Sr-90 Ophthalmic Applicator: Activity in reb/sec or in mCi?

December 16, 2009 · Posted in Miscellaneous, Radiation Safety · 2 Comments

Have you ever seen radioactive material labeled with the units Roentgen – Equivalent – Beta rays/second (reb/sec)? A medical physicist recently told me he came across these units on a Strontium-90 source at his new job while he was taking inventory of radioactive materials. This particular source was labeled with its model and serial number, as usual, but its radioactivity (the strength of the source) was given in Roentgen – Equivalent – Beta rays/second (reb/sec) instead of millicuries (mCi). Since the convention is to use miC when recording source strength in the inventory log book, he was wondering how to convert these units to mCi. Since I had not worked with Sr-90, I didn’t know the answer myself. I spoke to a couple of experienced physicists I know, and surprisingly no one had the answer. Like any good scientist, this peaked my curiosity…so I did some research. I am guessing many physicists may not know the answer, so I am sharing the fruits of my labor and the result of my due diligence in this post. This is for those who, like me, are curious and are interested to learn: Read more

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Recent NRC News Stresses Importance of Radiation Safety Officer Duties

August 2, 2009 · Posted in Radiation Safety · Comment

If you are a medical physicist who is also serving as the Radiation Safety Officer for your institution, it’s a good idea to take your responsibility as the RSO seriously and to give a higher priority to your duties as an RSO over your other responsibilitites as a medical physicist. “The NRC must be able to rely on individuals assigned to performing key safety functions at NRC-licensed facilities,” said Mark Satorius, Regional Administrator of the NRC Region 3 office in Lisle, Illinois. He continues: “A radiation safety officer is in the front line of ensuring the safe use of nuclear materials. It is a big responsibility and needs to be taken seriously.” These statements were published in a recent NRC press release dated July 31, 2009. The Nuclear Regulatory Commission staff has issued a confirmatory order to a radiation safety officer at the Department of Veterans Affairs Center in Lexington, Ky for failing to implement the radiation safety program in accordance with federal regulations. For details on the story you can click on this link:

http://www.nrc.gov/reading-rm/doc-collections/news/2009/09-024.iii.html

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NCRP Report No. 160

May 18, 2009 · Posted in Radiation Safety · Comment

NCRP Report No. 160, “Ionizing Radiation Exposure of the Population of the United State,” was released in March 2009. This report is an update of the NCRP report No. 93 that was published in 1987. A copy of this report should be in every physics office, and reviewing this report is a must if you are a medical physicist who is responsible for teaching radiation safety education to radiation workers or if you are a physicist who is planning to take the board exam.

In summary, the main message of NCRP No.160 is that the population dose (the collective effective dose) has doubled since the previously reported value. See table below.

	Early 1980	2006
Collective effective dose (person-Sv)	835,000	1,870,000
Effective dose per individual in the US population (mSv)	3.6	6.2
Background Radiation	83%	50%
Medical*	15%	48%

*The main increase in medical radiation is that the use of CT in diagnostic procedures has increased from a few million procedures per year in the 1980s to over 60 million procedures in 2006.

The other interesting piece of information to glean from the report is that commercial airline crews are the workers who received the highest annual individual dose at a little above 3 mSv. Another occupational category to note are the workers in nuclear power plants who received about 2 mSv. All other occupational categories received average annual dose exposures of less than 1 mSv.

For more information on this report go to the NCRP website.

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