Document: 10 CFR Part 50
Document ID: f3d5df11-b35b-4e81-b016-39463863b59a
Document Type: cfr
Title: Requirements for thermal annealing of the reactor pressure vessel.
Source: 10 CFR Part 50
Source URL: https://www.ecfr.gov/current/title-10/part-50/section-50.66
Revision Date: 
Chapter: 
Section ID: 50.66
CFR Part: 50
CFR Title: 10

Content:
ete structures to a degree that could affect the safe operation of the reactor. ( 3 ) Fracture Toughness Recovery and Reembrittlement Trend Assurance Program. The percent recovery of RT NDT and Charpy upper-shelf energy due to the thermal annealing treatment must be determined based on the time and temperature of the actual vessel thermal anneal. The recovery of RT NDT and Charpy upper-shelf energy provide the basis for establishing the post-anneal RT NDT and Charpy upper-shelf energy for each vessel material. Changes in the RT NDT and Charpy upper-shelf energy with subsequent plant operation must be determined using the post-anneal values of these parameters in conjunction with the projected reembrittlement trend determined in accordance with paragraph (b)(3)(ii) of this section. Recovery and reembrittlement evaluations shall include: ( i ) Recovery Evaluations. ( A ) The percent recovery of both RT NDT and Charpy upper-shelf energy must be determined by one of the procedures described in paragraph (e) of this section, using the proposed lower bound thermal annealing time and temperature conditions described in the operating plan. ( B ) If the percent recovery is determined from testing surveillance specimens or from testing materials removed from the reactor vessel, then it shall be demonstrated that the proposed thermal annealing parameters used in the test program are equal to or bounded by those used in the vessel annealing operation. ( C ) If generic computational methods are used, appropriate justification must be submitted as a part of the application. ( ii ) Reembrittlement Evaluations. ( A ) The projected post-anneal reembrittlement of RT NDT must be calculated using the procedures in § 50.61(c) , or must be determined using the same basis as that used for the pre-anneal operating period. The projected change due to post-anneal reembrittlement for Charpy upper-shelf energy must be determined using the same basis as that used for the pre-anneal operating