It's already been answered, but below is from the Maint Manual.
Also, during the replacement program from uranium to tungsten - quite a few of the old uranium weights ended up in "scuba diving belts"
Lotsa weight but no where near as bulky as lead.
There's nothing, and I mean nothing that an aircraft engineer can't find another use for.
RUDDER/ELEVATOR BALANCE WEIGHT - REMOVAL/INSTALLATION
1. General
A. This procedure includes removal and installation of balance weights for
the rudder and elevator while control surface is still installed on the
airplane. Balance weights can be made of tungsten or depleted uranium.
WARNING: THE RUDDER AND ELEVATOR MUST BE PROPERLY BALANCED AT ALL TIMES.
AN OUTBOARD ELEVATOR OR RUDDER THAT DOES NOT MEET THE
REQUIREMENTS SPECIFIED IN 51-80-02 OR 51-80-03 OF THE
STRUCTURAL REPAIR MANUAL CAN PRODUCE UNDESIRABLE FLUTTER AND
DYNAMIC INSTABILITY WHICH COULD AFFECT FLIGHT SAFETY.
B. Depleted Uranium Balance Weights
(1) Some balance weights on outboard elevator and upper rudder are made
from depleted uranium, which is a naturally occuring uranium that
has been "depleted" of most of the isotope U235. This remaining
low-level radioactive uranium, similar to other heavy metals, is
toxic if ingested, absorbed, or inhaled into the body. Those
weights are identified with legends permanently stamped into the
surface of each weight, to assure special handling during
maintenance. Protective coatings have been electro-plated on the
weights to contain the depleted uranium. If those coatings are
penetrated, certain precautionary measures are required to minimize
the small health risk.
WARNING: REWORK, SUCH AS FILING, SANDING OR MACHINING, THAT WOULD
DAMAGE THE PLATING OR REMOVE ANY BASE METAL IS PROHIBITED.
INHALATION OR INGESTION OF FILINGS, DUST, ETC., FROM THE
WEIGHTS MAY BE HARMFUL.
(2) Limited repair of damaged or corroded weights can be accomplished
safely if the procedures in subject 51-20-03, hazardous materials,
of the Structural Repair manual are used.
(3) Replacement of uranium balance weights with tungsten balance weights
can be obtained from Structural Repair manual (51-20-03).