ML20083D654

Requests Budgetary Constraints or Other Restrictions Needed for Consideration in Preparing Proposal to Study Buoyant Convective Motion within Pressurizer Surgeline.Unsolicited Proposal Under Review Encl.W/O Encl

ML20083D654
Person / Time
Site:	Neely Research Reactor
Issue date:	09/17/1991
From:	Desai P, Kadaba P Neely Research Reactor, ATLANTA, GA
To:	Kadambi N NRC
References
NUDOCS 9110010126
Download: ML20083D654 (2)

Text

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Q}fy/ t uitil o n.u i w isitui w awgu imutuir of ini.aolon Nian rewgu W2 oM September 17,1991 Dr. N. P. Kadambi Nuclear Regulatory Commission Mail Stop 8D22 Washington, D.C. 20555

Dear Dr. Kadambi:

We are writing to you in reference to a research proposal to study buoyant convective motion within a pressurizer surgeline, since we know about your interest in mselear reactor safety irsues. A copy of tl'c unsolicited proposal that is currently under review by the Division of Contracts at the NRC is enclosed with this letter. The budgetary consuaints verbally communicated to us by personnel at the NRC have been incorporated in the proposal budget, which does not reflect the significant time and effort commitment that both of us will be making to bring about a successful completen of the proposed research.

The primary motivation for the work is derived from safety concerns posed by potential thermal fatigue cracking in reactor piping. The specific problem that we have posed concerns some basic mechanisms common to a variety of stratified flow sitaations in reactor conduits. In particular, we are looking at a horizontal pipe, containing initially stagnant fluid that is subjected to differentially heated closed ends. In a gravitational field, this system is thermoconvectively unstable at any Rayleigh number based on the end temperature difference. Ilowever,it is only for a very limited range of Rayleigh numbers that the conventionally accepted "S"-shaped profile of stably-stratified flow develops. The stability map for the extended range of Rayleigh numbers and the bifurcations are not established even for this simple system. The evolution and growth of the cell pattern,its bifurcation to multi-cellular behavior and possible further bifurcations to a recombined pattern giving rise to time periodic flow fields form a fascinating subject. It is relevant both from the points of view of governing physical mechanisms as well as practical engineering concerns regarding cyclic wall-temperature fluctuations.

Such self-induced thermoconvective oscillations and their influence on (low-cycle) thermal fatigue have not been previously examined in connection with surgeline performance. The exploratory research in the proposal will document the cellular flow patterns for a limited range of geometrical and thermal parameters. j i

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Dr. N. P. Kadambi Septemler 17,1991 j Page 2 We would like you to note that the general method of approach presented in the proposal can be modified and extended to incorporate changes in end conditions (free sheat reservoir openings instead of closed ends) and geometry (aspect ratio and ir.elination) to accommodate configurations of immediate practical interest to the NRC, We are confident that the experimental research of the proposal, as well as planned analytical studies, will lead to a valuable insight to stability behavior of such transient thermal hydraulic systems. We would also like for you to personally review the proposal and encourage us to prepare an expanded proposal. Please suggest any new budgetary constraints or other restrictions that we need to consider in preparing the proposal. We are looking forward to your favorable response.

Sincerely, 3

Mh*W ._ ,

Prasanna V. Kadaba Associate Professor

[halu~ d. hQ<h Prateen V. Desai Professor PVD:mjk

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