Radiochemical Determination of Rare Earth Elements in

Article pubs.acs.org/ac

Radiochemical Determination of Rare Earth Elements in ProtonIrradiated Lead−Bismuth Eutectic Bernadette Hammer,†,‡ Jörg Neuhausen,‡ Viktor Boutellier,‡ Michael Wohlmuther,‡ Andreas Türler,†,‡ and Dorothea Schumann*,‡ †

University of Bern, 3012 Bern, Switzerland Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

‡

S Supporting Information *

ABSTRACT: Various types of proton-irradiated lead−bismuth eutectic (LBE) samples from the MEGAPIE prototype spallation target were analyzed concerning their content of 148Gd, 173Lu, and 146Pm by use of αand γ-spectrometry. A radiochemical separation procedure was developed to isolate the lanthanide fraction and to prepare thin samples for α-ray measurement. The results prove a substantial depletion of these three elements in bulk samples, whereas accumulation on the LBE/steelinterfaces was observed. The amount of material accumulated on surfaces was roughly estimated by relating the values measured on the sample surfaces to the total surface of the inner target walls. The amount of 148Gd, 173 Lu, and 146Pm was then quantified by summing up the contributions from every sample type. The results show a reasonable agreement with theoretical predictions. The obtained results are of utmost importance for the evaluation of the performance of high-power spallation targets, especially concerning the residual nuclide production, the physicochemical behavior of the produced radionuclides during operation, and in terms of an intermediate or final disposal.

H

In 2006, a joint test experiment named MEGAPIE (MEGAwatt PIlot Experiment), supported by six European research institutions, as well as DOE (U.S.A.), KAERI (Korea), and JAEA (Japan), has been performed at the Paul Scherrer Institute (PSI) using the spallation neutron source SINQ, aimed to design, build, operate, and explore a liquid LBE spallation target of 1 MW beam power.6 During four months, 844.6 kg of liquid LBE were circulated in a loop and continuously irradiated with protons. This pilot experiment included, besides the operational feasibility study, also an extended Post-Irradiation Examination (PIE) program7 covering material and analytical research. One of the essential issues in this context is to obtain more precise knowledge on the radionuclide inventory induced during irradiation, the physicochemical behavior of the radionuclides within the target and their distribution in the target system. The results of such studies are mandatory to guarantee a safe operation and to meet the requirements for dismantling and disposal. Since in spallation reactions a vast number of radionuclides are produced, covering the range of mass numbers between 1 and a few units higher than the target mass, the radionuclide inventory cannot be determined completely. Therefore, priority has been given to the analysis

igh-power neutron spallation sources are a state-of-theart tool for neutron physics and material research. Furthermore, a neutron spallation source is also a main component of a so-called Accelerator-Driven System (ADS). ADSs are a novel type of nuclear reactor, where neutrons sustaining the chain reaction in the core are generated by an accelerator delivering high-energetic particles to a heavy metal spallation target. The fast neutrons generated in this way can be used to transmute minor actinides retrieved from spent nuclear fuel. The principle is based on the energy amplifier concept proposed by Carlo Rubbia1,2 and fulfills a double function: it is supposed to produce energy while at the same time “burning” nuclear waste, thus reducing the hazard of long-lived radionuclides from the nuclear fuel cycle by transmuting them into short-lived or stable ones. Currently, a fast spectrum research reactor based on the ADS technique named MYRRHA is foreseen to be built at SCK-CEN (Mol, Belgium).3 For this application, a heavy metal as target material is needed for an efficient neutron yield. One candidate for a target and coolant material is liquid lead−bismuth eutectic (LBE), due to its favorable nuclear, thermophysical, and chemical properties.4,5 However, the performance of the material, for instance, its behavior under irradiation conditions and its influence on the mechanical properties of the surrounding structure material, as well as residual nuclide production in the liquid metal and the physicochemical behavior of the produced radioelements in the system have to be investigated in detail before it can be safely applied for routine operation. © 2015 American Chemical Society

