Validation

Run 2026-09-29 against version 1.4.1

Every number in the tables below was computed by the app’s own physics code — the same code the iOS, Android and web apps run — and compared with a value from outside it: a handbook table, a textbook identity, or an independent calculation written separately for the test. A check outside its tolerance fails the test suite, and this page is only regenerated when none does.

CHECKS: 174
OUTSIDE TOLERANCE: 0
AREAS: 8decay to reactor physics
VERSION: 1.4.12026-09-29

How to read the tables

REFERENCE: Where the comparison value comes from. A handbook, ENSDF, CIAAW or a textbook appendix is a published value. “Definition”, “round trip”, “RK4” and “by hand” are independent calculations: they show that the equations are solved correctly, not that the input data is right. The published-value rows cover the data.
TOLERANCE: How precisely the reference itself is quoted, fixed before the check ran — not how close the app happened to land. A rule of thumb such as Co-60 at 1.32 R/h per curie at 1 m gets ±6 %; an exact definition gets a millionth of a percent.
NOT CLAIMED: Conformance to NQA-1, 10 CFR 50 Appendix B or any software quality programme. If your work requires qualified software, use this app as a cross-check, not as the system of record.

Decay and specific activity 13

Closed-form identities

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
lambda = ln2/T½	7.3020 × 10⁻¹⁰	7.3020 × 10⁻¹⁰	< 0.01 %	± 1e-6 %	definition
A(1 T½)/A₀	0.5	0.5	< 0.01 %	± 1e-6 %	definition
A(10 T½)/A₀	9.7656 × 10⁻⁴	9.7656 × 10⁻⁴	< 0.01 %	± 1e-6 %	definition
t(1%) in half-lives	6.64386	6.64386	< 0.01 %	± 1e-4 %	definition
A(−1 T½) back-decay	2	2	< 0.01 %	± 1e-6 %	inverse decay

Specific activity vs published Ci/g

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
specific activity Co-60 (Ci/g)	1131.61	1131	+0.05 %	± 3 %	handbook
specific activity Cs-137 (Ci/g)	86.8113	87	−0.22 %	± 3 %	handbook
specific activity Ra-226 (Ci/g)	0.988559	0.988	+0.06 %	± 3 %	handbook
specific activity Sr-90 (Ci/g)	137.542	138	−0.33 %	± 5 %	handbook
specific activity H-3 (Ci/g)	9621.24	9650	−0.30 %	± 5 %	handbook
specific activity Pu-239 (Ci/g)	0.0620283	0.0621	−0.12 %	± 5 %	handbook
specific activity U-235 (Ci/g)	2.1605 × 10⁻⁶	2.1600 × 10⁻⁶	+0.02 %	± 5 %	handbook
specific activity I-131 (Ci/g)	1.2429 × 10⁵	1.2400 × 10⁵	+0.24 %	± 5 %	handbook

Decay chains 4

Ra-226 chain reaches secular equilibrium in one year

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
secular equilibrium Rn-222/Ra-226	1.00001	1	< 0.01 %	± 2 %	T½(daughter) ≪ T½(parent)
secular equilibrium Pb-214/Ra-226	0.999807	1	−0.02 %	± 2 %	T½(daughter) ≪ T½(parent)
secular equilibrium Bi-214/Ra-226	0.999807	1	−0.02 %	± 2 %	T½(daughter) ≪ T½(parent)

Ba-140 → La-140 reaches TRANSIENT equilibrium, not secular

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
La-140/Ba-140 activity at 30 d	1.15158	1.15157	< 0.01 %	± 1 %	λ_d/(λ_d−λ_p)

