Decay-in-storage area
Decay-in-storage is the primary disposal pathway for Ac-225 waste under 10 CFR §35.92. The storage area is a facility design decision, not just an operational one — its size, location, and access controls need to be planned before the first patient, sized for the full chain hold time rather than the 9.9-day parent half-life.
Storage-area design
Sizing
Size the storage footprint to the program's peak hold inventory, not the average. A reasonable planning basis is the maximum activity expected to be in storage at any one time × the hold-time multiplier for the full chain (typically ≥10 half-lives of the longest-relevant progeny).
Shielding & access
Shielded containers (or a shielded room) sized for Bi-213. Locked, posted per 10 CFR §20.1902, accessible only to authorized staff. Survey log at the door.
Segregation
Waste segregated by stream (sharps, dry combustible, absorbents, vials) and by receipt date. First-in / first-out staging so survey-and-release work cleanly without rummaging.
Release survey station
A dedicated survey bench with ZnS alpha probe, low-background alpha counter, and the release-survey log. Material does not leave the storage area without a documented survey at or below background, label removal, and a second signature.
Under-sizing the decay-storage room is a common — and expensive — facility mistake on new alpha programs. A 9.9-day parent and a hold-time multiplier of 10 alone implies roughly a quarter-year of inventory at steady state for a busy program, so it's worth sizing for the program you want in three years, not day one.
- 10 CFR §35.92 — Decay-in-storage.
- 10 CFR §20.1902 — Posting requirements.