Received: February 24, 2015 Accepted: May 4, 2015 Published: May 4, 2015 5656

DOI: 10.1021/acs.analchem.5b00955 Anal. Chem. 2015, 87, 5656−5663

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Analytical Chemistry of safety-relevant radionuclides such as α-emitters, radionuclides with very long half-lives, and volatile elements. In a number of previous experiments, we found evidence that a homogeneous distribution within the entire target cannot be expected for every radioelement. For example, in a preparatory study performed at CERN-ISOLDE, where LBE has been irradiated with 1.4 GeV protons in an ISOLDE Tantalum container, an accumulation of Lu in surface samples was observed.8 Therefore, we initiated an extended sampling of the MEGAPIE target in order to get detailed information on the total amount of produced radionuclides and their location within the target. A γ-spectrometric analysis of radionuclides in the MEGAPIE samples without prior chemical separation showed that noble metals soluble in LBE like Au, Hg, and Ag are rather homogeneously distributed in bulk LBE samples, whereas an accumulation of nuclides that are sensitive to oxidation was observed in the interface samples.9 Some of these isotopes like 172 Lu and 173Lu are depleted in the bulk LBE to such an extent that they could not be detected without prior chemical separation because of the Compton background and the overlap with other peaks in the γ-spectrum hampering a clear identification. α-Emitters represent, due to their harmful radiation, a considerable safety hazard both during operation and also after disposal. Therefore, special attention was drawn to the investigation of the radioelement polonium with the most hazardous isotopes 208Po (t1/2 = 2.898 a), 209Po (t1/2 = 102 a), and 210Po (t1/2 = 138 d), which are, as an additional drawback, also considerably volatile. Results of the Po analysis in MEGAPIE samples were reported previously.10 Another safety-relevant α-emitting radionuclide is 148Gd, with a half-life of 74.6 y and an energy of the α-ray of 3.183 MeV. Taking into account the above-mentioned observed surface accumulation of lanthanides in the ISOLDE LBE target and the findings of γ-spectrometry on the MEGAPIE target, it becomes evident that for the evaluation of the total content of 148 Gd and other lanthanides the investigation of their distribution within the target will be mandatory. In the present paper we report on the analysis of MEGAPIE samples taken from the bulk LBE and from the interface between the LBE and the steel walls of target components. Chemical procedures to separate the lanthanide fraction and a sample preparation method for the α-measurement of 148Gd have been developed. The amount of 173Lu, 148Gd, and 146Pm in the entire target was quantified and compared to theoretical predictions11 obtained using the nuclear physics codes Fluka and MCNPX.

Figure 1. Scheme of the MEGAPIE target assembly and its main components. The liquid metal flow is indicated by the black arrows in the inner part of the scheme. The locations of the segments used for the postirradiation examination are indicated by horizontal lines.9 Photographs of the segments after cutting are shown on the right-hand side.

H07. A detailed description of the irradiation and sampling of MEGAPIE was reported previously.9 Sampling. In the frame of the Post-Irradiation Examination (PIE), over 70 samples were taken at different positions in the target for the radiochemical analysis. In this paper we will focus on 11 samples taken from bulk LBE and the LBE/steel interfaces (see Table 1). Table 1. Summary of Analyzed Samples and Their Characteristics type H02-D2 H03-D2 H05-U2-b H07-U-b H03-D4 H03-U6 H05-D22 H06-D2-b H05-U4-b H06-D2S

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EXPERIMENTAL SECTION Irradiation. The MEGAPIE target has been irradiated for 123 days with an average current of 0.947 mA of 575 MeV protons.12 During this period, the LBE exposed to the proton beam was continually pumped through the target system with a flow rate of 4 L/s, corresponding to velocities of 0.2 to 1.2 m/s in different zones and components.11 After a decay period from 2006 to 2009, the target was cut in the Hot Cells of ZWILAG (interim storage facility in Switzerland), and the segments H01 up to H09 (Figure 1) were transferred to the PSI HotLaboratory to prepare samples for various chemical and material investigations.7 Samples for the radiochemical analysis described in this paper were taken from the segments H02 to

bulk bulk bulk bulk LBE/steel interface LBE/steel interface LBE/steel interface LBE/steel interface LBE/steel interface LBE/steel interface LBE/steel interface

material

LBE flow

LBE LBE LBE LBE LBE

down flow down flow up flow up flow down flow

LBE

up flow

LBE

down flow

LBE

down flow

steel

up flow

steel

down flow

LBE

down flow

comments

only LBE exists only LBE exists only LBE exists only LBE exists

part part part part

Bulk LBE Samples. Bulk LBE samples were obtained by core drilling in the top and bottom surfaces of the segments cut in ZWILAG using a self-made core drill. This sampling process is illustrated in Figure 2. The samples were visually homogeneous cylinders with a diameter of 2 mm and a length of 5 mm. From the 43 samples obtained in this way from the bulk, 4 samples from segments H02, H03, H05, and H07 were selected for the analysis of lanthanides (Figure 2 and Table 1). LBE/Steel Interface Samples. LBE/steel interface samples were obtained using the same core drilling procedure applied for the bulk LBE samples, but the center of the drill being placed directly at the LBE/steel interface, as illustrated in 5657

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solution for the separation of Po using spontaneous deposition on silver discs. The details of the chemical separation and the results of the iodine, chlorine and polonium determination are reported elsewhere.10,14 A flowchart of the entire procedure is shown in Figure 4.

