ML20041B120
| ML20041B120 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/19/1982 |
| From: | Sargent C COMMONWEALTH EDISON CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.28, TASK-TM NUDOCS 8202230290 | |
| Download: ML20041B120 (4) | |
Text
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' Commonwealth Edison
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__ l Addr:ss R ply to: Post Offica Box 767 one First National Pirza. Chicrgo. Illinois Chicago. Illinois 60690 February 1 glj@di
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- ,.,j,f 22 /ggg Mr. A. Schwencer, Chief 1
Licensing Branch #2
' i f"arex,N Division of Licensing
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U. S. Nuclear Regulatory Commission A
Washington, DC 20555 N,i,
MD.
Subject:
LaSalle County Station Units 1 and 2 Response to Questions on AOS Valves NUREG 0737 Item II.K.3.28 NRC Docke t Nos. 50-373 and 50-374 Reference (a):
R.
L. Tedesco letter to L. De1 George dated January 27, 1982.
Dear Mr. Schwencer:
The purpose of this letter is to provide a response to your questions concerning ADS Valves as requested in Reference (a).
Accordingly, the attached enclosure lists the questions and Commonwealth Edison Company's response.
If there are any further questions, please contact this office.
Very truly yours, W
C. E. Sargent Nuclear Licensing Administrator Enclosure l
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CES/Im J
cc:
NRC Resident Inspector - LSCS 3487N Yo$h0{
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ENCLOSURE 212 Reactor Systems Branch 212.148 It is our position that the availability and functional capability of all equipment essential to safety must be demonstrated by periodic testing.
For the automatic depressurization system (see TMI Item II.K.3.28), one essential component is the compressed air supply to the ADS valves.
The reliable air supply at La Salle consists of air accumulators backup by a bottled air system which may be valved in from outside primary containment. Our concern is that leakage through the accumulator check valves may disable the ADS before action is taken to provide the backup air supply. Since the time when the ADS would be needed during or after an accident is dependent upon a variety of scenario-specific unknowns such as equipment availability, operator actions, break size, etc., it is unacceptable to us to allow the ADS to be unavailable anytime the reactor is pressurized.
You should therefore provide the followirig information:
(1) The minimum accumulator pressure needed for 5 valve actuations y
against atmospheric pressure and 2 acutuations against 70 percent of drywell design pressure.
/ (2) A description of the action needed to introduce sufficient air The time pressure for ADS actuation using the backup system.
and manpower required to accomplish this should also be provided.
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2-(3) A summary of the plant procedures which instruct the operator to transfer to the backup air system. Also include a discussion of the control room indications and alarms (including setpoints) which are available to alert the operator to the need for action.
Explain how the operator would know that accumulator pressure had decayed to the minimum level where 1 ADS actuation against 70 percent of drywell design pressure was still possible.
(4) A periodic test plan to be included in plant Technica Specifications to verify that each accumulator, (or the ADS air system as a whole), will maintain the minimum pressure discussed in (1) above for the time period to be provided in (2) above plus a margin of 30 minutes.
Loss of normal charging air must be assumed and the timing should begin when the accumulator or system pressure is at,the control room alarm setpoint.
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RESPONSE
A bottled gas backup system comes on line automatically when the accumulators in either ADS valve group f all below 160 psig; each ADS group has its own dedicated bottle backup system.
It does not have to be valved in as' stated in the question.
In addition, at LaSalle each ADS gas supply line incorporates an emergency pressurization station f or long-term (greater than 1 week) ADS gas requirements.
See revised FSAR Section 9.3.1.2.2 for further details.
Following is the specific information reouested:
1.
The minimum accumulator pressure needed for 5 valve actuations against atmospheric pressure and 2 actuations against 70 percent of drywell design pressure is 150 psig.
2.
The primary backup systems (bottle banks) are continually on the line and provide gas to the accumulators automatically when the accumulator pressure drops below 160 psig.
This provides approximately 1 week s ADS gas requirements.
No time or manpower is required to accomplish this.
The secondary backup system consists of an emergency pressurization station in the auxiliary building.
It takes an operator approximately 10 minutes to provide and connect a nitrogen bottle at this location.
3.
The in-place nitrogen bottle bank gives a low pressure alarm at 500 psig tank pressure, even though the bottle bank continues supplying gas to the a cumulators at pressure much below this.
This 500 psig pressure alarm gives the operator plenty of time to hook up the emergency pressurization station bottle.
( At I week into the accident the ADS valve air requirements are very low).
4.
Because the primary backup systems have at least a 1-week gas supply, and are continually on the line and monitored by the nitrogen bottle-bank low pressure alarms, the loss of normal charging gas is not significant.
In addition, due to the large volume of gas in the bottle bank systems that are alw ays on line, a Technical Specification requiring holding pressure for 40 minutes (10 minutes + 30 minute margin) would be useless.
Any leakage that could reduce the bottle pressure low enough to cause the ADS accumulators to alarm on low pressure (at 151 psig) would also cause the bottle bank to bleed down very fast and reouire constant replacement at the emergency pressurization station in the auxiliary building.
Therefore, a problem of this nature cannot go undetected and no technical specification is reouired to monitor such a condition.
GRC/bmb/1216L*
2-18-82 J