Exposure Rate Constants

The "Specific Exposure Rate Constant", sometimes known as the "Gamma Factor", is the exposure rate at a specific distance from a given amount of a photon-emitting radionuclide. These constants are used frequently for radiation protection purposes. The following is a listing of Specific Exposure Rate Constants for a variety of radionuclides, in units of Roentgens per hour (R/hr) at a distance of one (1) meter from a one (1) curie point source of that radionuclide.

Actinium

Ac-225 - 0.191364
Ac-227 - 0.0087468
Ac-228 - 0.84397

Aluminum

Al-26 - 1.49739
Al-28 - 0.88208

Americium

Am-241 - 0.313723
Am-242 - 0.202612
Am-242m - 0.18315
Am-243 - 0.312872
Am-244 - 1.17216
Am-245 - 0.086617
Am-246 - 0.079513

Antimony

Sb-117 - 0.304103
Sb-122 - 0.304251
Sb-124 - 1.06671
Sb-125 - 0.38036
Sb-126 - 1.7982
Sb-126m - 1.04488
Sb-127 - 0.444
Sb-129 - 0.85655

Argon

Ar-41 - 0.69597

Arsenic

As-72 - 1.16476
As-73 - 0.140008
As-74 - 0.54464
As-76 - 0.274096
As-77 - 0.0062863

Astatine

At-211 - 0.22644
At-217 - 0.000160247

Barium

Ba-131 - 0.46028
Ba-133 - 0.45547
Ba-133m - 0.124764
Ba-135m - 0.110038
Ba-137m - 0.39997
Ba-139 - 0.0285529
Ba-140 - 0.164502
Ba-141 - 0.57794
Ba-142 - 0.56869

Berkelium

Bk-250 - 0.67858

Beryllium

Be-7 - 0.0343804

Bismuth

Bi-206 - 2.5234
Bi-207 - 1.33311
Bi-208 - 1.5207
Bi-211 - 0.047138
Bi-212 - 0.194768
Bi-213 - 0.11618
Bi-214 - 0.83916

Bromine

Br-77 - 0.71151
Br-80 - 0.080142
Br-80m - 0.703
Br-82 - 1.61949
Br-83 - 0.0051837
Br-84 - 0.88504
Br-85 - 0.039183

Cadmium

Cd-109 - 0.184371
Cd-111m - 0.313131
Cd-115 - 1505160000
Cd-115m - 0.0127021
Cd-117 - 0.6438
Cd-117m - 1.08595

Calcium

Ca-45 - 2.98664E-08
Ca-47 - 0.58497
Ca-49 - 1.33755

Californium

Cf-248 - 0.045473
Cf-249 - 0.41403
Cf-250 - 0.044844
Cf-251 - 0.42994
Cf-252 - 0.041847
Cf-253 - 0.0007696
Cf-254 - 4.8507E-08

Carbon

C-11 - 0.71669

Cerium

Ce-139 - 0.205498
Ce-141 - 0.073223
Ce-143 - 0.255041
Ce-144 - 0.0233174

Cesium

Cs-126 - 0.80142
Cs-129 - 0.359825
Cs-131 - 0.124431
Cs-132 - 0.57572
Cs-134 - 0.99937
Cs-134m - 0.070448
Cs-136 - 1.34384
Cs-137 - 0.38184
Cs-138 - 1.26614
Cs-139 - 0.15762

Chlorine

Cl-38 - 0.71854

Chromium

Cr-49 - 0.75073
Cr-51 - 0.023384

Cobalt

Co-56 - 1.92585
Co-57 - 0.151219
Co-58 - 0.61383
Co-58m - 9.7569E-05
Co-60 - 1.37011
Co-60m - 0.00335109
Co-61 - 0.084582

Copper

Cu-61 - 0.56832
Cu-62 - 0.7067
Cu-64 - 0.131942
Cu-67 - 0.087431

Curium

Cm-242 - 0.072113
Cm-243 - 0.47582
Cm-244 - 0.064417
Cm-245 - 0.4514
Cm-246 - 0.057387
Cm-247 - 0.267029
Cm-248 - 0.045399
Cm-249 - 0.0148259

