Application of shape-memory alloys in nuclear power

Abstract

Shape-memory alloys are materials which acquire a prescribed form when heated up to the so-called transformation temperature, and their initial shapes are restored on cooling. Such alloys are being developed because they possess unique properties: shape restoration on heating, slope of the characteristic (displacement versus temperature), possibility of compression on heating, repeated operation, large shear deformations, large stresses developed, effective damping, sound absorption, plasticity, superelasticity, prolonged retention of the properties, the possibility of combining sensitive and executing elements, constructional simplicity [1--3].An experimental industrial technology for fabricating different geometric forms of shape-memory materials has been developed and assimilated: rods with diameters ranging from 8 to 230 mm, wires with diameters from 0.2 to 7 mm, tubes with diameters from 14 to 60 mm, sheets with thicknesses from 0.5 to 10 mm, and ribbons with thicknesses from 0.04 to 3 mm [4]. Materials with a different transformation temperature have been obtained: up to ......Applications of shape-memory alloys in nuclear power. The possible applications of shape-memory alloys in nuclear power include passive safety systems, connecting, packing, and sealing elements (thermocouplings) for pipes and electric drives, equipment for efficient repair and assembly of units of a nuclear power plant, thermomechanical drives and motors, dampers, flow rate regulators, thermodetectors, direct-action (self-operating) emergency systems, units and elements (compensators) in electrical transmission lines, electric contact devices, and others [5].A direct-action emergency shielding is being considered primarily for action on the reactivity of the core of a nuclear reactor and/or on the temperature of the coolant or a structural element. Some of the units which have been developed, for example, couplings, caps for pipes, self-sealing interlayers, and direct-acting emergency units (for reactivity and flow rate). have been introduced into an information system developed at the Special Office of Machine Design (Nizhnii Novgorod) "constructions with the shape-memory effect in nuclear power technology" [6].Peculiarities of the application of shape-memory alloys in nuclear power [7--8]. Equipment with shape-memory alloys must be designed for use at temperatures ranging from below 100~ to above 600~ The temperature change that actuates the equipment ranges from 5--10 to 40--50~The equipment must remain operable under neutron fluences of up to 102~ cm -2. Moreover, such equipment can be located in different surrounding media (in nitrogen or helium, prepared or distilled water, melted sodium or lead). Equipment for application in nuclear power is developed on the basis of its functional peculiarities: required number of cycles, purpose (sealing, connection of pipes and ducts, covering of a pipeline, action on a working unit, safety systems, unsealing of vessels, rupture of an electric circuit, and so on), the working medium, and so ...

Microstructure, mechanical properties and shape memory effect of Cu–Hf–Al–Ni alloys

“…However, the operating temperature of Ni-Ti is usually less than 100°C due to its low martensitic transformation temperatures. Thus, hightemperature shape memory alloys (HTSMAs) have attracted increasing interest in high-temperature fields, such as nuclear power plant [2], electricity plant [3], aerospace and energy exploration [4]. Currently, several HTSMAs, such as Ti-Ni-Pd [5][6][7], Ta-Ru [8], Ti-Ta [9,10] and Ni-Mn-Ga [11][12][13][14] have been widely investigated in the past few decades.…”

Particle radiation effects on shape memory alloy couplers for ultra-high vacuum sealing: a preliminary study

“…Unfortunately, the literature about SMA irradiation is very scarce. Some early investigations were carried out in the 90s, with the aim of assessing possible application of SMAs in fission and fusion reactors [9][10][11]. The major damage produced by fast neutron irradiation in metals is mainly related to atomic displacement cascades creating stable Frenkel pairs [12].…”

“…These changes could lead to a degree of amorphization and therefore, to possible modification in the phase transition mechanisms. Most of the studies in literature refer to NiTi alloys irradiated with fast neutrons (energy E>1 MeV) to fluences ranging from 10 16 to 10 21 cm −2 [9][10][11][13][14][15][16][17][18][19][20]. In particular, three different types of NiTi alloys were analyzed by Hoshiya et al [15]; electrical resistance tests were carried out on neutron-irradiated specimens.…”

Martensitic Transformation and Shape Memory Effect in TiNi-Based Alloys during Neutron Irradiation

“…The shape memory alloys occupy an individual place among other materials as they demonstrate unique mechanical behaviour [1], and thus these materials are attractive for different applications such as switches, actuators, coupling, and others. In [2][3][4][5][6][7][8], it was suggested that shape memory alloys be used as direct action equipment for neutron absorber rods, controlling accessories for action on the coolant flux, self-clinching devices, tube sealing, thermo-mechanical coupling, and so on. However, there is no information about successful application of TiNi-based shape memory alloys for such technologies.…”