory.
  • The E n value related to the S2 steel was prescribes that one DMG-based precipitation step should be sufficient when the total activity concentrations of the other radionuclides are not 10 times higher in comparison in comparison to 63 Ni [21] , which is not in agreement with their experimental results.
  • This standard published in 2001 [21] might be no more adapted to the nuclear waste produced in the past decade from decommissioning operations of various radioactive facilities.
  • For method 3 based on Ni column, the E n values were lower than 1 whatever the studied samples, which demonstrated that the performances of method 3 were satisfactory.
  • To check this assumption, the S3 sample (corresponding to muds embedded in concrete) was analysed with and without performing the AG1-X4 separation before the purification of the Ni column.

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Journal of Radioanalytical and Nuclear Chemistry
1
A comparative study using liquid scintillation counting 1
to determine
63
Ni in low and intermediate level 2
radioactive waste 3
Names of the authors: Céline Gautier
1
, Christèle Colin
1
, Cécile Garcia
1♯
4
Title: A comparative study using liquid scintillation counting to determine
63
Ni in low 5
and intermediate level radioactive waste 6
Affiliation(s) and address(es) of the author(s):
1
Operator Support Analyses Laboratory, 7
Atomic Energy Commission, CEA Saclay, DEN/DANS/DPC/SEARS/LASE, Building 8
459, PC 171, 91191 Gif-sur-Yvette Cedex, FRANCE 9
on leave for
AREVA, Demantelement et Services/MSIS Assistance, 91196 Gif-sur-10
Yvette Cedex, FRANCE
11
E-mail address of the corresponding author: celine.gautier@cea.fr 12
13

Journal of Radioanalytical and Nuclear Chemistry
2
A comparative study using liquid scintillation counting 14
to determine
63
Ni in low and intermediate level 15
radioactive waste 16
Céline Gautier
1
, Christèle Colin
1
, Cécile Garcia
1♯
17
1
Operator Support Analyses Laboratory, Atomic Energy Commission, CEA Saclay, 18
DEN/DANS/DPC/SEARS/LASE, Building 459, PC 171, 91191 Gif-sur-Yvette Cedex, 19
FRANCE 20
On
leave for AREVA, Demantelement et Services/MSIS Assistance, 91196 Gif-sur-Yvette 21
Cedex, FRANCE 22
Abstract 23
A comparative study using liquid scintillation counting was performed to measure
63
Ni in 24
low and intermediate level radioactive waste. Three dimethylglyoxime (DMG)-based 25
radiochemical procedures (solvent extraction, precipitation, extraction chromatography) 26
were investigated, the solvent extraction method being considered as the reference 27
method. Theoretical speciation calculations enabled to better understand the chemical 28
reactions involved in the three protocols and to optimize them. In comparison to the 29
method based on DMG precipitation, the method based on extraction chromatography 30
allowed to achieve the best results in one single step in term of recovery yield and 31
accuracy for various samples. 32
Keywords 33
63
Ni, radiochemical analysis, liquid scintillation counting, decommissioning, radioactive 34
waste, dimethylglyoxime 35

Journal of Radioanalytical and Nuclear Chemistry
3
Introduction 36
In France, the National Radioactive Waste Management Agency (ANDRA) is in 37
charge of the long-term management of all radioactive waste. Several repository sites 38
have been built in order to accommodate nuclear waste packages. One is dedicated to the 39
Low and Intermediate Level short-lived Waste. The specifications for 143 radionuclides 40
have been defined by ANDRA which guarantees the safety of the facility [1]. Among this 41
long list,
63
Ni has to be declared as soon as its activity concentration is over 1 Bq g
-1
and 42
its maximum acceptance limit has been fixed to 3 x 10
6
Bq g
-1
[1].
63
Ni is produced by 43
neutron activation reactions of stable Ni and Cu which are components of various 44
materials used in the nuclear fuel cycle [2]. Consequently,
63
Ni can be present in many 45
radioactive materials and waste samples [2-17], such as graphites [6, 7], metals 46
(aluminium, lead, steel) [6-11], concretes [6, 7, 10, 12], ion-exchange resins and 47
charcoals [13], effluents [8, 14-17], sludges [14] and environmental samples [10, 18]. 48
63
Ni is a long-lived radionuclide with a half-life of 98.70 years (±24) [19]. It is a pure 49
beta emitter with a maximum energy of 66.98 keV [19]. As liquid scintillation counting 50
(LSC) has a high counting efficiency for
63
Ni (around 70 %) [2], this detection technique 51
is widely used for
63
Ni determination [2-17]. As a pure beta emitting radionuclide,
63
Ni 52
must be isolated from the matrix and the interfering radionuclides (especially
60
Co a 53
major radionuclide which has a similar chemical behavior) through chemical separations 54
prior to any analysis by LSC [2-17]. Consequently, a selective radiochemical method is 55
needed to measure
63
Ni in low and intermediate level radioactive waste [2-18]. Most 56
procedures of
63
Ni purification rely on the complexing agent of dimethylglyoxime 57
(DMG) implemented in three different types of methods: solvent extraction, precipitation 58
and extraction chromatography [2-18]. In all cases, the Ni(DMG)
2
complex is favourably 59
formed at basic pH, around 8-9 [2-18]. The recovery yield of the overall radiochemical 60
procedure is generally determined from the measurement of stable Ni by atomic 61
absorption spectroscopy (AAS) [12] or inductively coupled plasma - atomic emission 62
spectroscopy (ICP-AES) [5, 13, 15, 17]. 63

