Assessment of the Fingerprinting Method for Verification of Spent Fuel in MACSTOR KN-400 CANDU Spent Fuel Dry Storage

Abstract:

The Republic of Korea currently has 16 pressurized water reactors around the country and 4 CANDU reactors at Wolsong site. As the Wolsong site has not enough space for further extension of its existing more than 300 dry storage casks (also known as silo or canister), the Korea Hydro and Nuclear Power decided to build a new modular type of dry storage system, known as MACSTOR KN-400. Whereas a typical CANDU dry storage cask typically has 9 baskets in which there are 60 bundles of CANDU spent fuel assemblies, the MACSTOR can store up to 24000 bundles in a 4 rows x 10 columns arrangement.It is expected that fingerprinting method will be used for reverification purpose in the event of a loss of continuity of knowledge for MACSTOR KN-400. As the MACSTOR KN-400 is new, the conventional re-verification method of fingerprinting is not fully assessed. This study addresses the reverification issues for MACSTOR KN-400, which is a new dry storage system for CANDU spent fuel assemblies. The MACSTOR KN-400 stores spent fuel bundles in 40 cylinders. It employs two types of reverification tubes unlike single verification tube concept for the single cask storage system. Monte Carlo modeling for the MACSTOR is expected to be much more complicated than that of cask as radiation signals will be influenced by radiations coming from nuclear fuel in the surrounding cylinders and also due to different collimation geometry. Obviously the neutron and gamma signals at the reverification tubes of the MACSTOR KN-400 are expected to be significantly different from those signals at the tubes of a cask. The objectives of this study are to assess the finger printing method for verification of spent fuel and to analyze various diversion scenarios in the MACSTOR KN-400 CANDU Spent Fuel Dry Storage System.