ML20063A544
| ML20063A544 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 01/13/1994 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9401260126 | |
| Download: ML20063A544 (5) | |
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GENuclear Energy Gener$!ILtoc Company 175 Cunm Avenue. San Jose. CA 9512S
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January 13,1994 Docket No.52-001 Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License R.enewal Office of the Nuclear Reactor Regulation
Subject:
Submittal Supaorting Accelerated ABWR Schedule -
Containment Emergency Procedure Guidelines Issues
Reference:
R. W. Borchardt Letter to J. F. Ouirk,"GE ABWR Containment Systems and Severe Accident Review Issues",
December 29,1993
Dear Chet:
This letter responds to the Low-Pressure Venting Items 1,3,4, and 5 of the subject issues transmitted by the above reference. The issues are repeated below followed by responses:
1.
Revise EPGs (PC/P) to show the venting is restricted to the 2-inch line in the drywell.
Response
EPG Step PC/P has been revised in Amendment 33 of the SSAR to state that ventmg of the containment is restricted to the 2-inch (50A)
Atmosphere Control System (ACS) drywell bleed line.
3.
Address containment isolation configuration ofinterconnection in the ACS between the wetwell and drywell. GE should justify automatic control of the ACS over normally closed penetration ensuring containment integrity..
Response
See attached markup of Subsection 6.2.4.3.2.2.2.3, Page 6.2-27.
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4.
Address suppression pool level issue in EPGs relating to the wetwell to drywell interconnection level. The EPGs appear to be inconsistent with the design.
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Response
The purpose of the EPG steps that specify spraying the drywell only if suppression pool water level is below 11.7 meters is to preserve the functionality of the wetwell-to-drywell vacuum breakers. There is no requirement to limit the suppression pool water level below 8.6 meters which is elevation of the water return paths (either from lower drywell to suppression pool or from sup aression 3001 to lower drywell). The attached clarification.ppendix 18B, Ta ale 18B., Page 18B-11 provides this markup of A 5.
Address suppression pool level and pressure control sPGs for injection from sources outside of containment. The EPGs appear to require -
conflicting actions in the SP/1,3.3 directs operators to stop injection from sources outside containment when the suppression pool level reaches 27.2 meters. Whereas, PC/P-6 directs operators to spray the containment when the water level reaches 27.2 meters (using sources external to the containment).
Response
EPG Step PC/P-6 has been revised in Amendment 33 to allow containment spray only if containment water level is below 27.2 meters.
Item 2 is under preparation and scheduled for completion by January 28,1994.
Please provide a copy of this transmittal to Mark Reinhart.
Sincerely, p-c Jack Fox Advanced Reactor Programs ec:
Joe Quirk GE)
Alan Beard GE)
Norman Fletcher DOE)
Cal Tang.
GE)
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m
._m 23A6100 Rev. 3 ABWR stu, d:rds&tyAn:IysisRip:rt Table 18B-1 Differences Between BWROG EPG Revision 4 and ABWR EPG (Continued)
BWROG ABWR EPG Rev. 4 Differences from EPG Step Step BWROG Rev. 4 EPG Basis for Differences gg,. g Replaced phrase,
- In the ABWR containment, vents are a
" elevation of provided connecting the upper drywell to
.t (to d=<h bottom of internal the lower drywell. When the wetwell-to-suppression drywell vacuum breakers open, flow is chamber to drywell from the wetwell to the lower drywell and vacuum breakers then from the lower drywell to the upper less vacuum drywell through these vents.The vacuum breaker opening breakers are located above the vents. __
pressure in feet of
-Wate. con Oke rp!" : th; ls';;er dr,;;;"}
water", with the from the suppression poolif poollevel phrase, " elevation reaches the vents. Water can also flow
_4 of the bottom of -
from the lower drywell to the suppression pool-i suppression poolif lower drywellis
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to-lower-drywell (flooded to the elevation of these ventsu vent".
