MORE POWER TO YOU: SURFACE PREPARATION OF PIPES IN NUCLEAR PLANTS

Stoutamire adds that Aquilex worked with BRM to determine the proper abrasives for their ball-style hone, as well as the appropriate speeds for the tool to operate. “This tool is adaptable to the pipe cleanup requirements,” he says. “And because it is a contour-following tool – rather than the typical rigid hone – you can control the amount of pipe metal removed, rather than reaming it round and possibly violating NRC pipe thickness requirements.”

LOWERING THE MAN-REM
Because excessive dose exposure can limit workers’ availability and thereby require the use of more manpower, the reduction of mrem (man-hours of radioactivity environmental monitoring) can lead to substantial savings in time and money. Mechanical decon methods may not appear to directly cause excessive worker exposure to radiation, but certainly can contribute to it. In addition to the leavings of the contaminated oxide layer, the radioactive abrasives left behind after the actual blasting process require a mop-up, and that involves both time and exposure.

“This flexible honing method reduced dose rates from about 700 mrem per hour down to approximately 100 mrem,” Stoltz says. “Contamination levels were also reduced significantly.”

Sometimes referred to as a ‘dingleberry hone’, this is a relatively low-cost tool that is used for cleaning, resurfacing, de-burring and edge blending of critical metal surfaces and is characterized by the small, abrasive globules that are permanently mounted to flexible filaments.

This flexible hone uses some grit, which requires cleanup along with the pulverized oxide layer. Nevertheless, the residual contaminated matter is considerably less and cleans up faster. Because it is a controllable honing tool, this hone does a more thorough job in removing the tough oxide layer from contaminated piping, which also saves on mrem.

In the decontamination of nuclear water piping, much of the cost comes down to the time consumed to do the work as well the technology utilized. In the case of the recent decontamination project, the results of both criteria were dramatic. There was originally a 14-hour window requested by the decon service contractor to perform the work, four hours of which were for prep work and cleanup.

Use of the flexible hone cut the remaining eight hours budgeted to only one hour of honing through the oxide layer. When you consider that in the nuclear power plant industry such decontamination can cost up to $40,000 per hour, the dollar savings in just the honing operation were quite significant.

Brush Research Manufacturing Co., Inc., 4642 East Floral Drive, Los Angeles, CA 90022, 323-261-2193, Fax: 323-268-6587, [email protected], www.brushresearch.com.