Knowledge Hub · Saxsons Decay Drum

10 × T½ to 0.1 % residual — the operational hold cycle.

Decay drums hold contaminated solid waste for 10 half-lives — long enough for residual activity to fall below the clearance threshold for the standard biomedical-waste chain. Per-isotope hold cycles range from 18 h (F-18) to 67 days (Lu-177); drum sizing × Pb tier × isotope mix together set the decay-store fit-out plan.

10 × T½ framework

Why 10 half-lives is the standard hold cycle

Radioactivity decays exponentially. After one half-life, 50 % remains; after 10 half-lives, 2⁻¹⁰ ≈ 0.098 % remains — below the regulatory clearance threshold for transfer to the standard biomedical-waste chain. The "10 × T½" hold cycle is the operational standard for radiopharmacy decay-store rooms. Drum capacity is sized so the hold cycle does not overflow.

Source: IAEA Safety Reports Series No. 38; AERB Safety Code.

Per-isotope hold cycles

Why F-18 needs ~18 h and Lu-177 needs ~67 days

F-18 T½ = 110 min → 10 × T½ = 18 h. Ga-68 T½ = 68 min → 11 h. Tc-99m T½ = 6 h → ~ 60 h. Cu-64 T½ = 12.7 h → ~ 5 days. Lu-177 T½ = 6.7 days → ~ 67 days. I-131 T½ = 8 days → ~ 80 days. The drum capacity × Pb tier × number of drums is sized so the per-shift solid-waste volume can decay-out without pile-up.

Source: ICRP Publication 107 — nuclear-decay data.

Pb tier per radiopharmaceutical class

Why the drum-wall tier still matters at the decay-store room

The decay drum sits in a dedicated decay-store room — but the operator handles the drum at fill and at empty. Pb tier must match the radiopharmaceutical class so the dose-rate at the operator hand stays inside the AERB envelope at those handling intervals. SPECT 3 mm Pb, I-131 6 mm Pb, routine PET 12 mm Pb, Lu-177 theranostic 25 mm Pb.

Source: NCRP Report 49 HVL framework; NIST XCOM cross-section database.

100 L high-volume hold

Why Lu-177 theranostic centres need the multi-week buffer

Lu-177 has a 67-day clearance window vs F-18's 18-hour window. A theranostic suite running per-patient PRRT / PSMA-617 dispensing accumulates solid waste faster than the half-life can decay it in standard 14 L drums. The 530 × 1100 mm 100 L drum gives the multi-week buffer needed without forcing daily drum-swap.

Source: Saxsons hot-lab fit-out reference; AERB decay-store-design framework.

AERB chain-of-custody

Why the drum log is part of the licence-renewal audit

Each drum carries a chain-of-custody log — date of fill, isotope mix, expected decay-out date, drum-volume signature, final-disposal pickup record. The radiation-safety officer signs the log at each handoff event. The full log is part of the AERB licence-renewal audit trail; the Saxsons drum ships with the AERB-template log sheets.

Source: AERB Safety Code; CPCB Bio-Medical Waste Management Rules.