ThePeer commented 1 year ago

For some nuclides (alpha and beta emitters?) "ValueError: Photon energy is out of range" when using "lead" as buildup_factor_material. The issue does not appear when using e.g. "iron" as buildup_factor_material using same isotopes. The error can be replicated by modifying the test example as follows: from zap_me_not import model,source,shield,detector,material

sample_sink = model.Model()

create the source

a_source = source.PointSource(x=0, y=0, z=0) a_source.add_isotope_curies('Tc-99',2.1) a_source.add_isotope_curies('Cs-137',0.3) sample_sink.add_source(a_source)

define the location where the dose will be calculated

exposure_detector = detector.Detector(x=200, y=40, z=40) sample_sink.add_detector(exposure_detector)

define a shield and add it to the model

first_shield = shield.SemiInfiniteXSlab('lead', x_start=12, x_end=32.1) sample_sink.add_shield(first_shield)

define a second shield and add it to the model

second_shield = shield.SemiInfiniteXSlab('iron', x_start=32.1, x_end=33.1) sample_sink.add_shield(second_shield)

declare which shield material will be used for buildup factor calculations

buildup_factor_material = material.Material('lead') sample_sink.set_buildup_factor_material(buildup_factor_material)

(optionally) declare a meterial to fill all non-defined regions

sample_sink.set_filler_material('air')

calculate exposure in mR/hr

exposure = sample_sink.calculate_exposure() print('The exposure is ', exposure, ' mR/hr')

AlanFord commented 1 year ago

It appears that the buildup factor data for lead provided in ANSI/ANS 6.4.3 do not extend below 30 keV. Hence the low energy photons from Tc-99 are out of range for the lead buildup factor. Possible solutions to be evaluated in a patch will include extrapolating the buildup factors or using the lower energy data of the existing buildup factors. The former may be somewhat non-physical. The latter may be problematic if only low energy photons are present in the source.