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activation table of elements

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Activation table of the elements a

An updated version of this table is in preparation. Any comments to Sax Mason


This table allows you to calculate the activation of a sample after it has been in a neutron beam for one day and the amount of time for it to decay to 2nCi/g or less, which is the limit for shipping a sample as "nonradioactive". It also displays the anticipated exposure you may receive when removing the sample from the instrument. A sample calculation is included at the end of the table. Storage time is the time required for a sample of the pure condensed-phase element exposed to a "standard" neutron beam to decay to 2nCi/g or less. Prompt activation gives the anticipated activation for the pure solid elements 2 min after the neutron exposure ceases. Contact dose is that expected from a 1g sample of the pure element from the prompt activation. Elements with a dash for the entries in all three columns do not show any activation. Those marked with a single asterisk are radioactive before exposure to the neutron beam; apart from Tc and Pm, they are all a-particle emitters. Bismuth is a special case; it is stable before exposure to the beam, but the activation product is an a-emitter.


Symbol Name Mass Storage time Prompt activation Contact dose
        (nCi/g) (mr/hr/g at 1 in)
Ac actinium 227 * * *
Al aluminium 26.982 21m 1900 2.0
Am americium 243 * * *
Sb antimony 121.75 520d 800 0.7
Ar argon 39.948 19h 3500 3.0
As arsenic 74.922 18d 8.4x104 7.3
At astatine 210 * * *
Ba barium 137.34 <150h <80 <0.1
Bk berkelium 247 * * *
Be beryllium 9.012 - - -
Bi bismuth 208.980 ** ** **
B boron 10.811 - - -
Br bromine 79.909 18d 1.4x104 12† 
Cd cadmium 112.40 190d 370 0.3
Ca calcium 40.08 - - -
Cf californium 249 * * *
C carbon 12.011 - - -
Ce cerium 140.12 <86h <40 <0.1
Cs cesium 132.905 54h 4.6x105 400
Cl ch1orine 35.453 <2.8h <80 <0.1
Cr chromium 5 1.996 <6ld <40 <0.1
Co cobalt 58.933 24y 5.2x104 45
Cu copper 63.54 7.4d 1.0x104 8.5
Cm curium 247 * * *
Dy dysprosium 162.50 52h 5.0x105 430
D deuterium 2.015 - - -
Es einsteinium 254 * * *
Er erbium 167.26 78d 600 0.5
Eu europium 151.96 50y 2200 l.9
Fm fermium 253 * * *
F fluorine 18.998 - - -
Fr francium 223 * * *
Gd gadolinium 157.25 11d 7400 6.4
Ga gallium 69.72 8d 3.2x104 27
Ge germanium 72.59 <6d 1100 1.0
Au gold 196.967 29d 3000 2.5
Hf hafnium 178.49 1.6y 620 0.5
He helium 4.003 - - -
Ho holmium 164.930 20d 2.8x104 24
H hydrogen 1.008 - - -
In indium 114.82 12d 1.1x104 9.5
I iodine 126.904 7h 1.2x105 100
Ir iridium 192.2 4.2y 5.0x104 43
Fe iron 55.847 - - -
Kr krypton 83.80 42h 3200 2.8
La lanthanum 138.91 22d 1.9x104 16
Pb lead 207.19 - - -
Li lithium 6.939 - - -
Lu lutetium 174.97 1.8y 1.4 xl04 12
Mg magnesium 24.312 - - -
Mn manganese 54.938 38h 1.lx105 95
Md mendelevium 256 * * *
Hg mercury 200.59 24d 700 0.6
Mb molybdenum 95.94 30d 430 0.4
Nd neodymium 144.24 15h 1200 1.0
Ne neon 20. 183 - - -
Np neptunium 237 * * *
Ni nickel 58.71 <5.5h <30 <0.1
Nb niobium 92.906 80m 2.0x104 17
N nitrogen 14.007 - - -
Os osmium 190.2 41d 2300 2.0
O oxygen 15.999 - - -
Pd palladium 106.4 9d 7. lx104 60
P phosphorous 30.974 - - -
Pt platinium 195.09 20d 230 0.2
Pu plutonium 242 * * *
Po polonium 210 * * *
K potassium 39.102 <38h <300 <0.3
Pr praseodymium 140.907 11d 2.0x104 17
Pm promethium 147 * * *
Pa proctactinium 231 * * *
Ra radium 226 * * *
Rn radon 222 * * *
Re rhenium 186.2 53d 4.9x104 42
Rh rhodium 102.905 2h 2.6x104 22
Rb rubidium 85.47 56d 1800 1.6
Ru ruthenium 101.07 106d 230 0.2
Sm samarium 150.35 35d 6200 5.4
Sc scandium 44.956 <1 .8y <90 <0.1
Se selenium 78.96 10h 4900 4.2
Si silicon 28.086 - - -
Ag silver 107. 870 7.4y l.6x104 14
Na sodium 22.991 5.5d 5700 5.0
Sr strontium  87.62 <25h <100 <0.1
S sulphur  32.064 - - -
Ta tantalum  180.948 3y 1600 1.4
Tc technetium 98 * * *
Te tellurium  127.60 96h 2600 2.2
Tb terbium 158.924 2.ly 3300 2.8
Tl thallium 204.37 41m 460 0.4
Th thorium 232.038 * * *
Tm thulium 168.934 3.7y 7700 6.7
Sn tin 118.69 <50d <40 <0.1
Ti titanium  47.90 - - -
W tungsten 183.85 15d 3.7x104 32
U uranium  238.03 * * *
V vanadium 50.942 48m 4.7x105 41
Xe xenon 131.30 7d 3200 2.8
Yb ytterbium 173.04 275d 780 0.7
Y yttrium 88.905 24d 1000 0.9
Zn zinc  65.37 5d 1600 1.4 
Zr zirconium 91.22 79h <40 <0.1

