A computer code TERFOC-N has been developed to calculate doses to the public due to atmospheric releases of radionuclides in normal operations of nuclear facilities. The code calculates the highest individual dose and the collective dose from four exposure pathways; internal doses due to ingestion and inhalation, external doses due to cloudshine and groundshine.A foodchain model, which is originally referred to the U.S. NRC Regulatory Guide 1.109, has been improved to apply to not only L WRs but also other nuclear facilities.This report describes the models employed and gives a sample run performed by the code. The parameters which were sensitive to ingestion dose were identified from the results of sensitivity analysis. The models which significantly contributed to the dose were identified among the models improved and extended here.