Fe'"'ere re:::n,'it is appropriate to#
4'g gp spray the drywell only when suppression pool water level is below the bottom of
'pper dr,;;;ii40-lower-drywell vents {4 d' Wg fuffI to preclude drywell differential pressure v-capability to be exceeded.
a Deleted phrase The ABWR has internal recirculation U
" recirculation pumps, driven by motors located below (f pumps" from the RPV in the lower portion of the ti a
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instruction to '
drywell. Drywell spray only sprays the Mi (
shutoff upper portion of the drywell. An explicit Q)bb recirculation instruction to shut down the recirculation
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pumps and drywell pumps is not required.
cooling fans prior to
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containment spray initiation.
Specify RHR pumps RHR subsystems B and C provide used for simultaneous drywell and suppression i
containment spray pool spray capability, initiation of as "RHR containment sprays is by manual control subsystems B and action. ;t is possible to initiate spray when C".
RHR B or C is operating in other modes by opening spray valves, 4
Differences Between BWROG EPG Revision 4 and ABWR EPG - Amendment 33 188 11
.A
23A6100 Rev. 3
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ABWR Standard S:fityAn: lysis R:p:rt l
piping from the suppression pool must be available for long-term usage following a design basis LOCA, and, as such, is designed to the quality standards commensumte with its importance to safety. The RHR discharge line fill system suction lines have manual valves for operational purposes. These systems are isolated from the containment by the respective RHR pump suction valves from the suppression pool.
G.2.4.3.2.2.2.2 SPCU Suction Line The SPCU System suction line has two isolation valves. However, because the penetration is under water, both isolation valves are located outside the containment.
The first valve is located as close as possible to the containment, and the second is l
located to provide adequate separation from the first.
6.2.4.3.2.2.2.3 ACS Lines to Containment 550A 7
The Atmospheric Control System (ACS) has both influent and efIluent 1ines which 3
penetrate the containment. Both isolation valves on these lines are outside of the containment vessel to provide accessibility to the valves. The valves are located as close l
as practical to the containment vessel. Tl e piping from the containment to and including both valves is an extension of the primay containment bounday and is designed in accordance with the ASME Boiler and Pressure Vessel Code,Section III, Class 2 requirements. The arrangement of the isolation valves and connecting piping is such that a single active failure of an inboard valve, or a single active or passive failure in the connecting piping or an outboard valve, cannot prevent isolation of the ACS containment penetradons. The ACS containment isolation valve closure time is s 20 seconds. These valves close on the following signals: high drywell pressure, RPV low water level 3, and high radioactivity in the purge and vent exhaust line. The SRP 6.2.4 states that the 5-second closure speed is necessay to assure that the purge and vent valves would have closed before the onset of fuel failures following a LOCA. The ACS purge and vent valves are normally closed during plant operation and are allowed to open only during the inerting (startup) and de-inerting (shutdown) process where the reactor is at less than 15% power. The likelihood of LOCA during inerting/de-inerting is very low. If a LOCA does occur, these valves will have closed before the onset of fuel failure. Note that the onset of fuel failure is when the core is uncovered and that reactor water level 3 (when ACS valves isolates) is 3.8m above the core. In the event of a radioactivityleak during inerting/ de-inerting, the radiation detectors at the purge and vent exhaust line will detect the condition and isolate the ACS containment isolation valves. Note that the exhaust radiation detectors are verysensitive and are set at a lower setpoint compared to the ones inside containment to have an effective early detection.
For the ACS, a more reliable isolation valve is necessag to ensure containment integrity.
A fast closing valve is less reliable than valves with moderate speed. The difference between 5 and 20 seconds is considered to be insignificant. Thus, the risk isjudged to be sufficiently small and that the 2(Fsecond closure time, is deemed sufficient and reliable.
\\t4SEN N Contain, ment Systems - Amendment 33 6.2-67 e
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INSERT A 1
The ACS also has two 50A makeup line isolation valves which are normally open during normal reactor operation to provide nitrogen makeup into the ' containment, if these isolation valves are placed in the normally. closed position, nitrogen makeup will not be possible without opening.
In either position, these valves need -to open to provide nitrogen makeup.
The normally open position provides automatic nitrogen makeup without frequent - cycling that could cause damage to the valves.
In the event of a LOCA or an. event requiring primary containment isolation, these valves automatically close upon receipt of the following signals: high drywell pressure, low water level, high radioactivity in the purge and vent exhaust' line.
These.
valves are redundant and meet ESF requirements as described above for the 550A influent and effluent lines.
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