Dysprosium

Dy-157 - 0.309209
Dy-165 - 0.0229141
Dy-166 - 0.05735

Einsteinium

Es-253 - 0.0256077
Es-254 - 0.5513
Es-254m - 0.56203
Es-255 - 0.00315573

Erbium

Er-169 - 1.26022E-06
Er-171 - 0.29637

Europium

Eu-152 - 0.74444
Eu-152m - 0.212602
Eu-154 - 0.75554
Eu-155 - 0.066748
Eu-156 - 0.73704

Fermium

Fm-254 - 0.041477
Fm-255 - 0.322677

Fluorine

F-18 - 0.69523

Francium

Fr-221 - 0.044141
Fr-223 - 0.33041

Gadolinium

Gd-153 - 0.172383
Gd-159 - 0.039183
Gd-162 - 0.308617

Gallium

Ga-66 - 1.29648
Ga-67 - 0.111148
Ga-68 - 0.66193
Ga-72 - 1.45632

Germanium

Ge-68 - 0.060458
Ge-71 - 0.061161
Ge-77 - 0.71558

Gold

Au-194 - 0.66008
Au-195 - 0.087394
Au-195m - 0.152884
Au-196 - 0.369704
Au-198 - 0.291634
Au-199 - 0.069042

Hafnium

Hf-181 - 0.39257

Holmium

Ho-166 - 0.023199
Ho-166m - 1.0619

Indium

In-111 - 0.50172
In-113m - 0.242979
In-114 - 0.0230251
In-114m - 0.150738
In-115m - 0.197173
In-116m - 1.3542
In-117 - 0.50283
In-117m - 0.11322

Iodine

I-122 - 0.70337
I-123 - 0.276686
I-124 - 0.7585
I-125 - 0.274984
I-126 - 0.39035
I-128 - 0.059792
I-129 - 0.125837
I-130 - 1.40267
I-131 - 0.282939
I-132 - 1.42746
I-133 - 0.40885
I-134 - 1.57287
I-135 - 0.86099
I-136 - 1.26429

Iridium

Ir-190 - 0.99197
Ir-190m(1.2h) - 2.2644E-07
Ir-190m(3.2h) - 0.055463
Ir-192 - 0.59163
Ir-193m - 0.00037629
Ir-194 - 0.061901
Ir-194m - 1.61764

Iron

Fe-52 - 0.52281
Fe-59 - 0.66193

Krypton

Kr-79 - 0.60347
Kr-81 - 0.43364
Kr-83m - 0.118733
Kr-85 - 0.00156584
Kr-85m - 0.160136
Kr-87 - 0.43253
Kr-88 - 1.02453
Kr-89 - 0.97162
Kr-90 - 0.76701

Lanthanum

La-141 - 0.0226144
La-142 - 1.35272

Lead

Pb-203 - 0.67636
Pb-204m - 1.3505
Pb-205 - 0.251193
Pb-210 - 0.251637
Pb-211 - 0.0363932
Pb-212 - 0.273393
Pb-214 - 0.323454
Pd-103 - 0.230103
Pd-109 - 0.0004847

Lutetium

Lu-177 - 0.0282532
Lu-177m - 0.78144

Magnesium

Mg-27 - 0.53613
Mg-28 - 0.87875

Manganese

Mn-52 - 2.0091
Mn-52m - 1.44411
Mn-54 - 0.51134
Mn-56 - 0.92352
Mn-57 - 0.112147

Mercury

Hg-197 - 0.069338
Hg-197m - 0.076183
Hg-203 - 0.253117

Molybdenum

Mo-101 - 0.88467
Mo-91 - 0.70226
Mo-93 - 0.293632
Mo-99 - 0.112924

Neodynium

Nd-147 - 0.139453
Nd-149 - 0.300144

Neptunium

Np-235 - 0.258223
Np-236 - 1.04821
Np-236m - 0.23643
Np-237 - 0.46287
Np-238 - 0.55389
Np-239 - 0.51282
Np-240 - 1.41562
Np-240m - 0.42328

