Document: NRC Regulatory Guide
Document ID: 91c1459d-4ae6-4802-8c6d-e805db860e10
Document Type: regulatory_guide
Title: Post-tensioned Prestressing Systems for Concrete Reactor and Containment (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1221/ML12216A010.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.103
CFR Part: 
CFR Title: 

Content:
fittings on a common bearing plate. Bar Systems. Bar systems use a number of high- tensile-strength steel bars that are bundled into a tendon. 'The bars are made from an alloy steel conforming to ASTM Specifications A-322 and A-29. A-322 is a general specification that covers only the chemical composition of many grade designations of alloy steel bars, and A-29 is a specification giving general requirements for hot- rolled and cold-finished carbon and alloy steel bars. The mechanical and physical requirements for the pre- stressing bars are covered by ASTM Specification A-722, "Uncoated High-Strength Steel Bar for Prestressing Concrete." Bars are cold-stretched and also stress-relieved by heat treatment to produce the prescribed mechanical proper- ties. Both deformed bars and smooth bars with threaded ends are available, but only smooth bars have been used for nuclear power plant construction in the United States. The Stressteel Corporation in the United States uses a bar system. The bars are stressed by means of a hydraulic jack that consists of a coupler and pulling bar. The normal commercial technique for anchoring uses anchor nuts. During stressing, the anchor nuts are continuously screwed down on washers and bearing plates, and the prestressing force is then transferred to the anchorage assembly by releasing the force in the jack. Wedge and grip-nut anchorages are also available to anchor the bar; they have the advantage of being able to grip the bar at any point along its length. The containment structure of H.B. Robinson Unit No. 2 in Hartsville, S.C., uses the Stressteel bar system anchored with Howlett Grip Nuts. The tendon, which is composed of six 1-3/8-inch-diameter Stressteel bars, develops a capacity of 1428 kips. Grouted and Ungrouted Tendons All of the concrete reactor vessels and containments designed and built in the United States use ungrouted tendons except for H.B. Robinson Unit 2 (bar tendons), Three Mile Island Unit 2 (strand tendons), and