Welding and fitting apprentice students Tyrel Thompson, left, and David Yarbro, both of Vicksburg, climb into a Union mobile testing unit on Thursday outside the Local 619 Plumbers and Pipefitters Union building on North Frontage Road. Inside the trailer are spaces for up to 10 people to train and test simultaneously for welding certifications. The truck, which travels all over the country, was sent to Grand Gulf Nuclear Station to help test and certify some of the roughly 250 welders needed during the ongoing outage and upgrade, said the union’s business manager, Tommy Newell.