ML20206P410
| ML20206P410 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/26/1986 |
| From: | Warembourg D PUBLIC SERVICE CO. OF COLORADO |
| To: | Berkow H Office of Nuclear Reactor Regulation |
| References | |
| TAC-61894, NUDOCS 8607020118 | |
| Download: ML20206P410 (6) | |
Text
hPublic Service-
.,r Company of Colorado June 26, 1986 Fort St. Vrain Unit No. 1 P-86438 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Mr. H.N. Berkow, Director Standardization and Special Projects Directorate Docket No. 50-267
SUBJECT:
Role of Operators in Mitigating High Energy Line Breaks at Fort St. Vrain
REFERENCES:
- 1) NRC Letter Heitner to Walker, dated April 6, 1986 (G-86181)
- 2) PSC Letter Walker to Heitner, dated May 6, 1986 (P-86351)
- 3) PSC Letter Walker to Berkow, dated March 14, 1986 (P-86208)
Dear Mr. Berkow:
As a result of a meeting with your staff on February 22, 1986 to discuss the Fort St. Vrain (FSV) equipment qualification (EQ) program, the staff requested (Reference 1) that PSC provide responses to three questions relating to required operator manual actions a high energy line break (HELB).
PSC provided an interim following(Reference 2) with the final responses response to these questions presented herein.
The responses are based on the following assumptions:
- 1) no credit is taken for equipment located in 6 harsh environment that is not environmentally qualified and 2) a worst case single active failure is postulated.
This is in accordance with the equipment qualification guidelines of NUREG 0800.
Further for this letter,
" operator action" is defined as a, positive a:: tion to be taken by an operator (i.e., closing a valve), outside the Control Room.
8607020118 860626 DR ADOCK 0500 7
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P-86438 June 26, 1986 The operator actions described in the responses are based on the preliminary results of an ongoing analysis to verify the current cool down flow paths and procedures.
If the final results of this evaluation impacts PSC responses submitted herein, revised responses will be forwarded to the NRC as appropriate.
1.
NRC Question No. 1 List and briefly describe local manual actions that would be taken by the operators following a HELB accident or equivalent primary coolant leak.
PSC Response The Equipment Qualification Program flow path for the resumption of forced cooling following a HELB involves the use of firewater to drive one circulator and provide cooling water to the economizer, evaporator, superheater (EES) section of one steam generator (refer to attached Figure 1). Upon incorporation of the system modifications being installed during the current outage at FSV, several local manual actions will be required by the operators following a HELB:
Alignment of the firewater system to the emergency condensate system is required to provide a firewater flow path to the steam generator and circulator pelton wheel.
Two manual valves (HV-4518, HV-4519) must be opened to align the flow path, and two manual valves (HV-4520, V-45201) must be closed to isolate portions of the firewater system not required for safe shutdown to preclude firewater from being directed to any sprinklers activated by the elevated ambient temparatures.
These four valves are located outside the harsh environment.
The discharge valve (HV-5252) in the flow path for firewater cooling must be manually opened.
Al though this valve is located in the Turbine Building Access Bay (a potential high temperature environment), the valve handwheel is located outside the Turbine Building coupled to the valve by a long reach-rod.
l Local manual action would be required for certain pipe break locations in combination with specific single active i
j failures.
The valves are environmentally qualified and therefore should be operable from the control room.
However, if one did fail, the following actions would be i
performed.
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s P-86438 June 26, 1986 Break Location Single Active Failure Manual Action Feedwater or Main HV-2237 Note 1 Steam Loop 1 or Piping FV-2205 Note 2 Feedwater or Main HV-2238 Note 1 Steam Loop 2 or Piping FV-2206 Note 2 Note 1 Local operator manual action would consist of turning a handwheel to manually override the valve.
Note 2 Local operator manual action would consist of opening two small valves to admit hydraulic fluid to the valve actuator from a local accumulator. A modification to install this manual override is being installed this outage under CN-2012.
Following a primary coolant leak (i.e., Design Basis Accident No. 2, Rapid Depressurization/ Blowdown),
primary coolant circulation and secondary coolant heat removal could be interrupted by actuation of SLRDIS. Although there are a few actions which the operator would perform from the Control Room to further ensure or improve the safe shutdown of the plant, there are no immediate or necessary actions outside the Control Room which are required of him.
2.
NRC Question No. 2 Provide an evaluation of the ability of the operators to perform these actions in potentially high temperature environments. This evaluation should address the same factors covered in approving FSV operation at 35 percent power.
(Please see our letter dated February 7, 1986, Enclosure 5, Confirmatory Action 12.)
PSC Response There is only one manual action that may be required to be performed by the operator in the harsh environment.
That is, opening the emergency condensate isolation valve (HV-2237 or HV-2238) or feedwater inlet valve (FV-2205 or FV-2206). See the discussion under Question No. 1.
These valves are easily accessible for both loops. These valves would be in the harsh environment only for a Turbine Building break and local manual operation of these valves would be required only if the valve actuator were the single active failure.
However, as these actuators are qualified, there is only a very low probability that one of these valves would not function by remote operation from the Control Room after the EQ event. The approximate time that this action would be required would be 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> following break detection or interruption of forced circulation.
The composite EQ Program temperature profile shows that temperatures would be 135 degrees Fahrenheit or less.
As described in Reference 3, access with or without cool suits would be possible.
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I P-86438~ June 26, 1986 All other manual actions identified in our response No. I do not
. require access to the harsh environment, including the access routes from the Control Room to the action locations.
3.
NRC Question No. 3 If future modifications to the plant are contemplated that effect this issue, please describe these modifications and your proposed schedule for their completion.
PSC Response During the current outage at FSV, several system modifications are being implemented to reduce.the operator access requirements in areas of high temperature environment following a HELB, and to facilitate the initiation of safe shutdown cooling.
These modifications include:
Local hydraulic oil accumulator and manual valve lineup to manually override FV-2205 and FV-2206 (CN-2012).
This modification is scheduled during the associated loop shutdowns this outage.
New flow path to line up the firewater pumps to the emergency condensate system (CN-2270). This modification is l
scheduled during the two loop portion of this outage which is near the end of the outage.
New check valve to limit firewater flow path boundary (CN-2271). This modification is scheduled during the two loop portion of this outage.
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New circulator pelton wheel vent path (CN-2297). This l
modification is scheduled during the two loop portion of this outage.
New atmospheric vent off the bypass flash tank for firewater flow path discharge during cooling using an EES section (CN-2284). This modification is not loop associated and has j
been scheduled during the middle of this outage.
In order to further reduce the number of local manual actions to j
be performed by the operators to initiate safe shutdown cooling, actuators are being installed on the manual valves installed by i
CN-2270 and CN-2284 to allow operability of these valves from the Control Room.
Only local manual actuation capability will be i
installed during the current outage and the valves will be capable of remote actuation in the future.
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P-86438 June 26, 1986 If you have any questions on this subject please contact Mr. M. H. Holmes at (303) 480-6960.
Very truly yours,
- su D.W.Warembou7g, Manager Nuclear Engineering Division RFW/KD:pa i
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