What do you do when your sensor is maxed out?

At Fukushima when their radiation detectors pegged at 100 mS/hour they kept on going.

From the BBC story

The Tokyo Electric Power Company (Tepco) had originally said the radiation emitted by the leaking water was around 100 millisieverts an hour.

However, the company said the equipment used to make that recording could only read measurements of up to 100 millisieverts.

The new recording, using a more sensitive device, showed a level of 1,800 millisieverts an hour.

(BTW, that should read "less sensitive device", not "more." BBC science editor strikes again.)

To be fair, most of the readings were undoubtedly lower than 100 mS/hour, and unless they really are hiring "ne'er do wells and petty criminals" to do the cleanup the people should all be well versed in ALARA and the hot spots won't have seriously hurt anybody.

But seriously, if my radiation detector ever pegs, I'm out of there to look for something with a little more range. At Fermilab they had two sets of detectors for hoi polloi, and the simple scanner was switchable to different sensitivities. In theory, if something registered hot we could get a half-way decent estimate for how hot using just the equipment on hand. In practice we were told to just label it, toss it in the bin, and let the techs deal with it later--but at Fukushima the users are the radiation techs.

The hotspots they found may be new, and they may be transient. When you're dealing with reactor-waste levels of radiation, keeping track matters a lot. The 1.8S/hour hotspot would be lethal in about 4 hours, while 100mS for 4 hours would just increase your likelihood of cancer by a couple of percent. And if a crack opens in a tank, an area downstream that used to be tolerable might hit levels lethal in minutes.