Journal of Radioanalytical and Nuclear Chemistry
4
Two or three decades ago, the reference radiochemical method to analyse
63
Ni was 64
based on a liquid-liquid extraction procedure. The Ni(DMG)
2
complex is first extracted 65
in an organic solvent [20], commonly chloroform [8, 10, 11, 18, 20] which has a higher 66
Ni extraction capacity [20]. Ni is then back-extracted in aqueous solution, mostly with 67
hydrochloric acid [11, 16, 18]. In France, this extraction method has been standardized in 68
the standard NF M60-317 to determine
63
Ni in radioactive effluents and waste [21]. Ni 69
amount is generally less than 1 mg [8, 18, 20] whereas the DMG amount varies from 10 70
mg [20] to 250 mg [8]. By replicating several extractions, this type of separation 71
procedure enabled to achieve satisfactory decontamination factors of Co towards Ni (less 72
than 0.2% of Co was extracted) [8]. In spite of its efficiency, the implementation of this 73
solvent extraction procedure has tended to decrease in the last decades because of the 74
restrictions of chloroform use, notably through the European REACH regulation [22]. 75
An alternative method to solvent extraction is the precipitation of the Ni(DMG)
2
76
complex [4, 9, 12-14]. The French standard NF M60-317 also includes this alternative 77
option as a second
63
Ni purification method [21]. When the total activity concentrations 78
of the other radionuclides are 10 times higher in comparison to
63
Ni, this standard 79
indicates the necessity to perform a second precipitation step [21]. Higher Ni amount is 80
added (around 2 or 3 mg) [12-14] whereas the DMG amount varies from 50 mg [12, 13] 81
to 200 mg [21] to favour the precipitation of the Ni(DMG)
2
complex, in comparison to 82
the solvent extraction method. Prior to LSC, the precipitate is destroyed to recover
63
Ni in 83
solution by using concentrated nitric acid [4, 9, 12, 13] or hydrogen peroxide [14]. The 84
procedure based on Ni(DMG)
2
precipitation has been applied for the measurement of 85
63
Ni in various radioactive matrices [4], such as metals [9], concretes [12], ion exchange 86
resins [13] and sludges [14]. However, the destruction of Ni(DMG)
2
precipitate appears 87
to be a delicate and fastidious step before LSC analysis [21]. 88
To overcome these above problems, the technique of extraction chromatography 89
based on the Eichrom Ni
®
resin has been developed to isolate Ni from the interfering 90
elements [23]. Some authors also prepared in-house Ni resins which relies on the same 91
principle [15, 27]. Indeed, over the past 20 decades, extraction chromatography has 92
become a leading technique for separation and preconcentration of radionuclides in the 93

Journal of Radioanalytical and Nuclear Chemistry
5
environmental, biological and nuclear fields [24, 25]. The combination of an organic 94
extractant coated on an inert support delivers the selectivity of solvent extraction with the 95
ease of use of resin based methods. In the case of Ni resin, the DMG extractant is coated 96
on an inert support of acrylic ester based-resin [23]. As relatively high amounts of DMG 97
and Ni are involved (respectively 50 mg and 2 to 3 mg for a 2 mL pre-packed column 98
[23]), on-column precipitation of Ni with DMG occurs on Ni resin [23]. Elimination of 99
the interfering elements is mainly achieved with ammonium citrate during the rinsing 100
step. Then, Ni is generally stripped from the column using nitric acid [23, 26]. In recent 101
years, many radiochemical procedures based on Ni resin have been applied on many 102
nuclear materials [5, 6, 12, 13, 15, 17, 27]. 103
DMG is an effective and selective complexing agent of Ni but also of other metal 104
elements, such as Co, Cu, Cd and Pd [28], which can induce interferences for
63
Ni 105
purification. Indeed, the
60
Co activation product is often present in substantial amounts in 106
radioactive materials in comparison to
63
Ni. Correlation factors between
63
Ni and
60
Co 107
highly depend on the types of nuclear plants and samples [29]. In CEA France, the third 108
quartile of
63
Ni/
60
Co ratio has been determined at 0.4 in solid radioactive waste. 109
Consequently, from the literature, it is frequently necessary to complete the purification 110
step based on DMG with other separation procedures so as to eliminate Co efficiently. In 111
the French standard NF M60-317, the elimination of Co is achieved with a preliminary 112
liquid-liquid extraction step based on the use of 2-nitroso-1-naphthol [21]. In this 113
standard, it is recommended to implement this Co solvent extraction when the total 114
activity concentrations of the other radionuclides are 10 times higher in comparison to 115
63
Ni [21]. Furthermore, the presence of
55
Fe, another significant activation product, can 116
also hinder the formation of Ni(DMG)
2
complex/precipitate because of its precipitation at 117
basic pH [23, 26]. Organic complexing agents, such as citric acid [6, 12, 21], tartaric acid 118
[9, 21] or oxalic acid [5] are generally introduced to prevent the precipitation of Fe and 119
the other metal elements at basic pH. However, their chelating properties may not be 120
sufficient in case of high Fe amounts, such as in steels [6, 28]. Consequently, it is also 121
highly recommended to remove Fe to achieve accurate
63
Ni measurements. Precipitation 122
with ammonia [12-16, 18] or hydroxide [6, 14] and anion exchange chromatography [4, 123
5, 9, 10, 11, 14, 15, 17] have been mainly applied in order to eliminate the interfering 124

