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NASA Procedures and Guidelines |
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1. Determination of A2 Mission Multiple.
The A2 multiplier for each radioactive source is based upon the International Atomic Energy Agency (IAEA), Safety Series Number 6, Regulations for the Safe Transport of Radioactive Material, 1985 Edition as amended in 1990, Section III, paragraphs 301 through 306, and summed to determine the A2 mission multiple.
Table I of this Appendix contains the referenced IAEA document section which tabulates the A2 values for specific isotopes and forms of radioactive material. Except as noted, for radioisotopes whose A2 limit in Table I is "Unlimited" or is unlisted, the value of 3.7x10-2 teraBecquerals (TBq) (1.0 Curies (Ci)) shall be used as the A2 value.
Exceptions are Sm-147, use 9x10-4 TBq (0.024 Ci) and Th-232, use 9x10-5 TBq (0.0024 Ci) as their respective A2 values.
The A2 mission multiple shall be determined as follows:
where n represents each source or line on the report in paragraph 5.4.1.2 for each radioactive material on the launch vehicle and spacecraft.
2. Values of A1 and A2 for individual radionuclides, which are the basis for many activity limits elsewhere in this NPR, are given in Table I.
This section has been reproduced with permission of the IAEA.
DETERMINATION OF A1 AND A2
3. For individual radionuclides whose identities are known, but which are not listed in Table I, the determination of the values of A1 and A2 shall require competent authority approval or, for international transport, multilateral approval. Alternatively, the values of A1 and A2 in Table II may be used without obtaining competent authority approval.
4. In the calculations of A1 and A2 for a radionuclide not in Table I, a single radioactive decay chain in which the radionuclides are present in their naturally occurring proportions and in which no daughter nuclide has a half-life either longer than 10 days or longer than that of the parent nuclide shall be considered as a single radionuclide, and the activity to be taken into account and the A1 or A2 value to be applied shall be those corresponding to the parent nuclide of that chain. In the case of radioactive decay chains in which any daughter nuclide has a half-life either longer than 10 days or greater than that of the parent nuclide, the parent and such daughter nuclides shall be considered as mixtures of different nuclides.
5. For mixtures of radionuclides whose identities and respective activities are known, the following conditions shall apply:
(a) For special form radioactive material:
(b) For other forms of radioactive material:
where B(i) is the activity of radionuclide i and A1(i) and A2(i) are the A1 and A2 values for radionuclide i, respectively.
Table I. A1 And A2 Values for Radionuclides
Alternatively, an A2 value for mixtures may be determined as follows:
where f (i) is the fraction of activity of nuclide i in the mixture and A2 (i) is the appropriate A2 value for nuclide i.
6. When the identity of each radionuclide is known but the individual activities of some of the radionuclides are not known, the radionuclides may be grouped and the lowest A1 or A2 value, as appropriate, for the radionuclides in each group may be used in applying the formulas in paragraphs 3 - 5. Groups may be based on the total alpha activity and the total beta/gamma activity when these are known, using the lowest A1 or A2 values for the alpha emitters or beta/gamma emitters, respectively.
7. For individual radionuclides or for mixtures of radionuclides for which relevant data are not available, the values shown in Table II shall be used.
TABLE II. GENERAL VALUES FOR A1 AND A2
Contents A1 A2
TBq (Ci)a TBq (Ci)a
Only beta or gamma emitting 0.2 (5) 0.02 (0.5)
nuclides are known to be present
Alpha emitting nuclides are 0.1 (2) 2 x 10-5 (5 x 10-4) known to be present or no relevant data are available
aThe curie values quoted in parentheses are approximate values and are not higher than the TBq values
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