Tritium Production Calculations

Since the nuafber of Ll atou is vsryJarge oon pax d to the nuaherwhich will react to.form tritium it may be assumed to stay constant. 5he equation may then be Integrated to give 

If the flux in the lithium containing target element is calculable either absolutely or relative to the flux in the fissionable fuel elements then the solution of tiie equation is straightforward. 

If only materiOLl in the fuel, then every neutron absorb- 

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Lithium and Na are believed to be miscible under the operating conditions, and tritium production with a 50-50 Li-Na atomic mixture is calculated to be greater than 1.0. Lithium-potassium mixtures are also of interest for the Cauldron concept. 

Tritium and Li production were calculated for the reference AHTR configuration. The overwhelmingly dominant reactions are the Li(n, a) H reaction and the Be(n, a) He reaction with subsequent beta decay to Li. At 2400 MW(t), the equilibrium Li concentration in the coolant is 0.001 wt %, or about 10% of its initial concentration. This is due to the burnout of the initial Li loading balanced by the generation of new Li from the Be reaction. At this equilibrium concentration, tritium production is -500 Ci/day. However, the exponential decay constant for the Li concentration is -460 days, which means that it will take several years for the Li concentration and, hence, the tritium production rate, to reach an equilibrium value. The initial tritium production will be on the order of 5000 Ci/day. For comparison, an LWR produces -50 Ci/day, and a typical heavy water reactor produces 3500-6000 Ci/day. ... 

Neutron absorption of the poisons such as Xe and Kr has an important impact on the reactor reactivity. The calculation method of the source terms for the MSRE with online removal of radioactive gases was developed to analyze the radioactivity of hssion products and the tritium products (Zhang et ah, 2014b). OR1GEN2 was applied to study the variation of the xenon and krypton hssion gases varying with neutron spectrum and hux in Tri-lSOtropic (TRISO) fuel particles (Yin, 2014). 

Provided the natural production of 5TU is the only source of tritium in the groundwater, we would have at hand a water dating tool. For example, water pumped from a well with 3TU has preserved 3 x 100/5 = 60% of its natural tritium content, equivalent to an age of 9 years (readable from Fig. 10.1). However, a hydrologist s life is not that simple. Most aquifers have a capacity equal to several annual recharges, or, in other words, water accumulates in the aquifer for many years and the age we have just calculated from the tritium concentration is not a real age, but rather an... 

During the last decade a different track has been followed for the tritium dating method, namely, measurement of the decay product 3He (section 10.1) as a substitute for the initial tritium concentration. Tritium-derived 3He (tritiogenic helium) is built up in the groundwater as the contained tritium disintegrates hence, the 3H 3He ratio decreases with age. To facilitate the calculations both nuclides are expressed in TR (tritium ratio) units, that is, 3H H and 3He H ratios of 10-18. In principle, the age of groundwater can be determined by measuring the tritium concentration left... 

Reactions (8) to (10) not only explain qualitatively the formation of the three major products, but allow a rough evaluation of the abundance of labeled methyl ions former", from the decay. Assuming, in the absence of more detailed information, a statistical distribution of tritium between the products of reaction (9), the activity of HT from reaction (9) is equivalent to 2/5 of the activity contained in the ethyl ions, eventually isolated as tritiated ethane. Therefore, the yield of HT from reaction (9) can be calculated to be 7-0 x 2/5 = 2-8%, and the fraction of the methyl ion undergoing reaction (9), 9-8%. Comparing this figure with the fraction (78%) of labeled methyl ions that react with CgHg to yield... 

In these experiments a tritiated substrate was mixed with 1 -labeled protonated (for H/T KIE experiment) or deuterated (for D/T KIE experiment) substrate. The mixture was allowed to react in the presence of enzyme, under defined conditions of pH and temperature, and quenched at different fractional conversions. The quenched mixtures were analyzed by HPLC and liquid scintillation counting to determine the fractional conversion (f, determined from the counting) and tritium to ratio in the products ([ H/I cjy and pH/l4C]oo for the ratio at the time point and the infinity point, respectively). The L/T KIE (also denoted by (V/K)l or kt/kj) were calculated by equation 1 (Melander Saunders, 1987) ... 

Assumes fission-product tritium diffusing through fuel cladding oi escaping through pin-hole cladding failtires is equivalent to release of fission-product tritium from 0.5% of the fuel. Calculated as average over irradiation cycle. 

Hiis compares with 9.S9 X 10 Ci/year of fission-product tritium calculated to be present in the discharge fuel from a 1000-MWe HTGR [Gl]. 

Simultaneous measurement of tritium and its radioactive decay product, He, helps to at least partially eliminate these problems. Combined measurement of tritium and He allows us to calculate the tritium/ He age. This tracer age is a measure for the time that elapsed since a water parcel has been isolated from exchange with the atmosphere. During this process tritium is taken up and He is lost to the atmosphere by gas exchange,... 

Calculations of the tritium NMR spectra of 1,2-, 1,3-, and 1,4-ben-zene-T2, as well as of CeHsT, had been previously carried out and were used to interpret the experimental data. The results showed that the radioactive sample was mainly (>95 mol%) composed of an almost equimolecular (44 56) mixture of CeHsT and l,4-CeH4T2, free from appreciable amounts of isomeric products. 

Despite practical difficulties, tritium tracers can be used to dissect the various isotope effects which are incorporated in the direct rate comparisons for substrates having secondary or primary beta carbon. The requisite rate coefficients in reaction (66) can be calculated from a knowledge of the mole fraction reacted (/), the molar activity of the reactant (M,) and the product Mi) at that time, and the initial molar activity (Mo) of the reactant (67, 68) - ... 

After lyophilization, the dry material is assayed for radioactivity using liquid scintillation counting and the water content is calculated. A comparison was made between the tritium method and the gravimetric method. The sensitivity of the tritium method was stated to be 1 pg of water it measures the water content of 1 mg of dry material with an accuracy of 0.1%. It was noted that small amounts of tritium were found in the nontest ampoules after lyophilization. In addition, tritium oxide was used to measure the exchange of water molecules between stopper and material. Kassai and Sikos stated that the product distributed into the vial takes up water from the stopper until a state of equilibrium ensues. ... 

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