Calorimetry Assay

DOE-HDBK-1129-99

70.00

60.00

M%He3At-t

m% He3

M%DTAt-t

50.00

M%D2At-t

M%ArAt-t

40.00

m% DT

30.00

m% AR

20.00

m% D2

10.00

0.00

0.000

6.162

12.323

18.485

24.646

30.808

36.969

43.131

49.292

55.454

61.615

67.777

73.938

Elapsed Time In Increments Of 1/4 Half Life

FIGURE C-6. 40% DT, 40% 3He, and 20% Ar, Change in mole percent

of each component versus time

C.3 Calorimetry Assay

Calorimetry is the quantitative measurement of heat. A calorimeter is an apparatus for

measuring heat quantities generated in or emitted by materials in processes such as chemical

reaction, changes of state, and formation of solutions. Heat is generally measured in calories or

joules. A calorie is a unit of heat energy equal to the heat energy required to raise the

temperature of a gram of water from 14.5 to 15.5oC, at a constant pressure of 1 atmosphere. A

calorie is equal to 4.186 joules.

A calorimeter designed to be used in processes that continually generate heat (power sources)

and measures power instead of heat is called a Constant Heat Flow (CHF) calorimeter. A CHF

calorimeter measures the power (joules/second) of a source not the heat output (joules) of a

source. The power is usually measured in Watts, which is a unit of power equal to 1

joule/second.

A radioactive material is a power source, which deposits the energy due to decay in the

radioactive material itself and in the materials surrounding the radioactive material. The power

generated by the decay of tritium has been measured and is equal to 0.3240 0.0009

Watts/gram of tritium.

Mound Laboratory has been the leader in the design, fabrication, calibration, and operation of

CHF calorimeters for many years. Mound has specialized in the development of CHF

calorimeters to be used in the measurement of radioactive material quantities by measuring

their power output. CHF calorimeters are generally designed to meet the specific needs of the

items to be assayed and are limited in application by the following:

C-12