ML20205C580
| ML20205C580 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 07/30/1986 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1919K, NUDOCS 8608120377 | |
| Download: ML20205C580 (5) | |
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CONHINNueelth Esileen A. :. One First Nabonal Plaza, Chea00, minois (v
Address Reply 12: Post Omco Box 767 Chicago, minois 60600 0767 July 30, 1986 3
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Mr. Harold R. Denton, Director j
office of Nuclear Reactor Regulation i
U.S. Nuclear Regulatory Comunission I
Washington, DC 20555 i
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Subject:
LaSalle County Station Unit 2
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Facility Operating License NPF-18 Condition No. 4 of Attachment 2 Procedure Generation Package NRC Docket No. 50-374 References (a): License NPF-lG, Attachment 2, Condition 2 No. 4.
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(b): June 28, 1985 letter from H. L. Massin to
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H. R. Denton transmitting revised LGA Procedure Generation Package.
(c): August 20, 1985 letter from H. L. Massin i
to H. R. Denton.
(d): October 18, 1985 letter from W. Butler to 1
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D. L. Farrar transmitting SER.
(e): November 8, 1985 letter from H. L. Massin i
to H. R. Denton transmitting response to
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SER and Schedule for Completion of j
Remaining Concerns.
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Dear Mr. Denton:
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This submittal completes the response to the Unit 2 License 1
Condition to upgrade the Emergency Operating Procedures to BWROG Revision 3
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(Reference (a)). A partial response along with a schedule for completion of i
SER open items (Reference (d)) was given in Reference (e). References (b) and (c) are included for information only, l
j The remaining open items in the referenced SER (Reference (a)) were
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reviewed to address concerns of venting depressurization rates, vent valve t
operability and environmental effects in the area of potential vent path i
failure. The results of that investigation are summarized in the Attachment.
The items addressed are identified by the numbers in the SER.
8608120377 860730
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PDR ADOCK 05000374 ll (
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i PDR I
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Mr. H. R. Denton July 30, 1986 Based on the results of this study, we feel that our procedures, as they are presently written, will:
1.
Not result in adverse effects in the containment because of flashing and hydrodynamic loads.
2.
Allow Primary Containment integrity to be re-established following venting as Primary Containment isolation valves will remain operable.
3.
Not cause failure of equipment in the Reactor Building in areas of potential vent duct failure as this equipment has sufficient environmental qualifications to be reasonably assured of remaining operable in the expected environment.
Please direct any questions you may have concerning this matter to this office.
One signed original and fifteen copies of this letter are provided for your use.
Very truly yours, O 'k a M C. M. Allen Nuclear Licensing Administrator 1m Attachment cc: Region III Inspector - LSCS A. Bournia - NRR 1919K
f ATTAOSENT A.4.b Consideration of depressurization rate during venting to limit suppression pool flashing and hydrodynamic loads.
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During depressurization, the maximum steam production rate in the suppression pool was determined in the ongoing Plant Reliability Analysis to be 7000 lba/sec. This rate reflects the combined i
effects of decay heat and the depressurization on the suppression pool. An equivalent upward steam velocity for this steam production j
rate is 8.0 ft/sec. This is relatively minor compared to the LOCA
.i pool swell velocity. Also any impact or drag loads would be significantly less than LOCA swell loads because the density ratio between water and steam is large.
A.4.c Best estimate basis for the purge valve operability limit.
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The two type valves of concern are a 2" Motor Operated Anderson-Greenwood globe valve (purge valve bypass) and a 26" Clow i
Butterfly valve (Purge Valves).
i The 2" Motor Operated Valves have been used as a path for Primary containment D3 pressurization following the integrated leak rate tests (ILRT) at approximately 40 psig and no valve operability problems have been noted. Also this same type valve is used in numerous other applications with system pressures greater than 60 psig. Based on this alone, we feel that these valves will remain l
fully operable up to containment pressures of at least 60 psig.
