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NEUTRONIC AND PHYSICAL CHARACTERISTICS OF AN ACCELERATOR DRIVEN SYSTEM WITH A LEAD–208 COOLANT

NEUTRONIC AND PHYSICAL CHARACTERISTICS OF AN ACCELERATOR DRIVEN SYSTEM WITH A LEAD–208 COOLANT. Georgy KHORASANOV , Anatoly IVANOV, Anatoly BLOKHIN IPPE, OBNINSK, RUSSIA. INTRODUCTION.

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NEUTRONIC AND PHYSICAL CHARACTERISTICS OF AN ACCELERATOR DRIVEN SYSTEM WITH A LEAD–208 COOLANT

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  1. NEUTRONIC AND PHYSICAL CHARACTERISTICS OF AN ACCELERATOR DRIVEN SYSTEM WITH A LEAD–208 COOLANT Georgy KHORASANOV, Anatoly IVANOV, Anatoly BLOKHIN IPPE, OBNINSK, RUSSIA

  2. INTRODUCTION • In Europe creation the demonstration facility EFIT intended for transmutation of minor actinides (MA) and long-living fission products is planned for 2025-2030 years. • It is supposed, that thermal capacity of the EFIT subcritical reactor will be of 800-1000 MW, and it will be driven by a beam of protons with energy Ep=800-1000 MeV and current Ip=15-20 mA (Pp=15-20 MW cw). • In support of this project in 2002-2004 in the European laboratories the facility PDS-XADS with the thermal capacity of the subcritical reactor of 80 MW and the proton beam of 600 MeV х 6 mA was designed, and nowadays at Mol, Belgium, a pilot facility the XT-ADS (MYRRHA) with the thermal capacity of 50 MW and the proton beam of 350 MeV х 5 mA (Pp=1.75 MW cw) is under construction with the date of its finishing of 2016-2018. As a material of the coolant of the target and blanket, in this installation the usage of the conventional lead and bismuth eutectic (LBE), Pb-nat(45%)-Bi(55%), is proposed, and in future using Pb-nat is planned. • ADSs are also under construction in Japan, Korea and China.

  3. In the paper, with the aim of decreasing the capacity of high energy proton beam, a potential opportunity of using in the target and subcritical core a low neutron moderating and low neutron absorbing heavy isotope of lead,Pb-208, and the modified LBE, consisting of (80-90)% of lead-208 and (20-10)% of bismuth, is considered. The proposal of using the modified LBE in the ADS target instead of the conventional LBE for the first time has been offered by authors in the papers presented at the conferences: ICONE 13, Beijing, China, 2005 and GLOBAL 2005, Tsukuba, Japan.

  4. In Table 1 the well-known data of percentage of lead isotopes in the natural mix of lead isotopes and some nuclear cross-sections of lead isotopes are given.

  5. Table 1. Stable lead isotopes data

  6. The middle lead isotope, Pb-206, is low activating in the reactions of (n,g) and (n,xn) type. In this case generation of Po-210 and Bi-207 is reduced in comparison with case when Bi-209 is used as the target material. That is why the Pb-206 is considered as the perspective low activated ‘pure’ coolant for the ADSs and FRs. • The extreme heavy lead isotope,Pb-208, is the ideal coolant as a low neutron absorbing and low neutron moderating material, but it is strongly activated in the proton spectra of the ADS target due to the reaction Pb-208(p,2n)Bi-207. Nevertheless, this lead isotope can be considered as a rather perspective lead isotope for the use in not numerous installations for MA burning out. • With the aim of hardening the target neutron spectrum and reducing the target activation it has been proposed to increase the contents of lead in the LBE in spite of some increasing the LBE working temperature, for example from ~250°С, for the conventional LBE, up to ~350°С, for the modified LBE. Naturally, it leads to changing the target neutron spectrum.

  7. ADS Target Spectra

  8. Fig.2. Softening the neutron spectrum in the target from Pb-nat(80%)-Bi(20%) (DASH) and its hardening in the target from Pb-208(80%)-Bi(20%) (SOLID).

  9. Fig.3. Neutron yield from the target from Pb-208(80%)-Bi(20%) as compared with the target from Pb-nat(80%)-Bi(20%).

  10. Fig.4. Neutron fluxes in the subcritical core. Solid line – fluxes in the core cooled by Pb-208 (100%).Dash line – fluxes in the core cooled by Pb-nat. Spectra are very similar and correspond to mean neutron energy T=0.5 MeV. In this case Pb-208 acts as LOW ABSORBING material for neutrons, it does not increase the mean neutron energy as in the TARGET from ‘pure’ Pb-208.

