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NORM maps of interest
In NE MO where I live and have the Home Lab, background radiation runs around 10 uR/H from natural sources, mostly K-40. This radiation field will give far different counts on various probes, depending on their overall sensitivity and their sensitivity to the specific energies in the local radiation. For example K-40 has a radiation energy of 1460 keV, which is just above the normal range for GM tubes, therefore a GM tube will not give a totally accurate reading if K-40 is the main isotope. On the other hand, the low energies given off by U will be exaggerated by a good GM probe. On average though, GM tubes give very acceptable and particularly repeatable results.
By far the most common radioactive materials are the ones found in the soil
and rocks in most
every state of the Union in one form or another, and to a more or less
degree.
Almost all of the many isotopes represented in this group, are the decay
products or daughters of U235, U238 or Th-232. These include all the Radium's, Thorium's, Radon's, Polonium, all the way
down to the radioactive Leads. They all start out as one of the 3 parents
listed above, and here are a few excellent links that we continually refer to which give all the details.
and rocks in most
every state of the Union in one form or another, and to a more or less
degree.
Almost all of the many isotopes represented in this group, are the decay
products or daughters of U235, U238 or Th-232. These include all the Radium's, Thorium's, Radon's, Polonium, all the way
down to the radioactive Leads. They all start out as one of the 3 parents
listed above, and here are a few excellent links that we continually refer to which give all the details.
See:
http://www.ead.anl.gov/pub/doc/natural-decay-series.pdf
http://www.ead.anl.gov/pub/doc/Cover-Intro-Linked.pdf
http://www.ead.anl.gov/pub/doc/Cover-Intro-Linked.pdf
(click on link to download)
On this link print out at least item pages# 115,137,143,145 and 149
http://www.ocrwm.doe.gov/pm/program_docs/curriculum/unit_2_toc/50.pdf
and once again a link to the entire table of Nuclides:
http://atom.kaeri.re.kr/ton/nuc11.html
http://www.ocrwm.doe.gov/pm/program_docs/curriculum/unit_2_toc/50.pdf
and once again a link to the entire table of Nuclides:
http://atom.kaeri.re.kr/ton/nuc11.html
Background (B/G) is gamma rays, they travel far in air. Betas
do travel a distance too though and
shouldn't be overlooked, but are easily shielded out. Figure
12 feet per MeV in air for betas. Alphas not a problem,
only travel an inch or two in air.
Technically speaking, no amount of shielding will
*stop* gamma rays. Practically speaking, we refer to
Half Value Layer HVL, the amount that cuts it in half. Then you figure the
Tenth Value Layer or TVL as the most that can be achieved under
practical terms. The TVL depends on the energy of the
gammas, but 2" is TVL for a 1.5 MeV gamma. You can't have a 2 inch lead
shield in a handheld probe, so they are usually anywhere from 1/8" to
1/2" of lead.
In nature there are 3 decay chains headed by Uranium 235, Uranium 238 and
Thorium. U 235 in low abundance but U 238 and Thorium are everywhere. Each
of the decay chains have the long lived parent element and many shorter
lived daughters present in a stable mix called equilibrium. Sometimes
equilibrium is disturbed by natural means, but usually undisturbed ore has a
good mix. Keeping in mind that all U238 ores will have a similar "signature",
be it yellow cake or Torbernite, because it is all Uranium after all. Many
different types of U samples are not needed, but interesting nonetheless.
Other radioactive isotopes also exist in nature but do not have a decay
chain, that is, their decay products themselves are not radioactive, but
stable. Potassium is a very common element, and a portion of all K in nature
is radioactive K-40, which is a large part of natural background radiation.
For home lab use, we can get samples of K-40 in N0-Salt, Potassium Chloride
salt for water softeners, fertilizer and many other household items.
do travel a distance too though and
shouldn't be overlooked, but are easily shielded out. Figure
12 feet per MeV in air for betas. Alphas not a problem,
only travel an inch or two in air.
