ML20002A354
| ML20002A354 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/10/1976 |
| From: | Burger A Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8011130409 | |
| Download: ML20002A354 (5) | |
Text
UNITED STATES 3
NUCLEAR REGULATORY COMMisses, L._
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WASHINGTON, D. C. 20555 p
w November 10, 1976 DOCKET NO.: 50-29 FACILITY:
YANKEE-ROWE LICENSEE:
YANKEE ATOMIC ELECTRIC COMPANY (YAEC)
SUMMARY
OF MEETING HELD ON OCTCBER 22, 1976 WITH YANKEE ATOMIC ELECTRIC COMPANY TO DISCUSS ACCUMULATOR INJECTION DELAY FEATURE
- .y On October 22, 1976, representatives of YAEC met with the NRC staff and presented their plan for adding an ECCS accumulator injection
~p delay, feature to improve the performance capability of the ECCS.
A list of attendees is attached. Significant points are summarized below.
YAEC contends that the. Yankee-Rowe performance capability is presently m.
restricted by the operating limitations of the ECCS accumulator sub-system, because of the small water inventory in the single accumulator "I
and the low constant pressure being maintained in the accumulator.
They
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believe this accounts for the relative long period to refill the large
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Yankee-Rowe reactor vessel lower plenum following a LOCA, while the core heats up adiabatically until the time when BOC9EC (bottom of core recovery) occurs.- As a result of potentially higher peak clad temperatures, the limited performance capability of the existing ECCS. imposes restric-tions on the peak LHGR which could require operation of Yankee-Rowe at less than full licensed power.
To improve the performance capability of the ECCS for operation with the next core (Core.X111), YAEC plans to modify the ECCS accumulator subsystem to provide a feature for delaying injection of accumulator water into the core after a LOCA.
After a timed period of 26 seconds from the SIAS signal (compared with approximately 19 seconds in the present system due'to decrease in the reactor cooling system pressure) nitrogen would be admitted to the accumulator to build up to a pressure of about 515 psia (compared to the 385 psia constant pressure being maintained in the present system without delay). This would provide a greater driving force for injecting water into the core at a faster rate.
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The proposed higher pressure in the accumulator will be below the design pressure of the accumulator vessel. The proposed modification involves an increase.in the nitrogen gas supply and relief system and the addi-tion of valves and timers in sufficient number to meet the single failure criterion.
Following initial setup during pre-startup testing, the modtfied accumulator subsystem. will operate entirely automatic.
YAEC presented the results of preliminary scoping calculations to compare the performance of the modified ECCS accumulator subsystem with the exist-ing system. They show that up to E0BY (end of bypass), ECCS injection in the modified system would be about the same as in the existing system.
However, because of the greater driving force of the increased accumulator pressure and the resulting greater injection rate in the modified system.
The vessel would be refilled in'a short period of time (by about 10 seconds).
This would equally shorten the adiabatic heatup period and would be expected to result in lower peak clad temperatures at the temperature turn around during reflooding of the vessel.
YAEC will reanalyze the performance of the ECCS with the modified ECCS accumulator subsystem using the approved Appendix K evaluation models to demonstrate the improved capability to' meet the criteria in Appendix K
=== T; and 10 CFR 550.46 for operation with the Core X111.
.,Z With respect to YAEC's proposed action the NRC staff comnented that we believe the f1EC should be able to demonstrate the beneficial effects
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of the proposed injection delay feature on ECCS performance by calcula-tions using the Appendix K.model approved for Yankee-Rowe.
However, we indicated.that YAEC must also provide.all of the necessary information
- to demonstrate that the proposed modification will not result in any adverse effect on ECCS operation that might reduce the safety margin.
We said that such information should include a single failure modes and effects analysis for the modifie d subsystem, the design of the added instrumentation and power sources to demonstrate how the design meets the IEEE requirements, the effect of the higher nitrogen pressure on the accumulator intergrity, and the effect of the delayed injection on flow related phenomena.
YAEC stated that Yankee-Rowe is scheduled to be shutdown for refueling on June 1,1977, and for post-refueling startup on July 1,1977. YAEC also stated that they planned to make the refueling submittal including information on the proposed modification and the ECCS performance reevaluation 90 days before startup with Core X111. We commented that 1
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i I significantly more lead time than the proposed 90 days would be required for us to schedule and complete the unusually large refueling submittal for Core X111.
At the ccnclusion of the meeting YAEC agreed to provide in about 2 weeks its plan and schedule for the Core X111 submittal.
YJGbv Fred Burger, Project Manager Operating Reactors Branch #1 Division of Operating Reactors
Attachment:
List of Attendees
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i NRC STAFF MEETING WITH YANKEE ATOMIC ELECTRIC COMPANY (YAEC)
OCTOBER 22, 1976 NRC John A. Dyer, I&E Fred Burger, 00R, ORB #1 Newton Anderson, D0R-RS Frank Coffman: DOR-RS 2.
Carl Berlinger D0R-RS YAEC Ausaf Husain Bob Shone Bill Szymczak Alan Ladieu Joe Turnage Paul Rainey d
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I 4-Meeting Sumary for Yankee Atomic Docket File NRC PDR LOCAL PDR ORB #1 Reading NRR Reading B. C. Rusche E. G. Case V. Stello K. R. Goller D. Eisenhut T. J. Carter
%. Schwencer D. Ziemann G. Lear R. Reid R. Clark L. Shao R. Baer W. Butler
,g.:
B. Grimes Project Manager Attorney, OEl.D Ol&E (3)
S. M. Sheppard Participants (NRC)
R. Fraley, ACRS (16)
T. B. Abernathy J. R. Buchanan f