Dear Sir(s):

hereby reports a significant change in the calculated peak cladding temperature (PCT) for the Duane Arnold Energy Center (DAEC). Subsequent to our last annual report (Reference 1), we were notified by the General Electric Company (GE) of two related errors in our Design Basis Accident Loss-of Coolant Accident (DBA-LOCA) analysis. The first error involves a miscalculation in the computer code which caused the condensation effect in the vessel lower plenum region to be overestimated. The correction of this error results in an increase of 45 'F in the previously reported Licensing Basis PCT (LBPCT) for the DAEC. This error is applicable to all fuel types currently in use at the DAEC. The second error causes a premature termination of the condensation effects due to Emergency Core Cooling System (ECCS) injection subcooling. The correction of this error results in an increase of 10 'F in the calculated LBPCT. Again, all fuel types currently in use at the DAEC are affected. Notwithstanding any prior LBPCT errors, the new errors, in and of themselves, result in a cumulative PCT change of greater than the 50 'F reporting threshold under §50.4