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6,304 citations


"A comparative study using liquid sc..." refers background or methods in this paper

  • ...DMG is an effective and selective complexing agent of Ni but also of other metal elements, such as Co, Cu, Cd and Pd [28], which can induce interferences for (63)Ni purification....

    [...]

  • ...The relevant stability constants were obtained from Smith and Martell [28]....

    [...]

  • ...The complexing properties of this chelating agent are not sufficient to prevent Co and Fe precipitation in the case of steels (the formation constant of Fe2O3 hematite is much greater than the one of FeTart [28])....

    [...]

  • ...The complexing properties of this chelating agent are not sufficient to prevent Co and Fe precipitation in the case of steels (the formation constant of Fe2O3 hematite is much greater than the one of FeTart?...

    [...]

  • ...It can be noted that no stability constant was found for Fe with DMG: no stable complex might be formed [28]....

    [...]


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Abstract: A novel extraction chromatographic resin comprised of a quaternary amine-based liquid anion exchanger sorbed on an inert polymeric substrate for the sorption of actinides from nitric and hydrochloric acids is described. The resin is shown to exhibit preferential retention of tetravalent actinides over a wide range of acidities. The application of this material to the separation and preconcentration of selected actinides from high level nuclear waste solutions for subsequent determination is described.

400 citations



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TL;DR: These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches.
Abstract: The radiometric methods, alpha (alpha)-, beta (beta)-, gamma (gamma)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include (3)H, (14)C, (36)Cl, (41)Ca, (59,63)Ni, (89,90)Sr, (99)Tc, (129)I, (135,137)Cs, (210)Pb, (226,228)Ra, (237)Np, (241)Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.

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"A comparative study using liquid sc..." refers methods in this paper

  • ...materials used in the nuclear fuel cycle [2]....

    [...]

  • ...As liquid scintillation counting (LSC) has a high counting efficiency for (63)Ni (around 70 %) [2], this detection technique is widely used for (63)Ni determination [2–17]....

    [...]

  • ...Decontamination factors of 10(5) or higher can be obtained using a combination of these purification methods [2, 6]....

    [...]


Journal ArticleDOI
Abstract: An analytical method for the determination of 63 Ni and 55 Fe in nuclear waste samples such as graphite, heavy concrete, aluminium and lead was developed. Different decomposition methods (i.e. ashing, acid digestion and alkali fusion) were investigated for the decomposition of the samples and for the separation of Fe and Ni from the matrix. Hydroxide precipitation was used to separate 55 Fe and 63 Ni from the matrix elements and ion exchange chromatography was used to separate 55 Fe and 63 Ni from the interfering radionuclides as well as from each other. The separated 63 Ni was further purified by extraction chromatography. The purified 63 Ni and 55 Fe was then measured by liquid scintillation counting. The chemical yields of the separation procedures for 55 Fe and 63 Ni are above 90% and the decontamination factors for all interfering radionuclides are more than 10 5 . The detection limits of the analytical method for 55 Fe and 63 Ni are 0.018 and 0.014 Bq, respectively. The methods developed were used in the analysis of 55 Fe and 63 Ni in heavy concrete, aluminium and lead from two concrete cores and graphite from thermal column in the Danish research reactor DR-2 and the results are presented in this paper.

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"A comparative study using liquid sc..." refers background or methods in this paper

  • ...In recent years, many radiochemical procedures based on Ni resin have been applied on many nuclear materials [5, 6, 12, 13, 15, 17, 27]....

    [...]

  • ...Decontamination factors of 10(5) or higher can be obtained using a combination of these purification methods [2, 6]....

    [...]

  • ...[6, 23], it was decided to implement a separation on the anion exchange AG1-X4 resin before the purification step on the Ni resin....

    [...]

  • ...Consequently, (63)Ni can be present in many radioactive materials and waste samples [2–17], such as graphites [6, 7], metals (aluminium,...

    [...]

  • ...[6] as follows: Ni measured in the purified sample ð Þ = Ni added as carrier ð Þþ ð Ni measured in the sample ð ÞÞ....

    [...]


Frequently Asked Questions (1)
Q1. What are the contributions in this paper?

23 A comparative study using liquid scintillation counting was performed to measure 63 Ni in 24 low and intermediate level radioactive waste.