Ylipormestari Lauri Aho 12/2 1971

Kirje 12.2.1971

Ylipormestari Lauri Aho 22/2 1971

Kirje 22.2.1971

Simulation of the Interaction Mean Free Path between Neutrons and TRISO Particles

The interaction mean free path between neutrons and TRISO particles is simulated using scripts written in MATLAB to solve the increasing error present with an increase in the packing factor in the reactor physics code Serpent. Their movement is tracked both in an unbounded and in a bounded space. Their track is calculated, depending on the program, linearly directly using the position vectors of the neutrons and the surface equations of all the fuel particles; by dividing the space in multiple subspaces, each of which contain a fraction of the total number of particles, and choosing the particles from those subspaces through which the neutron passes through; or by choosing the particles that lie within an infinite cylinder formed on the movement axis of the neutron. The estimate from the current analytical model, based on an exponential distribution, for the mean free path, utilized by Serpent, is used as a reference result. The results from the implicit model in Serpent imply a too long mean free path with high packing factors. The received results support this observation by producing, with a packing factor of 17 %, approximately 2.46 % shorter mean free path compared to the reference model. This is supported by the packing factor experienced by the neutron, the simulation of which resulted in a 17.29 % packing factor. It was also observed that the neutrons leaving from the surfaces of the fuel particles, in contrast to those starting inside the moderator, do not follow the exponential distribution. The current model, as it is, is thus not valid in the determination of the free path lengths of the neutrons.

Development of an HTR-10 model in the Serpent reactor physics code

The use of exact coordinates of pebbles and fuel particles of pebble bed reactor modelling becoming possible in Monte Carlo reactor physics calculations is an important development step. This allows exact modelling of pebble bed reactors with realistic pebble beds without the placing of pebbles in regular lattices. In this study the multiplication coefficient of the HTR-10 pebble bed reactor is calculated with the Serpent reactor physics code and, using this multiplication coefficient, the amount of pebbles required for the critical load of the reactor. The multiplication coefficient is calculated using pebble beds produced with the discrete element method and three different material libraries in order to compare the results. The received results are lower than those from measured at the experimental reactor and somewhat lower than those gained with other codes in earlier studies.

Tao antin'Imano : vieille chanson ; Arie faly aho leitsy : [chanson moderne pour la Circoncision] / Hirran'ny tanoran'ny ntaolo mpilaloa ao Fenoarivo [chants ancestraux chantés par un groupe de musiciens de Fenoarivo]

[Traditions. Afrique. Madagascar]

Akateemikko Lauri Posti 21/5 1975

Kirje 21.5.1975

Vuorineuvos Lauri J. Kivekäs 30/3 1973

Kirje 30.3.1973

Herra Lauri J. Mäki 10/4 1964

Kirje 10.4.1964

Professori Lauri Posti 21/5 1963

Kirje 21.5.1963

Professori Lauri Posti 31/1 1973

Kirje 31.1.1973

Professori Lauri Posti 15/12 1973

Kirje 15.12.1973

Verkställande direktören Lauri Kirves 20.4.1964 Helsingfors

Kirje

Reino Halla-aho 2/9 1968

Kirje 2.9.1968