Gamma dose and shielding 47

Gamma constants vs published R/h per Ci at 1 m

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Γ Co-60 (R/h per Ci @1 m)	1.29091	1.32	−2.20 %	± 6 %	handbook
Γ Cs-137 (R/h per Ci @1 m)	0.325846	0.33	−1.26 %	± 6 %	handbook
Γ Ir-192 (R/h per Ci @1 m)	0.50333	0.48	+4.86 %	± 12 %	handbook
Γ Na-22 (R/h per Ci @1 m)	1.18349	1.2	−1.38 %	± 8 %	handbook
Γ I-131 (R/h per Ci @1 m)	0.220196	0.22	+0.09 %	± 15 %	handbook
Γ Mn-54 (R/h per Ci @1 m)	0.463421	0.47	−1.40 %	± 8 %	handbook
Γ Au-198 (R/h per Ci @1 m)	0.238276	0.23	+3.60 %	± 20 %	handbook
Γ Zn-65 (R/h per Ci @1 m)	0.303571	0.27	+12.43 %	± 20 %	handbook

Geometry, linearity, and the HVL/TVL definitions

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
inverse square 1 m → 2 m	4	4	< 0.01 %	± 0.01 %	1/r²
linearity in activity	2	2	< 0.01 %	± 1e-6 %	rate ∝ A
spectrum HVL halves the rate	0.5	0.5	< 0.01 %	± 1 %	definition
spectrum TVL → 10 % of rate	0.1	0.1	< 0.01 %	± 1 %	definition

Narrow-beam HVL equals ln2/µ from the shipped NIST table

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Cs-137 narrow HVL Pb (cm)	0.549926	0.5499	< 0.01 %	± 1 %	ln2/µ @662 keV
Co-60 narrow HVL Pb (cm)	1.03932	1.0367	+0.25 %	± 1 %	ln2/µ @1.25 MeV
Buildup ≥ 1 and rising with depth (Pb, 1 MeV)	B = 1.367 at 1 mfp, 2.444 at 5 mfp		pass	—	physical requirement

H*(10)/Ka lies in the ICRP 74 band

CHECK	APP	DEVIATION	TOLERANCE	SOURCE
H*(10)/Ka for Cs-137	ratio 1.2035, band 1.00–1.35	pass	—	ICRP 74 Table A.21
H*(10)/Ka for Co-60	ratio 1.1588, band 1.00–1.35	pass	—	ICRP 74 Table A.21
H*(10)/Ka for Ir-192	ratio 1.1724, band 1.00–1.35	pass	—	ICRP 74 Table A.21

Solvers reproduce their own targets (round trips)

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
shield Ir-192 in lead: rate at answer	2.5000 × 10⁻⁶	2.5000 × 10⁻⁶	< 0.01 %	± 1e-3 %	round trip
shield Co-60 in concrete: rate at answer	2.5000 × 10⁻⁶	2.5000 × 10⁻⁶	< 0.01 %	± 1e-3 %	round trip
shield Pb-212+ in lead: rate at answer	2.5000 × 10⁻⁶	2.5000 × 10⁻⁶	< 0.01 %	± 1e-3 %	round trip
shield Ba-140+ in iron: rate at answer	2.5000 × 10⁻⁶	2.5000 × 10⁻⁶	< 0.01 %	± 1e-3 %	round trip
distance Co-60: rate at answer	1.0000 × 10⁻⁴	1.0000 × 10⁻⁴	< 0.01 %	± 1e-3 %	round trip
distance Tc-99m: rate at answer	1.0000 × 10⁻⁴	1.0000 × 10⁻⁴	< 0.01 %	± 1e-3 %	round trip
distance F-18: rate at answer	1.0000 × 10⁻⁴	1.0000 × 10⁻⁴	< 0.01 %	± 1e-3 %	round trip
Co-60 concrete: transmission at HVL	0.5	0.5	< 0.01 %	± 0.5 %	definition
Co-60 concrete: transmission at TVL	0.1	0.1	< 0.01 %	± 0.5 %	definition
Ir-192 tungsten: transmission at HVL	0.5	0.5	< 0.01 %	± 0.5 %	definition
Ir-192 tungsten: transmission at TVL	0.1	0.1	< 0.01 %	± 0.5 %	definition

+progeny entries equal their members summed by hand

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Γ Pb-212+ = Pb-212 + Bi-212 + Tl-208	0.00654472	0.00654953	−0.07 %	± 0.3 %	ENSDF, by hand
Γ Ba-140+ = Ba-140 + La-140	0.0127361	0.0127358	< 0.01 %	± 0.3 %	ENSDF, by hand
Γ Mo-99+ = Mo-99 + 0.876 Tc-99m	0.00125906	0.00125906	< 0.01 %	± 0.3 %	ENSDF, by hand