Figure 2. Sampling of a bulk LBE sample, H02-D2. Segment surface before drilling (1), after drilling (2), and the final sample (3).

Figure 3. In this way, samples were obtained that consisted both of an LBE part and a steel part, each corresponding to

Figure 3. Sampling of a LBE/steel-interface sample, H06-D2S. Segment surface before (1), after drilling (2) and the final sample, broken into two parts (3).

approximately a half cylinder with the dimensions mentioned above. However, in practically all cases, these half cylinders were slightly smaller than the ideal case due to asymmetrical drilling caused by the largely different mechanical properties of LBE and steel. There were also cases where only the LBE part could be retrieved because it proved impossible to break off the steel pin. In this study, the LBE and the steel parts of one almost ideal sample (H06-D2S) were analyzed separately. Furthermore, either the LBE or the steel parts of five more samples have been analyzed (Table 1). Apart from the samples analyzed in the frame of this paper, four samples from the interface between the LBE and the cover gas in the expansion tank as well as noble metal foils from an absorber installed in the cover gas to catch volatile radionuclides were available for estimating the lanthanide content. On the free surface of the LBE that was in contact with the cover gas during operation of the target, indeed a strong enrichment of lanthanide nuclides was observed, similar to the findings from the ISOLDE target.8 However, due to the comparably small area of the free surface, the contribution of this sample type to the total radioactivity is 98%) from the steel by leaching in 7 M HNO3. Afterward, the steel is left almost free of adhering radionuclides, indicating that the lanthanide nuclides are present as a surface layer on the steel samples. For the LBE part of the interface samples studied here, we found roughly a factor 30−100× higher activities per mass unit for 173Lu compared to the activity concentrations of the bulk LBE samples. As a consequence of this nonuniformity of the interface samples, it does not make sense to present the results of analysis in form of activity concentrations. Instead, we give the results as activity per unit surface in Table 4. The surface area was determined in the following way: The interface area of LBE with the steel container material in a complete and fully symmetrical core drill of 2 mm diameter and 5 mm length, as depicted in Figure 10 is 1.0 × 10−5 m2. However, none of the

Figure 9. Activity concentrations of 173Lu at EOB (21.12.2006) in four representative bulk LBE samples compared to activity concentrations obtained from Fluka (red line) and MCNPX (dashed blue line) predictions11 assuming homogeneous distribution of all produced 173 Lu in the LBE. The error bars represent 1σ uncertainties.

this set of samples is rather homogeneous. The averaged 173Lu concentration in bulk LBE samples amounts to (2.7 ± 0.7) × 104 Bq per gram. Extrapolating to the total 844.6 kg of LBE in the target, we arrive at a 173Lu content of (2.2 ± 0.6) × 1010 Bq, corresponding to about 7% of the predicted amount of this nuclide11 (Fluka: 3.1 × 1011 Bq; MCNPX: 3.4 × 1011 Bq). The content of 148Gd could, similar to 146Pm, also not be determined in bulk samples because of the detection limit. Larger amounts of sample material and extremely long measurement times would have been necessary to obtain a reasonable signal/noise ratio in the α-spectrum. However, since lanthanides behave chemically very similar, we assume that Table 4. Results of sample H03-U6 H06-D2-S H06-D2-b H05-D22 H03-D4 averagec H05-U4-b H06-D2S averagec

148

material LBE

steel

173

Gd,

Lu, and

analyzed samples was fully ideal. Most of them were drilled slightly asymmetrically. Furthermore, in many cases, the core was slightly shorter than the nominal 5 mm. Thus, all of the

Pm Analysis in Steel and LBE Parts of Interface Samplesa

146

Gd activity per unit surfaceb (Bq/m2)

148

(6.6 (2.3 (5.5 (4.5 (4.4 (4.7 (1.7 (5.2 (1.1

Figure 10. Illustration of area estimation for LBE/steel interface samples, broken into two parts.

