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Title: Inherent limitations of fixed time servo-controlled radiometric calorimetry

Abstract

There has been some interest in low precision, short run time calorimetry measurements. This type of calorimetry measurement has been proposed for use when high precision measurements are not required, for example, to screen scrap containers to determine if there is enough material to be measured more accurately of for confirmatory measurements that only require low precision results. The equipment needed to make these measurements is a servo-controlled calorimeter with a sample preequilibration bath. The preequilibration bath temperature is set to the internal temperature of the calorimeter running at a fixed servo-controlled wattage level. The sample power value is determined at a fixed time form the sample loading into the calorimeter. There are some limitations and areas of uncertainties in the use of data obtained by this method. Data collected under controlled conditions demonstrate the limitations. Sample packaging, preequilibration time, and item wattage were chosen as the variables most likely to be encountered in a plant environment.

Authors:
; ;
Publication Date:
OSTI Identifier:
5745300
Report Number(s):
CONF-871110-
Journal ID: ISSN 0003-018X; CODEN: TANSA; TRN: 89-028034
Resource Type:
Conference
Resource Relation:
Journal Name: Transactions of the American Nuclear Society; (USA); Journal Volume: 55; Conference: 3. international conference on facility operations safeguards interface, San Diego, CA (USA), 29 Nov - 4 Dec 1987
Country of Publication:
United States
Language:
English
Subject:
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; NUCLEAR FACILITIES; NUCLEAR MATERIALS MANAGEMENT; CALORIMETRY; ACCURACY; PACKAGING; SAFEGUARDS; SAMPLE PREPARATION; TIME DEPENDENCE; MANAGEMENT; 055001* - Nuclear Fuels- Safeguards, Inspection, & Accountability- Technical Aspects; 440100 - Radiation Instrumentation

Citation Formats

Wetzel, J.R., Duff, M.F., and Lemming, J.F. Inherent limitations of fixed time servo-controlled radiometric calorimetry. United States: N. p., 1987. Web.
Wetzel, J.R., Duff, M.F., & Lemming, J.F. Inherent limitations of fixed time servo-controlled radiometric calorimetry. United States.
Wetzel, J.R., Duff, M.F., and Lemming, J.F. 1987. "Inherent limitations of fixed time servo-controlled radiometric calorimetry". United States. doi:.
@article{osti_5745300,
title = {Inherent limitations of fixed time servo-controlled radiometric calorimetry},
author = {Wetzel, J.R. and Duff, M.F. and Lemming, J.F.},
abstractNote = {There has been some interest in low precision, short run time calorimetry measurements. This type of calorimetry measurement has been proposed for use when high precision measurements are not required, for example, to screen scrap containers to determine if there is enough material to be measured more accurately of for confirmatory measurements that only require low precision results. The equipment needed to make these measurements is a servo-controlled calorimeter with a sample preequilibration bath. The preequilibration bath temperature is set to the internal temperature of the calorimeter running at a fixed servo-controlled wattage level. The sample power value is determined at a fixed time form the sample loading into the calorimeter. There are some limitations and areas of uncertainties in the use of data obtained by this method. Data collected under controlled conditions demonstrate the limitations. Sample packaging, preequilibration time, and item wattage were chosen as the variables most likely to be encountered in a plant environment.},
doi = {},
journal = {Transactions of the American Nuclear Society; (USA)},
number = ,
volume = 55,
place = {United States},
year = 1987,
month = 1
}

Conference:
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  • Interest has been shown in using fixed-time, servo-controlled calorimetry to shorten the measurement times for certain samples that require low precision values (3 to 5%). This type of calorimeter measurement could be particularly useful for screening scrap samples to determine whether there is a need for a more accurate measurement or for certain confirmatory measurements for which low precision numbers are sufficient. The equipment required for this type of measurement is a servo-controlled calorimeter and a preconditioning unit. Samples to be measured are placed in the preconditioning unit, which is maintained at the internal temperature of the calorimeter. The powermore » value for the sample is determined at a fixed time after loading into the calorimeter, for example, 30 min. When a calorimeter is operated using a fixed cutoff time, there are additional sources of uncertainty that need to be considered. The major factors affecting the uncertainty of the calorimetry power values are discussed. 2 refs., 4 figs.« less
  • Research was performed to develop an endpoint prediction algorithm for use with calorimeters operating in the digital servo-controlled mode. The purpose of this work was to reduce calorimetry measurement times while maintaining the high degree of precision and low bias expected from calorimetry measurements. Data from routine operation of two calorimeters were used to test predictive models at each stage of development against time savings, precision, and robustness criteria. The results of the study indicated that calorimetry measurement times can be significantly reduced using this technique. The time savings is, however, dependent on parameters in the digital servo-control algorithm andmore » on packaging characteristics of measured items.« less
  • Research was performed to develop an endpoint prediction algorithm for use with calorimeters operating in the digital servo-controlled mode. The purpose of this work was to reduce calorimetry measurement times while maintaining the high degree of precision and low bias expected from calorimetry measurements. Data from routine operation of two calorimeters were used to test predictive models at each stage of development against time savings, precision, and robustness criteria. The results of the study indicated that calorimetry measurement times can be significantly reduced using this technique. The time savings is, however, dependent on parameters in the digital servo-control algorithm andmore » on packaging characteristics of measured items. 7 refs., 4 figs., 1 tab.« less
  • A method of operating a calorimeter is called the servo controlled method. An internal heater is driven by a controlled voltage source to produce a constant internal temperature. The heater power is controlled by a digital computer program that uses as one of its inputs the bridge potential. The heater power can be calculated by multiplying the heater current by the heater voltage. A bridge potential can then be determined that will produce the desired internal power level. When a sample is placed in the calorimeter the servo system reduces the heater power to maintain the set point bridge potential.more » There will be four calorimeters in the system - two for large sizes and two for small sizes. They will be servo controlled using a DEC Micro-11 computer with a IEEE-488 interface buss. (LEW)« less
  • The calorimeter is a device that measures the heat output of the material contained in the calorimeter cell. A special class of calorimeter is used for the measurement of nuclear materials and is referred to as a twin bridge resistance calorimeter. The measuring cell is contained in some type water bath at constant temperature. The associated electronics are used to convert the heat output signal into watts of power. The measuring cell is constructed of four resistance arms connected in a Wheatstone bridge configuration. Two of the arms are maintained at a constant reference temperature by a controlled circulating bathmore » which acts as an infinite heat sink. The other two arms are wound around the sample chamber so they are physically between the sample and the heat sink. Connecting the four arms in a Wheatstone bridge configuration produces double the output voltage.« less