During the last Unit 1 ILRT (June 1986) the 26" Air Operated Clow i
Butterfly valve was also used when primary Containment pressure was approximately 36 psig. Because we desired to control the depressurization rate, a special regulator was used to limit the pressure to the valve operator in order to throttle the valve to control the depressurization rate.
It was noted during the
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depressurization that it took a very small percentage of the normal operating pressure to cause the valve to move off of its seat.
l Also, the Clow Corporation Report No. 7-25-85 entitled " Purge and Vent Valve Operability Qualification Analysis" which was referenced l
in the safety Evaluation Report for Amendment 37 to facility operating License No. NpF-11 supports operability at the Design pressure of 45 psig with a minimum actuator torque margin over that required to overcome worst case aerodynamic torque being better than 3.06.
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ls Because the Fisher Butterfly Valves in Unit 2 will be replaced by I
the Clow Butterfly Valves during the First Refuel Outage scheduled
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for late 1986, they were not analyzed.
Based on the above, we feel that the valves selected as the Primary j
Containment Vent Path will remain fully operable for cycling at the j
60 psig Primary Containment Emergency Venting Pressure.
A.4.d
. Effects of containment venting on ductwork failure (if used as a pathway), and the consequence of subjecting equipment near the failed duct to the steam / radiation environment.
The path downstream of the venting valve interconnects the Reactor Building air return, Primary Containment Purge filter train, Standby Gas Treatment System (SGTS), and the Reactor Building Ventilation System. With the exception of the path to SGTS, the flow paths may be isolated by motor operated valves or check valves experiencing a reverse flow condition. The path to SGTS may be isolated upstream of the SGTS filter train but the crosstie between Units 1 and 2 i
cannot be isolated from a source in either Unit 1 or Unit 2.
The flow path from the containment to SGTS is 26-inch pipe that transitions to ducting then transitions back to pipe in the fuel pool heat exchanger room on el. 807'-0".
During venting, the pressures in the vent pipe at this point are expected to be higher a
than the ducting can withstand (approximately 50 psi). A simplistic model of the two units has been constructed to evaluate the flow i
from the vent valve, the rupture of the ducting and the.tsulting i
environmental conditions in the reactor buildings.
(NOTE: Because i
the cross-tie on the SGTS inlets cannot be isolated, the effect of venting will be experienced in both unit 1 and Unit 2.
The effect will be the strongest in the unit being vented). With this model, enviornmental conditions in the plant have been estimated as follows:
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- 1) The primary containment is initialized in a degraded core condition, i.e. pressure is 60 psig and temperature is at saturation for the pressure.
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- 2) The energy addition rate to the containment is represented by
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the FSAR prescribed decay heat curve starting at 10 minutes after SCRAM.
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- 3) The Reactor Building areas are assumed to be at 100*F prior to opening the venting valve.
- 4) The 26-inch butterfly valve on Unit 1 is opened to commence the venting.
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- 5) Heat sinks in the Reactor Building are ignored.
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. The results of this evaluation are as follows:
1.
The pressure in the vent line exceeds the capability of the ducting in the fuel pool heat exchanger rooms area. The ducting ruptures and the steam mixture is released.
2.
The resulting flow into Unit 1 and Unit 2 Reactor Buildings will cause significant increase in the pressure, temperature and relative humidity in the areas adjacent to the release point. The fuel pool heat exchanger rooms will experience pressure temperatures and relative humidities as shown below:
Unit 1 Unit 2 pressure 2.2 psig 0.6 psig Temperature 280*F 270*F Relative Humidity 100%
100%
3.
From the fuel pool heat exchanger room the break effluent propagates to the adjacent areas at elevation 807'-0".
Tne maximum conditions experienced are:
Unit 1 Unit 2 Pressure 1.0 psig 0.6 psig Temperature 260*F 170*F Relative Humidity 60%
90%
These resulting environmental conditions will be short-livec and are within the bounds of the environmental quality of all required plant equipment subjected to these conditions.
1919K 1
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