Radioactive Waste Disposal at Sea: Public Ideas ... - IMO

22 Chapter 2
it enters the body, though generally less of a hazard than an alpha emitter.
Gamma rays, a very high-energy form of radiation, penetrate a relatively
great thickness of matter, such as steel and concrete, before being absorbed.
Overexposure of the body to gamma radiation results in deep-seated
organic damage. Gamma radiation is by far the most serious external hazard
of the three types of radiation from radioactive substances, and it
requires heavy shielding and remotely controlled operations.
One curie (Ci) is defined as the amount of radioactive material that will
produce 37 billion (3.7 × 10 10 ) disintegrations per second. This is approximately
the number of disintegrations per second in a gram of radium. A
more recent unit is the becquerel (Bq), which is the amount of radioactive
material that produces one disintegration per second. One terabecquerel
(TBq) is approximately equal to 27 curies. Minute radiation is measured in
nanocuries, one nanocurie being a billionth (10 –9 ) of a curie.
The two basic options for managing radioactive wastes are (1) to concentrate
and then store them and (2) to dilute them and then disperse them
in the environment. 2 Many forms of radioactive wastes exist, and all must
ultimately be disposed of. Disposal signifies the final fate of the waste without
the intention of retrieval later; storage means a temporary scheme. 3
Disposal does not imply continuous monitoring; storage does. Low-level
radioactive waste, which also can be disposed of on land, is the only form
of radioactive waste that has been dumped in the oceans. 4 Most of this
waste has been packaged in 55-gallon drums filled with concrete to ensure
that the drums would sink to the ocean bottom. These drums were not
designed to remain intact for long periods on the sea bottom, and it was
assumed that the contents would be released almost instantly (Templeton
1982, p. 39).
Fallout from atmospheric testing of nuclear weapons, which also has
reached the oceans, is regulated under the Limited Test Ban Treaty. 5
Volcanic eruptions on the sea bed, fallout from atmospheric nuclear
weapons tests, the Chernobyl nuclear disaster, and operational discharges
from the British Sellafield nuclear reprocessing plant (previously known as
Windscale) have been by far the greatest contributors to the radioactivity
of the marine environment. As the marine scientists Bewers and Garrett
summarize (1987, p. 106): “The total amount of radioactivity dumped in
the ocean, some 6 × 10 4 TBq, is much less than the approximately 2 × 10 8
TBq that were added to the oceans as a result of atmospheric testing of