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Posted: Asked by course participant (21-23 March 2012 Melbourne, Australia)
From:

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Does high energy beta become low energy beta?

Question:
Is dividing beta emissions into two categories: low energy (< 10keV) and high energy (> 10 keV) an adequate simplification or does this introduce significant uncertainty for beta energy that is degrading as it enters the biota, losing energy in the process?
The low beta component is calculated separately because a higher relative biological effectiveness (RBE) has been observed for tritium (see references). It is prudent to assume that the experimental RBEs for tritium reflect the elevated LET values for low energy beta particles and electrons, and thus we recommend application of a weighting factor of 3, greater than unity to all such beta particles and electrons, regardless of the radionuclide from which they originate. For high-energy betas and electrons the weighting factor is 1, indicating same RBE than the reference radiation (gamma).

We think that the uncertainty introduced in the assessment is marginal – intermediary energy beta rays would have to be between these two extremes so no more than a factor of 3 uncertainty would be expected as a beta particle slows down in matter, becoming a low-energy electron. The lack of experimental data prevents us from making a more conclusive statement.
Answer:

Answered by Jordi Vives i Batlle (SCK•CEN, Belgium) 12/05/2012

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