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Future steam generator designs. Single wall designs

Abstract

The easily removable 'U' tube design style adopted in the UK for the existing PFR Steam Generators, the Replacement Units now in production and for the future CDFR, gives the operator an extremely valuable option in the event of a water/steam leak occurring inside the Steam Generator. He can choose to shut-down, attempt to find the leak, assess damage, repair, revalidate and return to service in situ, or he can elect to remove the defect unit and replace with a 'proven' spare before returning the circuit to power. With the latter approach the resultant outage time is a known entity of about two weeks. If a repair is attempted in situ, predictions of outage time can become a matter of guesswork since one has no 'guaranteed' method of leak location and the assessment of secondary damage may be very time consuming, depending on the size and type of the original leak together with the particular design style of the Steam Generator. A further significant advantage of the removable 'U' tube design concept is that periodic interchanging of bundles with a spare enables routine chemical cleaning and thorough scheduled tube inspections, with specimen tube sample removal if required for monitoring purposes.  More>>
Authors:
Hayden, O [1] 
  1. Nuclear Power Company Ltd, Warrington, Cheshire (United Kingdom)
Publication Date:
Oct 01, 1978
Product Type:
Conference
Report Number:
IWGFR-25
Resource Relation:
Conference: IAEA-IWGFR specialists meeting on leak detection and location in LMFBR steam generators, Dimitrovgrad (USSR), 6-9 Jun 1978; Other Information: 3 figs; PBD: Oct 1978; Related Information: In: Specialists meeting on leak detection and location in LMFBR steam generators. Summary report, 144 pages.
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; CDFR REACTOR; DESIGN; LEAKS; MOLTEN METAL-WATER REACTIONS; PFR REACTOR; SODIUM; SPECIFICATIONS; STEAM GENERATORS; SUPERHEATERS
OSTI ID:
20236782
Research Organizations:
International Atomic Energy Agency, International Working Group on Fast Reactors, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
TRN: XA0200840011347
Availability:
Available from INIS in electronic form
Submitting Site:
INIS
Size:
page(s) 87-90
Announcement Date:
Apr 03, 2002

Citation Formats

Hayden, O. Future steam generator designs. Single wall designs. IAEA: N. p., 1978. Web.
Hayden, O. Future steam generator designs. Single wall designs. IAEA.
Hayden, O. 1978. "Future steam generator designs. Single wall designs." IAEA.
@misc{etde_20236782,
title = {Future steam generator designs. Single wall designs}
author = {Hayden, O}
abstractNote = {The easily removable 'U' tube design style adopted in the UK for the existing PFR Steam Generators, the Replacement Units now in production and for the future CDFR, gives the operator an extremely valuable option in the event of a water/steam leak occurring inside the Steam Generator. He can choose to shut-down, attempt to find the leak, assess damage, repair, revalidate and return to service in situ, or he can elect to remove the defect unit and replace with a 'proven' spare before returning the circuit to power. With the latter approach the resultant outage time is a known entity of about two weeks. If a repair is attempted in situ, predictions of outage time can become a matter of guesswork since one has no 'guaranteed' method of leak location and the assessment of secondary damage may be very time consuming, depending on the size and type of the original leak together with the particular design style of the Steam Generator. A further significant advantage of the removable 'U' tube design concept is that periodic interchanging of bundles with a spare enables routine chemical cleaning and thorough scheduled tube inspections, with specimen tube sample removal if required for monitoring purposes. If necessary, bundle decontamination can be undertaken to assess engineering deterioration to various degrees of thoroughness ranging from 100% equivalent factory final assembly inspection, to partial decontamination operating via a glovebox type of maintenance bag arrangement, examining local points of both shell and tube areas of the bundle. Many lessons from the last five years' experience of PFR will be incorporated into the design of the CDFR and PFR Steam Generators have two very good examples of how the designer can ease or severely handicap the operator in coping with sodium/water leakages. Good, quick access to tube ends is achieved in the existing PFR Evaporator by simply unbolting the steam/water closure head, but on the superheater and reheater hand-caps have to be cut off and only extremely limited and difficult access to the tube plate can be obtained. Thus, for the replacement PFR superheater and reheater now in production, design changes have been introduced which improve the facilities for inspection, improve the engineering integrity of the sodium/water boundary and will enable NPC to prove the new units under real power station operating conditions. The CDFR design is a scaled up replica of the replacement Units and we, therefore, hope to validate the CDFR design by the successful operation in PFR of the new prototype units some time during 1981. It is worthwhile to comment upon the potential advantages of the gas space' requirement in the PFR type of removable 'U' tube. With regard to sodium/water reaction events in the high risk area of the PFR Steam Generators has proved to be in the tube to tube sheet welds and it is fortuitous that the provision of a sodium side gas space enables the designer to incorporate a highly sensitive leak detection system, with a large 'window of protection' value for the monitoring of the critical weld feature. Thus, if the operator wishes, he can lower the level of the sodium during leak location operations and convert what would be a more onerous under-sodium leak into a gas space. leak. If any opening up operations are required, then this could be of some advantage. Design changes from PFR to CDFR as incorporated into the prototype replacement steam generators are shown.}
place = {IAEA}
year = {1978}
month = {Oct}
}