US states using the concept of IDR?

[sky8710]

US states using the concept of IDR??

While I'm reading IAEA safety report 47, I've learned the concept of IDR, instantneous dose rate, which is commonly used in UK. IDR is the tool for recommendation of the limit of high dose rate in a short time, e.g., an hour.

Generally, in US, NCRP is the common recommendation as I know, there is not recommendation for the limit of high dose rate in any hour but just averaged over a week or a year.

However my prof. said that there are some states in US using the concept of IDR and asked me to find that states.

Do you guys know anything about my question? I'm waiting.

 

[daveb]

All regulatory authorities in the US have a limit for dose rate for unrestricted areas. For some, such as the NRC, it is a dose rate such that a member of the public would not receive a dose in excess of 2mrem in 1 hour (meaning it could for a short time exceed 2mR/hr). Some states restrict that further to an exposure rate of less than 2mR/hr, so you couldn't even exceed that for very short periods. I'm not aware of any dose rate restrictions for occupational workers (some states may have it), other than ensuring that Radiation, High Radiation, and Very High Radiation Areas are properly posted, and that doses remain ALARA.

 

[sky8710]

As you said, I've found the design limit for public area(unrestricted area) in 10CFR20 and still looking for the IDR limit for occupational exposure(controlled, restricted area). Anyway, thanks for your kind comment!

 

[ThinkToday]

I've never worked anywhere that used an IDR (nuc plants, med centers, cancer centers, research labs) for “unrestricted areas”. It's always been dose in anyone hour, week, etc. for "unrestricted areas". To do otherwise would make some shielding situations impractical. For example, I can go in a public area around any cancer center exterior primary barrier wall (~7-8’ concrete) and measure exposure rates far in excess of 2mR/hr. However, when occupancy, utilization, beam energy, etc. are factored in, the “exposure in an hour" is well below 2. Same can be said for diagnostic x-ray rooms.

Now Occupational Exposure is a different thing. Most nuc sites I've worked require an RWP (radiation work permit) for any work within a "controlled area". Additionally, any are =>100 mR/hr is generally access limited (locked), and requires an RWP and someone from HP to open the door and monitor your activities. Also, if the man-hours exceed a threshold (established by the site ALARA program), shielding my need to be engineered and placed prior to work onset, even for lower exposure rate areas.

FWIW, contrary to what some might think, radiation is much more carefully controlled in a nuclear facility than a medical setting. I couldn’t tell you the number of times I’ve seen a doctor step on a C-arm peddle, un-pulsed, and press the peddle far enough to engage boost flouro (~40 R/min on some units).

 

[daveb]

The 2 mrem in 1 hour is true for the NRC and most Agreement States. Back when I was in charge of licensing for nuclear pharmacies in just about every state, I recall some states (don't remember which ones) that limited the dose rate rather than the dose in 1 hour. Yes, it sucked for shielding applications. But those were the regs and we had to abide by them.

Yeah, it is weird that nuclear facilities areheld to a higher standard than medical faciltiies when it comes to doses.