Subseabed Disposal Program In-Situ Heat Transfer Experiment (ISHTE)

A heat transfer experiment is being developed in support of the Subseabed Disposal Program. The primary objectives of this experiment are: to provide information on the in situ response of seabed sediment to localized heating; to provide an opportunity to evaluate theoretical models of the response and to observe any unanticipated phenomena which may occur; and to develop and demonstrate the technology necessary to perform waste isolation oriented experiments on the seafloor at depths up to 6000 m. As presently envisaged, the heat transfer experiment will be conducted at a location in the central North Pacific though it could be performed anywhere that the ocean bottom is of the type deemed suitable for the disposal of nuclear waste material. The experiment will be conducted of the seafloor from a recoverable space-frame platform at a depth of approximately 6000 m. A 400-W isotopic heat source will be implanted in the illite sediment and the subsequent response of the sediment to the induced thermal field evaluated. After remote initiation of the experiment, a permanent record of the data obtained will be recorded on board the platform, with selected information transmitted to a surface vessel by acoustic telemetry. The experiment will be operational for one year, after which the entire platform will be recovered. Current plans call for the deployment of the experiment in 1986. Specific activities which will be pursued during the course of the experiment include: measurement of the thermal field; determination of the effective thermal conductivity of the sediment; measurement of pore pressure; evaluation of radionuclide migration processes; pore water sampling; sediment chemistry studies; sediment shear strength measurements; and coring operations in the immediate vicinity of the experiment for postexperiment analysis