Decontamination efforts were completed last week on the seventh floor of Medical Science Research Building I (MSRB I), where a small spill of low-level radioactive fluid during the weekend of Sept. 12–13 was unknowingly spread around the floor on the shoes of staff members and researchers.
Mark L. Driscoll, U-M radiation safety officer, emphasizes that the few drops of Phosphorus-32 that got on the floor are not considered a health hazard because of the small amount of the substance involved and its very short half-life of 14 days.
“However, this was definitely a regulatory concern,” Driscoll says. “The spill should not have gone undetected and the Phosphorus-32 should not have been tracked out of the lab where it was being used. We (the Radiation Safety Service) are obligated to trace every particle we can to dispose of it.”
He adds that cleanup was fairly simple “because soap and water picks it up easily.” The water is then dumped down a drain—allowed because of the low level of radioactivity involved.
The lab involved is in Room 7514. The P-32 is used as a biomedical tracer in medical research. About a dozen staff use the lab. The principal researcher in charge of the project is Vishva M. Dixit, associate professor of pathology.
Driscoll and seven other radiation service staff worked most of Monday afternoon and night to handle and oversee the cleanup of the seventh floor of MSRB I.
Driscoll says the search extended to cars and homes as an extra precaution, both to meet the requirements of the Nuclear Regulatory Commission (NRC) and to alleviate people’s anxieties. Minor contamination was found in two cars and four houses.
He adds that any tiny radioactive particles that might be missed will “disappear” in the normal radiation that surrounds us all the time, and in a few weeks these particles will lose their ability to emit even weak amounts of radiation.
The Radiation Safety Service and the University’s Radiation Policy Committee will conduct a full investigation as to how and why the spill occurred and why it was not detected earlier. The NRC also was promptly informed and NRC representatives were on campus last Wednesday and Thursday.
After being closed Tuesday and Wednesday, MSRB I was reopened for occupation on Thursday except for two laboratory rooms where there was more concentrated contamination. Some floor tiles must be removed to complete the cleanup.
As radiation safety officer for the University, Driscoll has suspended the permit of Dixit’s research group to use radioactive materials “until all safety considerations have been answered.”
William B. Krumm, associate vice president for business operations (parent unit of the Radiation Safety Service), added that the research would not resume unless and until full approval is given by the radiation safety officer, the Radiation Policy Committee and Medical School administration. The purpose, he said, is to prevent even a remote chance that possible violations will recur.
“The University’s goals and NRC goals are identical regarding safety,” Krumm added. “The Medical School leadership, faculty and staff; the Office of Occupational Safety and Environmental Health; and the radiation safety staff led by Mark Driscoll are to be commended for their major efforts to deal with this situation.”
In an exit conference Thursday with U-M researchers and administrators, Darrel Weideman, head of the NRC inspection team, said that although there did not appear to be any health hazards or significant radiation exposure involved in the incident there did seem to be clear violations of protocol and procedures. The NRC will issue a final ruling in a few weeks.
Dixit defended his staff at the conference. “I am proud of my staff and the way they handle safety checks,” he said. “We are careful workers and once a week (although not required), we have a different person do an unannounced safety check, collecting wipes of all surfaces and analyzing these for possible radiation. … If one mishap, a human error, were to be characterized as carelessness, this would be a great injustice.”
Driscoll said that the handling protocol for radioactive substances requires researchers or staff members using the isotope do a thorough “survey” with a radiation meter after the experiment is over. If a spill is discovered, it is immediately cleaned up, limiting the contamination to a brief time and only to the room involved.
In the MSRB I incident, the spread of the isotope was not discovered until last Monday afternoon (Sept. 14) when a researcher in another lab was doing a radiation survey and tracked the contamination back to the lab where the spill occurred.
A second spill of the same fluid occurred early the morning of Sept. 16 in the Medical Science Building I. It was immediately detected by the researcher, confined to the laboratory room and its foyer, and cleaned up with no problem. There was no spread of the isotope to other parts of that building.
