ALARAAs Low As Reasonably Achievable

ALARA is the second of three classical radiation-protection principles — justification (no practice involving radiation unless it does more good than harm), optimisation (ALARA), and dose limitation (numeric ceilings that must never be exceeded). The optimisation step says that operating under the dose limit is not enough; the licensee must actively drive dose down to the lowest level reasonably achievable given the technology, cost, and benefit of the practice. NRC codifies it at 10 CFR 20.1003; ICRP frames it in Publication 103; IAEA folds it into the Basic Safety Standards.

• 10 CFR 20.1003 (US NRC) defines ALARA; 10 CFR 20.1101(b) requires every licensee to apply procedures and engineering controls based on sound radiation-protection principles to achieve occupational and public doses ALARA.
• NRC Regulatory Guide 8.10 — operating philosophy for maintaining occupational radiation exposures ALARA — sets management commitment, dose review thresholds and corrective-action expectations.
• ICRP Publication 103 (2007) — the modern international framework that pairs optimisation with dose constraints and reference levels.
• IAEA GSR Part 3 (Basic Safety Standards) — globally referenced text adopted into national law by most Member States outside the US.
• EU: Council Directive 2013/59/Euratom (Basic Safety Standards Directive) implements ALARA across EU Member States.

ALARA is implemented in the dispense lab using the three classical exposure-reduction tools:

• Time — minimise dwell time near the source. Rehearse procedures with non-active phantoms; pre-stage syringes, vials, labels and shielding before touching the source.
• Distance — exposure follows the inverse square law (dose rate ∝ 1 / r²). Doubling distance from a point source cuts dose rate to one-quarter. Tongs, remote handlers, and well-counters move the worker away from the source.
• Shielding — typical materials are lead (gamma), tungsten (compact syringe and vial shields for PET energies), and acrylic / polycarbonate (beta-only emitters such as Y-90). Shielding is sized against the isotope's gamma energy and the dose-rate target at the surface of the shield.

All three are combined in the radiopharmacy SOP: short procedure time, maximum reasonable distance, isotope-appropriate shielding, plus engineering controls (fume hoods, dose calibrators behind L-blocks, automated dispense systems for high-energy PET tracers).

10 CFR 20.1201 sets US occupational annual dose limits: 5 rem (50 mSv) total effective dose equivalent; 50 rem (500 mSv) to any organ except the lens of the eye; 15 rem (150 mSv) to the lens of the eye; 50 rem (500 mSv) shallow-dose equivalent to the skin or any extremity. Public dose limit (10 CFR 20.1301) is 0.1 rem (1 mSv) per year. ALARA goes further by requiring administrative ALARA goals — typically a fraction of the limits (e.g. an investigation level at 10 % and an action level at 30 % of the annual limit) — that trigger documented review before the limit itself is approached.

10 CFR 20.1502 requires individual monitoring for adults likely to receive in one year a dose >10 % of the annual limit, plus monitoring of declared-pregnant workers and minors at lower thresholds. Typical radiopharmacy implementation:

• Whole-body OSL or TLD badge worn at trunk level.
• Ring dosimeter on the dominant hand for any worker who manipulates unshielded sources (extremity dose drives the radiopharmacist's binding limit, not whole-body).
• Optional real-time electronic personal dosimeter (EPD) with audible dose-rate alarm for high-activity workflows.
• Quarterly dose review by the Radiation Safety Officer (RSO); investigation / action / management-review escalations triggered at the administrative ALARA levels.

21 CFR 212 PET-drug CGMP and USP <825> push toward early conditional release (the unit dose ships before sterility / endotoxin results are back, because half-life would otherwise destroy the dose). ALARA influences several decision points in that workflow:

• Synthesiser hot-cell design — heavily shielded automated module; no manual contact with bulk activity.
• Dose calibrator behind L-block shielding; tongs for vial handling; tungsten syringe shields for unit-dose draws.
• Dispense before or after calibration time — driven by half-life + ALARA + patient injection slot. Calibration time entered in the dispense record; activity-at-administration computed from A(t) = A₀·e^(−λt).
• Conditional release per 212.70(d) — release without sterility result is acceptable only if positive sterility result would not have prevented administration; ALARA does not justify skipping release tests, but it does justify a workflow that gets the sterility result back as quickly as physically possible.
• Radwaste decay-in-storage — store short-lived waste behind shielding for >10 half-lives, then survey to RG 1.86 surface limits before release.

• Treating the legal dose limit as the target — ALARA requires lower goals than the limits.
• No documented administrative ALARA investigation / action levels.
• Extremity dosimetry skipped because whole-body badge readings are low — extremity dose can be 10–50× whole-body in radiopharmacy.
• Shielding sized against the wrong photon energy (e.g. lead sized for 99mTc 140 keV but used for 18F 511 keV positron annihilation gammas — that needs tungsten).
• Beta-only emitters shielded with lead — bremsstrahlung X-rays generated in lead increase rather than reduce dose. Use low-Z materials (acrylic) for pure beta.
• Dispense workflow optimised for throughput, not dose — running multiple unit-dose draws without re-shielding between draws.
• ALARA review meetings held without RSO sign-off, or never held at all.
• Conditional release sign-off treated as a substitute for the sterility result — it is not; the test still has to complete and the record reconciled.