Technically speaking, no amount of shielding will
*stop* gamma rays. Practically speaking, we refer to
Half Value Layer HVL, the amount that cuts it in half. Then you figure the
Tenth Value Layer or TVL as the most that can be achieved under
practical terms. The TVL depends on the energy of the
gammas, but 2" is TVL for a 1.5 MeV gamma. You can't have a 2 inch lead
shield in a handheld probe, so they are usually anywhere from 1/8" to
1/2" of lead.
In nature there are 3 decay chains headed by Uranium 235, Uranium 238 and
Thorium. U 235 in low abundance but U 238 and Thorium are everywhere. Each
of the decay chains have the long lived parent element and many shorter
lived daughters present in a stable mix called equilibrium. Sometimes
equilibrium is disturbed by natural means, but usually undisturbed ore has a
good mix. Keeping in mind that all U238 ores will have a similar "signature",
be it yellow cake or Torbernite, because it is all Uranium after all. Many
different types of U samples are not needed, but interesting nonetheless.
Other radioactive isotopes also exist in nature but do not have a decay
chain, that is, their decay products themselves are not radioactive, but
stable. Potassium is a very common element, and a portion of all K in nature
is radioactive K-40, which is a large part of natural background radiation.
For home lab use, we can get samples of K-40 in N0-Salt, Potassium Chloride
salt for water softeners, fertilizer and many other household items.
The USGS has some cool maps that show distribution of radon
throughout the US as well as similar maps showing background Gamma
radiation. See:
http://energy.cr.usgs.gov/radon/radonhome.html
and
http://energy.cr.usgs.gov/radon/rnus.html
throughout the US as well as similar maps showing background Gamma
radiation. See:
http://energy.cr.usgs.gov/radon/radonhome.html
and
http://energy.cr.usgs.gov/radon/rnus.html
One of the first questions we hear on this board from a new member is "How hot
is this if I get a reading of XXX?).
Well, the answer depends on a lot of factors, namely the distance you are from
the radiation source, the size and shape of the radiation source, what is
between you and the source (including the source itself, can have large
self-absorption), and most importantly, what is the source material Quality
Factor "QF" ( i.e. what type, energy, and abundance of radiations does it
emit?)
In the field, one seldom encounters a single source of radiation, rather a
mixture of NORM ( naturally occurring radioactive material) which has an array
of different Gamma energies. Chief among the NORM are Uranium, Thorium and K-40.
A portion of all background (B/G) radiation detected will be from Cosmic Rays.
I've seen references that claim as much as 1/3 of all B/G is from Cosmic Rays,
although I personally cannot corroborate this. ( My experiments on bodies of
water yield very low residual counts, being well away from soil/rock and
soil/rock spawned radon).
From the lab standpoint, where shields can remove most of the B/G, individual
isotopes may be measured and formulae employed to ascertain the needed data.
One formula, taken from the Health Physics Handbook is shown here:
R (@1 ft)= 6 x CE
Or
R (@ 1 cm)= 5.6 x10^3 x CE
Where
R= RADs/H
C= activity in Curies
E= Gamma energy in MEV
x= multiplication symbol
Fortunately for us, the US Gov't has worked all this out for some useful
isotope, and an excerpt is included below. For a full read and printout , refer
to the source document at:
http://www-rsicc.ornl.gov
is this if I get a reading of XXX?).
Well, the answer depends on a lot of factors, namely the distance you are from
the radiation source, the size and shape of the radiation source, what is
between you and the source (including the source itself, can have large
self-absorption), and most importantly, what is the source material Quality
Factor "QF" ( i.e. what type, energy, and abundance of radiations does it
emit?)
In the field, one seldom encounters a single source of radiation, rather a
mixture of NORM ( naturally occurring radioactive material) which has an array
of different Gamma energies. Chief among the NORM are Uranium, Thorium and K-40.
A portion of all background (B/G) radiation detected will be from Cosmic Rays.
I've seen references that claim as much as 1/3 of all B/G is from Cosmic Rays,
although I personally cannot corroborate this. ( My experiments on bodies of
water yield very low residual counts, being well away from soil/rock and
soil/rock spawned radon).
From the lab standpoint, where shields can remove most of the B/G, individual
isotopes may be measured and formulae employed to ascertain the needed data.
