Monday, March 10, 2014

WIPP Update: probes show no radioactive contamination

Monitoring instruments in the Salt Handling Shaft Hoist at
WIPP prior to an unmanned entry, which was held Friday.
The instruments included two air monitors, a gas monitor,
a data logger to capture information underground
and an air sampler. More photos available at WIPP site

Over the weekend, WIPP lowered radiological and air quality instruments down the Salt Handling and the Air Intake Shafts (see image below). Preliminary findings indicate that there is no detectable radioactive contamination in the air around the shaft areas nor was there any on the equipment that was lowered and returned to the surface. Air quality results were also normal.

WIPP officials say that these results were expected because the shafts sampled were not in the air flow path coming from the area where the radiation release was detected (see image below).

A final analysis of the sampling results will be conducted to aid in finalizing entry plans for personnel. They are also conducting  safety inspections of the hoisting equipment and the Salt Handling and Air Intake Shafts. WIPP currently expects to send specially trained site personnel into the underground facility by the end of the week. Their task will be to check mine stability and attempt to determine the source of the release. Once the source is located, the plan is to isolate it and remove/contain the contamination hazard. 

Additional bioassay testing results for potentially exposed employees were also released. As of March 8th, a total of 17 people "tested positive for just over background contamination" including the 13 people already identified, who were tested immediately after the event. Contamination has been isolated to fecal samples and is not appearing in urine samples, which indicates that the contamination was not inhaled into the lungs. The levels of exposure are reportedly very low and none of the employees is expected to suffer health effects. The four new positive results were barely detectable (about 0.1 disintegrations per minute). 

CORRECTION - WIPP (3/10) issued a correction to the above statement as follows:
"In yesterday’s WIPP Update, it was incorrectly stated that negative results for urinalysis of employees indicated “contamination was not inhaled into the lungs.” It is possible that a small amount of contamination was inhaled; however, the negative urinalysis indicates that no detectable contamination was passed through the blood stream and urine." 

The air sampling data on the WIPP website has also now been updated. The data show that "no significant contamination" has been detected off-site. 

"This table provides screening analyses for the amount of alpha and beta activity that has been detected since the February 14 radiological event. Radioactive contamination at WIPP is measured and reported in a unit called disintegrations per minute (dpm) or in units of Becquerel (Bq).
Dose is calculated and reported in millirem. Dose varies based on factors such as length of exposure and distance from the source of the radiation. The average person living in the United States receives an annual dose from exposure to naturally occurring and other sources of radiation of about 620 millirem. A person receives about 10 millirems from a single chest x-ray procedure. 
Dose estimates have been calculated based on the low-volume air sampler results. Low-volume air samplers collect samples at a rate of 2 cubic feet/minute to simulate a person’s normal breathing rate. The initial dose estimate assumes the person who might be exposed is standing next to the air sampler for 8.5 hours. The subsequent dose estimates assume the person who might be exposed is standing next to the air sampler throughout the sampling period. Dose assessment modeling from the release data shows a potential dose of less than one millirem at the environmental sample locations outside the Land Withdrawal Area."

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