Accelerator radiation protection program

[Jhon81]

Hi everyone,

I have this question attached from the ABHP exam in part B you are asked to list and justify 4 major elements for accelerator radiation protection program for this specific facility, I have written some answers which are :
1) ALARA which includes :
time
distance
shielding
source reduction

2) Interlock system includes alarm when operating the system

3) Contamination check: for leakage and dark current which can occurs when the accelerator is off.
in and out of the accelerator ( in the soil and in air)

4) Area and personal monitoring.

Any other suggestions?

Thanks

 

[PSRB191921]

Neutrons activation (air, devices, ...)

 

[gleem]

Some states require periodic shielding surveys. Along with this might be a periodic assessment of the design criteria and assumptions vis-a-vis the actual use and workload of the source as well an adjacent spaces.

 

[Jhon81]

Thanks all.
I am not sure if the major elements I wrote are for that specific accelerator design in the question or is it a general protection program elements!

Any thoughts?

 

[gleem]

I would interpret it for that particular facility.

 

[Jhon81]

I would interpret it for that particular facility.

Hi Gleem could you give me an example?
Thanks

 

[ZapperZ]

There are a few things that appear to be wrong in this response:

2) Interlock system includes alarm when operating the system

Not sure what kind of interlock system you are using, but typically, an interlock system is not an "alarm" when the system is in operation. Instead, it will either trigger an alarm and/or shut down operation when the interlock is broken or breached.

3) Contamination check: for leakage and dark current which can occurs when the accelerator is off.
in and out of the accelerator ( in the soil and in air)

Dark current is the field-emission current when something is under high gradient. When an accelerator is off, there is usually no dark current because, by definition, the field in the accelerating structure will also be off. So dark current will produce prompt radiation, which will be gone as soon as the accelerator stops operation. Unless you have a DC field that operates continuously (which will be very puzzling), you will not have dark current when the accelerator is off.

What you may have is residual radiation, i.e. materials that are activated during operation. The target and possibly the accelerator walls may still be "hot" for a period of time after the accelerator shuts down. Health Physics personnel would have monitored and surveyed the area during commissioning to know when it will be safe enough to enter the accelerator facility, and there should be an established procedure during every first entry to verify that it is safe to enter.

I must say, I don't quite understand what the question really is. I don't understand what "... accelerator radiation protection program... " actually means. It seems that many of these seem to focus on engineering control, and there doesn't seem to be any administrative controls (safety documentation, procedure, training, etc.). Any safety program requires both to be in place, so maybe your question only focuses on the former. I don't know.

Zz.

 

[Klystron]

The answer to part A of the exam where you calculate the minimum wall thickness required to keep the dose rate in the lab area below a given level, informs and helps you justify your answers in part B; radiation protection. I suggest "as low as reasonably achievable" (ALARA) provides a guiding principle for setting protection guidelines and establishing cost/benefit analysis.

Answer C where the test writer specifies lead and polyethylene for a temporary shield, though only 5 points, gives a broad hint of the expected answers to Part B. If we assume the examiners are primarily concerned with personnel exposure, not so much with environmental degradation, consider writing Part B answers accordingly. [Note: editorial comments in square brackets.]

"Utilizing risk management principles of as low as reasonably achievable (ALARA), major elements protecting this lab space from neutron radiation include:

1. Minimum shielding of the work space calculated to be [answer A]. Then [justify your answer.] In an emergency [use your answer to Part C].
2. Strictly monitoring individual dosimeters of lab workers according to [industry standard schedule you devise and justify given Part A and the data sheet.]
3. Limiting exposure times based on distance to the source [only first 4 answers are graded. Consider combining parameters such as time and distance.]
4. Actively monitoring [define/describe the measurements] in the lab space and surrounding soil during operations then [describe emergency response such as visual and aural alarms, automated off-site alerts and response, evacuation , etc. Tie answer back to 2 (dosimeters).]
5. Establish operations checklists to ensure safety interlocks correctly engaged, [security perimeter intact, lab workers are wearing fresh dosimeters, etc.]. "

Justify your answers using the given data and detailed diagrams provided by the examiners. My suggestions emphasize protecting lab workers. Your answers might concentrate on establishing outer safety perimeter based on the given data and facility design.

 

[gleem]

I'm a little confused about what they might wanted too. Presumably a rad safe program is currently implemented for the facility. So the question ought be how you augment the program after the facility is modified. I suppose neutron production was not an issue previously. so activation would be a new factor, Handling, storage and security of a high activity Tritium source would also need to be addressed. Management of activated substance including use, handling and disposal might be an issue as well as regulatory issues regarding the licencing of the production of regulated isotopes. Not specifically noted the max beam on target time (workload) needs to be stipulated for neutron production. As ZapperZ noted this must be properly documented with all appropriate in-service provided for all new activities and the creation of new policies like the logging of the use of the accelerator and production of isotopes and surveys.