In the following, you refer to heavy water as H₂O₂.  Actually, it would be more correct to say D₂O, as H₂O₂ is Hydrogen Peroxide.  Deuterium is as follows:

Deuterium --

The isotope of the element hydrogen with atomic weight 2.0144 and symbols ²H or D.  The terrestrial natural abundance of deuterium is 1 part in 6700 parts of ordinary hydrogen (protium).  Deuterium is a gas (D₂) at room temperature.  it is prepared from heavy water, D₂O either by electrolysis or by reaction of D₂O with metals such as zinc, iron, calcium, and uranium,  It is also prepared directly by the fractional distillation of liquid hydrogen.

Deuterium is used mainly in the form of heavy water (again, D₂O).

In the startrek universe, things may be different as to the use and actual state of the substance, but I doubt its symbol would change much.

With the highest respect and honor,
Scot
Extreme novice of the Klingon language
 

: > nIn: bIQSIp 'ugh
: > Fuel - Deuterium Isotope
:
: Heavy water gas. Apparently hydrogen. Daj.

{bIQSIp 'ugh} "heavy hydrogen" = deuterium (i.e. H2O2, "heavy water").  We can
now add {bIQSIp} "hydrogen" to {voQSIp} "nitrogen" and {yInSIp} "oxygen" from
S27.