ML19294C271
| ML19294C271 | |
| Person / Time | |
|---|---|
| Issue date: | 02/27/1980 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Anderson T WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 8003100004 | |
| Download: ML19294C271 (3) | |
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FEB : 71930 Mr. Thomas M. Anderson, Manager Nuclear Safety Department Westinghouse Electric Corporation P. O. Box 355 Pittsburgh, Pennsylvania 15230
Dear Mr. Anderson:
SUBJECT:
REVIEW 0F WCAP-9639 Additional infomation is needed to complete our review of Westinghouse Electric Corporation topical report WCAP-9639 entitled " Report on Small Break Accidents for Westinghouse Nuclear Steam Supply System (NSSS) with Upper Head Injection (UHI)." The requested additional information is enclosed.
This additional infomation is needed by March 7,1980 to meet our review schedule.
If you cannot meet this date, please infom us within ten days after receipt of this letter of the date you plan to submit your response.
Sincerely, Jo n F. Stolz, Chief
'ght Water Reactors Branch No.1 Division of Project Management
Enclosure:
Request for Additional Information cc: Mr. W. Spezialetti Mr. A. Ball Westinghouse Electric Corporation Westinghouse Electric Corporation P. O. Box 355 P. O. Box 355 Pittsburgh, Pennsylvania 15230 Pittsburgh, Pennsylvania 15230 800310000 4
ENCLOSURE REQUEST FOR ADDITIONAL INF0Pf4ATI0t1 ON WCAP-9639 1.
We require that Westinghouse provide emergency procedure guidelines for the small break accident for Upper Head Injection (UHI) plants. This can be done by including specific guidance related to UHI in the Westinghouse E-0 (Safety Injection Procedure) and E-1 (LOCA Procedure) guidelines.
In addition, provide the basis for including or excluding the following items from the guidelines:
a.
verification of UHI actuation; b.
verification of UHI isolation; c.
instructions for manual actuation; d.
instructions for manual isolation;-
e.
criteria for manual isolation; f.
criteria for restart of the reactor coolant pumps.
2.
Provide a commitment to verify the analysis of the influence of UHI on natural circulation. This could be based on a pre-prediction of a Semiscale UHI test or some equivalent test.
3.
What would the symptoms of interrupted natural circulation be? How can these be included in the E0I's and in operater training?
4.
Define the appropriate and inappropriate operator actions for the conditions under which UHI causes an interruption in natural circulation.
5.
Define the conditions for Reactor Coolant Pump restart.
6.
How can an operator distinguish inadequate core cooling, which requires operator action, from the expected core uncovery during a large or small LOCA, for which no actions are requiredt Show that any action taken as a result of using the inadequate core cooling guidelines is appropriate and desirable for a small or large break LOCA.
2-7.
Address the influence of UHI on the symptoms of inadequate core cooling.
8.
Can and should UHI be used to combat a condition of inadequate core cooling?
9.
Address the probability and consequences of failure of the UHI isolation system.
10.
Provide a comitment to address UHI effects on " Transient & Accident
' Analyses" (2.1.9-3) in the submittal on this subject which is scheduled for early 1980 (per NUREG-0578).
11.
The WFLASH model uses one volume to represent the core and upper plenum.
Also thermal equilibrium is assumed in every volume. This would appear to maximize the core inventory during an small break LOCA with UHI. The drift flux study in WCAP-9639 attempted to show that UHI water delivered abu.
the core would penetrate into the core. While this may be true, the study did not show now fast this delivery would occur. Obviously it would not occur as rapidly as in the WFLASH model used in the UHI/non-UHI study. Therefore,
the core inventory in the UHI cases may not be as much as indicated by the calculations.
In light of these effects discuss the usefulness of this model for analyzing small break LOCA behavior and operator actions.
12.
In some small breaks, UHI water may be injected into a steam filled or partially voided upper head. What is the effect of using the equilibrium model under such conditions. Also discuss thermal shock to the vessel and upper head components in such cases.
Provide plots of fluid temperature, saturation temperature, and mixture level in the upper head for the breaks analyzed in WCAP-9539, 13.
Perform a UHI injection line break analysis to assure physical behavior is correctly understood. Also address the possibility of control rod
" levitation" for this accident.
14.
WCAP-9639 shows that the larger small break (6 & 8 inches) are worse (higher PCT, longer uncovery) for UHI than for non-UHI. Explain why this is so and
~
how this is compatible with conclusions about increased inventory during UHI SB LOCAs.
Is this effect completely explained by the pressure setting on the UHI plant cold leg accumulators?
15.
The Small Break Accident analyses in WCAP-9639 (4 in. break, for example) show a rapid doressurization when UHI injection begins.
Rapid depressurizations are also calculated to occur when the cold leg accumulators inject, but this behavior has A been observed in LOFT or Semiscale tests. The rapid depressurizations may be an artificiality of the thermal equilibrium model.
Would Wis behavior be expected in the reactor small break accident? Should the operators expect to see such behavior? Has this behavior ever been observed experimentally? Describe the importance of this phenomenon to the results of the small break accident calculations.