ABSNM RP cheat sheet

Photon attenuation follows I = I0·e^(−μx); the half-value layer HVL = ln2/μ ≈ 0.693/μ.

Mass attenuation coefficient μ/ρ is approximately independent of physical state and density for a given material and photon energy.

Inverse-square law: exposure rate varies as 1/r² from a point source; doubling distance reduces dose rate to one quarter.

Gamma constant (exposure rate constant) relates activity to exposure rate at 1 m: Ẋ = Γ·A/r².

Beta particles have a continuous energy spectrum with maximum energy E_max ≈ 3× average energy; range in matter is finite and roughly proportional to E_max.

Alpha particles are monoenergetic, highly ionizing, and short-range; a sheet of paper or the dead layer of skin stops them.

Bremsstrahlung production increases with beta energy and with atomic number of the absorber; use low-Z shielding for beta sources.

Photoelectric effect dominates at low energy and varies approximately as Z³–Z⁴/E³; Compton scattering dominates at intermediate energies and depends on electron density.

Pair production requires photon energy ≥ 1.022 MeV (2 × 511 keV) and dominates at high energy in high-Z materials.

GM counters operate in the Geiger plateau where pulse height is independent of deposited energy; they cannot discriminate energy and have dead-time losses at high count rates.

Ionization chambers measure exposure or dose rate directly; proportional counters operate in a region where pulse amplitude is proportional to initial ionization.

Scintillation detectors (NaI(Tl), plastic) convert energy deposition to light; NaI(Tl) has high detection efficiency but limited energy resolution versus HPGe.

HPGe gamma spectrometry provides high energy resolution (~1–2 keV at 1332 keV) for radionuclide identification.

Dead-time correction: true rate = observed rate / (1 − observed rate × τ), where τ is resolving time.

Liquid scintillation counting is used for low-energy beta emitters such as H-3 and C-14.

Survey meters must be calibrated and their response checked with a check source before use; energy dependence affects reading accuracy.

Neutron detection commonly uses BF3 or He-3 proportional counters via the (n,α) reaction, or moderating detectors for dose equivalent.

Absorbed dose D is energy imparted per unit mass, unit gray (Gy) = 1 J/kg; 1 Gy = 100 rad.

Equivalent dose H = w_R × D, unit sievert (Sv); radiation weighting factor w_R is 1 for photons/electrons, 20 for alpha particles and fission neutrons (per ICRP 60).

Effective dose E = Σ w_T × H_T, where w_T are tissue weighting factors summing to 1.

Committed effective dose integrates dose over 50 years (adults) following intake of a radionuclide.

Collective effective dose is the sum of individual effective doses, unit person-sievert.

Exposure X is charge produced per unit mass of air, unit coulomb/kg; the roentgen = 2.58×10⁻⁴ C/kg.

Dose equivalent rate relationships: 1 Sv = 100 rem; 1 mSv = 100 mrem.

Dose limits are expressed as effective dose; equivalent dose limits apply to the lens of the eye and skin/extremities.

Deterministic (tissue reaction) effects have a threshold dose and increase in severity with dose; examples include erythema, cataract, and acute radiation syndrome.

Stochastic effects (cancer, heritable effects) are assumed to have no threshold under the linear no-threshold model; probability increases with dose, severity does not.

Acute radiation syndrome thresholds: prodromal symptoms may appear near 1 Gy; hematopoietic syndrome ~1–6 Gy; gastrointestinal ~6–10 Gy; cerebrovascular >10 Gy.

LD50/60 for whole-body acute exposure without medical support is approximately 3.5–4.5 Gy.

Cataract formation is a deterministic effect with threshold around 0.5 Gy (ICRP) to lens; lens dose limits reflect this.

Radiosensitivity is greatest in rapidly dividing cells (bone marrow, GI epithelium, gonads); lymphocytes are among the most radiosensitive.

DNA double-strand breaks are the principal lesion leading to cell death and mutation; repair pathways influence outcome.

Fetal exposure carries risks of malformation (high dose, early gestation) and childhood cancer; the embryo/fetus is more radiosensitive than the adult.

Three basic protective measures: time, distance, and shielding.

ALARA: doses kept as low as reasonably achievable, economic and social factors taken into account.

Dose constraint is a prospective restriction on individual dose from a single source, below the dose limit.

Shielding calculation: transmission factor B = I/I0; required thickness from HVL or TVL data: n = log(I0/I)/log(2) for HVL.

Distance rule: increase distance to reduce dose by inverse square; use tongs, remote handling, and long tools.

Contamination control: prevent spread, use containment, monitor hands and surfaces, and change gloves/PPE.

Shielding for photons uses lead, concrete, or tungsten; for neutrons use hydrogenous material (polyethylene, water) plus a gamma shield for capture gammas.

Justification, optimization, and dose limitation are the three fundamental principles of radiological protection.

ICRP recommendations underpin national regulations; IAEA GSR Part 3 sets international radiation protection requirements.

Occupational effective dose limit: 20 mSv per year averaged over 5 years (100 mSv in 5 years), with no more than 50 mSv in any single year.

Public effective dose limit: 1 mSv per year.

Lens of eye equivalent dose limit: 20 mSv per year averaged over defined periods (ICRP 2011) with 50 mSv in any single year.

Skin and extremities equivalent dose limit: 500 mSv per year.

Pregnant worker: declared pregnant worker dose to fetus should not exceed 1 mSv during the remainder of the pregnancy (ICRP 103/84 framework).

Apprentices aged 16–18: effective dose limit 6 mSv per year; persons under 16 generally not exposed occupationally.

Dose records, personal dosimetry, and reporting requirements are regulatory obligations; classification of areas (controlled/supervised) governs access and monitoring.

External dose control hierarchy: reduce time, increase distance, add shielding, and use remote handling.

Personal dosimetry: whole-body TLD/OSL badges, extremity dosimeters, and neutron dosimeters as needed; dosimeters worn at the appropriate location.

Internal dose control: use fume hoods, glove boxes, respiratory protection, and bioassay (whole-body counting, urine/feces sampling).

Investigation levels and action levels trigger review when dosimeter readings exceed expected values.

Public dose control: 1 mSv/y limit, dose constraints for a single source often set at a fraction of the limit, and shielding design targets.

Area monitoring: survey meters for dose rate, contamination monitors for removable activity, and air samplers for airborne activity.

Workplace classification: controlled areas require dose assessment and access control; supervised areas require monitoring.

Record keeping and dose trending identify trends and support ALARA program review.

Emergency response priorities: protect people, secure the scene, assess dose rates, and establish control zones (hot, warm, cold).

Triage and decontamination: remove contaminated clothing, wash skin with lukewarm water and mild soap, and monitor before and after decontamination.

Radioactive waste classification depends on activity concentration, half-life, and form; segregation at source reduces volume.

Decay-in-storage is used for short-lived radionuclides; waste is held until activity falls below clearance levels.

Dose limits for emergency workers are higher than routine limits but require justification and recording.

Spill response: contain, absorb, and decontaminate; prevent spread by ventilation control and restricting access.

Waste disposal routes include decay, incineration, and licensed disposal; transport is governed by IAEA transport regulations.

Emergency planning includes drills, communication, and pre-identified routes and reception centers.