Document Details


Title:
A TECHNIQUE TO COMPENSATE FOR GEOMETRY-INDUCED ERRORS IN A PHOTON IRRADIATOR CALIBRATION
Subject Terms:
DOSIMETRY; CALIBRATION; PROCEDURES; DIAGRAMS; CALCULATION METHODS; COMMENTARY; ERRORS; MEASURING INSTRUMENTS; DATA
Document Location:
Location - NNSA/NSO Nuclear Testing Archive Address - P.O. Box 98521 City - Las Vegas State - NV Zip - 89193-8521 Phone - (702)794-5106 Fax - (702)862-4240 Email - CIC@NV.DOE.GOV
Document Type:
REPORT
Publication Date:
1977 Dec 09
Declassification Status:
Never classified
Document Pages:
0008
Accession Number:
NV0062685
Document Number(s):
IAEASM22208
Originating Research Org.:
BATTELLE PACIFIC NORTHWEST LABORATORY
OpenNet Entry Date:
1994 Aug 26
Description/Abstract:
THE CALIBRATION OF THE EXPOSURE RATE INSTRUMENTATION USED AT HANFORD N ECESSITATES THE EXPOSURE OF THE INSTRUMENTS TO PHOTON BEAMS AT VARIOUS RADIATION INTENSITIES. TO SIMULATE THE WIDE VARIETY OF PHOTON ENERGI ES ENCOUNTERED, HALF A GRAM OF RADIUM-226 + DAUGHTERS IS USED. SO THA T A MINIMUN EXPOSURE TO CALIBRATIONS PERSONNEL IS ASSURED, THE SOURCE IS CONTAINED IN AN OPEN-TOPPED CONCRETE WELL ABOUT 8 M DEEP. INSTRUME NTS TO BE CALIBRATED ARE PLACED IN A HOLDER AT THE TOP OF THE WELL AND THE SOURCE IS RAISED TO THE PRESCRIBED POSITION WHICH GIVES THE DESIR E EXPOSURE RATE. THE PRIMARY CALIBRATION OF THE WELL POSES UNIQUE PRO BLEMS BECAUSE THE EXPOSURE RATES VARY FROM PLACE TO PLACE ACROSS THE T OP SURFACE OF THE WELL. THEREFORE, A TRANSFER STANDARD, BEING OF A DI FFERENT VOLUME AND SHAPE FROM THE INSTRUMENTS BEING CALIBRATED, RESPON DS DIFFERENTLY TO A SOURCE POSITION THAT DOES A SERVICE INSTRUMENT. T O COMPENSATE FOR THIS VARIATION, A SERVICE INSTRUMENT HAS BEEN MODIFIE D TO ACCOMMODATE AN INTEGRATION DEVICE AND A DIGITAL READOUT. THE INS TRUMENT IS FIRST CALIBRATED, FREE-IN-AIR, BY COMPARISON TO THE TRANSFE R STANDARD, AND IS THEN PLACED OVER THE WELL IN EXACTLY THE SAME POSIT ION AT WHICH ALL INSTRUMENTS OF THAT TYPE ARE CALIBRATED. THE EXPOSUR E RATE IS INTEGRATED OVER A SUFFICIENTLY LONG TIME TO ELIMINATE THE ME ASUREMENT ERRORS RESULTING FROM A RATE-ONLY READOUT. THE CALIBRATION ACCURACY IS DISCUSSED IN THIS PAPER AND AN ANALYSIS OF THE ERROR CONTR IBUTIONS AT EACH STEP IS PROVIDED.


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