RECOMMENDATION 90-3 TO THE SECRETARY OF ENERGY
                   pursuant to Section 312(5) of the
                Atomic Energy Act of 1954, as amended.



Dated:  March 27, 1990



During the visit of members of the Defense Nuclear Facilities
Safety Board to the Hanford site on December 11-12, 1989, one of
the topics discussed was the question of the susceptibility of the
old single shell high level waste tanks to an explosion of a
spontaneous nature, with resulting release of large amounts of
radioactive material to the environment.  This potential problem
had been brought to the attention of the Board during its
confirmation hearing.  The Board members received a briefing on the
subject during their visit and they were later furnished additional
relevant documents.

The Board subsequently obtained the assistance of three highly
qualified experts, who visited the Hanford site on March 20-21,
1990, to explore questions that had surfaced through its earlier
reviews.  The experts developed information on the chemical
contents of the tanks and the implications for the possibility of
a spontaneous explosive reaction.  The experts have now made their
preliminary oral report to the Board.

As a result of these activities, the Board concludes that the
probability of an explosion in the old single shell waste tanks is
low.  All evidence available indicates that the conditions that
might have contributed to a higher probability of such an explosion
were more prevalent in the past than they are now, and these
conditions are continuing to lessen as time passes.  The principal
factor contributing to this moderating of conditions is the
reduction of the radiation field in the tanks through radioactive
decay of their active contents.  This serves to lower both the rate
of ionization of the components of the waste and the heat source
that might elevate the temperature.

However, the Board does have some residual concerns resulting from
the uncertainty of information on the details of composition of the
contents of these tanks, the physical conditions within them, and
the recent information concerning high levels of hydrogen in some
of the double-walled waste tanks.  These concerns prompt the Board
to recommend the following for future programs for monitoring the
single shell tanks:

      o    That a study be undertaken of the possible chemical
           reactions that could be the source of heat generation
           locally or globally in the single shell tanks, thereby
           elevating the temperature to a value where explosive
           ferrocyanide reactions can take place rapidly.
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      o    That the Department of Energy develop a program for
           continuous monitoring of these conditions in the single
           shell tanks that can serve to indicate development of
           conditions indicating an onset of instability in their
           contents.  These conditions might include such features
           as abnormal temperatures in local areas, physical
           deformation of the surface of the waste, or unusual
           components (including hydrogen) in the cover gas within
           the tanks.

      o    That the instruments used in monitoring the tanks be
           provided with alarm indicators at a location where
           decisions can be made and action taken to start a series
           of measures to neutralize a perceived abnormality.

      o    That an action plan be developed for the measures to be
           taken to neutralize the conditions that may be signaled
           by alarms.

The Board considers the matter of hydrogen generation in the double
walled tanks to be potentially more serious than questions related
to the single shell tanks, and is pursuing it separately.



                                                                                                                                                                                                                                                   /s/

                                                                                                                                                                                                   John T. Conway
                                                                                                                                                                                                   Chairman