NUREG-0582, Clarifies Reasons to Proceed W/Development of Preliminary Calculational Tool for Steam Bubble Induced Water Hammer. Proposed Use Need Is Essential Adjunct to Efforts in Resolving Water Hammer Task.Graphs Encl
| ML19254F853 | |
| Person / Time | |
|---|---|
| Issue date: | 10/25/1979 |
| From: | Colmar R Office of Nuclear Reactor Regulation |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-01, REF-GTECI-PI, RTR-NUREG-0582, RTR-NUREG-582, TASK-A-01, TASK-A-1, TASK-OR NUDOCS 7911190192 | |
| Download: ML19254F853 (7) | |
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3 DISTRIBUTION Central file OCT '2 b M NRC PDR PSB Reading MEPORANDUM FOR:
E. Adensam, Section Lerder, Plant Systems Branch, D0R FROM:
.R. J. Colmar, Plant Systems Branch, D0R
SUBJECT:
RR0 POSED USER NEED; REQUEST FOR A PR'ELIMINARY CALCULATIONAL METHOD DEVELOPMENT FROM RES O'l STEAff-BUBELE-COLLAPSE WATER Haft 4ER, INITIATED IN MAY 1979 As-an update on the proposed user need it seems worthwhile to clarify the reasons to pmceed with the development of a prelininary cklcula-tional tool for steam bubble induced water hammer. The reasons fall into two principal categories and these are surriarized below for your infonnation.
I.
Licensing Needs 1.
Water hamer continues to be one of the twenty unresolved safety issues in NRC (TAP. A-1).
2.
Many, if not most, of the LER's en water hamer are related' to steam bubble collhpse.
3.
To establish the safety significance of actual and potential steam bubble collapse events beyond generalizations requires:
a.
a calculated estinate of the limits on the danage potential since the consequences are system-dependent.
b.
a calculational tool with which to perfonn sensitivity i
studies in order to identify which parameters or design j
features are limiting and/or controlling the water j
hammer intensity.
i
- c. ~a calculational capability with which to dianose nuclear plant systems for specific water hamer effects before or after their occurrence. -
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To provide an audit function in order to enable this tap to review and evaluate licensee methods and calculational results and/or responses to staff requirements to mitigate these_
water nanner occurrences, ao calcui tional tooi p resenay
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5.
To have a licensing approach to steam bubble collapse water hamner that is consistent with NRC calculational l
requirements for other water hammer events, such as those caused by discharge into a voided line or check l
valve. Closure associated with an opstream pipe break (i.e.,' NUREG-0582, P A-16).
6.
" Water Harner in Nuclear Plants" (NUREG-0582, July 1979) is a cormitment for NRC to fomulate a calculation tool fb.= steam bubble collapse water hammer (f.e., p 4-3).
7.
There is no way to guarantee that steam bubble formation can be precluded under all conditions for nuclear plant systems, so that some design basis will be needed. The installation of jockey pump for this purpose in come systens, for example, has not been a complete success.
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8.
The ARRS has voted the following in a meno from R.F. Fraley to the NRC Commissioners, dated October 3,1979:
"... insufficient effort is being devoted to determining the pressure pulse amplitude needed as input to computer model analysis.
In particular, additional studies should be made of the amplitQde of the pressure pulse resulting from..... steam bubble collapse." -
9.
The formulation of a long-term position on water hammer, as required by TAP A-1, would be better substantiated by an i
evalustion of the problem which is supported by reasonable calculations which help define the limits of the consequences.
TECHNICAL CONSIDERATIONS l.
Existing studies show that the steam bubble collapse water-hammer problem is a matter of concern when the situation is inertially dominated. That is the case wherein the bubble condensation is so rapid that only the acceleration of the water mass (es) i determines the magnitude of the pressure spikes.
(See the attached, page A-1, and page A-2 figures 5 and 9).
2.
Modelling of the steam bubble condensation dynamics is not necessary for this problem because when the collapse rate is important (that is, thermally dominated) then the water mass (es) is cushioned and the resulting pressure pulses are minor. On the other hand, when the culses are significan't, the condensation is so rapid'as to be virtually instantanecus so that no elaborate Wellino is nocosurv
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When the collapse is inertf ally dominated the initiating conditions of the water harmer sequence appear to be qualitatively similar to a ca'vitation condition, as illustrated in the figure of page A-3 (the Tihange data) and page A-4, a simulation of pump cavita.
tion. Analytical methods presently exist in textbook examples that show very good prediction capability fpr complex cavitation water hamme, pressure pulses; see page A-4.
4 Experimental data are available that indicate that.certain critical parameters, such as subceoling, can be established as engineering limits by which to define the conditions of greatest concern to the development of significant water hammer force, see page A-1.
S.
In the past, simplistic attemots to bound the magnitude df the water hammer pressure pulses, such as those done in the limited effortsby CREARE, INC., produced super-conservative results that were not useful and illustrated that a more realistic approach to this problem is required.
The technical foundations for a preliminary calculational tool appears to' be presently available in the state-of-the-art and this technology could possibly be nobilized for NRC use at a cost in the order of $100,000. This would be an interim effort to provide a timely and reasonable assessment of this problem as a first step. Future efforts may include an experimental program to provide data or verification on essential parameters as needed.
For the reasons noted above, I believe that the proposed user need is an essential adjunct to our efforts in resolving the water hammer task.
R.J. Colmar Plant Systems Branch Division of Operating Reactors cc:
S. Hanauer G. Lainas M. Aycock C. Burger F. Cherny D. Fischer l Zw linski 1353 095 k
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S-6 Esperimental Comg arison; Simulated Pump and Pipeline j
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