There was recently a discussion here about the agreement with Iran
regarding their nuclear program. I expressed an opinion that unless
Iran demonstrated the ability to produce nuclear weapons, we should try
to make it work.

Someone ... I think it was John H ... questioned the agreement and my
opinion on it. He suggested that waiting to find out that they *had*
nuclear weapons would be a mistake and also that the weapons could end
up in the hands of others less responsible.

Here's the thing:

Enriching uranium to weapons grade is not a "one step" process. A
nuclear power plant uses uranium enriched to about 2-3 percent. Medical
use uranium is enriched a bit more. However weapons grade uranium must
be processed and enriched to 90 percent or more.

The agreement with Iran limits their enrichment of uranium to 20 percent
which makes it unusable for making weapons. Furthermore, trying to go
from 20 percent to 90 percent is a time consuming and laborious process.
It wouldn't happen overnight and with proper monitoring, it wouldn't
go unnoticed.

The success of the agreement is the "trust but verify" part. Iran has
agreed to international monitoring of their enrichment facilities. If
enrichment levels exceed 20 percent, flags will be raised well before
they obtained the necessary 90 percent level required to make a bomb.