Checking and improvements of the multigroup data library EURLIB-4

Multigroup data libraries, which are widely distributed and used in many projects, must be checked properly before release. The zero version calculated with given flux weighting from evaluated nuclear data files is checked automatically by consistency tests in particle and energy transfer as far as possible. For EURLIB two data sets are produced with different processing codes independently at EURATOM/Ispra and at IKE/Stuttgart, so that a good check is given. With the help of several generic shielding problems the differences to US and Japanese group data sets have been studied in detail showing the effect of other group structures or other concepts of resonance weighting. It is shown that an improved treatment of thermal neutrons is very important. Finally the cross section requirements for deep penetration in iron are discussed. The present status of the library is presented