One formula, taken from the Health Physics Handbook is shown here:
R (@1 ft)= 6 x CE
Or
R (@ 1 cm)= 5.6 x10^3 x CE
Where
R= RADs/H
C= activity in Curies
E= Gamma energy in MEV
x= multiplication symbol
Fortunately for us, the US Gov't has worked all this out for some useful
isotope, and an excerpt is included below. For a full read and printout , refer
to the source document at:
http://www-rsicc.ornl.gov
Here the "inverse square law" applies, so halving the distance will X4 the
intensity.
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 - 0.122729
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
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 - 0.122729
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
Taking a Radiation Reading" is a simple matter. Understanding that
reading may be a little more complex. Yes you can point your CDV700
at something, and get a reading. The next question is "what does that
reading mean?".
The passage that follows is a direct quote from a book, so that the
details are preserved. My comments at the conclusion.
QUOTE:
"To be effective in your radiological work, you must get a first
grasp on the ways radiation is measured. "Radiation", like "distance"
is a general concept. You would have a weak understanding of distance
if you were vague about "foot", "inch", "mile", "kilometer", "light
year", and the other ways by which distance is measured. The same is
true for radiation.
The Curie (Ci) is the unit used to measure the activity of all
radioactive substances. It is a measurement of rate of decay or
nuclear disintegration that occurs within the radioactive material.
The Curie initially established the activity ( that is, decay rate)
of Radium as the standard with which the activity of any other
substance was compared.
By using a formula that takes into account the number of atoms per
gram and the value of the half-life in seconds, scientists have
determined that the activity of Radium is equal to 3.7 X 10E10
nuclear disintegrations per gram per second. This value is now the
standard of comparison. A Curie of ANY radioactive isotope,
therefore, is the amount of that isotope that will produce 3.7 X
10E10 nuclear disintegrations per second. Since the measure is based
on number of disintegrations, the weight of the radioisotope will
vary from that of Radium. A Curie of pure CO60 would weigh less
than .9 milligrams, while a Curie of U238 would weigh over two metric
tons.
The Curie is a large unit. In training, a milliCurie, mCi (one-
thousandth Curie) and the microCurie, uCi ( one millionth Curie) are
common units in use. At the opposite extreme, the Curie is too small
a unit for convenient measurement of the high-order activity produced
by the nuclear explosion. For this purpose, he MegaCurie ( one
million Curies) is used.
The Roentgen,(R) by definition measures exposure to Gamma and X-rays.
It is an expression of the ability of Gamma or X-ray to ionize air.
One R will produce 2.083 X 10E9 ion pairs per cubic centimeter in
air.
The Curie measures Radioactivity
The Roentgen measures X or Gamma rays"
END QUOTE
My comment:
Armed with the above information, consider the added confusion when
you include the fact that every radioisotope puts out a different
type of radiation mixture. Some have Alphas and Betas(Betas
themselves which have a range, not a discrete energy). Then the Gamma
rays are of different energies. This soup of different radiations
would be difficult enough to quantify in a perfect world, but our
probes are far from perfect. Some respond way differently than
others, some over respond to certain radiation, or under respond. The
probe housing also has a big affect on the final readings..........
some being "compensated", some "uncompensated. Throw in the distance,
geometry and other geotropic factors, shielding, and it would be very
difficult indeed to say "this material is 20 mCi" First you would
have to know exactly what the material was in the first place, so you
could analyze which radiations the probe was ( or was not) reading.
Since the R is a unit of field charge and not of radioactivity, it is
perfectly valid to use a CDV700 to make these measurements ( shield
closed). It is also valid to use a Beta check source to "calibrate" a
probe/meter combination and have that "calibration" apply to the
Gamma response as well*. That reading is valid for the location of
the probe. It offers no help as to the quantity or energy level of
the material producing the Gamma Rays, or the distance it is from the
probe. It does not matter in this context, the ionization field is
being produced by whatever quantity and energy mix that exists, and
the distance factor is automatically integrated into the reading. R
is a measure of the effects of Gamma rays, only valid with the Beta
shield close.
That's fine from a health-physics or CD standpoint, as far as it
goes.