a These entries are derived by Mike Johnson of ISIS for decay times to 105 and to 104Bq/cm3 for 5-cm3 pure solid samples of the elements exposed to a neutron beam for 1 day at an intensity comparable to that on HIPD with LANSCE operating at 100mA. They are augmented by calculations from NIST of the activation from a 1-day exposure to a 107n/s-cm2 reactor thermal beam (marked ).

Estimating activation

Using the following procedure and example, estimate the anticipated activation of a sample exposed to the neutron beam in a LANSCE instrument from the table. If you cannot estimate the activation, call your LANSCE contact.

Example: For 5g YBa2Cu3O7 sample on NPD at 75mA for 24 hours (1 day).

1. Compute the mass fractions for all elements in the sample.

Example: The mass fractions are 0.13 Y, 0.4l Ba, 0.29 Cu, & 0.17 O

2. Obtain the prompt activation from the product of these mass fractions and the corresponding elemental activation values in the table. Multiply the contact dose by the sample mass that is exposed to the beam to obtain the expected contact dose from the entire sample.

Example continued:

prompt activity = 0.13x 1000 + 0.41x80 +0.29x 10000 + 0.17x0.0 = 3060nCi/g

contact dose = 5x(0.13x0.9 + 0.41x0.1 + 0.29x8.5 + 0.17x0.0) = 13.1mR/hr

3. Scale these activation values by the instrumental factor (below) and the beam current as a fraction of l00mA to obtain the estimated values for the sample and actual beam conditions.

Instrumental factors for LANSCE

HIPD 1.00 (reference)
SCD 1.44
FDS 0.50
CQS 1.65
NPD 0.025
PHAROS 0.060
LQD 0.033
SPEAR 0.04 1

Example continued:

prompt activity = 3060x0.025x75/100= 57nCi/g

contact dose = 13.lx0.025x75/100 = 0.25mR/hr

4. To obtain the storage times, t, for each element in the sample, correct the appropriate times given in the table, ts, by:

t = ts(0.693+0.lxlogeC),

where C is the product of the mass fraction, instrumental factor and beam intensity ratio to l00m A. This expression assumes that the storage times given in the table are roughly 10 half-lives for the slowest decaying isotope of significant concentration in the activated element The storage time for the sample is then the largest of the resulting times.

Example continued

Y storage time = 24d(0.693+0.lxloge(0.13x0.025x75/100)) = 2.2d

Ba storage time = 150h(0.693+0.lxloge(0.41x0.025x75/100)) = 1.3d or less

Cu storage time = 7.4d(0.693+0.lxloge(0.29x0.025x75/100)) = 1.3d

O storage time = 0 (no activation expected)

Thus the storage time for this sample of YBa2Cu3O7 is determined by the decay of the Y as 2.2 days. At that time, the sample should show residual activation of less than 2nCi/g.

These estimates are based on a neutron exposure time of 1 day. The actual level of activation can drastically change if the exposure is more or less than 1 day. Determining this change cannot be accomplished using these simplistic calculations. Therefore, we require that all samples (no matter how long the neutron exposure is) be surveyed before they leave the facility.


LANSCE 12 / 1 / 92

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