The right approach to radiological protection

06 January 2015

There is certainly nothing wrong with the basic tenets of radiological protection, but their application without heed to non-radiological hazards can lead seriously astray, writes Jack Valentin, an independent radiological protection consultant.

How to prevent the next major release of radioactive material from turning into a human disaster emerged as the most important consideration at the panel session on radiological protection at the WNA 2014 Symposium last September.

The panel session, now available as a podcast, provided much food for thought. Wolfgang Weiss of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) had set the stage by stating that the Fukushima Daiichi accident had caused no clinically observable radiation effects and that, in all likelihood, any cancer due to radiation will not be discernible. That means some cancers are expected but would be too few to detect statistically.

The UNSCEAR assessment team had also noted a considerable impact on social and psychological wellbeing, but it was not within their remit to assess such indirect effects. This may seem odd, and Malcolm Grimston, honorary senior research fellow at Imperial College Centre for Energy Policy and Technology, pointed out that precisely those effects the UNSCEAR team was not tasked to investigate appear to be by far the most serious outcome of the Fukushima Daiichi accident.

However, I think it must be kept in mind that several UN bodies, each with a carefully defined mandate, are involved in assessments of the accident. The 2013 'Health Risk Assessment … based on a preliminary dose estimation' by the World Health Organization (WHO) discusses social and mental effects, albeit only briefly. The International Atomic Energy Agency (IAEA) will issue a 'Fukushima Comprehensive Report' in 2015 and this is expected to cover social and psychological effects in some more detail.

Roger Coates, vice-president of the International Radiation Protection Association (IRPA), underlined that science can only take us so far, particularly with regard to low doses of radiation, and societal judgments are inevitable.

I want to stress that this is actually a cornerstone of the Recommendations of the International Commission on Radiological Protection (ICRP). Their primary aim is to contribute to an appropriate level of protection against the detrimental effects of radiation exposure, without unduly limiting the desirable human actions that may be associated with such exposure.

This aim, says ICRP, cannot be achieved solely on the basis of scientific knowledge of radiation exposure and its health effects. Scientific data are a necessary prerequisite, but the societal and economic aspects of protection have also to be considered (which requires value judgments). Any decision that alters radiation exposure should do more good than harm. The likelihood of incurring exposures, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factors (my emphasis).

Coates noted that we should make better links to the levels of radiation to which we are all exposed through natural background, where everyone receives at least 2-3 millisieverts per year (mSv/y), with many of us getting significantly higher doses. This helps to contextualize other sources of exposure, most of which in practice do not substantively change this overall exposure picture.

However, I would like to focus here on protection strategies after an accident. ICRP has pointed out that the justification of such strategies goes far beyond the scope of radiological protection as they may also have various economic, political, environmental, social, and psychological consequences. The proper consideration of many of these non-radiological factors may require expertise other than radiological protection, and could dominate decisions on protection strategies.

But is this the approach usually taken after serious radiation accidents? Not according to Grimston, who said that there is a demonstrable, dangerous, but almost invisible myth that one should ‘err on the side of caution’ in radiological protection. That myth, he felt, has led to a 'wickedly irrational response' to the Fukushima Daiichi accident. In particular, he said, preventing those who were forcibly evacuated from returning to moderately contaminated areas is causing untold costs to society and significant non-radiological health detriment.

Radiological protection director Willie Harris of Exelon Nuclear added that while the nuclear industry considers the total risk panorama for their workers, the same does not always seem to apply to members of the public – that is, radiation risks tend to be viewed in isolation. Coates emphasized the importance of empowering the public since their confidence and wellbeing improves significantly if they can influence their own radiation situation – again, a point also stressed by ICRP.

My own take is that at the population level and for all cancers combined, a linear, no-threshold model seems to be a good approximation of the true dose response, so even small doses entail a risk - but a small one. Doses should of course be below pertinent limits, and given the dose-response pattern they should be kept as low as reasonably achievable. The cost of protection cannot be excessive - an excessive cost would not be reasonable!

A large radiation accident will generate an existing exposure situation with increased radiation levels, and in the short term it may be impossible or at least forbiddingly expensive to keep doses below the limits for planned situations. This does not necessarily imply an extreme danger; for protection of the public in such situations ICRP recommends a dose band of up to 20 times the dose limit for planned situations.

There is some concern in the radiological protection profession that the public may not understand why a higher dose is tolerable after an accident, when they would expect extra protection. However, this is analogous to many other kinds of accident: we tolerate temporarily higher (but not excessive) risks in connection with flooding, fire, unintended releases of chemicals, etc. In the long run, we expect the situation to return to normal, with normal safety and protection requirements, for radiation and for other problems.

This, I believe, is also how we should handle large radiation accidents. During the accident phase, several pre-planned emergency actions are taken, some of them quite disruptive. Once the accident is over, protective actions should be geared towards a reasonable level of protection against both radiation and other risks, avoiding significant competing risks, tolerating in the short term somewhat higher radiation risks than those accepted in planned situations, but aiming for a long-term return to the same level of protection that prevailed before the accident.

This is essentially what existing ICRP guidance recommends, but as Weiss pointed out, both emergency preparedness and the practical implementation of the recommendations often leave something to be desired. In part, this reflects that more practical advice is needed on justification and optimization when non-radiological factors dominate, and ICRP needs to (and will) supplement its recommendations in this respect. Protective post-accident actions that are truly in line with the existing recommendations and their intentions would hopefully satisfy the requirement suggested by Grimston at the end of the panel session: that we should prevent the next nuclear/radiological accident from becoming a human disaster.

Jack Valentin

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Jack Valentin joined the Swedish Radiation Protection Authority in 1983, initially supervising medical and industrial uses of radiation, then rising to deputy director in charge of supervision of nuclear installations. From 1997, until his retirement at the end of 2008, he was employed by ICRP as its Scientific Secretary.