In case you're wondering what happened to the precise measurement of the hydrogen gas inside the pipe that leads to the Reactor 1 Containment Vessel, the worker who tweets from Fukushima I Nuke Plant says (in Japanese) it will be a few more days till TEPCO can even get the instrument for measurement.
"I'm so glad that we didn't cut the pipe. It may sound incredible but there was no measurement [of flammable gas] scheduled in the initial work plan. But they decided to measure one day before they were going to cut the pipe. Close call. There is no instrument that can measure hydrogen alone, at Fuku I. It will come on September 28, so the measurement may be done on either September 28 or 29. The result seems obvious, but..."
You have to give TEPCO some praise for their dare. They were going to cut the pipe without measuring what could be inside the pipe. But don't breathe a sigh of relief just yet, because the worker also says TEPCO currently plans to cut the pipe anyway while purging the hydrogen gas inside the pipe with nitrogen gas. There seems to be no plan to deal with anything else than this particular pipe, although the regulatory agency NISA has asked TEPCO to conduct similar tests in Reactors 2 and 3.
TEPCO sort of knows how to operate a nuclear power plant. They have zero expertise in how to fix an utterly broken nuclear power plant, but they continue to be allowed to attempt, to the horror and dismay of the northern hemisphere.