Nickel

Ni-56 - 1.08817
Ni-57 - 1.07707
Ni-65 - 0.297406

Niobium

Nb-90 - 2.44089
Nb-91 - 0.326784
Nb-91m - 0.26492
Nb-92 - 1.26318
Nb-92m - 0.89281
Nb-93m - 0.052577
Nb-94 - 0.97976
Nb-94m - 0.202797
Nb-95 - 0.48026
Nb-95m - 0.23643
Nb-96 - 1.5244
Nb-97 - 0.43475
Nb-97m - 0.46694

Nitrogen

N-13 - 0.71706
N-16 - 1.47408

Osmium

Os-185 - 0.4847
Os-190m - 1.11666
Os-191 - 0.067969
Os-191m - 0.0053613
Os-193 - 0.052318

Oxygen

O-15 - 0.7178

Platinum

Pt-191 - 0.243756
Pt-193m - 0.0172013
Pt-195m - 0.075073
Pt-197 - 0.0208939
Pt-197m - 0.071447

Plutonium

Pu-236 - 0.088985
Pu-237 - 0.38443
Pu-238 - 0.078995
Pu-239 - 0.0301365
Pu-240 - 0.07511
Pu-242 - 0.062308
Pu-243 - 0.092833
Pu-244 - 0.054094
Pu-245 - 0.38702

Polonium

Po-209 - 0.00363007
Po-210 - 5.2688E-06
Po-211 - 0.0049136
Po-213 - 1.90402E-05
Po-214 - 5.1726E-05
Po-215 - 0.000105857
Po-216 - 8.9688E-06

Potassium

K-40 - 0.081696
K-42 - 0.143153
K-43 - 0.67007

Praseodynium

Pr-142 - 0.0299922
Pr-143 - 5.6388E-09
Pr-144 - 0.01702
Pr-144m - 0.0367521

Promethium

Pm-143 - 0.266992
Pm-144 - 1.09446
Pm-145 - 0.089466
Pm-146 - 0.54094
Pm-147 - 2.67584E-06
Pm-148 - 0.330669
Pm-148m - 1.31979
Pm-149 - 0.0085729
Pm-151 - 0.262182

Protactinium

Pa-230 - 0.88319
Pa-231 - 0.37407
Pa-233 - 0.49395
Pa-234 - 1.98172
Pa-234m - 0.0102712

Radium

Ra-222 - 0.0078255
Ra-223 - 0.325193
Ra-224 - 0.0109779
Ra-225 - 0.154068
Ra-226 - 0.0121138

Radon

Rn-218 - 0.00050579
Rn-219 - 0.052503
Rn-220 - 0.000359751
Rn-222 - 0.00027343

Rhenium

Re-182 - 1.13886
Re-182m - 0.73778
Re-183 - 0.157509
Re-184 - 0.58201
Re-184m - 0.284086
Re-186 - 0.0181633
Re-188 - 0.040478

Rhodium

Rh-103m - 0.0255744
Rh-105 - 0.058756
Rh-105m - 0.157287
Rh-106 - 0.138158

Rubidium

Rb-81 - 0.83768
Rb-82 - 0.77848
Rb-83 - 0.77145
Rb-84 - 0.86062
Rb-86 - 0.053946
Rb-88 - 0.321937
Rb-89 - 1.0952
Rb-90 - 0.94276
Rb-90m - 1.63873

Ruthenium

Ru-103 - 0.33189
Ru-105 - 0.51689
Ru-97 - 0.44178

Samarium

Sm-151 - 9.0354E-05
Sm-153 - 0.09028

Scandium

Sc-44 - 1.33274
Sc-46 - 1.16735
Sc-46m - 0.066933
Sc-47 - 0.08029
Sc-48 - 1.89329
Sc-49 - 0.00052059

Selenium

Se-73 - 1.09853
Se-75 - 0.85951

Silicon

Si-31 - 0.00048322

Silver

Ag-106m - 1.93769
Ag-108 - 0.0162763
Ag-108m - 1.27132
Ag-109m - 0.100714
Ag-110 - 0.0205646
Ag-110m - 1.65242
Ag-111 - 0.0197173