± ± ± ± ± ± ± ± ±

173

Lu activity per unit surfaceb (Bq/m2) ± 0.1) × 10 ± 0.08) × 109 ± 0.4) × 109 ± 0.04) × 109 ± 0.7) × 1010 ± 2.3) × 109 ± 0.04) × 109 ± 0.1) × 108 ± 1.3) × 109 148 Gd (Bq)

0.02) × 10 0.1) × 106 0.3) × 106 0.2) × 106 0.2) × 106 0.7) × 106 0.05) × 106 1.4) × 105 0.6) × 106 6

(1.5 (3.1 (8.4 (6.3 (1.5 (9.5 (3.2 (5.6 (1.9 material

extrapolation to total target inner surface (16 m2)

(7.5 ± 1.1) × 107 (1.8 ± 0.9) × 107 (9.2 ± 2.1) × 107 60 ± 14

LBE steel sum % of predictionf

146

Pm activity per unit surface (Bq/m2) (2.0 ± 0.7) × (6.6 ± 2.0) × not detected (1.4 ± 0.6) × (8.5 ± 3.8) × (1.3 ± 0.3) × (3.3 ± 0.7) × not detected (3.3 ± 2.3) ×

10

173

Lu (Bq)

(1.5 ± 0.4) × 1011 (3.0 ± 2.1) × 1010 (1.8 ± 0.6) × 1011 57 ± 18

108d 107d 108d 107d 108 107d 107e Pm (Bq)

146

(2.0 ± 0.5) × 109 (5.3 ± 3.7) × 108 (2.5 ± 0.9) × 109 56 ± 22

a All activities are corrected to EOB. The upper part compiles surface activity concentrations for the individual samples and their averages. The lower part shows the results of extrapolating to the total inner surface of the target (16 m2). bUncertainties given are standard errors of the mean value of two independent analyses calculated according to eq 2. cUncertainties given for the averages are standard errors of the mean according to eq 2. dFor 146 Pm, only one analysis was performed per sample. Uncertainties were derived by error propagation, as outlined in the text. eFor the single measurement of 146Pm on a steel sample, we assume an uncertainty equivalent to the highest relative uncertainty value found in this measurement series (173Lu in the steel samples). fAverage of Fluka and MCNPX calculation.11

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samples investigated had a smaller area than the ideal 1.0 × 10−5 m2. In a few cases, only fragments of a core were analyzed. The interface area of the individual samples was determined from the length and width of the sample or the remaining fragment. We assume that the uncertainty of the estimation of the surface area is smaller than 20%. More detailed results of the analyses and surface activity evaluation are provided in the Supporting Information. The distribution of the three different lanthanide nuclides across the set of LBE/steel interface samples is very similar, as expected due to their chemical similarity (Figure 11). The

Article

SUMMARY AND CONCLUSION

Samples from the MEGAPIE target representing the bulk LBE and the interface of LBE with the steel walls of the target container were analyzed for the lanthanide radionuclides 148Gd, 146 Pm, and 173Lu. From the analysis results, the individual contributions of these different sample types to the total radioactivity were roughly estimated. The results of this estimation are summarized in Table 5 and compared to predictions on the radionuclide production during the MEGAPIE irradiation obtained by two different nuclear physics codes employing different nuclear models.11 Table 5. Summary of 173Lu, 146Pm, and 148Gd Activity Distribution over the Different Types of Samples estimated total activity (GBq) 173 Lu bulk LBE/steel interface total target 146 Pm bulka LBE/steel interface total target 148 Gd bulka LBE/steel interface total target

Figure 11. Distribution of 148Gd, 173Lu, and 146Pm across the LBE/ steel interface samples. Filled symbols: LBE part of interface sample; Open symbols: steel part of interface sample. Activities corrected to EOB.

22 ± 6 181 ± 58

predicted averaged11 (GBq)

% of predicted amount

% of estimated total activity

321

7±2 57 ± 18

11 87

203 ± 64 0.3 ± 0.1 2.5 ± 1

64 ± 20 4.5

2.8 ± 1.1 11 ± 3 92 ± 21 103 ± 24

7±2 56 ± 22

10 86

63 ± 24 153

7±2 60 ± 14

11 88

67 ± 16

a

Estimated content in bulk LBE, assuming a distribution similar to that of 173Lu.

