There are many things you should consider here. First, is the x-ray device a pulsed or continuous current device? Usually the mean peak voltage that the x ray device mfg. gives is NOT the effective peak voltage (tube potential). A kVp meter could tell you the true operating kVp, however, the company should be able provide that information to you. It may well be 150 kVp (max).
Energy-compensated GM detectors that use a wrap of rather heavy metal around the detector provide reasonably uniform energy dependence, but they will normally attenuate the x rays to a greater extent than is desirable. One then uses the thin-window detectors without energy compensation, and such detectors, often calibrated at higher photon energies (e.g., 662 keV from 137Cs), will usually overrespond at the dominant x-ray energies. (Usually by a factor of 2-3 times depending.) There is a question of what type of inherent filtration they are using to harden the beam and what material you will be x raying that will contribute to the scatter x ray radiation-which can be tough to measure. The beam on time is also important as well as the angle of the x ray beam considering the 150 kVp max. An ion chamber is your best bet, but whatever the detector, it must have a reasonably thin window or wall for measurements of the x rays. For a machine operating at 100 kV, the effective beam energy is probably between 30 and 40 keV, with photons ranging from energies lower than this up to 100 keV. Jessica Soileau Sr. Health Physicist/ Chemical Specialist River Bend Nuclear Station ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of BREHM, DAVID M Sent: Wednesday, July 17, 2013 8:56 AM To: [email protected] Subject: Powernet: RE: X-Ray Radiography Experience? The only thing that comes to mind is that you may want to use a pressurized ion chamber dose rate instrument (e.g., Fluke 541P or Ludlum 9DP). They have a lower energy threshold than the standard ion chamber. We use the 451P for checking our x-ray machines to good effect. David Brehm Radiological Engineer Office: 402.533.7582 Radiation Protection - Nuclear Operations Cellular: 402.237-9840 Omaha Public Power District - Fort Calhoun Nuclear Station Pager: 402.561.3310 9610 Power Lane, Blair, NE 68008 [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Holmes, Stephen J Sent: Wednesday, July 17, 2013 8:03 AM To: '[email protected]' Cc: Eaton, Eric; Pell, Bryan; James, Scott; Garcia, Joseph D Subject: Powernet: X-Ray Radiography Experience? We have a proposal for a vendor to come on site and perform radiography using x-ray equipment. This equipment will emit x-rays of considerably lower energy (150 kVp max) than our typical gamma source term, and we are concerned about whether our instrumentation/dosimetry (calibrated to Cs-137) will adequately measure the dose from this device. We have previously performed pulsed x-ray radiography at Ginna, and had proven that our instrumentation performed satisfactorily, but this was at a significantly higher x-ray energy (300-400 kVp max). We plan on using the Fluke-Biomedical 451B ion chamber, Landauer BA series OSLs, and SRDs (pocket ion chambers) paired with the DMC2000s EDs to monitor the work. Do you have experience with x-ray radiography at your facility? If so, did you do any testing, or anything else (such as a white paper), to justify your ability to properly monitor the exposure from the x-ray source? If so, would you be willing to share the results or can you provide contact information? Thanks, -Steve Stephen J Holmes, CHP, PE Sr. Plant Health Physicist, CENG-RE Ginna NPP [email protected]<mailto:[email protected]> 585-771-3577 This e-mail and any attachments are confidential, may contain legal, professional or other privileged information, and are intended solely for the addressee. If you are not the intended recipient, do not use the information in this e-mail in any way, delete this e-mail and notify the sender. -EXCIP ________________________________ This e-mail contains Omaha Public Power District's confidential and proprietary information and is for use only by the intended recipient. Unless explicitly stated otherwise, this e-mail is not a contract offer, amendment, or acceptance. If you are not the intended recipient you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited.
