ALARA | SPECIAL REPORT
monitored individuals at commercial light-water reactors in Calendar Year 2022 were below any measurable dose. The UK’s NRR also had concerns over the application of ALARA . It says, “The focus by dutyholders and regulators has increasingly been on the ‘as low as’ and less on the ‘reasonably practicable’ parts of the ALARP principle, and a culture of over-conservatism and risk aversion has become entrenched. This has resulted in a slow overall decision-making environment where innovative choices are discouraged.” Both the INL paper and the NNR argue that the ALARA principle has had the effect of stepping up measures until they are far beyond the ‘reasonable’ definition. The UK’s ALARA principle is also expressed as being
‘as low as reasonably practicable’ (ALARP). Rather than focusing on the dose itself, the UK authors’ concern was the tendency to go on reducing doses far past what was practicable, given the cost. They say the application of ALARP has become “overly stringent” and “It sometimes
functions as a ratchet that demands ever-lower risk levels and radiation exposures, even when the benefits are negligible or the costs disproportionate.” This is in part due to a lack of clear direction on the
tolerability of risk and in the assessment of proportionality. The nuclear sector “frequently neglects to consider a portfolio view of risk” in applying ALARP, which drives local risk reduction without accounting for strategic factors, and the risks associated with inaction and poor programme delivery. The report said this was a government responsibility. It should define the Tolerability of Risk for the nuclear sector with regard to the modern state of the nuclear sector, and the societal demand for its outputs across energy, decommissioning and defence. This should be clearly communicated and periodically reviewed. Risks at or below broadly acceptable levels should be deemed to be ALARP and ALARA “unless there are strong and compelling reasons to the contrary.”
Overly stringent approaches to radiation exposure are “leading to disproportionate decisions and designs, which in many cases provide no greater protection to the public, at higher costs to the taxpayer.”
Radiation dose measurement
The Sievert (Sv) and rem are both measures of radiation dose. The rem has been defined since 1976 as equal to 0.01 Sv, which is the unit commonly used outside the USA. The UK Health Security Agency calculated that on average people are exposed to about 2.7mSv of radiation a year, 99% of it from natural background radiation and medical procedures. Cornwall in the UK’s southwest is an example of an area with high background radiation due to high naturally occurring levels of radon gas. Here exposure is typically 8.3mSv/yr. A transatlantic flight will incur approximately 0.08mSv. ■
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