Radiation: Part 3 of a 4-part series

In the last two installments, we talked about where radiation comes from, and how we measure it. In this installment, we’ll start putting the pieces together, and you can see where your current concepts about incidents lie.

Now that I’ve told you about what radiation is, and how to measure it, lets’ talk about how much of it you need to see before abandoning incident.

In order to help give you some perspective on these figures, here are some approximate statistics for everyday things you might see during your patrol shift:

• Yearly dose from being near the Earths’ crust - 15 to 140 mrem
• Yearly dose from eating food - 39 mrem
• Yearly dose from inhaling radon trapped in your house- 200 mrem
• Yearly dose from watching TV - 1.5 mrem
• Yearly dose from smoking - nearly 8 rem
• Activity from hanging around the coal at a power plant - 174 Bq/kg
• Total Dose from getting an Xray - 5 to 170 mrem per exposure
• Total Dose the driver of the lead-lined tank got driving around Ground Zero of the first nuclear weapons test for three trips immediately post-detonation - 15 R
• Total Dose the Neutron detector retrieval crew got spending ten minutes within 730 meters of Ground Zero 9 hours post-shot - 1R
• Total Dose if you stood at the fenceline of Three Mile Island for the whole incident - 80mrem
• Dose rate from wandering around in the Vatican - 500 mrem / hr
• Dose rate currently at the exclusion zone boundary around Chernobyl - 400 mrem / hr

One benchmark I hear often is that the level of concern is double the background rate. I think that we pretty much beat that one to death in the first installment. You can live your whole life at background levels, so twice background can’t be the death knell. It also, as we discussed, isn’t prima facie evidence of a RDD or improvised nuke (IND). There can be a wide variation of background due to perfectly legit reasons.

So, twice background should be about equivalent to a Terry stop. It’s enough evidence to stop someone and ask some questions, and potentially search further, but it is nowhere near enough to be calling for a lot of assistance or warrant a felony stop.

The next figure I hear a lot is 5 rem. I will agree that 5 rem in one sitting is a monster dose, but I disagree that its’ the level at which emergency operations should cease. This number is a nuclear industry standard (it is found in 10CFR835, section 1003, subsection (a)(1), if you are keeping count). This number is the amount a worker can receive in a year. Keep in mind, that the nuclear industry is no different from the chemical or metalworking industry. The name of the game is to minimize long-term exposure to hazards. But, in the non-emergency fields, they take it to severe extremes. Which is great if you are a worker exposed to a hazard every day. It doesn’t translate well to single-event emergency responses. However, many states see you as an occupational worker, and quote this number because it is the law for people like Homer Simpson.

Also keep in mind that the worker can receive their total dose in one shift, or over the course of the year. It doesn’t matter to them, as you’ll see, because it is far below accepted figures for where even temporary injury occurs.

At the other end of the scale is what the military uses for combat. I understand the concept of the potential disposability of the individual Soldier in achieving a significant goal, but you should understand that it would be counterproductive to tell Soldiers in general, you don’t have to worry until your meter reads X , when the Soldier will be dead long before X. In other words, sending a small team of briefed volunteer personnel into an area of extreme value is different than sending large numbers of troops to their deaths. They can’t afford large numbers of casualties due to the environment. In fact, there is a manual on exactly that subject: Nuclear Contamination Avoidance. So, I trust their judgment.

The military divides their risk into three categories: negligible risk is 75 rads, moderate risk is 100 rads, and emergency risk is 125 rads. (I say rad (R) here instead of rem (r), because when you get into incredibly large doses {over 15-20 rem}, the dose equivalence formula doesn’t apply anymore.)

Keep in mind, that for planning purposes, the figures the military are quoting are the thresholds that produce a percentage of casualties. There will be no casualties (a casualty is a Soldier who has 25% of their ability degraded) until the exposure rate reaches the moderate risk category.

Other sources I looked at include the following:

• Thumbing through the EPA’s site I never saw specific guidance for terrorism or RDD issues. Which is strange because by law, with the exception of a nuclear weapon detonation in wartime, the EPA’s Protective Action Guides apply to all continental US radiological incidents, including accidents involving a nuclear power plant or other nuclear facility, weapons, transportation, and even satellites. They list 1 rem as a threshold for evacuating the public, 10 rem for protecting valuable property, 25 rem for lifesaving operations, and greater than 25 rem only on a voluntary basis in extremely special circumstances.
• The Department of Homeland Security website pointed to FEMA for guidance.
• FEMA, in their Radiological Emergency Response student guide, quote EPA PAG recommendations directly. However, the Federal Radiological Emergency Response Plan has no guidance as to dose, but changes the definition of Lead Federal Agency from what the EPA PAG states.
• The NRC (Nuclear Regulatory Commission), had more basic info, but I still couldn’t find a directive or law stating a turn back and a lifesaving value for Public Safety (aka, you) during a terrorist event.
• The Health Physics Society, like the FOP of nuclear physicists, know a great deal about radiation but very little about standing in the middle of a baking highway with an overturned tractor trailer. They offered a ceiling of 10 rem/hour as their recommended turn back limit. On their site, they also reference the EPA single incident total of 25 rem. They go on to say that any radiation field of 100 mrem/hour or greater is a Very High Radiation Area.
• The International Council on Radiation Protection says that for lifesaving efforts, 500 rem is the safe limit.
• The NCRP, who are the US version of the ICRP, have set 50 rem as their limit.
• Los Alamos National Labs’ internal emergency plan offered the following guidance:
  “Emergency Rescue and Recovery operations should be carried out according to the following guidelines: When protecting major property where lower dose limits are not practical, the wholebody dose limit is 10 rem. When providing lifesaving recovery or protection of large populations, the wholebody dose limit is 25 rem. When providing lifesaving recovery or protection of large populations where lower limits are not practical, greater than 25 rem is allowed, only on a voluntary basis to personnel fully aware of the risks involved.”

Surprisingly, I couldn’t find a NFPA standard for radiation exposure in emergencies. I’m certain it’s pending…

What I find most interesting is that none of the standards come anywhere near the numbers they quote for where serious injury starts occurring. Because every persons’ constitution is different, there can be no single ‘magic’ number for when ill effects begin to show. Consulting my friends in the nuclear industry, 100 rad is about all you want. All agree that when you get to about 450 rads at one time, like Spock in the Enterprise engine room, saving the ship, you also should be stopping what you’re doing and see a doc. 450 rads is the point where 50 percent of those exposed will die even with treatment.

Somewhere in the neighborhood of 600 to 1000 rads is agreed upon as the ‘beyond all hope’ threshold. Consider the order of magnitude from a 1000 rad dose to double background (two or three thousandths of one rad!)

SO, what have we learned?

1. There really isn’t a good standard for the special environment an RDD or IND incident might create.
2. There isn’t much agreement among the various agencies as to what constitutes a safe working level, a turn back level, or what the maximum safe level is you can receive in a heroic rescue attempt.
3. The levels that seem to be in place are far, far below anything that will kill you. You may increase your risk from cancer slightly, but you are probably going to be nowhere near the threshold for acute radiation syndrome.

In the final installment, we’ll try to put this all together for you, and offer some insight regarding radiological incident response.

Until next time,

-Shawn