**4. Conclusions**

66 Nuclear Reactors

approximately to 3.5 tons of thorium and 0.5 tons of the lead enriched with 208 isotope. Now monazite is considered as a harmful radioactive impurity and it is not produced.

The composition of monazite from the Malyshevsky placer as to the amounts of U, Th and Pb for dating purposes is well studied in work [21] by means of X-ray-fluorescent technique specially developed for individual grain analysis. In Table 3 the data about the contents of thorium, uranium and about isotope contents of lead for monazite of the Malyshevsky deposit is cited. The average composition of lead is confirmed by direct mass spectrometry

3,52 0,23 0,30 0,04 13,11 1,43 85,42 0,06 3,63 0,33 3,8 0,4 95,7

Table 3. Contents of thorium, uranium, lead and isotopic composition of lead for monazite

As is seen from Table 3, enrichment by 208Pb in the average for all monazite is insufficiently high. However, there is a probability of monazite separation by the flotation, magnetic or

Extraction of total monazite concentrate by working out of the Malyshevsky placer scattering of an average almost won't demand additional costs and its price as at first approximation can be accepted as the equal to zircon concentrate, i.e. ~ 1 US \$/ kg. Cost of hydrometallurgical emanation of lead from monazite by analogy with similar processes can be estimated as (2430 US \$/ kg). The removal of differences with low U/Th ratio and the high content of 208Pb from monazite concentrate will require additional researches and will

In Ukraine there are insufficiently studied shows of monazite in ancient radical breeds, their barks of aeration and in placers, i.e. enriched 208Pb. According to the available analytical

Average value of 70 uranium depleted samples. Elements – mass %%, Lead isotopes –relative %%.

Lead isotopes

206Pb 207Pb 208Pb

Isotopic composition of lead by mass spectrometry analysis of average sample, relative %%.

Th U Pb 204Pb 206Pb 207Pb 208Pb U Th Pb

other characteristics with release of low uranium fraction of the mineral.

data there is a possibility to detect monazite with highly enriched 208Pb.

determinations.

Average values from 224 X-rayfluorescent determinations according to [21] data, wt %.

of the Malyshevsky placer (Ukraine)

cause some rise in price of a product.

The paper is dedicated to the proposal of using lead enriched with the stable isotope 208Pb in FRs and ADSs instead of lead natural, natPb.

It seems that unique neutron features of 208Pb make it as one of the best among the molten metal coolants now assumed for FRs and ADSs: sodium, lead-bismuth, lead natural and others.

The main advantage of 208Pb is its low neutron absorption ability: for neutron energies En=0.1-20.0 MeV the microscopic cross sections of radiation neutron capture by 208Pb are by 1.5-2.0 times smaller as compared with natPb, and for energies, En<50 keV, the difference in the cross section values reaches 3-4 orders of magnitude. Averaged over neutron spectra of the LFR or ADS the one-group cross sections for a coolant from 208Pb are by 5-6 times smaller than those for the coolant consisted from natPb.

The second advantage of using 208Pb consists in achievement the core neutron spectra hardening on 5-6% due to low energy losses. Low neutron absorbing and moderating features of 208Pb permit to reach the gain in the multiplication factor Kef on 2-3% for critical or subcritical core fueled with U-Pu mix. In this case to have the multiplication factor Kef =1.01 for the LFR or Keff =0.97 for the ADS, both cooled with lead-208, the enrichment of power grade Pu in the U-Pu fuel can be reduced approximately on 0.7- 0.8%.

The third important advantage of using 208Pb is coupled with increasing the small share of neutrons of low energies, 5-10 eV in spite of the neutron spectra hardening in whole. In this region of neutron energies the microscopic cross sections for such nuclides as 238U and 99Tc are maximum and very high, and the one-group cross sections for these nuclides averaged over neutron spectra of LFRs and ADSs cooled with lead-208 are equal to 0.6 and 0.8 barn respectively which are comparable with the one-group cross sections for typical breeders and transmutters.

The possibility of using 208Pb as coolant in commercial fast critical or subcritical reactors requires a special considering but relatively high content of this isotope in natural lead, 52.3%, and perspectives of using high performance photochemical technique of lead isotope separation permit to expect obtaining in future such a material in large quantities and under economically acceptable price. In the paper it is shown that principal possibility of acquisition of radiogenic lead containing high enriched lead -208, up to 93%, exists. Nowadays in Russian Federation and Ukraine thorium- containing loparit ores and monazite minerals are reprocessed for production of rаre metal raw. Thorium and lead are not required now and they are deposited in sludge. Nevertheless, the scales of future thorium and radiogenic lead production for innovative nuclear reactors have some prospects in near-term future. The conclusion is made that to obtain the minimum amount of required in future radiogenic lead (65 t/year) for small sized FRs and ADSs the very large

New Coolant from Lead Enriched with the Isotope Lead-208 and

Semiconductor Physics, ISP), 2004-2005.

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Possibility of Its Acquisition from Thorium Ores and Minerals for Nuclear Energy Needs 69

[11] A.L. Bortnyansky, V.L.Demidov, S.A. Motovilov, F.P. Podtikan, Yu.I. Savchenko, V.A.

