Lead—bismuth eutectic

The most commonly used Hquid metal is sodium—potassium eutectic. Sodium, potassium, bismuth, lithium, and other sodium—potassium alloys also are used. Mercury, lead, and lead—bismuth eutectic have also been used however, these are all highly toxic and appHcation has thus been restricted. 

Further away in time are possibilities of using fast reactors, though, at least for some decades, not as breeders. The Soviet navy has been using such reactors, using a lead/bismuth eutectic mixture as coolant, for some decades in some of their high performance submarines and it is understood that work is now going on to see whether this design could be made suitable for small commercial power production... 

Liquid metals are used when temperature requirement is so high that even the nitrate/nitrite salt mixture becomes unsuitable. The most commonly used liquid metal is a eutectic mixture of sodium and potassium (44%). This has a very broad temperature range (40-760°C) and very high thermal conductivity. Lead and lead-bismuth eutectic can be used up to 900° C. There are several disadvantages with the use of liquid metals. Special precautions must be taken while using alkali metals because they react violently with water and burn in air. Mercury, lead, and bismuth-based mixtures are highly toxic, hence their applications are restricted. One common use of liquid metals is in the cooling of nuclear reactors. 

Konys, J., Muscher, H., Vofi, Z. and Wedemeyer, O. (2004) Oxygen measurements in stagnant lead-bismuth eutectic using electrochemical sensors. J. Nucl. Mater, 335 (2), 249-53. 

Li, N., Active control of oxygen in molten lead-bismuth eutectic systems to prevent steel corrosion and coolant contamination, J. Nuclear Mater. 399 (2001) 73-81. 

Gromov, B.F., Subbotin, V.I., and Toshinskii, G.I., Application of the melts of the lead-bismuth eutectic and lead as heat carriers at nuclear power facilities. At. Energy 73 (1992) 19-24. 

GIDROPRESS, in which a great deal of experience has been accumulated in the course of the development and operation of submarine reactors cooled with lead-bismuth eutectic. However, bismuth is expensive and the resources are limited. It is possible that its use must be confined to special applications, such as small reactors or to a limited number of fast reactors. For this reason lead cooling is also being studied in the IPPE, Kurchatov Institute, and other organization [2.19-2.26]. 

The thermohydraulic features of lead-bismuth and lead coolants are high boiling temperatures and the relative inertness compared with sodium. The melting and boiling points of sodium are respectively 98°C and 883 C. For lead-bismuth eutectic the respective figures are 123.5°C and 1670°C and for lead 327 C and 1740°C at atmospheric pressure. The boiling points are well above cladding failure temperatures. The specific heats per unit volume of lead-bismuth and lead are similar to those of sodium but the conductivities are about a factor of 4 smaller. 

The main thermophysical properties of sodium, lead, bismuth and lead-bismuth eutectic alloy (44.5% Pb-55.5% Bi) are presented in the Table 3.4. [3.3]... 

TABLE 3.4. THERMOPHYSICAL PROPERTIES OF SODIUM, LEAD, BISMUTH AND LEAD-BISMUTH EUTECTIC ALLOY (44.5% PB 55.5% BI)... 

Preliminary studies on lead-bismuth and lead cooled reactors and ADS (accelerator driven systems) have been initiated in France, Japan, the United States of America, Italy, and other countries. Considerable experience has been gained in the Russian Fedaration in the course of development and operation of reactors cooled with lead-bismuth eutectic, in particular, propulsion reactors. Studies on lead cooled fast reactors are also under way in this country. 

In the USSR the lead-bismuth eutectic alloy was chosen as LMC [1]. 

It should be highlighted that there is no sharp boundary between lead-bismuth eutectic alloy and pure lead. As bismuth has been in deficiency, one can consider non-eutectic alloy with bismuth content decreased up to 10% (versus 56% in eutectic alloy). Being compared with lead coolant, its melting temperature is decreased by 77°C (to 250°C) and that facilitates RI operation and reduces maximal temperatures of fuel elements claddings up to the values tested for eutectic coolant under the conditions of long-term operation tests. 

The possibility and expediency of developing the NP based on unified small power reactor modules SVBR-75/100 with fast neutron reactors cooled by lead-bismuth eutectic coolant (LBC) is substantiated for the nearest decades in the paper. 