ANS-6.4.3 buildup and the coherent-free μ it requires

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
B lead, 1 MeV, 4 mfp	2.20577	2.21	−0.19 %	± 3 %	ANS-6.4.3 Table 3
B lead, 0.5 MeV, 10 mfp	2.08471	2.1	−0.73 %	± 3 %	ANS-6.4.3 Table 3
B water, 1 MeV, 10 mfp	26.4353	26.1	+1.28 %	± 3 %	ANS-6.4.3 Table 3
B water, 0.5 MeV, 5 mfp	18.1154	18.4	−1.55 %	± 3 %	ANS-6.4.3 Table 3
B concrete, 1 MeV, 10 mfp	20.7183	20.7	+0.09 %	± 3 %	ANS-6.4.3 Table 3
B iron, 1 MeV, 10 mfp	15.733	15.8	−0.42 %	± 3 %	ANS-6.4.3 Table 3
B iron, 0.5 MeV, 5 mfp	7.70649	7.68	+0.34 %	± 3 %	ANS-6.4.3 Table 3
B aluminum, 1 MeV, 10 mfp	21.0423	21	+0.20 %	± 3 %	ANS-6.4.3 Table 3
coherent share of μ, lead, 662 keV (%)	6.03338	5.99455	+0.65 %	± 5 %	NIST XCOM

Behind a wall the point kernel stays at or above a slab Monte Carlo

CHECK	APP	DEVIATION	TOLERANCE	SOURCE
Cs-137, 20 cm of concrete, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.55 (transmission 1.84e-1 vs 1.19e-1)	pass	—	Klein–Nishina slab Monte Carlo
Co-60, 30 cm of concrete, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.36 (transmission 1.05e-1 vs 7.77e-2)	pass	—	Klein–Nishina slab Monte Carlo
Cs-137, 40 cm of water, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.66 (transmission 2.64e-1 vs 1.58e-1)	pass	—	Klein–Nishina slab Monte Carlo
Cs-137, 5 cm of lead, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.13 (transmission 5.53e-3 vs 4.88e-3)	pass	—	Klein–Nishina slab Monte Carlo
Ir-192, 2 cm of lead, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.08 (transmission 2.74e-2 vs 2.55e-2)	pass	—	Klein–Nishina slab Monte Carlo
Co-60, 10 cm of lead, 1 m behind: app at or above slab Monte Carlo	app/MC = 1.19 (transmission 4.82e-3 vs 4.05e-3)	pass	—	Klein–Nishina slab Monte Carlo

Metastable isomers 20

Decay law and published half-lives

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
isomer T½ Tc-99m (s)	21625.9	21625.9	< 0.01 %	± 3 %	IAEA/ENSDF
isomer T½ Ba-137m (s)	153.12	153.12	< 0.01 %	± 3 %	IAEA/ENSDF
isomer T½ Ag-110m (s)	2.1585 × 10⁷	2.1585 × 10⁷	< 0.01 %	± 3 %	IAEA/ENSDF
isomer T½ In-113m (s)	5968.56	5968.56	< 0.01 %	± 3 %	IAEA/ENSDF
isomer T½ Kr-83m (s)	6588	6588	< 0.01 %	± 3 %	IAEA/ENSDF
isomer T½ Sr-87m (s)	10134	10134	< 0.01 %	± 5 %	IAEA/ENSDF
Tc-99m A(1 T½)/A₀	0.5	0.5	< 0.01 %	± 1e-6 %	definition
Ba-137m excitation = 661.66 keV line	661.659	661.657	< 0.01 %	± 0.1 %	ENSDF

Branching ratios are physical

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
isomers reporting 0 % for every branch	0	0	exact	exact	conversion rule

Delayed channels are not counted as competing branches

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Rb-98m primary branches	100	100	< 0.01 %	± 0.01 %	NUBASE2020 §2.4
Rb-98m β-delayed channels held apart	delayed: B-2N,B-N		pass	—	NUBASE2020 §2.4
delayed channels leaked into decayModes	0	0	exact	exact	NUBASE2020 §2.4

