
Leading South African scientists and explosive experts believe
that the mystery substance Red Mercury, subject of an
international debate regarding alleged arms smuggling, may well
be used in the manufacture of nucleur bombs.

Sensationalized conclusion by the jpurnalist, contradicts with:

Leading physicist Dave Aschman said it seemed that all South
African explosive experts and nuclear specialists agreed that the
sale of Red Mercury, by its formula a normal detonator explosive
and not necessarily the best, was part of an international scam.
"None of the people involved in physics research can see how it
could participate in a nuclear reaction. The normal chemical
reaction forcing nuclear material together to form a critical
mass is the only way it can work," he said.
The scientists agreed that "layman's pseudo-science" was being
used to sensationalise alleged special properties for the
substance.

In short: it may be used as an explosive in a nuke, just as any explosive, but wouldn't be remotely near the best choice. Other than that it has no
special properties and does not participate in a nuclear reaction. I do believe red mercury could exist as an old Soviet code name for something else,
lithium-6 has been named for that.
nti.org...