This is a Sources Sought notice, not a solicitation for proposals, to determine if other qualified sources exist for a proposed sole-source contract. The Defense Threat Reduction Agency (DTRA) intends to procure three sealed sources each of Pu-239 and Sr-90 radioisotopes from Eckert & Ziegler Analytics, Inc. Interested parties have 15 days from the synopsis publication date to submit written evidence of their qualifications to potentially justify a competitive procurement. The procurement is proposed as a firm-fixed-price award. Responses must be submitted in writing to the specified points of contact.