Dr. Thorsten Schumm, a research group leader at Vienna University, is working on what they call "The Thorium Project". Here they utilize the unique properties of thorium which show promising features to be used as a time and frequency standard. Time and frequency measured with atomic clocks are the most well defined physical quantities today and their accuracies are crucial for most modern high precision physics measurements and is used on a daily basis in GPS and satellite communications. Different ways to improve the atomic clock further have been discussed lively in recent years.
The answer to an even more accurate definition of time might not be an atomic clock but rather a nuclear clock based on thorium. It might be possible that thorium in the future could provide the world with a solid state time standard device which is less sensitive to its noisy surroundings than the now available atomic clocks.
Time and energy are two of the most fundamental units in nature and thorium might now prove to be the best solution to both of them.
www.thorium.at, Thorium research group at Vienna University
arXiv.org, Optical transition in thorium paper