* the idea here is that the characteristics of the QPL 6993 probe are
so well known, both Beta and Gamma, that exposure to a know Beta
source ( shield open) will give a reasonable expectation of a know
Gamma response ( shield close). This is the basis of the QPL or
Quality Product List classification on the 6993 tubes. In the case of
the radioactive check source that comes with the CDV700 set, there
has been a considerable time elapse since these were installed, and
in some cases at least, they have been replaced or refreshed. Also it
is indicated that the material itself is of different compositions,
between makers. All this affects the present day strength of he
sample. Since we have a "standard" radioactive source readily
available, long half-life, namely the radioactive lantern mantles,
assuming them to be from the same batch lot ( mine are), it would
seem that anyone could measure his probe/meter against the mantle,
then apply a K factor to the onboard test spot. All we would need is
a representative measurement made with a new or know good tube at the
specified high voltage. A suggestion is to leave the mantle in the
plastic bag, with the red side towards the probe, and wrapped around
the open Beta window with a rubber band. Perhaps someone out there
has an actual assayed or calibrated lab sample that could provide the
NIST trace to legitimize the project.
My personal interest goes in another vector. I want to know
quantitatively ( assay) and qualitatively ( is it Alpha?, Beta?,
Gamma?, and what energy levels). I continue to give reading as CPM,
with probe and other conditions listed.
Geologists have a keen interest in radioactivity, as it can foretell
the
nature of the earth in the vicinity. Some even use the small
differences to
detect the probable presence of petroleum. Others use it to prospect
for
minerals.
In practice the 3 main of interest are Potassium, Uranium and
Thorium. By knowing the concentration and relationship of these three, the
geologist can make many conclusions.
A small percentage ( .12%)of all natural Potassium is a radioactive
isotope
K-40 which has only one Gamma decay product, a ray of 1.461 MeV. This
can be
measured directly by the instrument.
Uranium itself is an strong Alpha emitter and it's gamma rays are
unsuitable
for direct measurement in this field, so a daughter of unique
properties,
Bismuth-214 is used instead, where the 1.76 MeV Gamma can easily be
distinguished.
Thorium has similar difficulties in direct measurement, so in this
instance
the daughter - Thallium-208 with it's 2.62 MeV gamma are chosen for
scrutiny.
We you see prospectors with their PRI's clicking away in the movies,
the
real science of today has moved way beyond that. Grids are set up for
a
routine survey and many measurements of the 3 minerals mentioned
above are
made. Sometimes the detector is winched down a well drill hole to take
measurements ( other methods of radioactive investigation are also
used in
well logging). Airborne and carborne surveys can easily be made too.
In all these cases, the 3 different energy level gammas are measured
separately by means of a gamma spectrometer. Some instruments are more
complex than others, thereby giving readings that are easier to
understand.
Some even use isotope stabilized probes to prevent temperature
variations
form affecting readings ( NaI(Tl) - PMT scintillators sensitivity
drifts
with temperature, about 1% for each 2 degrees). A closed feedback loop
measures the Alphas given off by Am-241 which is actually inside the
crystal, and the high voltage is adjusted for a standard reading
automatically.
As you should know if you read the Primer in GCE message 266, scintillator
detectors put out pulses that vary in height, according to the energy
level
of the radiation that caused the pulse. In the Gamma Ray
Spectrometer, those pulses are sorted out and dealt with on a case by case basis.
reading may be a little more complex. Yes you can point your CDV700
at something, and get a reading. The next question is "what does that
reading mean?".
The passage that follows is a direct quote from a book, so that the
details are preserved. My comments at the conclusion.
QUOTE:
"To be effective in your radiological work, you must get a first
grasp on the ways radiation is measured. "Radiation", like "distance"
is a general concept. You would have a weak understanding of distance
if you were vague about "foot", "inch", "mile", "kilometer", "light
year", and the other ways by which distance is measured. The same is
true for radiation.
The Curie (Ci) is the unit used to measure the activity of all
radioactive substances. It is a measurement of rate of decay or
nuclear disintegration that occurs within the radioactive material.
The Curie initially established the activity ( that is, decay rate)
of Radium as the standard with which the activity of any other
substance was compared.
