HTGR Knowledge Base

Conference Article: Development and testing of nuclear graphite for the German pebble-bed high temperature reactor

Haag, G.; Delle, W.; Nickel, H. (Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.)); Theymann, W.; Wilhelmi, G

Abstract

Several types of high temperature reactors have been developed in the Federal Republic of Germany. They are all based on spherical fuel elements being surrounded by graphite as reflector material. As an example, HTR-500 developed by the Hochtemperatur Reaktorbau GmbH is shown. The core consists of the top reflector, the side reflector with inner and outer parts, the bottom reflector and the core support columns. The most serious problem with respect to fast neutron radiation damage had to be solved for the materials of those parts near the pebble bed. Regarding the temperature profile in the core, the top reflector is at 300 deg C, and as cooling gas flows from the top downward, the temperature of the inner side reflector rises to about 700 deg C at the bottom. Fortunately, the highest fast neutron load accumulated during the life time of a reactor corresponds to the lowest temperature. This makes graphite components easier to survive neutron exposure without being mechanically damaged, although the maximum fast neutron fluence is as high as 4 x 1022/cm2 at about 400 deg C. HTR graphite components are divided into four classes according to loading. The raw materials for nuclear graphite, the development of pitch coke nuclear graphite, the irradiation behavior of ATR-2E and ASR-IRS and others are reported.

view the full text of this article (5 pages, format: PDF, size= 347kB)

key words: graphite; high temperature; htgr type reactors; mechanical properties; neutron beams; pebble bed reactors; physical radiation effects; production; reactor cores; reactor materials; beams; carbon; gas cooled reactors; graphite moderated reactors; homogeneous reactors; particle beams; radiation effects; reactor components; solid homogeneous reactors
Reference:
Specialists' meeting on graphite component structural design, JAERI Tokai (Japan), September 8-11, 1986
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--11, pp:128-132