Isomer gamma sources are reachable in the Dose tab

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Tc-99m selectable as a dose source	4 lines		pass	—	IAEA decay_rads
Ba-137m selectable as a dose source	6 lines		pass	—	IAEA decay_rads
Ag-110m selectable as a dose source	35 lines		pass	—	IAEA decay_rads
Xe-135m selectable as a dose source	6 lines		pass	—	IAEA decay_rads
Kr-85m selectable as a dose source	7 lines		pass	—	IAEA decay_rads
Tc-99m dominant γ (keV)	140.511	140.511	< 0.01 %	± 0.1 %	ENSDF
Tc-99m dominant γ intensity (%)	89	89	< 0.01 %	± 5 %	ENSDF
Ba-137m dominant γ (keV)	661.657	661.657	< 0.01 %	± 0.1 %	ENSDF

Neutron cross sections and activation 30

Literature anchors and internal identities

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
σ₀ B-10 (n,α) (b)	3837	3837	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ Li-6 (n,α) (b)	940	940	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ He-3 (n,p) (b)	5330	5330	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ H-1 (n,γ) (b)	0.3326	0.3326	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ Cd-113 (n,γ) (b)	20600	20600	< 0.01 %	± 1 %	Mughabghab 2006
σ₀ Gd-157 (n,γ) (b)	2.5400 × 10⁵	2.5400 × 10⁵	< 0.01 %	± 1 %	Mughabghab 2006
σ₀ Sm-149 (n,γ) (b)	40140	40140	< 0.01 %	± 1 %	D&H Ch. 15
σ₀ U-235 (n,f) (b)	582	582	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ U-238 (n,γ) (b)	2.68	2.68	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ Pu-239 (n,f) (b)	748	748	< 0.01 %	± 1 %	Lamarsh App. II
σ₀ Au-197 (n,γ) (b)	98.65	98.65	< 0.01 %	± 1 %	Mughabghab 2006
U-235 σ_f+σ_γ = σ_a (b)	681	681	< 0.01 %	± 0.01 %	definition
Pu-239 σ_f+σ_γ = σ_a (b)	1017	1017	< 0.01 %	± 0.01 %	definition
σ_Xe cross_sections vs xenon.ts (b)	2.6500 × 10⁶	2.6500 × 10⁶	< 0.01 %	± 0.01 %	internal consistency
U-235 α = σ_γ/σ_f	0.170103	0.169	+0.65 %	± 3 %	Lamarsh §4
U-235 η = ν·σ_f/σ_a	2.06819	2.068	+0.01 %	± 2 %	Lamarsh §4 (η ≈ 2.07)
H weighted sigma_a (b)	0.332552	0.3326	−0.01 %	± 3 %	Lamarsh & Baratta 3rd ed., App. II
C weighted sigma_a (b)	0.0035071	0.0035	+0.20 %	± 3 %	Lamarsh & Baratta 3rd ed., App. II
N weighted sigma_a (b)	1.89777	1.9	−0.12 %	± 3 %	Lamarsh & Baratta 3rd ed., App. II
Fe weighted sigma_a (b)	2.5641	2.56	+0.16 %	± 3 %	Mughabghab (2006), elemental value
Pb weighted sigma_a (b)	0.174208	0.171	+1.88 %	± 3 %	Mughabghab (2006), elemental value

Høgdahl rate for gold, by hand

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Au saturation, thermal 1e12	3.0162 × 10¹¹	3.0162 × 10¹¹	< 0.01 %	± 1 %	Mughabghab σ₀
Au saturation, φₑ = φ_th/30	4.5958 × 10¹¹	4.5958 × 10¹¹	< 0.01 %	± 1.5 %	Høgdahl, Mughabghab I₀