GROMOV, B.F., SUBBOTIN, V.I., TOSHINSKY, G.I., "Application of Lead-Bismuth Eutectic and Lead Melts as Nuclear Power Plant Coolant", (Atomnaya Energiya, July 1992), Vol.73, Issue 1, Page 19. 

PYLCHENKOV, E.H., "The Problems of Maintaining the RIs Operation Ability under the Regimes of Coolant (Lead-Bismuth Eutectic Alloy) Freezing-Unfreezing" (Rep, Conf. HLMC-98, Obninsk). 

Analysis of the characteristics of liquid-metal coolants, such as sodium (Na), lead (Pb) and lead-bismuth eutectic (Pb-Bi), makes it possible to decide on the coolant for the new fast reactor considered as a basic component of large-scale nuclear power, which will be capable of taking over the greater part of the electricity generation increase and, possibly, of providing for other energy-intensive processes. 

The LFR is a fast-neutron spectrum reactor cooled by molten lead or a lead-bismuth eutectic liquid metal. It is designed for the efficient conversion of fertile uranium and the management of actinides in a closed fuel cycle. 

The lead-cooled fast reactor uses either lead or lead-bismuth eutectic in the primary coolant loop. This gives similar advantages as with the SFR in terms of operational safety. Several of these reactor designs were built and operated on Russian submarines. 

A single ENHS reactor consists of nine factory-fabricated modules - one ENHS and eight steam generators. All these modules are transported to the power plant site completely assembled ready to be inserted into the secondary coolant (lead-bismuth eutectic) pool. These modules are supported from the top by a seismically isolated structural platform. There is no mechanical connection between the modules. This makes it easier to install, inspect and replace them in an existing plant. The reactor pool is located inside an underground silo. The pool vessel with the secondary coolant are supported either from the top on the seismically isolated structural platform, or from the bottom. The preferred design choice is yet to be made. 

LEAD-BISMUTH EUTECTICS COOLED LONG-LIFE SAFE SIMPLE SMALL PORTABLE PROLIFERATION RESISTANT REACTOR (LSPR)... 

Lead-bismuth eutectics cooled fast reactor... 

At present, sodium is considered the best coolant for fast reactors due to its superior cooling ability, which can help to increase the core power density and shorten the doubling time. Short doubling time was an indispensable requirement in the early phases of development and construction of fast breeder reactors from 1960s through 1980s. It is reported that for safety reasons, the lead-bismuth eutectic (LBE) cooled fast reactor was originally considered [XXV-2]. 

To achieve a long-life safe simple small portable proliferation-resistant reactor, a lead-bismuth-eutectic (LBE) coolant was selected as the best candidate. The original concept of a long-life small LBE cooled fast reactor was proposed more than 10 years ago [XXV-3], which was the world s first trial of this kind. The name of this reactor, the LBE cooled long-life safe simple small portable proliferation-resistant reactor (LSPR) distinguishes it from similar reactors proposed by other institutes. 

Nuclear heat from the reactor core is removed passively by a lead-bismuth eutectic alloy coolant [XXIX-4], which flows due to natural circulation between the bottom and top plenums, upward through the fuel tubes and returning through the downcomer tubes. On top of the upper plenum, the reactor has multi-layer heat utilization vessels to provide an interface to systems for high temperature heat applications. A set of sodium heat pipes is in the upper plenum of the reactor to passively transfer heat from the upper plenum to the heat utilization vessels with a minimum drop of temperature. Another set of heat pipes transfers heat from the upper plenum to the atmospheric air in the case of a postulated accident. To shut down the reactor, a set of seven shut-off rods has been provided, which fall by gravity in the central seven coolant channels. Appropriate instmmentation like neutron detectors, fission/ ion chambers, various sensors and auxiliary systems such as a cover gas system, purification systems, active interventions etc. are being incorporated in the design as necessary. 

The CHTR incorporates a passive power regulation system (PPRS) [XXIX-5]. This system includes a gas header filled with helium gas at moderate pressure. The header is attached to a niobium driver tube, which contains lead-bismuth eutectic alloy as driven liquid. The driver tube is housed within a control tube that contains an annular control rod made of boron carbide with niobium cladding. The annular space between the driver and control tube contains lead-bismuth eutectic, on which the control rod floats. The space above the liquid... 

Coolant Lead-bismuth eutectics with argon average gas content- 31% vol. 

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