[12] V.D. Borisevich, G.A. Sulaberidze, A.Yu. Smirnov. Production of highly enriched

[13] G.N Manturov, M.N. Nikolaev, A.M. Tsiboulia, Group constant system ABBN-93. Part

[14] Alekseev P.N., Mikityuk K.O., Vasiljev A.V., Fomichenko P.A., Shchepetina T.D.,

[15] A.I Blokhin, N.A. Demin, V.N. Manokhin et al. Code ACDAM for study nuclear and

[16] V.M. Decusar, B.Ya. Zil'berman, A.I. Nikolaev et al. Analysis of potential sources of

[17] J.A. Seneda , C.A.L.G. de O. Forbicini, C.A. da S. Queiroz, M.E. de Vasconcellos, S.

[18] G.G. Kulikov, A.N. Shmelev, V.A. Apse, V.V. Artisyuk. On the possibility of using

[19] A.A. Alekseev, A.A. Bergman, O.N. Goncharenko et al. Investigation of the neutron-

[20] V.I. Yurevich. Production of Neutrons in Thick Targets by High-Energy Protons and

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(Obninsk, Leypunsky Institute, IPPE) and P.A. Bokhan (Novosibirsk, Institute for

Usanov, A.M. Yudin, B.P. Yatsenko, 2005. Experimental Laser Complex for Lead Isotope Separation by means Selective Photochemical Reactions. Proc. of the X Int. Conf. "Physical and Chemical Processes on Selection of Atoms and Molecules", 3-7 October 2005. Moscow, TSNIIATOMINFORM, 76-82. (ISBN 5-

lead-208: separation problems. Paper presented at the Russian-Chinese Bilateral Workshop "Possibility of using stable isotope lead-208 in nuclear engineering and its acquisition", 12-13 October, 2010. Tsinghua University, Beijing, P.R.

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Forbicini, S.M. da R. Rizzo, Vera L.R. Salvador and A. Abrão. Study on radiogenic lead recovery from residues in thorium facilities using ion exchange and electrochemical process. Progress in Nuclear Energy, 2010, v. 52, No 3, pp.

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quantities of loparit ores or monazite minerals must be reprocessed and acquisition of radiogenic lead-208 can be economically acceptable as a co-product of rare metal raw.

#### **5. References**


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[1] G.L. Khorasanov, A.P. Ivanov, A.I. Blokhin Isotopic tailored materials for nuclear

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[5] G.L. Khorasanov and A. I. Blokhin. Macroscopic cross sections of neutron radiation

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[8] D.A. Blokhin, E.A. Zemskov, G.L. Khorasanov. The influence of the coolant from lead-

[9] G.L. Khorasanov and A.I. Blokhin. A low neutron absorbing coolant for fast reactors and

[10] ISTC #2573 project: "Investigation of Processes of High - Performance Laser Separation

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**1. Introduction**

calculations and future perspectives.

**1.1 The discovery of nuclear fission**

**0**

**5**

*Spain*

**Decay Heat and Nuclear Data**

*Instituto de Fisica Corpuscular, CSIC-Univ. de Valencia, Valencia*

The recent incidents at the Fukushima Daiichi nuclear power plant, following the great tsunami in Japan, have shown publicly, in a dramatic way, the need for a full knowledge

In this chapter, after a short introduction to decay heat from the historical perspective we will discuss, how the decay heat is calculated from available nuclear data, and how the quality of the available beta decay data plays a key role in the accuracy and predictive power of the calculations. We will present how conventional beta decay experiments are performed and how the deduced information from such conventional measurements can suffer from the so-called pandemonium effect. Then we will introduce the total absorption technique, a technique that can be used in beta decay experiments to avoid the pandemonium effect. Finally, we will present the impact of some recent measurements using the total absorption technique, performed by an international collaboration that we lead on decay heat summation

In 1934 Fermi bombarded an uranium target with neutrons slowed down in paraffin in an attempt to produce transuranic elements. The first impression after the experiment was that uranium did undergo neutron capture and the reaction product was beta radioactive. Subsequent investigation of this reaction showed that the final activity produced included a range of different half-lives. This puzzle triggered intensive research from 1935 to 1939.

The identification of one of the activities produced as the rare-earth lantanum, first by Curie and Savitch in 1938 and then by Hahn and Strassmann in 1939, started to shed light on the puzzle. Indeed it was this fact that lead Hahn and Strassman to interpret the experimental activities as barium, lanthanum and cerium instead of radium, actinium and thorium. Shortly afterwards Meitner and Frisch (1939) suggested that the uranium nucleus, after the absorption of a neutron, splits itself into two nuclei of roughly equal size. Because the resemblance with the biological process in a living cell, the process was called fission. A typical example of the splitting is represented in Equation 1. Later measurements established the asymetric character of the process, the large energy release (∼ 200 MeV) and the emission of prompt neutrons,

<sup>38</sup> *Sr* <sup>+</sup> 21

<sup>0</sup>*n* + *γ*+ ∼ 200*MeV* (1)

which could trigger new fission processes and produce a chain reaction.

<sup>54</sup> *Xe* <sup>+</sup><sup>94</sup>

<sup>0</sup> *<sup>n</sup>* <sup>→</sup><sup>140</sup>

235 <sup>92</sup> *<sup>U</sup>* <sup>+</sup><sup>1</sup>

and proper handling of the decay heat in reactors and spent-fuel pools.

A. Algora and J. L. Tain

[21] A.A. Andreev. Monazite age, geochemical peculiarities and possible sources of origin on the territory of Ukraine. Ph. D. Thesis's. Kiev, 2011, 190 p.
