Anyone who’s bought a rebuilt alternator knows the deal. You pay a core charge, hand over the dead one, and the shop ships it back to a factory somewhere to be torn down and rebuilt for the next guy. Nuclear plants do pretty much the same thing with some of their most important hardware. The difference is that the core going back to the factory is radioactive, it rides a regular semi on public highways, and somebody with a meter has to check the truck when it shows up.<\/p>\n
On October 6, one of those trucks pulled into GE Vernova Hitachi’s Wilmington Field Services Center in Wilmington, North Carolina, with a load of used control rod drives from the James A. FitzPatrick plant on Lake Ontario. The package passed. The trailer passed. The driver’s cab didn’t.<\/p>\n
That’s the short version of an event report the NRC published on October 15<\/a>, based on an email from North Carolina’s Radioactive Materials Branch. Per the state, the Wilmington shop surveyed the truck on arrival and found radiation levels in the cab of up to 2.2 millirem an hour. Federal rules cap that spot at 2. Both the package’s exterior and the outside of the truck came in under their own limits, the carrier followed the shipping instructions, and North Carolina says it doesn’t suspect anyone got an excessive dose or that anything leaked. The state’s assigned an inspector to figure out what happened.<\/p>\n So the cargo was fine and the seat up front wasn’t. That’s a slightly odd result, and it’s the whole reason I’m writing about a shipment that’d otherwise be as newsworthy as a UPS delivery.<\/p>\n If you’ve ever seen a diagram of a nuclear reactor, you’ve seen the control rods: the things that slide in and out of the core to speed the chain reaction up or shut it down. FitzPatrick is a boiling water reactor, a General Electric design, and in a BWR the rods come up from underneath. Each one is pushed and pulled by a long hydraulic drive that hangs off the bottom of the reactor vessel. That drive is the part we’re talking about.<\/p>\n The drives sit in reactor water for years, so they wear, and plants swap a batch of them out during refueling outages and send the old ones off to be rebuilt. The rebuilt ones come back for the next round. It’s a core charge with a lot more paperwork.<\/p>\n FitzPatrick itself is a single-unit plant in Scriba, New York, about six miles up the lakeshore from Oswego. Constellation, which runs it<\/a>, rates it at up to 842 megawatts, and the NRC lists its operating license<\/a> as good through October 2034. The NRC report doesn’t say how many drives were on the truck or which outage they came out of, and Constellation hasn’t said either, so I can’t tell you whether this was a handful or a full batch.<\/p>\n This is the part I kept turning over. The rules for hauling radioactive stuff on a truck are laid out in 10 CFR 71.47<\/a>, and they’re basically a set of nested limits that get stricter the closer you get to a person. On an “exclusive use” shipment like this one, where the truck carries nothing else, the surface of the package can read up to 200 millirem an hour. The outside of the vehicle can read 200. About 6.6 feet (2 meters) out from the side of the truck, the limit drops to 10. And in any normally occupied space, which in practice means the cab, it’s 2.<\/p>\n Every one of those numbers held except the last one. The package and the outside of the trailer were under their limits, per the state, and the cab read 2.2.<\/p>\n How? Frankly, I don’t know, and the report doesn’t say. Radiation falls off fast with distance, so the obvious guess is that the load sat closer to the front of the trailer than the shielding math assumed, or the cab happened to line up with a gap in whatever was packed around the drives. It’s also possible the hot spot was somewhere in the cab nobody normally sits. North Carolina’s inspector is presumably going to answer that, and I’d rather wait for the answer than guess harder. As of the NRC’s October 21 event report, the state hadn’t filed its follow-up yet.<\/p>\n There’s one more wrinkle in 71.47 that I think is interesting. The 2 millirem limit in the cab doesn’t apply to private carriers if their exposed people wear radiation badges. Dibble is a for-hire carrier, as far as I can tell from its federal registration, so that exemption shouldn’t cover this run. The report doesn’t say whether the driver was wearing a badge.<\/p>\n Not for anyone who wasn’t sitting in that cab for a very long time. For scale, the NRC puts the average American’s dose from all sources at about 620 millirem a year, and most of that’s radon and medical scans. At 2.2 an hour, you’d need to sit in the seat for roughly 280 hours to pick up a year’s worth of background. The trip from Scriba to Wilmington is somewhere around 750 miles by road, by my count on a map, which is about a day and a half behind the wheel under federal hours rules, not 280 hours.<\/p>\n Still, 2.2 is over 2, and the rules don’t have a rounding allowance. The NRC’s receiving rule, 10 CFR 20.1906, is what triggered the report: a licensee that takes delivery of a radioactive package has to survey it, and if the numbers are over, it has to tell the regulator. GE Vernova Hitachi’s radiation safety officer and the facility manager decided it was reportable, told Dibble, and North Carolina passed it up to the NRC the next morning. That’s the system working as designed, which I’ll admit is a less exciting headline than the alternative.<\/p>\n Three companies, one state and one federal agency. Constellation shipped the drives from FitzPatrick. Dibble Trucking, an outfit based in Gardner, Illinois, hauled them; its federal registration lists 50 tractors and 55 drivers, and the NRC report gives the specific rig as USDOT 465872 with trailer HT004. GE Vernova Hitachi received them under North Carolina license 065-317-3. The state’s Radioactive Materials Branch filed the report, and the NRC posted it.<\/p>\n An Illinois carrier running New York to North Carolina may sound like an odd choice, but hauling radioactive packages is a specialty, and a lot of freight companies won’t touch it, so the ones that do get called from a long way off.<\/p>\n If this all sounds familiar, it’s because radioactive hardware moving around the country on wheels has been a running theme lately. There was the fracking trailer sold at a Texas auction<\/a> with two cesium gauges still bolted on, and there’s the 12-axle railcar the Energy Department built<\/a> to carry spent fuel, still waiting on its first real load. Control rods themselves showed up here last week too, when a Georgia reactor dropped all of its rods<\/a> after a turbine trip. Compared with those, a used drive going back to the factory on a semi is about as routine as the nuclear business gets, and frankly that’s why I think it’s worth the space. It’s the routine runs where the small misses turn up.<\/p>\n North Carolina’s Radioactive Materials Branch assigned an inspector and said it would follow up to complete the record, and the NRC posted the state’s report on October 15, nine days after the Dibble truck pulled into Wilmington.<\/p>\nSo what’s a control rod drive?<\/h2>\n
How does the cab end up hotter than the trailer?<\/h2>\n
Is 2.2 millirem an hour a big deal?<\/h2>\n
Who’s actually involved here<\/h2>\n