values of surface activity of 148Gd, 173Lu, and 146Pm on the interface samples varies within a little more than 1 order of magnitude. The highest value for all three nuclides is found on the LBE part of sample H03-U6, while the lowest surface activity is always found on a steel sample (H06-D2S for 148Gd and 173Lu, for 146Pm on the only measured steel sample: H05U4-b). This indicates that the major part of the lanthanide nuclides sticks to the LBE part when the interface samples are broken apart. To obtain a crude estimation of the total amount of 148Gd, 173 Lu, and 146Pm associated with the surface layer sticking to the target’s inner walls, the averages of the surface activities found for both the steel and the LBE samples were multiplied with the total inner surface of the target (16 m2) reported in Groeschel et al.19 and summed up. The total activity for the three nuclides obtained in this way is 92 ± 21 MBq, 181 ± 58 GBq, and 2.5 ± 1 GBq for 148Gd, 173Lu, and 146Pm, respectively, corresponding to 60, 57, and 56% of the averaged predictions of the two nuclear physics codes.11 The uncertainty arising from the small number of samples and the relatively large scatter among the data is reflected in the standard errors given for the mean values. For the case of 146Pm, where only one steel sample was measured, we give an estimated uncertainty by assuming the same relative uncertainty as that derived for the activity of 173Lu, that is, the higher one of the two individual steel samples.

The major part of the studied nuclides is found to be deposited on the steel walls of the liquid metal container. Bulk samples contain only a minor fraction of the total 173Lu (about 11%) detected in the target. Though the content of 148Gd and 146 Pm in the bulk samples could not be measured in this study, it is likely because of the very similar chemical properties of all the lanthanide elements that similarly small fractions of these nuclides also remain in the bulk LBE. These results indicate that the lanthanides are separated from the liquid metal during operation of the MEGAPIE target and are accumulated on the surfaces of the target container and on the free surface in the expansion tank where the liquid metal was in contact with the cover gas. A plausible chemical explanation for this separation effect is the incorporation of the lanthanides into oxide layers that are formed at the interfaces. The lanthanides have a very high affinity to oxygen, documented, for example, by the high stability of their sesquioxides Ln2O3.20 Thus, it is unlikely that they remain in the metallic state but rather react with oxygen impurities in LBE and/or with oxygen in the protective oxide layers of the steels. The very small amounts of the lanthanides produced by nuclear reactions are certainly not sufficient to produce a continuous layer of lanthanide oxides throughout the target. Therefore, it is more likely that the lanthanides in the oxidation state +III are incorporated into macroscopic oxide layers formed from the target or construction materials or impurities therein. Oxides, because of their polar nature, are not well soluble in liquid metals and thus tend to precipitate on the 5662

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structure material and on the free surface of the liquid metal. On the free surface samples contaminations with a dark or in some cases gray and yellow solids have indeed been observed.9,13 To be able to compare the experimental results to predictions obtained by nuclear physics modeling we estimated the total amounts of all three lanthanides associated with the bulk LBE and the LBE/steel interface surfaces. The results are compiled in Table 5. The estimation performed here is certainly not of high precision, both because only a relatively small number of samples could be analyzed and due to the relatively large scatter of the experimental data within the interface samples. Nevertheless, the results agree reasonably well with the predictions obtained by nuclear codes.11 Similar agreements of predictions and radiochemical analysis have been observed for nuclides that are more or less homogeneously distributed in the LBE such as 208−210Po, 207Bi, and 194Hg/ Au.9,10 Together, these results indicate that state-of-the-art nuclear physics codes can deliver fairly reliable information on the nuclide production in complex facilities. The deposition processes observed for lanthanide nuclides within the MEGAPIE target may have consequences for the operation of future nuclear systems based on liquid LBE. For example, the accumulation of α-emitting radionuclides such as 148 Gd on the walls of the structural materials will lead to contaminations that certainly will have to be considered when handling or disposing components that have to be repaired or replaced. More generally, such depositions will lead to increased dose rates in the vicinity of liquid metal containing structures, as already observed in the liquid mercury spallation source JSNS at J-PARC.21 Similarly, these depositions will increase locally the decay heat, a phenomenon that could potentially increase evaporation of volatile nuclear reaction products from the free surface of the liquid metal. Depositions could also induce changes in heat transfer, which alter the characteristics of heat exchangers. Additionally, the influence of such surface depositions on the corrosion resistance of structural materials is unexplored so far. Finally, the precipitation of solid suspended particles that are carried with the flowing metal may cause plugging of filter systems and enhance erosion of the construction materials. All these effects remain to be explored in more detail in future studies.

