Ceramic materials for high-temperature nuclear reactors must possess a certain combination of characteristics including the ability to withstand the high temperatures and strong neutron irradiation together with mechanical properties necessary for installation of such a device. This is achieved by the use of a combination of low-ductility materials in the core of the nuclear reactor and the most ductile steel or metal alloys for the cladding of fuel rods. For example, zirconium and the alloys thereof, because of their high stability and thermal resistance as well as relatively low cost, have been developed as structural materials for use in fuel rods for such high-temperature reactors. At the same time, molybdenum and its alloys with nickel or iron are well known as fuel rod cladding materials. As illustrated in FIGS. 1A and 1B, such fuel rod constructions contain pellets (not shown) of nuclear fuel (typically uranium oxide) disposed within a hollow tubular cladding material. The cladding material serves to provide structural stability and to prevent the radioactive fission products (such as I.sup.131, I.sup.132, Zr.sup.90, and Nd.sup.144) from being released from the fuel rod into the coolant fluid in the reactor (see, e.g., U.S. Pat. No. 4,645,602 to Kaczmarczyk et al.). Various alloys have been considered for use as fuel rod cladding materials. Such alloys are disclosed in, for example, U.S. Pat. No. 5,096,389 to Coffin et al., U.S. Pat. No. 4,889,647 to Roush et al., and U.S. Pat. No. 4,678,627 to Dai et al., each of which is incorporated by reference herein in its entirety. For example, one cladding material for use in reactors developed by the assignee of the present invention (GE-Hitachi Nuclear Energy) is designated ZIRLO.RTM. and consists of an alloy (about 90 wt. % Mo, about 8 wt. % Fe, about 2 wt. % Cr and about 0.005 wt. % C) in which about 0.3 to 0.5 wt. % carbon has been uniformly distributed throughout the alloy, such as by gas atomization. One problem associated with the use of molybdenum and molybdenum alloys as the core material in high-temperature fuel rods is that such core materials tend to develop a thin, high-resistivity layer called M-layer upon exposure to high temperature, hydrogen, and water vapors. This M-layer is characterized by high resistance, causing significant increases in the temperature drop across a fuel rod during irradiation as compared with the same rod made of a higher conductivity material. Thus, while ZIRLO.RTM. (e.g., a molybdenum alloy containing about 0.3 to 0.5 wt. % carbon) has a high thermal conductivity, it has also a relatively high electrical resistivity. Thus, M-layer formed on a ZIRLO.RTM. cladding in an operating fuel rod could result in a temperature drop of as much as about 5% in comparison to a cladding formed from a material having a lower resistivity, such as pure molybdenum. See, e.g., U.S. Pat. No. 5,126,398 to Fong. The resulting temperature drop has a direct effect on the efficiency of a nuclear reactor operating with such a rod cladding. As previously mentioned, there have been attempts to improve the electrical conductivity of Mo and Mo alloys by incorporating relatively small amounts of carbon in the alloying elements. See, e.g., U.S. Pat. No. 4,964,957 to Schrems et al., which relates to improving the thermal conductivity of a high-temperature alloy by incorporating a small amount of carbon (less than 0.5 wt. %) therein. Schrems et al. discloses that, due to its relatively high diffusion coefficient for carbon and aluminum, the desired carbon content of the alloy can be reached by means of an inert gas atmosphere in a vacuum furnace having an aluminum evaporation unit. Schrems et al. specifically states that "pure Mo is not used due to the tendency of this material to form reaction products (such as carbides and nitrides) during high temperature heat treatment, and as a result, is unsuitable as a nuclear fuel." U.S. Pat. No. 5,036,040 to Harner discloses a Mo-based alloy having 0.01 to 0.1 wt. % carbon, and preferably 0.03 wt. % or less, which is said to be resistant to the loss of Mo and can be used in heat generating components exposed to temperatures up to about 1,000.degree. C. Harner indicates that these Mo-based alloys preferably comprise 0.5 to 8 wt. % of at least one element selected from the group consisting of Fe, Ni, Cr, Ta, W, V and Ti. Although the incorporation of carbon in molybdenum alloys to improve the fuel rod cladding for use in high-temperature reactors has been attempted in the past, the resulting structures have not been shown to achieve the necessary mechanical and structural stability required of nuclear fuel rod cladding materials. For example, while the MoC alloy proposed by Schrems et al. may be capable of withstanding the high temperatures required of fuel rod cladding in a high-temperature reactor, the processing requirements and small carbon content (0.01 wt. %) of the MoC alloy of Schrems et al. would not be sufficient to significantly improve the mechanical properties of the MoC alloy cladding. Further, while the Mo-based alloy described in Harner has a significantly higher carbon content than Schrems et al. (up to 1 wt. %), the resulting high carbon content in combination with the large amounts of other alloying elements proposed in Harner would be likely to result in the formation of undesirable carbides and nitrides, thereby causing insufficient mechanical properties, including inadequate creep resistance, ductility, and toughness, in the resulting Mo-based alloy, which is ultimately undesirable. Further, while molybdenum alloys containing up to about 3 wt. % carbon have been suggested in the prior art, such as in U.S. Pat. No. 4,964,957 to Schrems et al., it is believed that the maximum carbon content in a molybdenum alloy is about 1 wt. %. Thus, further improvements are required to address the need to use a higher percentage of carbon in a Mo-based alloy for the purpose of improving its electrical and structural characteristics. In light of the foregoing, it would be desirable to develop a molybdenum-based alloy having a higher carbon content (i.e., at least about 1 wt. %), and a method for using such an alloy as a cladding material for nuclear fuel rods that results in significant improvements in the mechanical properties of the alloy without the need to use complicated processes to incorporate a relatively high carbon content in the alloy. The present invention meets these and other needs.