IRDFF-II averages and an independent fission spectrum

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
σ̄ Fe-54(n,p), U-235 fission (mb)	76.635	76.66	−0.03 %	± 1 %	IAEA IRDFF-II
σ̄ Ni-58(n,p), U-235 fission (mb)	105.16	105.19	−0.03 %	± 1 %	IAEA IRDFF-II
σ̄ Al-27(n,α), U-235 fission (mb)	0.68689	0.6872	−0.05 %	± 1 %	IAEA IRDFF-II
σ̄ S-32(n,p), U-235 fission (mb)	66.826	66.846	−0.03 %	± 1 %	IAEA IRDFF-II
fission neutrons above 0.5 MeV (fraction)	0.8685	0.871544	−0.35 %	± 2 %	Watt spectrum
fission neutron mean energy (MeV)	2	2.03084	−1.52 %	± 2.5 %	Watt spectrum
Ni-58(n,p) saturation, 1 g (Bq)	4.2288 × 10⁷	4.2152 × 10⁷	+0.32 %	± 3 %	IRDFF-II σ̄ + Watt, by hand

Reactor physics 14

Equilibrium poisoning saturates and is Σf-independent

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
[Xe] saturation ratio 1e13→1e14	1.66276	1.66276	< 0.01 %	± 1 %	φ/(λ_Xe+σ_Xe·φ)
Xe-135 reactivity saturates with flux	-1517 pcm at 1e13 → -2523 pcm at 1e14		pass	—	φ/(λ_Xe+σ_Xe·φ)
[I] linear in flux	10	10	< 0.01 %	± 1 %	I has no burnup term

Transients agree with an independent RK4 of the same equations

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
startup 1e14: Xe at 10 h	7.2284 × 10¹⁴	7.2284 × 10¹⁴	< 0.01 %	± 0.01 %	RK4
startup 1e14: Xe at 48 h	1.1488 × 10¹⁵	1.1488 × 10¹⁵	< 0.01 %	± 0.01 %	RK4
step 100→50 %: Xe at 5 h	1.7603 × 10¹⁵	1.7603 × 10¹⁵	< 0.01 %	± 0.01 %	RK4
step 100→50 %: Xe at 30 h	1.1319 × 10¹⁵	1.1319 × 10¹⁵	< 0.01 %	± 0.01 %	RK4
iodine pit peak after 1e14 shutdown (h)	10.15	10.147	+0.03 %	± 1 %	closed form, D&H §15

Inhour periods satisfy the six-group equation

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
inhour ρ = 0.05$ → T 226.9 s	0.05	0.05	< 0.01 %	± 0.1 %	inhour eq.
inhour ρ = 0.1$ → T 98.5 s	0.1	0.1	< 0.01 %	± 0.1 %	inhour eq.
inhour ρ = 0.25$ → T 25.4 s	0.25	0.25	< 0.01 %	± 0.1 %	inhour eq.
inhour ρ = 0.5$ → T 5.7 s	0.5	0.5	< 0.01 %	± 0.1 %	inhour eq.
inhour ρ = 0.8$ → T 0.9 s	0.8	0.8	< 0.01 %	± 0.1 %	inhour eq.
small ρ: T·ρ[$] → Σaᵢ/λᵢ (s)	12.9985	13.03	−0.24 %	± 1 %	Keepin mean delay

Mixtures and enrichment 31

4.5 % LEU cascade vs the textbook case

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
SWU per kg product (4.5 % LEU)	6.87111	6.9	−0.42 %	± 6 %	value function
feed per kg product (4.5 % LEU)	9.21909	9.2	+0.21 %	± 6 %	mass balance
mass balance F − P − W	-1.7764 × 10⁻¹⁵	0	-1.7764 × 10⁻¹⁵ abs	± 1e-6 %	conservation

Elemental fractions vs IUPAC atomic weights

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
H₂O hydrogen (wt%)	11.1901	11.19	< 0.01 %	± 1 %	IUPAC masses
UO₂ uranium (wt%)	88.1498	88.15	< 0.01 %	± 1 %	IUPAC masses
H2O wt% sums to 100	100	100	< 0.01 %	± 0.01 %	conservation
UO2 wt% sums to 100	100	100	< 0.01 %	± 0.01 %	conservation
Ca(OH)2 wt% sums to 100	100	100	< 0.01 %	± 0.01 %	conservation

