“Self assessment is a process by which an organization evaluates its compliance with external regulatory requirement and commitments and with its own internal radiation safety program requirements. It is a proactive component of an effective management plan for a radiation safety program. This report will cover the types of assessments, their purposes, and the processes for conducting them. It will discuss the frequency, the program areas to be assessed, the documentation, and the follow-up of assessments. The report will also discuss guidance for the scheduling and resolution of corrective actions.”

The report provides information and guidance on the following topics:

- Definition and purposes of self assessment;

- Types of self assessment (i.e., performance based, risk based, compliance based, task, process and program level, formal and informal);

- Responsibilities for establishing self-assessment programs including upper management, line management, the radiation safety committee, radiation safety program personnel including the radiation safety manager or radiation safety officer, and the workers;

-Self assessment program planning for an institution, including determining the purpose and type of self assessment, selecting the program elements to be assessed, allocating the necessary resources, and developing a self assessment program review plan;

- Qualification and selection of individuals performing the self assessments;

- Self assessment methods and techniques including evaluation of radiation safety program survey and monitoring results, workplace observations, interviews, document reviews, checklists, review of metrics, and questionnaires;

- Types of deficiencies that can be identified in the self-assessment process, ranging from the minor ones that are most likely to be found to those that are more serious;

- Identification of noteworthy practices;

- Planning an individual self assessment including the program elements to be assessed, the schedule for performing the self assessment, and the types of self assessment to be used;

- Conducting the self assessment including the entrance meeting, performing the assessment activities, daily team conferences, upper management briefings, exit meeting, and documentation;

- Documenting the self assessment including writing reports, report approval, communicating the results, and legal consideration; and

- Developing corrective-action plans including tracking and resolution of corrective actions and reviewing the effectiveness of the corrective-action program.

In a recent newsletter of the Health Physics Society (Volume XXXVIII Number 4 April 2010), it was noted that David Myers, an HPS member, worked on NCRP Report 162.  In the newsletter, he provides more information about the latest report and its importance to the radiation safety programs of all institutions. The report can be purchased through the NCRP web site for $50 or $40 in pdf format.

The 1950s marked the first use of Sr-90/Y-90 sources for treating wedge-shaped benign ophthalmic lesions. Because of the long (~28.8 years) half-life of Sr-90, many of these ophthalmic applicators are still in use today. The US NRC now requires that the long lived radioactive sources have accredited calibration traceable to the NIST dose to water standard established in 1978 by Pruitt¹ and revised by Soares² in 1991.

Several different units have been used to describe source input of Sr-90/Y-90. Soares described these units and the historical progression of these values³:
1- Roentgen Equivalent Beta (reb)
2- Roentgen Equivalent Physical (rep)
3- Rad
4- Gy

So, what exactly is a “reb”? A reb is equal to “the amount of beta radiation that would produce ionization per unit mass in air equivalent to that produced by 1 R of photons.”⁴

Soares suggested using the conversion factors 0.0093 and 0.00982 (Gy/reb) to convert reb to Gy. For derivation of these conversion factors see Reference 3. According a to recent paper published in Medical Physics by the University of Wisconsin Accredited Dosimetry Laboratory (UWADCL), mCi (1 mCi = 37 MBq) is also used to describe nearly all planar Sr-90 sources⁴. Though for most applicators, these values represent estimated nominal contained activity rather than precisely known or determined values.

If a Sr-90 source is described with reb rather than nominal activity in mCi, one way to find out the activity in mCi is to calibrate the source at an Accredited Dosimetry Calibration Laboratory (ADCL), such as UWADCL, in Gy/sec. Then the activity can be estimated in mCi by using the conversion coefficients derived by Soares to convert reb to Gy¹.

For more information see the following references:
1- J. S. Pruitt. “Calibration of beta-particle-emitting ophthalmic applicators.” NBC special publication No. 250-9, 1978.
2-C. G. Soares. “Comparison of NIST and manufacturer calibration of Sr90+Y90 ophthalmic applicators.” Med. Phys. 22, 1487-1493 (1995).
3- C. G. Soares. “Calibration of ophthalmic applicators at NIST: A revised approach.” Med. Phys. (18), 787-793 (1991).
4- Shannon M. Holmes, John A. Micka, and Larry DeWerd. “Ophthalmic applicators: A review of calibration following the change to SI units.” Med. Phys. 36 (5), 1473-1477, May 2009.

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

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.

*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.