A vehicle backed over a road crew’s radioactive gauge in Louisiana and crushed the housing around two sources

A Troxler model 3400 gauge owned by the Louisiana Department of Transportation and Development was backed over by a vehicle at Ville Platte, Louisiana, on October 10, 2026, and its housing was crushed. The device holds two sealed radioactive sources, 8 millicuries of cesium-137 and 100 millicuries of americium-241/beryllium, and both stayed in a shielded condition. The state told the Nuclear Regulatory Commission on October 12, and no worker was exposed.

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The incident is small by nuclear-safety standards. It is also a good look at a device that sits on construction sites all over the country.

NRC Event 58491 at Ville Platte

The NRC event notification report lists the incident as Event 58491. The licensee is the Louisiana Department of Transportation and Development, license LA-2467-L01, and the site is Ville Platte in NRC Region 4. Louisiana is an Agreement State, meaning it licenses and inspects this kind of material itself, so the report came through the Louisiana Department of Environmental Quality, which carries the state’s own event number LA20260012. The NRC logged the notification at 3:56 p.m. Eastern on October 12 as a non-emergency, and it names Jim Pate as the person who notified the agency.

According to the report, the gauge was being checked for stabilization before it left the licensee’s facility when a vehicle backed over it. The equipment housing was crushed, “but the sources were still in a shielded condition,” and the device was placed in a yellow transport container.

Cesium-137 and americium-241/beryllium inside the Troxler 3400

Portable moisture-density gauges like this one are built around two sources for two jobs. A gamma-emitting source, here the 8 millicurie cesium-137, is used to gauge the density of soil, asphalt or aggregate, while a neutron source, here the 100 millicurie americium-241/beryllium, responds to the hydrogen in water and gauges moisture. Both are sealed inside a rugged housing, with the cesium source on a rod that lowers into the material under test, so the shielded position is the default and the exposed one is brief.

The housing is therefore the safety-critical part. A gauge that is dropped, driven over or hit is dangerous only if the damage keeps a source from being fully shielded or from being returned to the shielded position, and the report says neither happened here. Cesium-137 and americium are long-lived materials, so a crushed housing is not a problem that fades on its own. It is a problem that is contained only as long as the shielding holds, which is why the sources were surveyed.

The scale of the sources is worth stating plainly. The NRC guidance describes gauges of this type as often containing up to 10 millicuries of cesium-137, and the Louisiana unit’s 8 millicuries sits under that figure. The much larger 100 millicurie rating belongs to the neutron source, which is a separate component with a separate role. NRC training material on licensing portable gauges treats these devices as a routine class of licensed equipment, handled under procedures for storage, transport and damage reporting.

Why damaged gauges are reportable, and what comes next

The NRC’s long-standing guidance on reporting damaged portable moisture-density gauges says that whether a report is required depends on the extent of the damage, especially whether the source can still be fully shielded, and on radiation levels and doses to individuals. It cites 10 CFR 30.50 for the case in which the shielding is damaged. Here the report went to the state regulator within two days of the event, and it then appeared in the NRC’s daily event notification list for October 18 and 19, alongside other licensee events that are unrelated to this one.

LDEQ and the licensee surveyed the gauge and confirmed that the sources remained shielded, and the report states that no radiation exposures to workers had occurred. The licensee reported the event to LDEQ on October 12 and will perform leak tests on the sources. A leak test checks that the sealed capsules holding the radioactive material were not breached by the crushing, and it is the step that would show whether any material escaped.

The NRC has published background on these devices in its overview of industrial uses of nuclear materials. For the Ville Platte gauge, the open items are the leak test results and whatever follow-up Louisiana requires. Nothing in the NRC report suggests any release or any member of the public coming near the damaged device. The report also describes the gauge as having been placed in a yellow transport container after the incident, a sensible interim step for a damaged device whose shielding has been confirmed but whose housing can no longer be relied on to hold its shape. Until the leak tests are reviewed, that container and the survey are the two safeguards the report documents.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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