Atomic weights and molar masses vs IUPAC/CIAAW 2021

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
atomic weight H	1.00797	1.008	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight B	10.8135	10.81	+0.03 %	± 0.1 %	CIAAW 2021
atomic weight C	12.0106	12.011	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight N	14.0069	14.007	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight O	15.9994	15.999	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Na	22.9898	22.99	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Al	26.9815	26.982	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Cl	35.4521	35.45	+0.01 %	± 0.02 %	CIAAW 2021
atomic weight Ca	40.078	40.078	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Fe	55.8451	55.845	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Cu	63.546	63.546	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Zr	91.2236	91.224	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Cd	112.414	112.41	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Gd	157.252	157.25	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight W	183.842	183.84	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight Pb	207.217	207.2	+0.01 %	± 0.1 %	CIAAW 2021
atomic weight Th	232.038	232.04	< 0.01 %	± 0.02 %	CIAAW 2021
atomic weight U	238.029	238.03	< 0.01 %	± 0.02 %	CIAAW 2021
molar mass UO₂ (g/mol)	270.028	270.03	< 0.01 %	± 0.03 %	from CIAAW weights
molar mass UF₆ (g/mol)	352.019	352.02	< 0.01 %	± 0.03 %	from CIAAW weights
molar mass B₄C (g/mol)	55.2647	55.255	+0.02 %	± 0.1 %	from CIAAW weights
Pu (no stable isotope) = Pu-244 mass	244.064	244.064	< 0.01 %	± 0.01 %	AME2020
Ra (no stable isotope) = Ra-226 mass	226.025	226.025	< 0.01 %	± 0.01 %	AME2020

Counting statistics and units 15

Currie critical level and detection limit

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
Currie L_c (B=100)	23.2638	23.3	−0.16 %	± 1 %	Currie 1968
Currie L_d (B=100)	49.2337	49.21	+0.05 %	± 1 %	Currie 1968
Currie L_c (B=400)	46.5276	46.6	−0.16 %	± 1 %	Currie 1968
Currie L_d (B=400)	95.7613	95.71	+0.05 %	± 1 %	Currie 1968
Currie L_c (B=2500)	116.319	116.5	−0.16 %	± 1 %	Currie 1968
Currie L_d (B=2500)	235.344	235.21	+0.06 %	± 1 %	Currie 1968

Units, isomer specific activity, detection decision, optimum tails

CHECK	APP	REFERENCE	DEVIATION	TOLERANCE	SOURCE
1 Ci in Bq	3.7000 × 10¹⁰	3.7000 × 10¹⁰	< 0.01 %	± 1e-9 %	definition
1 R in C/kg	2.5800 × 10⁻⁴	2.5800 × 10⁻⁴	< 0.01 %	± 1e-9 %	definition
1 MeV in J	1.6022 × 10⁻¹³	1.6022 × 10⁻¹³	< 0.01 %	± 1e-9 %	SI 2019 exact e
1 Gy in rad	100	100	< 0.01 %	± 1e-9 %	definition
1 Sv in rem	100	100	< 0.01 %	± 1e-9 %	definition
1 y in s (Julian)	3.1558 × 10⁷	3.1558 × 10⁷	< 0.01 %	± 1e-9 %	IAEA half_life_sec
Tc-99m specific activity (Ci/g)	5.2744 × 10⁶	5.2700 × 10⁶	+0.08 %	± 1 %	handbook
Currie decision at the boundary, B = 100	net 24 → detected, net 23 → not; L_c = 23.26		pass	—	Currie 1968
optimum tails assay (cost ratio 0.5)	0.00302462	0.003025	−0.01 %	± 0.1 %	brute-force scan

Corrections

Errors found by earlier audits, and the release that fixed them. If you used one of these calculations in an earlier version, recompute it.

