ML17252B488
| ML17252B488 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/22/1968 |
| From: | Harold Denton Commonwealth Edison Co |
| To: | Boyd R Office of Nuclear Reactor Regulation |
| References | |
| Download: ML17252B488 (5) | |
Text
May 22, 1968 Roger S. Boyd, Assistant Director for Reactor Projects Division of Reactor Licensing THRU: Robert L. Tedesco, Chief, RPB-2, DRL MINUTES OF MEETING ON DRESDEN UNITS 2 AND 3 DOCKET NOS. 50-237 & 50-249 The principal topics discussed at the meeting on April 25 and 26, 1968, with representatives of the Commonwealth Edison Company and the General Electric Company were:
- a. The lack of electrical independence between the unit and standby diesel generators, the core spray subsystems, and the low pressure coolant injection system pumps;
- b. The design, operation, and testing of the turbinefor the high pressure coolant injection system; and
- c. A proposed addition of a feedwater temperature interlock to the automatic pressure relief system.
A GE presentation on safety valve sizing under Section III of the ASME Code was also discussed (Ref. 1). The meeting attendance is listed in Table I.
Independence of ECCS Power Sources The arrangement of the emergency power sources for the core spray system and the low pressure coolant injection system (LPCIS) was discussed in detail, with the staff voicing reservations about the lack of independence between redundant systems.
The emergency power system for Dresden Units 2 and 3 is sho~n schematically in Figure I. As indicated, there are _a total of three diesel generators and four emergency buses. In Unit 2, for example, the 4160 volt emergency buses are labeled 23-1 and 24-1. One core spray pump- end -one' LPCIS pump is connected to bus 23-1, another core spray pump and LPCIS pump is connected to bus 24-1, and the two remaining LPCIS pumps can be supplied with power from either bus. In the event of a LOC accident and loss of off-site power in Unit 2, diesel generators #2. and #2./3 would both be started. However, generator
- 2./3 would not be utilized unless bus 23-1 was not energized~-
Assuming that generator #2 did energize both buses, three LPCIS pumps would be sequentially started. The fourth ~CIS pump would be started only if a protective breaker on one of the first three pumps had opened. Next, one of
Roger s. Boyd May 22, 1968 the two core spray pumps would be started. The second would be attempted only if a protective _breaker on the first opened. Therefore~ the system is designed so that if no failures occur the standby diesel, one core spray pump, and one LPC.IS pump are not uti_lized. In addition, the redundancy provided by this. equipment appears compromised by the interconnections between timers, protective circuits, sensing circuits, interlocks, etc. For example, questions by the staff indicated that the failure of dies~l #2 during the LPCIS pump starting sequence had not been considered and would probably negate all automatic starting of the core spray and LPCIS pumps. Also,* if the pipe break was in the line of the core. spray pump started, and the failure of the LPCIS injection valve was postulated, both systems would be completely negated with no other failures.
If diesei #2 failed to start, only bus 23-1 would be energized by diesel
- 2/3. In this event, there is no redundancy in_pumps because the core spray pump and LPCIS pump on 24-1 would triot be automatically energized, even if one of the other pumps failed.
One methodfbr achieving independence would be the use of the split bus concept, with one diesel, one core spray pump, and two LPCIS pumps on each bus. This type of arrangement, with a standby diesel supplying a redundant, independent bus in either unit, has been proposed for VEPCO's Surry'Units 1 and 2 (Ref. 2).
HPCIS Turbine The turbine for the high pressure coolant injection system (HPCIS) wHl be a slightly modified version of the fE;!edwater pump*:type manufactured by GE for conventional plants. The modifications, designed to increase the quick-start capability and ruggedness of the- turbine, are as follows:
- a. Increased internal tolerances
- b. Increased bucket and nozzle thickness
- c. Oversized thrust bearings An analysis of the potential damage from water slug phenomena has riot been made even though the specific question was raised in an earlier meeting (Ref. 3).
The only test to be pe~formed by the manufacturer will be a check of the governor speed controller. The only other test planned prior to operation on reactor steam is a load test at 155 psig with steam from an on-site boiler. The staff indicated that additional information would be required on the similitude of test and accident conditions.
Roger So Boyd May 22, 1968 APRS Temperature Interlock In an earlier meeting, the staff had indicated that certain feedwater line breaks could both prevent HPCIS water from entering the core and prevent automatic depressurization. GE indicated that under consideration was a delayed interlock to actuate the automatic pressure relief system (APRS) if the temperature of the water in the feedwater inlet line was above 25o°F, indicating a feedwater line break. A number of questions we"'e raised by the'*
staff and we have since been informed that the interlock ~as been dropped from consideration in favor of other concepts.
H. Ro Denton, Project Leader Dresden Units 2 & 3
Enclosures:
L Table I 2o Figure I cc: Po Ao Morris Fo Schroeder Do Skovholt S. Levine Branch Chiefs, DRL H*. Denton co (2)
LIST OF REFERENCES
- 3. Memo, Denton to Boyd, dated 3/27/68
TABLE I LIST OF ATTENDEES Commonwealth Edis.on Sargent & Lundy R. E. Reder G. F. Hoveke B. B. Stephenson w. G. Schwartz D. McClintock AEC - DRL Do L. Levine H. R. Denton
- c. A. Palmer D. F. Sullivan J. s. Bi tel T. A. Ippolito.
General Electric Co. R. L. Tedesco R. McWhorter G. c. Lainas J. Barnard J. Embley R. J. Ascherl R. P. Barr
- w. A. Richards J. F. Osborn M. c. Leverett
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