  11. ECONOMICS • The advantage of using Pb-208 considered above as the core coolant and nitrides of the depleted uranium and power plutonium as the fuel allow to reduce essentially requirements for capacity of the proton beam for the maintenance a long-term operation of the ADS in the mode of delivering thermal capacity of 80 MW. • As it has been shown above, replacement of the coolant from natural lead by the coolant from lead-208 results in economy of capacity of the proton beam on the value of P=0.91 MW, and using the uranium - plutonium nitride fuel allows to establish the stock of capacity of the proton beam on burning out the fuel in limits of less than 10 %, due to the core breeding ratio equal to ~1. • It allows in the ADS core with thermal capacity equal to 80 MW to reduce capacity of the required proton beam to the value about • ~2 MWinstead of capacity of the proton beam equal to 3.6 MW considered the PDS-XADS project. Hence, the proposed variant of the ADS allows to save capacity of the proton beam approximately equal to P=1.6 MW.

  12. ECONOMICS • The estimated cost of expenses for construction of the superconducting LINAC with proton beam of the capacity equal to 3.6 MW, according experts estimation, amounts 303 million Euro. It means, that the cost of the proton beam on the output of the accelerator with proton energy Ep=600 MeV is estimated as 84.2 Euro or $100 per 1 Watt. • It is possible to define a maximum price of Pb-208 that can be considered as the acceptable price in the proposed ADS variant. In the correctly designed FR with the lead coolant the specific need for the coolant quantity is equal to 0.7 ton/MW thermal. Then the minimized quantity of the coolant for the ADS blanket with thermal capacity 80 MW will be equal to ~56 tons of lead. • Taking into account economy of capacity of a proton beam equal to P=1.6 MW, caused by the chosen variant of materials of the coolant and the fuel, and the additional sum potentially released in the chosen ADS variant, equal to ~ $160 million, it is possible to estimate the acceptable price C of the isotope product Pb-208: • C = P (W) x 100 ($/W) / 56,000 (kg) = $2,860/kg • The current price of the lead-208 product that is usually obtained at gas centrifuges is higher than the above mentioned price approximately by one order of magnitude. However, it is possible to believe, that in future, in developing the technical equipment for stable isotope separation the lead-208 product will be obtained under the acceptable price.

  13. CONCLUSIONS • Lead isotope, Pb-206, is the best low activated ADS target coolant among the liquid heavy metal coolants. • From the neutronic characteristics point of view, another lead isotope, Pb-208, is better than Pb-206 or Pb-nat. In using such the isotope the target neutron spectrum is enriching with fast neutrons, Еn>2 МeV, which can penetrate into the subcritical core without essential losses. • The lead isotope, Pb-208, is also the ideal coolant for the ADS subcritical core due to its low neutron absorbing features. In its using as the core coolant, instead of Pb-nat, the required proton beam capacity, for delivering about 80 MW thermal capacity, can be reduced by 1.55 times. • It will be required about 56 tons of Pb-208, as a minimum, for the ADS blanket of 80 MW thermal capacity. Charges for it obtaining can be recovered at the expense of the economy of the proton beam cost.

  14. As the lead coolant has relatively high operation temperature and some technological issues of its using are not solved yet, it is proposed to use the modified low temperature coolant consisted from Pb208(80%)-Bi(20%) or Pb-208(90%)-Bi(10%) as the low neutron moderating and low neutron absorbing material. Such the modified Pb-Bi eutectic can be used as in the target as well in the core for the next generation ADSs. • The considered benefits of using stable lead isotopes, Pb-206 and Pb-208, in the next generation nuclear installations are the background for the R&D of new techniques for lead isotope separation and industrial obtaining large quantities of Pb-206 and Pb-208.

  15. Из Воспоминаний Н.И. Тарантина, ЭЧАЯ, 2005, т.36, в.6, с.1489 • 1954 году на одном из семинаров ЛИПАНа, с участием Г.Н.Флерова, И.И.Гуревича, С.М.Фейнберга и др. обсуждались возможности получения высоких КВ, коэффициентов воспроизводства реакторного горючего. • По-видимому обсуждение на семинаре подтолкнуло Г.Н.Флерова предложить для воспроизводства ядерного горючего другой генератор нейтронов – реакцию рождения нейтронов в тяжелой мишени под действием ускоренных до высокой энергии протонов. • Эту идею Г.Н.Флеров подробно изложил в докладе «Использование ускорителя заряженных частиц для энергетических целей» на семинаре в ЛИПАНе 26 октября 1955 года. • On 1955 Russian academician Georgy Flerov presented a paper entitled “Usage of charged particle accelerator for nuclear power needs”

  16. THANK YOU VERY MUCH FOR YOUR ATTENTION !

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