nuclear graphite

https://doi.org/10.1351/goldbook.N04233
A polygranular graphite material for use in nuclear reactor cores consisting of graphitic carbon of very high chemical purity. High purity is needed to avoid absorption of low-energy neutrons and the production of undesirable radioactive species.
Note:
Apart from the absence of @[email protected] impurities, modern reactor graphites are also characterized by a high degree of @[email protected] and no preferred bulk orientation. Such properties increase the dimensional stability of the nuclear @[email protected] at high temperatures and in a high flux of neutrons. The term nuclear @[email protected] is often, but incorrectly, used for any @[email protected] in a @[email protected], even if it serves only for structural purposes.
Source:
PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 498 (https://doi.org/10.1351/pac199567030473)