Thermal Methods.

DOE-STD-6003-96

isotopes of helium. Both of these techniques can be used for real-time measurements.

For the mass spectrometer system a sample is bled to a high vacuum system for mea-

surement. The RAMAN system is easily adopted to real-time measurements. The gas

stream at atmospheric pressure is passed through an optical cell. The spectrum for a

mixture hydrogen isotopes can be determined in ~1 min. The total accuracy of these

measurements is ~3 to 5%. The mass spectrometer technique has been the standard

method that DOE facilities have used for the determination of the tritium inventory. It is

a proven system although it requires an expensive spectrometer ($200K) and accurate

determination of the temperature, pressure, and volume. The RAMAN system has not

been accepted. Experiments are currently being performed to demonstrate that this will

be an acceptable technique.

b. Thermal Methods. The primary method to inventory large quantities of tritium in the

liquid or solid form is to use a calorimeter. The sample is placed in a thermally iso-

lated container. The power required to maintain the temperature of the container is

then a measure of the amount of tritium in the sample. Containers can accept sam-

ples that vary from several inches in diameter up to a 55-gal drum. The lower limit

of accuracy can be as low as 100 Ci. Calorimeters are expensive ($200K+). They

require high-tech electronics. They are the primary methods used to measure tritium

in waste such as HTO on molecular sieve. They have not been used to measure

process tritium except in a very specific application. For example, solid tritium storage

beds that can be disconnected and moved have been placed in a calorimeter

designed to accept the bed. New methods are being developed to allow for the deter-

mination of the amount of tritium stored on a solid storage bed, When tritium is stored

on a uranium bed the temperature increase of the bed can be used to determine the

amount of tritium stored on the bed. When tritium is stored on a material such as

LaAlNi, usually gas is passed through the secondary containment to maintain the

temperature. The temperature rise of the gas as it passes through the bed can then

be used to determine the amount of tritium. Both of these methods are being pro-

posed for tritium accountability. Their acceptance is now based on a case-by-case

system, and they are not used widely. Development of these methods will be impor-

tant for the operation of fusion facilities. They offer potential savings in time and effort

to account for the tritium in a facility.

c. Tritium Concentration Measurement. A Beta scintillation counter has been used for

tritium measurement if only the total tritium composition is required. In this instrument,

the gas is passed over a crystal that will scintillate with the beta from the tritium decay.

A photomultiplier tube is used to detect the light. The tritium concentration can then be

determined from the signal from the photomultiplier tube. This method is commonly

used for gas inventory requirements. Liquid scintillation is commonly used to

determine small concentrations of tritium. The tritium liquid or compounds containing

tritium are placed in a scintillation liquid. The liquid is then placed in a counter that

determines the amount of tritium by the light emitted from the sample. Ion chambers

are commonly used to determine environmental tritium releases and to monitor the

atmosphere for personnel safety. Process ion chambers are used for determining

tritium concentrations in secondary containment. Specially designed ion chambers