Curium is not currently used as a nuclear fuel due to its low availability and high price. 245Cm and 247Cm have very small critical masses and therefore could be used in tactical nuclear weapons, but none are known to have been produced. Curium-243 is not suitable for this purpose because of its short half-life and strong α emission, which would result in excessive heat. Curium-247 would be highly suitable due to its long half-life, which is 647 times longer than plutonium-239 (used in many existing nuclear weapons).