Postirradiation testing of N Reactor process tubes. Summary

The N Reactor process tubes were fabricated from Zircaloy-2 primarily due to the excellent corrosion resistance, low neutron absorption, and high strength properties of this alloy. Irradiation data available at the time the tubes were installed indicated that fast neutron irradiation damage mechanisms would not decrease the ductility to unacceptable levels over the estimated plant life of 25-30 years. However, because the tubes are a primary coolant system component and only limited data are available on irradiation effects at high fluences, a Postirradiation Examination (PIE) Program is conducted to assure that service factors do not compromise tube properties essential to reactor safety. The program required periodic removal of process tubes from N Reactor for destructive examination. The N Reactor Technical Specifications currently require a process tube to be removed for PIE during the 1976 summer outage. The 1976 summer outage has been markedly disrupted by the current labor situation. This review was conducted to determine if the specified tube removal could be postponed one year without jeopardizing nuclear safety