By using a formula that takes into account the number of atoms per
gram and the value of the half-life in seconds, scientists have
determined that the activity of Radium is equal to 3.7 X 10E10
nuclear disintegrations per gram per second. This value is now the
standard of comparison. A Curie of ANY radioactive isotope,
therefore, is the amount of that isotope that will produce 3.7 X
10E10 nuclear disintegrations per second. Since the measure is based
on number of disintegrations, the weight of the radioisotope will
vary from that of Radium. A Curie of pure CO60 would weigh less
than .9 milligrams, while a Curie of U238 would weigh over two metric
tons.
The Curie is a large unit. In training, a milliCurie, mCi (one-
thousandth Curie) and the microCurie, uCi ( one millionth Curie) are
common units in use. At the opposite extreme, the Curie is too small
a unit for convenient measurement of the high-order activity produced
by the nuclear explosion. For this purpose, he MegaCurie ( one
million Curies) is used.
The Roentgen,(R) by definition measures exposure to Gamma and X-rays.
It is an expression of the ability of Gamma or X-ray to ionize air.
One R will produce 2.083 X 10E9 ion pairs per cubic centimeter in
air.
The Curie measures Radioactivity
The Roentgen measures X or Gamma rays"
END QUOTE
My comment:
Armed with the above information, consider the added confusion when
you include the fact that every radioisotope puts out a different
type of radiation mixture. Some have Alphas and Betas(Betas
themselves which have a range, not a discrete energy). Then the Gamma
rays are of different energies. This soup of different radiations
would be difficult enough to quantify in a perfect world, but our
probes are far from perfect. Some respond way differently than
others, some over respond to certain radiation, or under respond. The
probe housing also has a big affect on the final readings..........
some being "compensated", some "uncompensated. Throw in the distance,
geometry and other geotropic factors, shielding, and it would be very
difficult indeed to say "this material is 20 mCi" First you would
have to know exactly what the material was in the first place, so you
could analyze which radiations the probe was ( or was not) reading.
Since the R is a unit of field charge and not of radioactivity, it is
perfectly valid to use a CDV700 to make these measurements ( shield
closed). It is also valid to use a Beta check source to "calibrate" a
probe/meter combination and have that "calibration" apply to the
Gamma response as well*. That reading is valid for the location of
the probe. It offers no help as to the quantity or energy level of
the material producing the Gamma Rays, or the distance it is from the
probe. It does not matter in this context, the ionization field is
being produced by whatever quantity and energy mix that exists, and
the distance factor is automatically integrated into the reading. R
is a measure of the effects of Gamma rays, only valid with the Beta
shield close.
That's fine from a health-physics or CD standpoint, as far as it
goes.
* the idea here is that the characteristics of the QPL 6993 probe are
so well known, both Beta and Gamma, that exposure to a know Beta
source ( shield open) will give a reasonable expectation of a know
Gamma response ( shield close). This is the basis of the QPL or
Quality Product List classification on the 6993 tubes. In the case of
the radioactive check source that comes with the CDV700 set, there
has been a considerable time elapse since these were installed, and
in some cases at least, they have been replaced or refreshed. Also it
is indicated that the material itself is of different compositions,
between makers. All this affects the present day strength of he
sample. Since we have a "standard" radioactive source readily
available, long half-life, namely the radioactive lantern mantles,
assuming them to be from the same batch lot ( mine are), it would
seem that anyone could measure his probe/meter against the mantle,
then apply a K factor to the onboard test spot. All we would need is
a representative measurement made with a new or know good tube at the
specified high voltage. A suggestion is to leave the mantle in the
plastic bag, with the red side towards the probe, and wrapped around
the open Beta window with a rubber band. Perhaps someone out there
has an actual assayed or calibrated lab sample that could provide the
NIST trace to legitimize the project.
My personal interest goes in another vector. I want to know
quantitatively ( assay) and qualitatively ( is it Alpha?, Beta?,
Gamma?, and what energy levels). I continue to give reading as CPM,
with probe and other conditions listed.
Geologists have a keen interest in radioactivity, as it can foretell
the
nature of the earth in the vicinity. Some even use the small
differences to
detect the probable presence of petroleum. Others use it to prospect
for
minerals.
