** Shares of ASP Isotopes drop 18.5% to $6.3, hitting a four-week low

** Short-seller Fuzzy Panda says it is short on the advanced materials firm; adds in a post on social media platform X that ASPI has the "makings of the next nuclear meltdown"

** Short-seller alleges ASPI uses 'failed tech from 20 years ago and indulges in paid stock promotion'

** ASPI did not immediately respond to a Reuters request for comment

** Including session's losses, ASPI up more than 250% YTD

(Reporting by Shashwat Chauhan in Bengaluru)

((Shashwat.Chauhan@thomsonreuters.com))