Sodium

Na-22 - 1.3394
Na-24 - 1.93769

Strontium

Sr-82 - 0.39405
Sr-85 - 0.75924
Sr-85m - 0.222148
Sr-87m - 0.29637
Sr-89 - 8.1585E-05
Sr-91 - 0.41366
Sr-92 - 0.72002
Sr-93 - 1.35605

Tantalum

Ta-182 - 0.77182

Technetium

Tc-101 - 0.255892
Tc-95 - 0.77404
Tc-95m - 0.71743
Tc-96 - 1.81263
Tc-96m - 0.16391
Tc-97 - 0.281052
Tc-97m - 0.193621
Tc-98 - 0.8991
Tc-99 - 4.5954E-07
Tc-99m - 0.06122

Tellurium

Te-121 - 0.53835
Te-121m - 0.248011
Te-123 - 0.099419
Te-123m - 0.194657
Te-125m - 0.228216
Te-127 - 0.00348836
Te-127m - 0.073149
Te-129 - 0.067821
Te-129m - 0.073889
Te-131 - 0.298775
Te-131m - 0.90724
Te-132 - 0.279313
Te-133 - 0.58608
Te-133m - 1.36493
Te-134 - 0.64047

Terbium

Tb-157 - 0.0089762
Tb-160 - 0.66156
Tb-162 - 0.71188

Thorium

Th-226 - 0.067266
Th-227 - 0.42365
Th-228 - 0.079254
Th-229 - 0.73593
Th-230 - 0.068857
Th-231 - 0.54501
Th-232 - 0.068376
Th-233 - 0.095719
Th-234 - 0.075406

Thullium

Tm-170 - 0.0061901
Tm-171 - 0.00096089

Tin

Sn-113 - 0.179228
Sn-117m - 0.251452
Sn-119m - 0.103193
Sn-123 - 0.0039294
Sn-125 - 0.172938
Sn-126 - 0.126096

Titanium

Ti-200 - 0.83361
Ti-201 - 0.087764
Ti-202 - 0.349206
Ti-204 - 0.00111518
Ti-207 - 0.00130388
Ti-208 - 1.70385
Ti-209 - 1.29352
Ti-210 - 1.70237
Ti-44 - 0.144633
Ti-45 - 0.61161
Ti-51 - 0.26381

Tungsten

W-181 - 0.051393
W-185 - 2.02205E-05
W-187 - 0.328782
W-188 - 0.00133755

Uranium

U-230 - 0.091131
U-231 - 0.7844
U-232 - 0.088911
U-233 - 0.0291042
U-234 - 0.077589
U-235 - 0.338883
U-236 - 0.073704
U-237 - 0.58793
U-238 - 0.065231
U-239 - 0.13431
U-240 - 0.284382

Vanadium

V-48 - 1.70126
V-52 - 0.76109

Xenon

Xe-122 - 0.180079
Xe-123 - 0.52392
Xe-125 - 0.356014
Xe-127 - 0.345247
Xe-129m - 0.228105
Xe-131m - 0.093721
Xe-133 - 0.102971
Xe-133m - 0.112258
Xe-135 - 0.189477
Xe-135m - 0.320087
Xe-137 - 0.123802
Xe-138 - 0.62123

Ytterbium

Yb-169 - 0.326969
Yb-175 - 0.0304621

Yttrium

Y-86 - 2.32804
Y-87 - 0.68857
Y-88 - 1.78303
Y-90m - 0.48692
Y-91 - 0.00199911
Y-91m - 0.38036
Y-92 - 0.146927
Y-93 - 0.051652

Zinc

Zn-62 - 0.33263
Zn-65 - 0.330188
Zn-69 - 4.3216E-06
Zn-69m - 0.295371

Zirconium

Zr-86 - 0.88171
Zr-88 - 0.6327
Zr-89 - 0.98494
Zr-95 - 0.46546
Zr-97 - 0.108114

**Listing partially extracted from ORNL/RSIC-45, "Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment", 1981.

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