Within the 4th Framework Program for the European Atomic Energy Community in the Nuclear Fission Safety, the BWR Physics and Thermohydraulic Complementary Action to the BWR Cluster (BWRCA project) intends to perform complementary efforts on items already proposed in the IPSS-BWR R & D Cluster project. The design of innovative components, which could improve the performances of the passive systems studied under the BWR R & D Cluster, is one of the objectives of BWRCA. On this purpose the Work Package 1 is specifically devoted to the implementation and assessment of the Thermal Valve (TV) concept on Isolation Condenser Systems. This concept is able to avoid the implementation of mechanical valves on DHR system with in-pool heat exchanger. As a first step a conceptual design of the TV/IC system is proposed on the basis of innovative BWRs to develop an analytical model. The assessment, performed by CEA/DRN with CATHARE and by ENEA/ERG with RELAP, includes steady state and transient calculations to veryfy that the functional specifications as well as the performance requirements are fulfilled. The results are interesting but not completely conclusive owing to unexplained discrepancies which are still present, likely because the codes are used out of their validation domain. The issues motivate the effort that is currently requested to improve their capacity for the design of passive systems.