In practice the 3 main of interest are Potassium, Uranium and
Thorium. By knowing the concentration and relationship of these three, the
geologist can make many conclusions.
A small percentage ( .12%)of all natural Potassium is a radioactive
isotope
K-40 which has only one Gamma decay product, a ray of 1.461 MeV. This
can be
measured directly by the instrument.
Uranium itself is an strong Alpha emitter and it's gamma rays are
unsuitable
for direct measurement in this field, so a daughter of unique
properties,
Bismuth-214 is used instead, where the 1.76 MeV Gamma can easily be
distinguished.
Thorium has similar difficulties in direct measurement, so in this
instance
the daughter - Thallium-208 with it's 2.62 MeV gamma are chosen for
scrutiny.
We you see prospectors with their PRI's clicking away in the movies,
the
real science of today has moved way beyond that. Grids are set up for
a
routine survey and many measurements of the 3 minerals mentioned
above are
made. Sometimes the detector is winched down a well drill hole to take
measurements ( other methods of radioactive investigation are also
used in
well logging). Airborne and carborne surveys can easily be made too.
In all these cases, the 3 different energy level gammas are measured
separately by means of a gamma spectrometer. Some instruments are more
complex than others, thereby giving readings that are easier to
understand.
Some even use isotope stabilized probes to prevent temperature
variations
form affecting readings ( NaI(Tl) - PMT scintillators sensitivity
drifts
with temperature, about 1% for each 2 degrees). A closed feedback loop
measures the Alphas given off by Am-241 which is actually inside the
crystal, and the high voltage is adjusted for a standard reading
automatically.
As you should know if you read the Primer in GCE message 266, scintillator
detectors put out pulses that vary in height, according to the energy
level
of the radiation that caused the pulse. In the Gamma Ray
Spectrometer, those pulses are sorted out and dealt with on a case by case basis.
In the simple self-contained ( probe is inside the instrument) units like the DISA
300, there is often only a LLD ( Lower Level Discriminator) sometimes
called a threshold control. It can be preset for the different channels of
interest, but basically it will ignore all the energy pulses BELOW a certain
point, and count all the ones above that. The K channel ( Potassium) will
ignore all below 1.46 but count all above that, which of course includes the
U and Th channels. Similarly the U ( Uranium) channel will include the Th
energies., so to get an individual picture of each, some readings are
taken, and mathematical subtraction employed.
In the case of the more complicated Scintrex, there is also a Upper
Limit control or "window" applied which ignores all the pulses ABOVE a
certain level, so that the counter only recognizes the pulses above the LLD
but below the Window.
These same controls exist on all SCA's ( Single Channel Analyzers)
except that in the geologists special unit there a 4 different ones that are
simply preset, then switch selected ( K-U-Th and the 4th channel is wide
open or Total Counts).
Rather large scintillators must be utilized for good sensitivity and reasonable count
rates. Even though the count rate "wide open" will be huge, when all the
random pulses are screened out, the actual reading can become quite small
for the energy levels of interest.
300, there is often only a LLD ( Lower Level Discriminator) sometimes
called a threshold control. It can be preset for the different channels of
interest, but basically it will ignore all the energy pulses BELOW a certain
point, and count all the ones above that. The K channel ( Potassium) will
ignore all below 1.46 but count all above that, which of course includes the
U and Th channels. Similarly the U ( Uranium) channel will include the Th
energies., so to get an individual picture of each, some readings are
taken, and mathematical subtraction employed.
In the case of the more complicated Scintrex, there is also a Upper
Limit control or "window" applied which ignores all the pulses ABOVE a
certain level, so that the counter only recognizes the pulses above the LLD
but below the Window.
These same controls exist on all SCA's ( Single Channel Analyzers)
except that in the geologists special unit there a 4 different ones that are
simply preset, then switch selected ( K-U-Th and the 4th channel is wide
open or Total Counts).
Rather large scintillators must be utilized for good sensitivity and reasonable count
rates. Even though the count rate "wide open" will be huge, when all the
random pulses are screened out, the actual reading can become quite small
for the energy levels of interest.
Have fun
Geo
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