Cover Gas Seals Research Articles

Development of inflatable seals for the rotatable plugs of sodium cooled fast breeder reactors: a review – Part II: R&D necessities and development across the world

Abstract Identification of development areas and their implementation for rotatable plug (RP) inflatable seals of Na cooled, 500 Mw (e) Prototype Fast Breeder Reactor (PFBR) and 40 MW (t) Fast Breeder Test Reactor (FBTR) are described, largely based on a late 1990s survey of cover gas seal development (1950s–early 1990s) which defined a set of shortlisted design options and developmental strategy to minimize effort, cost and time. Comparative study of top shield sealing and evolving FBR designs suggest suitability of inflatable seal as primary barrier in RPs. International experience identified choice and qualification of seal elastomer under synergistic degrading environment of reactor as the prime element of development. The low pressure, non-reinforced, unbeaded, PFBR inflatable seal (made of 50/50 blend of Viton® GBL 200S/600S) developed for 10 y life provides a unification scheme for nuclear elastomeric sealing based on 5 peroxide cured fluoroelastomer blend formulations, 1 finite element analysis approach, 1 Teflon-like plasma coating technique and 2 manufacturing processes promising significant gains in standardization, economy and safety. Uniqueness was ab initio development in the absence of established industry or readymade supply. R&D necessities for inflatable seals and their development across the world are given closer look in Part II of the review in continuation of Part I.

Development of inflatable seals for the rotatable plugs of sodium cooled fast breeder reactors: a review – Part I: key areas

Abstract Identification of development areas and their implementation for rotatable plug (RP) inflatable seals of Na cooled, 500 Mw (e) Prototype Fast Breeder Reactor (PFBR) and 40 MW (t) Fast Breeder Test Reactor (FBTR) are described, largely based on a late 1990s survey of cover gas seal development (1950s–early 1990s) which defined a set of shortlisted design options and developmental strategy to minimize effort, cost and time. Comparative studies of top shield sealing and evolving FBR designs suggest suitability of inflatable seal as primary barrier in RPs. International experience identified choice and qualification of seal elastomer under synergistic degrading environment of reactor as the prime element of development. The low pressure, non-reinforced, unbeaded, PFBR inflatable seal (made of 50/50 blend of Viton® GBL 200S/600S) developed for 10 y life provides a unification scheme for nuclear elastomeric sealing based on 5 peroxide cured fluoroelastomer blend formulations, 1 finite element analysis approach, 1 Teflon-like plasma coating technique and 2 manufacturing processes promising significant gains in standardization, economy and safety. Uniqueness was ab initio development in the absence of established industry or readymade supply. Part I addresses key areas of design shortlisting, strategy, development and unification with a backdrop of international evolution.

A Recommended Design Approach for Breeder Reactor Cover Gas Seals

Technological progress requires that lessons learned in initial design efforts be incorporated into the following design effort. One area where improvement can be made is in the design of elastomer seals for containment of breeder reactor cover gases. Liquid metal fast breeder reactor (LMFBR) vessels, unlike PWR’s, operate at a very low pressure. The reactor cover gas may be maintained at a pressure of less than 1 psia. This low pressure level and moderate temperatures of the vessel head-mounted refueling and monitoring equipment permit the use of elastomer seals in this equipment to contain the cover gas. Existing seal designs are based on a conservative design philosophy which was established in the late 1960’s when the FFTF project was in its formative stages. The information gained in the design and development of LMFBR seals during the past decade indicates that some changes in the approach to seal design could result in improved seals and reduced downtime for seal maintenance. This document presents the design approach currently used for cover gas seals, and points out how improvements can be made based on today’s knowledge of breeder reactors and elastomer seals. A suggested new seal design concept is presented which may better meet the LMFBR commercial program needs. The basic assumption used to design cover gas seals conservatively states that elastomer seals, even when new, can leak, and primary consideration must be given to preventing the outflow of radioactive cover gas. The suggested new design concept acknowledges that elastomer seals are effective, and the primary consideration should be one of controlling the gases which permeate through the elastomer seal material. Finally, information which was obtained from the cover gas seal development program for FFTF, which is of value to all LMFBR equipment designers, is summarized.