Document: NRC Regulatory Guide
Document ID: a12b2f8d-d334-4fb6-8a51-8bf551a23833
Document Type: regulatory_guide
Title: Surveillance Program for New Fuel Assembly Designs
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1335/ML13350A277.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.119
CFR Part: 
CFR Title: 

Content:
increase, coolant temperature, and coolant pressure. Surveillance of fuel assemblies in operating reactors has proved successful in uncovering unpredicted behavior such as fuel densification, channel box wear, and fuel rod bowing. Therefore, verification that a new fuel assembly design can meet its design and performance criteria should be determined through a comprehensive surveillance program which includes precharacterization of selected fL l assemblies. Directed post- irradiation destructive examinations of fuel assembly components may also have to be performed to establish causes for unpredicted behavior of safety significance. Precharacterization involves the examination and measurement of selected fuel rods individually and in the fuel assembly. Fuel rod measurements should include diameter and length, and assembly measure- ments may include rod-to-rod spacing and spacer perpendicularity. Surveillance of fuel rod performance may include the monitoring of reactor offgas and coolant activity; wet or dry "sipping" of fuel assem- blies to identify leakers; visual observations of structural integrity with various optical aids (i.e., borescope, periscope, etc.) or closed- circuit underwater TV; and remote dimensional measurements of length, diameter, and degree of bowing. Postirradiation examinations may involve visual inspections, dimen- sional measurements, and both nondestructive and destructive examinations of the fuel rod, cladding, and fuel pellet. .. Nondestructive examinations of the fuel rod are used to locate defects; these can include profilometry, pulse eddy current, ultrasonic, and leak tests. Ganma scanning is used to determine axial distributioz of fission product activity, fuel column length, and gaps, and neutron radiography is an additional means to locate the ful* column. Analyses of internal gas composition and measurement of total gas volume are other measurements important in design verification. .Cladding examinations and tests are designed