The Editor, Sir:

In Thursday's paper, in response to a cautionary letter from another writer Nam Singh, letter writer Donald Chung referred to Pebble Bed Modular Reactors (PBMRs) as "idiot proof". I would like to point out that, to my knowledge, the only such prototype currently in use is in China, and a PBMR prototype plant was abandoned in Germany because of an accident in which a jammed pellet was damaged by operators trying to dislodge it from a feeder tube.

Conceptually attractive

While the idea is conceptually attractive, the fact is that many concerns still have to be addressed:

a) The radioactive fuel is encased in potentially combustible graphite;

b) The silicon carbide used to coat the graphite to mitigate against combustion is vulnerable to shear and expansion forces and gases such as xenon-133 which are not absorbed in carbon can build up within pebbles, causing them to rupture;

c) What do we do with the radioactive by-products from the PBMR? As Nam Singh pointed out, we either have to store it safely for thousands of years or reprocess/transmute it in a different type of reactor. Is it fair to unborn generations to ask them to deal with the consequences of our polluting activities?

Unfortunately, even solar and wind energy produce some (minimal) local pollution, but we need to look at these renewable energy sources as a priority rather than nuclear energy in any form which simply adds to the global environmental crisis which looms before us.

I am, etc.,

TREVOR BLAIR

tblair_ja@yahoo.com

Irish Town