1.4.1 · HIGH: Shielding behind lead, tungsten and iron. Buildup came from Taylor fits that stopped at 0.5 MeV and borrowed other materials’ data, and the attenuation counted coherent scattering as removal. Now: the ANSI/ANS-6.4.3 standard buildup factors for every material, 15 keV–15 MeV, with the coherent-free attenuation the standard requires. Dose behind thick lead was low: Cs-137 behind 10 cm of lead read about half the corrected value, and a third below an independent slab Monte Carlo that itself leaves out lead fluorescence; behind 5 cm about 25 % below the corrected value. A low-energy source immersed in water read up to 2× low.
1.4.1 · MEDIUM: Fast-neutron activation. Threshold cross sections were order-of-magnitude estimates, applied to every source as if it emitted fission neutrons. They are now IAEA IRDFF-II averages over each source’s own spectrum. Reactor results were 9–43 % low (O-16(n,p), the N-16 source, most); Fe-54(n,p) with Am-Be was 3.4× low; the D-D generator reported activation for reactions a 2.45 MeV neutron cannot cause.
1.4.1 · LOW: Activation data consistency. Four product half-lives and two abundances now match the NUBASE2020 data the tab cites (W-187 was 0.8 % long). The on-screen formula still showed the epithermal factor 0.45 retired in 1.4.0; the calculation already used 1.
1.4.0 · HIGH: Dose and shielding, ten parent nuclides. Pb-212, Bi-212, Ba-140, Np-237, Zr-95, Ce-144, Mo-99, Ra-228, Pb-214 and Ba-131 were offered without the short-lived progeny that carry most of their gamma dose. An aged Pb-212 source read about 10× low, and the shield solver asked for 0.32 cm of lead where 9.95 cm is needed. Each now has a “+progeny” entry at transient-equilibrium activity.
1.4.0 · MEDIUM: Reactor period. The one-group stable period was 2.3× too long at +$0.50. It now solves the six-group inhour equation (Keepin U-235 thermal groups).
1.4.0 · MEDIUM: Decay Chain tab. The followed branch was credited with every decay (Po-212 1.56× high). Activities now come from the full branching solution, with the other branches and any truncation shown.
1.4.0 · MEDIUM: Neutron activation. The epithermal term used a factor matching no published convention; Au-197 read 24 % and Mo-98 40 % low. It now follows the Høgdahl convention with φ_e per unit lethargy.
1.0.5 · HIGH: Bateman chains. Members below a short-lived one were starved: Ra-226 over one year reported Bi-214 about 10⁴× low. The integrator was replaced with a closed-form solution, checked above against secular and transient equilibrium.
1.0.5 · LOW: H*(10) above 1.5 MeV. The conversion from air kerma fell away where ICRP 74 Table A.21 plateaus, so ambient dose equivalent for high-energy photons read low. All 25 rows now match the printed table.

Known limitations

Stated because a validation page that lists only strengths is marketing.

Point sources only, single-layer shields, gamma only — no neutron dose.
Buildup factors are the ANSI/ANS-6.4.3 infinite-medium values applied to a slab, which overstates the dose behind a wall — per the slab Monte Carlo above, 1.1–1.2× behind lead and 1.4–1.7× behind concrete and water, 1 m back. Per-line transmission is capped at 1.
Air is optional and off by default (vacuum, as published dose constants assume). Switched on, it is an infinite-air kernel: no ground or room scatter.
Neutron cross sections cover 298 of 3,383 nuclides (8.8 %). A missing value is shown as missing, never as zero.
Fast-neutron cross sections are IAEA IRDFF-II averages over the chosen source’s spectrum. For Am-Be, three reactions have no value: the published spectrum is too coarse above 10 MeV for them.
Activation neglects target burn-up and self-shielding.
Reactor period uses Keepin’s U-235 thermal delayed-neutron groups; Pu-239 and fast-spectrum cores differ. Xe-135 is a one-group, spatially uniform model.
Evaluated data is shown as published: 91 ground states and 11 isomers have branches that NUBASE2020 sums past 100.5 %, and they are not renormalised.
No uncertainty propagation. Evaluated values are used as point estimates.

Found a number that disagrees with your reference? Email [email protected] with the inputs and units you used, the value the app showed, and the value you expected with its source. Accuracy reports are looked at first, and a confirmed one is added to this page.