NEUTRONIC AND PHYSICAL CHARACTERISTICS OF THE ADS CORE

NEUTRONIC AND PHYSICAL CHARACTERISTICS OF THE ADS CORE

WITH A LEAD-208 COOLANT

Georgy L. Khorasanov, Anatoly P. Ivanov, Anatoly I. Blokhin.

Tel.: +7-48439-9 85 05, Fax: +7-48439-6 82 25, E-mail: khorasan@ippe.ru

Institute for Physics and Power Engineering named after A.I.Leypunsky

1, Bondarenko square, Obninsk, Kaluga region, 249033 Russian Federation

Presently, several research centers of the European Community are planning to construct in 2025-2030 a demonstration facility EFIT with the aim to transmutate minor actinides (MA) –wastes of nuclear power plants. It is supposed that the thermal capacity of the EFIT subcritical core will be equal to several hundreds of MW and it will be driven by a proton beam of energy E_p= 1000 МeV and current about I_p=20 mA. In supporting this project, in 2001-2004 in Europe the facilities PDS-XADS with 80 MW thermal capacity and MYRRHA with 50 MW thermal capacity were considered within a design phase. In these facilities a traditional eutectic of natural lead (Pb-nat) and bismuth, Pb-nat(45%)-Bi(55%), was proposed as a coolant material for a target and a subcritical core. With the aim of hardening the ADS target neutron spectrum, in the papers [1, 2] a potential opportunity of using the modified lead-bismuth eutectic consisted from (80-90) % of a slow moderation lead isotope, Pb–208, and (20-10) % of Bi-209 has been proposed.

In this paper a possibility of using molten pure Pb-208 as a coolant for a subcritical core of 80 MW thermal capacity of a PDS-XADS type facility is considered. Calculations of neutronic and physical characteristics of the core were performed using Monte Carlo technique, the MCNP/4A code, the program NJOY and the library ENDF/B-VI.

The following initial data were chosen: an annulus core with a target – the neutron source in its center; a core coolant – Pb-208 (100%); a fuel – mix of mono nitrides of depleted uranium and power plutonium with a small share of neptunium and americium; a target coolant – the modified eutectic, Pb-208(80%)-Bi(20%); proton beam energy – 600 MeV; effective multiplication factor of the core – K_eff= 0.97;thermal capacity of the core – N = 80 MW.

From calculations performed it follows that in using Pb-208 as a core coolant the necessary intensity of external source neutrons to deliver 80 MW thermal capacity is equal to S = 2.29·10¹⁷ n/s, that corresponds to proton beam current I_p= 2.8 mA and beam capacity Р_p = 1.68 МW.

In using natural lead instead of Pb-208 as a core coolant, effective multiplication factor of the core in normal operating regime falls down to the value equal to K_eff=0.95. In these conditions multiplication of external source neutrons in the core and its thermal capacity are below nominal by 1.55 times. For achievement the rated core power N=80 МW it is required on ~20-30 % to increase the fuel loading and volume of the core, or by 1.55 times to increase intensity of external source neutrons. In the last case, the required parameters of proton beam and its target are following: intensity of external source neutrons S = 3.55·10¹⁷n/s., beam current I_p= 4.32 mA, beam capacity Р_p = 2.59 МW.

Thus, in using Pb-208 instead of conventional Pb-nat the operating beam current of the accelerator for the 80 MW_thPDS-XADS type facility can be cut from 4.32 mA to 2.8 mA. To exploit the accelerator with this lower proton beam current it will be required about 20-60 tons of Pb-208, as a minimum, for the core coolant. Charges for its obtaining can be recovered at the expense of the economy of the proton accelerator construction cost. In this case, the accepted price of the lead isotope Pb-208 must be less than 1,500-5,000 $/kg.

REFERENCES

1. Georgy L. Khorasanov, Anatoly P. Ivanov, Anatoly I. Blokhin. Regulation of the ADS neutron spectrum by changing the target material isotopic composition (I). In: CD-ROM Proceedings of the 13^th International Conference on Nuclear Engineering ICONE 13, May 16-20, 2005, Beijing, China, Paper # 50410. Book of Abstracts, Beijing: Atomic Energy Press, 2005, p.143.

2. Georgy L. Khorasanov, Anatoly P .Ivanov, Anatoly I. Blokhin. Regulation of the ADS neutron spectrum by changing the target material isotopic composition (II). In: CD-ROM Proceedings of the 7^th International Conference GLOBAL 2005, October 9-13, 2005, Tsukuba, Japan, Paper # 113. Book of Abstracts, 2005, p. 79.