Multi-technique characterization of neutron fields from moderated /sup 252/Cf and /sup 238/PuBe sources
At the Lawrence Livermore Laboratory, /sup 252/Cf and /sup 238/PuBe neutron sources are used for calibration of personnel neutron dosimeters and neutron monitoring instrumentation. The sources, with emission rates of approximately 2 x 10/sup 9/ and 2 x 10/sup 7/n x sec/sup -1/, respectively, have been calibrated by the U.S. National Bureau of Standards. The sources are transferred into a 815-m/sup 3/ concrete calibration cell through a remotely operated pneumatic system. Calibrations can be made without source moderation, or with spherical moderators of aluminum, polyethylene, water, or deuterium oxide placed over the end of the pneumatic irradiation tube. The source is located in the tube at one meter above a false floor in the center of the cell. Nine different moderators are available in sizes up to 56 cm in diameter. Several techniques used to characterize the neutron fields produced by each source--moderator configuration to improve the quality of the calibrations. Measurements and calculations are made to determine neutron flux, kerma rate, neutron spectrum, quality factor, dose equivalent rate, and linear energy transfer (LET) spectrum. Neutron spectra are determined by calculation using the ANISN discrete ordinates transport code, Bonner sphere measurements using the LOUHI unfolding code, and measurement with proton recoil counters and liquid scintillation detectors. The spectra are then folded into published energy-dependent conversion factors to yield kerma, quality factor, and dose equivalent values. LET spectra are obtained by a tissue-equivalent LET chamber and the GANDALF unfolding code. Chamber data are used to determine kerma and quality factor. Finally, a 80-cm/sup 3/ tissue-equivalent ion chamber and neutron-insensitive Geiger counter are used to measure the neutron kerma. Results of the various techniques are presented and compared. Comparisons are made with results obtained from conventional health physics instrumentation such as moderated rem counters.
- Research Organization:
- California Univ., Livermore (USA). Lawrence Livermore Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5420502
- Report Number(s):
- UCRL-79483; CONF-771209-1; TRN: 78-002458
- Resource Relation:
- Conference: IAEA symposium on national and international standardization of radiation dosimetry, Atlanta, GA, USA, 5 Dec 1977
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NEUTRON SOURCES
NEUTRON SPECTRA
BERYLLIUM
CALIBRATION
CALIFORNIUM 252
DOSE EQUIVALENTS
KERMA
LET
MODERATORS
NEUTRON DETECTORS
NEUTRON DOSIMETRY
NEUTRON FLUX
PLUTONIUM
PLUTONIUM 238
QUALITY FACTOR
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTINIDES
ALKALINE EARTH METALS
ALPHA DECAY RADIOISOTOPES
CALIFORNIUM ISOTOPES
DOSIMETRY
ELEMENTS
ENERGY TRANSFER
EVEN-EVEN NUCLEI
HEAVY NUCLEI
ISOTOPES
MEASURING INSTRUMENTS
METALS
NUCLEI
PARTICLE SOURCES
PLUTONIUM ISOTOPES
RADIATION DETECTORS
RADIATION FLUX
RADIATION SOURCES
RADIOISOTOPES
SPECTRA
TRANSURANIUM ELEMENTS
YEARS LIVING RADIOISOTOPES
655002* - Medical Physics- Radiation Source Calibration & Standardization