Elimination of quarterly urinalysis of radiation workers based on detection capability of portal monitors for internal contamination

Covidien is a radiopharmaceutical manufacturing company in Missouri, USA. The facility produces radionuclides for diagnostic and therapeutic use. The radionuclides of interest, 123I, 67Ga, 99Mo, 99mTc, 201Tl, 111In, and 131I are fairly short lived with the exception of 51Cr. The operating license document for the company mandated quarterly urinalysis (bioassay) of all radiation workers in the facility. This was labor intensive and did not enhance the quality of radiation protection program. Nuclear Regulatory Commission (NRC) required a technical basis to prove that there was no compromise in the radiological safety and accurate dose assessment in the event of internal contamination of radiation workers if quarterly urinalysis was discontinued. Measurements in a phantom, gamma spectroscopy analysis, as well as calculations showed that there was no need to perform quarterly urinalysis and that portal monitors and other radiological controls were sufficient to detect any chronic or acute intake of radioactivity by radiation workers. Technical evaluation showed Portal monitors can detect an Effective Dose Equivalent of 0.1 mSv (10 mrem) in a year. NRC allowed revision of operating license document and operating procedures to discontinue quarterly urinalysis. (author)