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REFERENCES

(1) Rubbia, C. Nucl. Instrum. Methods Phys. Res., Sect. A 1989, 278, 253−265. (2) Rubbia, C. Nucl. Phys. A 1993, 553, 375−395. (3) Aït Abderrahim, H.; Baeten, P.; De Bruyn, D.; Fernandez, R. Energy Convers. Manage. 2012, 63, 4−10. (4) Gorse-Pomonti, D.; Russier, V. J. Non-Cryst. Solids 2007, 353, 3600−3614. (5) Handbook on Lead-Bismuth Eutectic Alloy and Lead. Properties, Materials Compatiblility, Thermal-hydraulics and Technologies. NEA No. 6195; OECD Nuclear Energy Agency: France, 2007. (6) Bauer, G. S. Nucl. Instrum. Methods Phys. Res., Sect. A 2001, 463, 505−543. (7) Wohlmuther, M.; Wagner, W. J. Nucl. Mater. 2012, 431, 10−15. (8) Noah, E.; Boutellier, V.; Brütsch, R.; Catherall, R.; Gavillet, D.; Krbanjevic, J.; Linder, H. P.; Martin, M.; Neuhausen, J.; Schumann, D.; Stora, T.; Zanini, L. J. Nucl. Mater. 2012, 431, 60−65. (9) Hammer, B.; Neuhausen, J.; Boutellier, V.; Linder, H. P.; Shcherbina, N.; Wohlmuther, M.; Türler, A.; Schumann, D. J. Nucl. Mater. 2014, 450, 278−286. (10) Hammer, B.; Schumann, D.; Neuhausen, J.; Wohlmuther, M.; Türler, A. Nucl. Data Sheets 2014, 119, 280−283. (11) Zanini, L.; David, J.-C.; Konobeyev, A. Y.; Panebianco, S.; Thiolliere, N. PSI Rep. Nr 08−04; Paul Scherrer Institute: Switzerland, 2008. (12) Konobeyev, A. Y.; Fischer, U.; Zanini, L. Nucl. Instrum. Methods Phys. Res., Sect. A 2009, 605, 224−232. (13) Hammer, B.; Neuhausen, J.; Boutellier, V.; Wohlmuther, M.; Zanini, L.; David, J.-Ch.; Türler, A.; Schumann, D. Eur. Phys. J. Plus 2015, submitted for publication. (14) Hammer, B.; Neuhausen, J.; Boutellier, V.; Wohlmuther, M.; Schumann, D.; Türler, A. Radiochim. Acta 2015, submitted for publication. (15) Horwitz, E. P.; Bloomquist, C. A. A. J. Inorg. Nucl. Chem. 1975, 37, 425−434. (16) Hammer, B.; Schumann, D.; Neuhausen, J.; Alfimov, V. Annual Report Laboratory Radio-Environ. Chem., Univ. Bern; PSI: Switzerland, 2010. (17) Cornejo Díaz, N. A.; Martín Sánchez, A.; de la Torre Pérez, J. Appl. Radiat. Isot. 2011, 69, 822−824. (18) Wawra, E.; Pischek, G.; Müllner, E. Chemie Berechnen: Ein Lehrbuch für Mediziner und Naturwissenschafter; UTB: Stuttgart, 2002. (19) Groeschel, F.; Neuhausen, J.; Fuchs, A.; Janett, A. Intermediate Safety Report, Treatment of the Reference Accident Case, Deliverable D14 of WP1 of the MEGAPIE-TEST Program, 5th EURATOM Framework Program, Paul Scherrer Institute: Switzerland, June 2006. (20) Barin, I. Thermochemical Data of Pure Substances; Wiley-VCH Verlag GmbH: New York, 1995. (21) Kai, T.; Ooi, M.; Kasugai, Y.; Wakui, T.; Kogawa, H.; Haga, K.; Hanano, K. Proceedings of the 19th Meeting on Collaboration of Advanced Neutron Sources ICANS XIX, Grindelwald, Switzerland, March 8−12, 2010, Paul Scherrer Institut, PSI: Switzerland, 2010.

ASSOCIATED CONTENT

S Supporting Information *

Detailed results of 148Gd, 173Lu, and 146Pm analysis in steel and LBE parts of interface samples. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.analchem.5b00955.

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Article

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by the EC projects ANDES and GETMAT in the frame of EURATOM FP7. We acknowledge the EC financial support. 5663

DOI: 10.1021/acs.analchem.5b00955 Anal. Chem. 2015, 87, 5656−5663