From Japan Times-
Three experts, from Northwestern Univ.(3), Franciscan Univ.(2), and Nuclear and Industrial Safety Agency(1), say it is too early to consider burying the reactors.
(1) Not a realistic option at this time. In the future, after the radiation has cooled, as part of long term strategy.
(2) Structures that confine the radioactivity could be damaged by dumping of sand and other matterials. Such sand dumps were part of the containment at Chernobyl. Fukushima is different, the reactors are surrounded by multiple barriers designed to contain radiation from the reactor cores. If a heavy dumping cracked the inner vessels and exposed the reactor cores, "that would be absurdity." Dr. Alex Sich, nuclear engineer, is an expert on Chernobyl.
(3) Other risks focus on the spent fuel rods. While pouring tons of sand on the rods would block radiation from escaping, it wouls also insulate them and make them heat up faster. The heat could decompose the concrete floor, allowing the rods to fall through, which could complicate efforts to contain the radiation, said Elmer Lewis of Northwestern (he has consulted on reactor issues with U. S. National Labs.
(2) Spraying of dust-supressing materials that was done at Chernobyl is recommended by Sich. This in combination with sprayers to tamp down the dust.
(3)Lewis said the time to entomb the reactors with concrete might come when the radioactive materials have cooled.