Gamma Buddy

Activity (Ci)

Steel thickness

SE-75 steel HVL = 8 mm (0.315″)

Lead sheets

Each sheet = 3 HVL (≈ 3 mm lead for SE-75)

Collimator

Applies outside the primary beam only (sides / behind). In the beam direction the collimator gives no reduction.

SE-75 · stand-off to 10 mR/h

— m

— ft

Total HVLs—

Unshielded—

CollimatorOff

SE-75 assumptions

Γ = 203 mR/h per Ci at 1 m · Lead HVL ≈ 1 mm · Steel HVL = 8 mm · Sheet = 3 HVL

d = √( Γ × Ci ÷ (10 × 2^HVLs) )

Collimator ON adds its HVLs to the total (off-beam only). Default 16 HVL for Se-75 from QSA Global TCN799 (TCN827 ≈26, TCN846 ≈28, TCN828 ≈33.7). Tungsten HVL for Se-75 ≈ 0.8 mm.

Activity (Ci)

Steel thickness

Ir-192 steel HVL ≈ 13 mm (0.51″)

Lead sheets (3 mm each)

Same physical 3 mm sheets · Ir-192 lead HVL ≈ 5.1 mm → ~0.59 HVL per sheet

Collimator

Applies outside the primary beam only (sides / behind). In the beam direction the collimator gives no reduction.

Ir-192 · stand-off to 10 mR/h

— m

— ft

Total HVLs—

Unshielded—

CollimatorOff

Ir-192 assumptions

Γ = 480 mR/h per Ci at 1 m (0.48 R/h/Ci @ 1 m, QSA) · Lead HVL ≈ 5.1 mm · Steel HVL ≈ 13 mm

Lead sheets counted as 3 mm each (same physical sheets as your SE-75 3-HVL sheets).

d = √( Γ × Ci ÷ (10 × 2^HVLs) )

Collimator ON adds its HVLs to the total (off-beam only). Default 4.3 HVL for Ir-192 from QSA Global TCN799 (TCN827 ≈6.8, TCN846 ≈7.8, TCN828 ≈8.3; SPEC 4/5/8/13.5/16 HVL). Tungsten HVL for Ir-192 ≈ 3.3 mm.

Units

Source / focal size f

Distance entry

ASME uses SOD. If you measure FFD, pick that — SOD = FFD − OFD.

Source-to-object a / SOD

Object-to-film b / OFD

SW contact ≈ wall thickness. DW viewing: often OD (source-side wall to film).

Material thickness (for ASME max)

ASME V T-274.2 / T-285 limits by nominal thickness

Geometric unsharpness Ug

— mm

— in

SOD used—

FFD—

ASME max—

Ug checkenter values

Ug formula

Ug = f × OFD ÷ SOD

Similar triangles (ASME V Art. 2). Not FFD in the denominator.

If you enter FFD: SOD = FFD − OFD, then same formula.

ASME max Ug (nominal thickness):
< 2″ → 0.020″ · 2–3″ → 0.030″ · 3–4″ → 0.040″ · > 4″ → 0.070″

Isotope

Activity (Ci)

Steel thickness

Source-to-film distance FFD

Film 'R' Factor

Exposure time (H : M : S)

— : — : —

Dose rate at film—

Ci·s—

How shot time is calculated

t (min) = R × SFD_in² × 2^(steel_in ÷ HVL) ÷ (Ci × C)

Matched to iPhone X-Ray Timer (Lance Henderson).

Worked checks:
Ir-192 · 59 Ci · 15 mm · R=4 · 394 mm → 0:2:5
Ir-192 · 60 Ci · 0.75″ · R=2.5 · 16″ → 0:1:42
SE-75 · 10 Ci · 9.3 mm · R=2.5 · 136 mm → 0:2:8
SE-75 · 40 Ci · 1.124″ · R=2.5 · 42″ → 2:53:26

Ir-192: HVL=0.5″ (12.7 mm), C=17.75
SE-75: HVL=8 mm, C=7.55
Co-60: HVL=21 mm, C≈48.1 (not phone-checked)

NOMINAL SIZE

SCHEDULE

ASME B36.10M · carbon steel (nominal)

Outer Dim. (OD) —

Inner Dim. (ID) —

Thickness (wall) —

Weight (Steel) —

Nominal / standard dimensions — not measured. ID = OD − 2×wall. Weight from steel density ≈ 7.85 g/cm³.

About pipe sizes

Outside diameter is fixed by NPS. Schedule sets wall thickness (and therefore ID and weight). Only schedules published for the selected NPS are listed.

Values follow ASME B36.10M wrought steel pipe tables (common NPS ⅛″–72″).