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C. GAMMA-RAY SPECROMETRIC ANALYSIS
Pages 229-244

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From page 229...
... standard source, or a calibrated radioactive source, with stated accuracy, whose calibration is certified by the source supplier as traceable to NIST, should be used in energy and efficiency calibrations. The standard sources to be used in energy and efficiency calibrations should contain gamma-ray energies ranging from ~60 to ~2000 keV.
From page 230...
... Energy Calibration - Determine the energy calibration (channel number versus gamma-ray energy) of the detector system at a fixed gain by determining the full energy peak channel numbers from gamma rays emitted from one or more known energy standarcl sources.
From page 231...
... if the standard source is calibrated as to activity, the gamma ray emission rate is given by No, = APT, where A = number of nuclear decays per second P., = probability or intensity per decay for the gamma ray `0 After obtaining the full energy peak efficiency for at least 10 gamma rays, spreading from ~60 to ~2000 keV, plot the values for full energy C-3
From page 232...
... The form of the calibration curve or function wait be better clefined by using more gamma ray stanclards, particularly in the ~60-300 keV region. C.3 MEASI~EMENT OF GAMMA RAY EMISSION RATE OF THE SAMPLE Place the sample to be measured at the source-to-detector distance for efficiency calibration.
From page 233...
... That is A= C.4 CORRECTIONS OF COUNTING DATA C.4.! Decay Corrections ~ ~ ~ Simple Decay Correction No, Py The measured activities are corrected for the clecay between the times of sampling and counting by using where A Ao = Ae\t = measured activity Ao = activity at t=0 t = time between counting and t=0 ~ = decay constant Generally, the midpoint of the sampling an(1 counting is used for decay correction if the sampling or counting duration is less than I/3 of the clecay half-life.
From page 234...
... T = duration of counting ~ = decay constant The same correction factor is also used in correction for decay during sampling. In this case A = A = XT T m 1-e-~T = where AT = total activity collected in the sample Am= activity measured at end of sampling T = duration of sampling = decay constant C-6
From page 235...
... However, the correction factors maY be negligible for most of the radionuclides observed in nuclear power plants. , v v C.4.3 Sample Geometry Calibration The gamma-ray full energy peak efficiency is sensitive to the following counting geometry factors: (1)
From page 236...
... An example of reactor water sample containing N-13, F-18 and Cu-64 is given in Section C.9. C.6 ACTIVITY DECAY-GROWTH CALCUIATIONS The parent-daughter decay-growth relationship, described in the following equations, is used in correction for activities which may grow into the sample from the decay of its parent nuclide: A= ~ ~ A1O (e-71t -e \2~)
From page 237...
... :-131 can be measured accurately. The procedure for sample preparation is given in Appendix B
From page 238...
... C.S OFFGAS SAMPI E ANALYSIS (1) Place the sample vial on a shelf position where the counting geometric factor, or the vial sample calibration, is available.
From page 239...
... (3) The following gamma-ray energies and intensities for major nuclides in the offgas sample should be used in gamma ray spectrometric analysis: Gamma Ray ~Gamma Ray 2 Gamma Ray 3 IsotopeTo /2 keV (%)
From page 240...
... The sample should be counted as soon as possible so that the 10 min N-13 can be measured. The decay curves obtained from the 511 keV photopeak in each fraction can be easily constructed and graphically resolved into two components: 10 Inin N-13 and 110 min F-18 in the anion fraction, and 10 min N-13 and 12.7 hr Cu-64 in the cation fraction.
From page 241...
... (4) Search for the expected gamma rays which may be missing due to energy shift or interference from high intensity gamma rays, particularly in highenergy regions.
From page 242...
... 11 DATA PROCESSING FOR FISSION PRODUCT REIEASE CHARACTERISTICS (~) Calculate the measured individual nuclide concentrations at the sampling time.
From page 243...
... (2) "A Handbook of Radioactivity Measurements Procedures," second edition NCRP Report No.


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