Evaluation of Scattered Radiation in a Calibration Range Using Exposure Rate Energy Spectra

Petrie, Christian M.; Blue, Thomas E.; Herminghuysen, Kevin

doi:10.1097/hp.0b013e3182259a98

Cited by 3 publications

(2 citation statements)

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“…A MCNP model of the OEMA calibration range has been constructed and improved previously to identify the origins of scattering radiation (Steele et al 2011;Petrie 2011). However, only the high source had been modeled.…”

Section: Mcnp Model Of Oema Calibration Laboratorymentioning

confidence: 99%

“…The total photon yield is necessary in the calculation, because MCNP normalizes the emission probabilities from Table 2 to total 1.0. For more details on the process used to calculate the exposure rate from the MCNP results, refer to Petrie (2011). For more details on the process used to calculate the exposure rate from the MCNP results, refer to Petrie (2011).…”

Section: Calculating Exposure Rate Using Mcnpmentioning

confidence: 99%

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Calculating an Unknown Source Activity Using Modeled and Experimental Results

Rowan¹,

Blue²,

Herminghuysen³

2014

Health Physics

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A method is presented that provides a way to calculate the unknown activity of a source by using experimental exposure rate measurements from an ion chamber and exposure rates calculated using the MCNP radiation transport code. The method consists of fitting experimental data to MCNP results with both data sets in the form of (Equation is included in full-text article.)where r is the distance from the source at which the measurement was taken, X˙ is the exposure rate, and An is an assumed nominal activity of the source. The fit is done by calculating a correction factor for the nominal activity that shifts the experimental data to match the MCNP results. The actual activity of the source in question is found by multiplying the assumed nominal activity by the activity correction factor. The method was used to calculate the activities of the three Cs sources used in the Ohio Emergency Management Agency's instrument calibration range. It was found that the activities were less than the decay-corrected nominal activities by factors ranging from 3% to 10%.

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Section: Mcnp Model Of Oema Calibration Laboratorymentioning

confidence: 99%

Section: Calculating Exposure Rate Using Mcnpmentioning

confidence: 99%

Calculating an Unknown Source Activity Using Modeled and Experimental Results

Rowan¹,

Blue²,

Herminghuysen³

2014

Health Physics

Self Cite

View full text Add to dashboard Cite

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Evaluation of the Effects of Scattered Radiation on Dosimeter Calibration in a Calibration Range

Petrie¹,

Nimps²,

Blue³

et al. 2013

Health Physics

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ISO standard 4037 specifies limits for scattered radiation for "gamma reference radiation" for the calibration of "protection-level dosemeters and rate dosemeters." More specifically, it specifies that scattered radiation should contribute less than 5% to the total exposure rate for source-center-to-dosimeter-center distances (henceforth called downrange distances) over which dosimeters are calibrated. In a previous paper by the authors, the results of an MCNP analysis of a calibration range with a Cs irradiator (henceforth called Cs calibration range) were reported. In that paper, simulations of the singly differential photon fluence rate (i.e., flux) energy spectra (henceforth called photon flux energy spectra) from the Cs (an ISO standard 4037 gamma reference radiation) irradiator were reported. In that paper, the spectra were examined to determine the contribution of scattered photons to the exposure rate in the Cs calibration range for various downrange distances. In this paper, the simulations of the photon flux energy spectra for the Cs irradiator photons for various downrange distances are convolved with response functions, creating an ideal exposure meter and two commercially available ion chamber survey meters, in order to predict the meters' response rates versus downrange distance. The simulated response rates indicate that the Cs calibration range satisfies an operational check of the contribution of scattered radiation to the exposure rate that is specified in the ISO standard 4037, although as shown in the previous paper by the authors, the Cs calibration range does not satisfy the ISO standard 4037 specification that scattered radiation should contribute less than 5% to the total exposure rate for downrange distances over which dosimeters are calibrated. The ISO standard 4037 operational check is that the measured exposure rate varies from an inverse square dependence by less than 5% for the downrange distances over which dosimeters are calibrated.

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