US Nuclear Regulator Proposes Rule Change, Keeps Core Radiation Science Intact

Last week, just before the US started its break for the July Fourth holiday, the Nuclear Regulatory Commission (NRC) proposed a new rule that would change how it regulated exposure to radiation. The Trump administration has been pushing to restart construction of nuclear power plants in the US, and many pro-nuclear advocates have been complaining about the US’s existing regulations, portraying them as the main barrier to the flourishing of the industry. So, it had seemed likely that major revisions were coming.

Instead, the NRC’s proposed new rules endorse the science behind its current rules and suggest that any problems are largely in the vagueness of the terminology that it has been using. So, instead, it’s endorsing standards that are meant to accomplish the same thing, but avoid using some of the language it had relied on. Probably the clearest indication of the evolutionary change at play is that the NRC estimates the changing rules will save industry—not just power, but also medical and research applications—only about $9.5 million a year.

LNT and ALARA

There are two technical abbreviations at the center of US nuclear regulations. The first is LNT, which stands for “linear non-threshold.” It’s in reference to the issue of whether there’s any level of radiation that is so low that it no longer produces harmful biological effects—the “threshold” in LNT. The “non-threshold” implies that it doesn’t, and that’s in keeping with biology, which has demonstrated that even single particles or photons of radiation can damage DNA and that the mechanisms cells have for repairing that damage are inherently error-prone. The “linear” in LNT simply describes how the impact of radiation scales directly with the dose.

Despite the solid foundation in basic biology, LNT has been difficult to demonstrate in the real world. Humans are exposed to many factors that can influence the development of cancer, including naturally occurring radiation. Teasing out the impact of a small dose of radiation that occurs in addition to all those other exposures is extremely challenging, and the impact of extremely low exposures has not been decisively demonstrated.

Complicating matters, a number of people have advocated for something called hormesis, in which small doses of radiation purportedly promote the cellular repair of damage from other sources. The evidence for this is even spottier, and when the NRC was petitioned to adopt hormesis as part of its scientific framework during Trump’s first term, it rejected the petition.

Given its acceptance of an LNT model of exposure risks, the NRC had chosen exposure standards that fell under the general term of ALARA: as low as reasonably achievable. If any exposure to radiation poses a risk, then minimizing it is the clearest way to protect the health of people who work with radioactive substances. The challenge there is that it’s possible to set exposure limits that people outside the industry regularly exceed each time they board a commercial aircraft.

So, the word “reasonable” plays an outsized role while remaining highly subjective. Critics have charged that it precipitates an endless cycle of reasonable exposure limits leading to searches for additional ways to lower them further, or of adoption without cost considerations. And here, the NRC is acknowledging that there have been issues. “In essence, the reasonableness test that is supposed to be inherent to ALARA-related decision-making has gradually become an expectation that if a means of dose reduction is available, regardless of its reasonableness in relation to the total dose and the amount of reduction, it should be applied without further consideration,” its new proposal suggests.

In the past, the NRC has attempted to address this by attaching a financial value to each unit of exposure based on estimates of the value of healthy life developed elsewhere. But in the new proposal, it accepts that “there have been challenges in the implementation of the ALARA requirement, namely a lack of clarity of when dose reduction is deemed sufficient, excessive subjectivity, and susceptibility for selective or inconsistent enforcement.” So, it’s giving up on a term that it now views as a source of confusion.

What’s different

One of the key things here is that the LNT model of exposure risks isn’t going away. In its earlier denial of petitions that it change its standards, the NRC had concluded that “in the absence of convincing evidence that there is a dose threshold or that the health effects of low levels of radiation are fully understood, the LNT model for cancers and genetic effects was appropriate for formulating radiation protection standards and planning radiation protection programs.” In the proposed new rules, that logic is left intact. “The NRC finds that no consensus-supported, regulation-ready alternative model to the LNT model exists at this time,” it states.

More specifically, it states, “It is unlikely there might be a threshold level of exposure below which biological response does not occur. Such a threshold could only occur if DNA repair processes were totally effective in that dose range or if a single radiation track were unable to produce an effect.”

It’s worth noting that the NRC is making that decision despite the fact that Trump issued an executive order that describes LNT and then calls it irrational. “The NRC utilizes safety models that posit there is no safe threshold of radiation exposure and that harm is directly proportional to the amount of exposure,” the order reads. “Those models lack sound scientific basis and produce irrational results.” The agency is keeping LNT in place despite being specifically ordered to reconsider it.

With LNT intact, the scientific backing for ALARA remains in place. So, the new proposed regulations largely focus on calling it something else. “The NRC proposes to remove references to the ALARA principle, which rests on the LNT model’s assessment of risks from very low doses of radiation, from its regulations,” the proposed changes say. “Instead, the NRC would apply a less-subjective, graded approach to managing doses below regulatory limits.”

To replace ALARA, the NRC will start with a limit at which evidence clearly indicates radiation impacts would be apparent and set exposure thresholds below that. From lowest to highest exposure, these thresholds will require increasingly aggressive efforts to limit exposures.

The language of the details is a bit confused, however. As its name implies, the LNT model suggests there are no thresholds below which biological risks go away, and the NRC accepts that model. Yet it’s regulated based on thresholds. It’s also referring to those thresholds as an implementation of an “optimization” approach to safety. But it also quotes a definition of optimization that refers to it as a form of ALARA—which, again, is a term that the NRC wants to get rid of.

Beyond that action, the rule changes the NRC is proposing largely focus on updating regulations on the use of equipment to monitor exposures. Technology has advanced since the agency last modified its requirements there, and it’s using this proposal to update them accordingly.

Number crunching

Regardless of the confusion, it’s clear that the changes aren’t going to cause the sort of boom in nuclear power that the Trump administration expected in its executive order. One of the key features of the planned rules is that any organization that’s currently in compliance will remain that way without making any changes. Changes will only make sense if an organization thinks it can save money by adopting them.

And, as noted above, those savings for industry will be pretty minimal, with the total estimated at $9.5 million a year. Even if we assume that these savings go only to nuclear power and are ascribed only to dropping ALARA (as opposed to cheaper exposure monitoring, for example), spread out across the 57 nuclear plants in the US, that means just an average savings of a bit over $150,000 per plant.

So, those who viewed ALARA as the cause of all the nuclear industry’s woes will likely be excited to see the NRC eliminate it. But they’ll also be disappointed to find that its scientific foundations remain intact, and the regulatory environment will be minimally changed as a result.