ML20064C415
| ML20064C415 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/28/1982 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Clark R, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| TASK-2.K.3.25, TASK-TM TAC-48426, TAC-48427, NUDOCS 8301040395 | |
| Download: ML20064C415 (4) | |
Text
'
- c 2
+
e s
1 I%SCORSin Electnc rom comu
+
231 W. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201
\\
v December 28, 1982 s
's Mr.
H.
R.
Denton, Director Office of Nuclear Reactor Regulation N '-
- ' p,
U.
S. NUCLEAR REGULATORY COMMISSION Washington, D.
C.
20555 Attention:
Mr.
R.
A. Clark, Chief
~
Operating Reactors Branch 3 s
Gentlemen:
t DOCKET NOS. 50-266 AND 50-301 REQUEST FOR ADDITIONAL INFORMATION TMI ITEM II.K.3.25, POWER TO PUMP SEALS POINT BEACil NUCLEAR PLANT, UNITS 1 AND 2 In response to your request for additional information dated October 19, 1982, enclosed is our response to the Statf's position on TMI Item II.K.3.25, Power to Pump Seals, which 1
includes detailed information regarding the design and operation of the affected cooling systems.
Very truly yours, f
JJ;m Assistant Vice President C.
W.
Fay Enclosure Copy to NRC Resident Inspector 0
8301040395 821228 PDR ADOCK 05000266 p
~
RESPONSE TO REQUEST FOR APDITIONAL INFORMATION TMI ITEM II.K.3.25, POWER TO PUMP SEALS NRC Position 1:
- The, cooling water supply should be adequate to provide seal cooling and prevent seal failure T
for a period of two hours during a loss of off-site power event.
s
RESPONSE
s g
a This cooling water supply is available under two scenarios:
loss of AC power without an accident requiring safety injection (SI) and loss of AC power with an accident requiring SI.
The reactor coolant pump (RCP) is designed to accommodate the temporary loss of seal injection flow and component cooling water'{CCW)'that accompanies a loss of off-site power, including the normal time delays associated with reestablishing these RCP support systems on AC emergency power.
This temporary cooling is accomplished by the volume of cool water in the seal area for the duration of time this water leaks through the RCP seals prior to hot water entering the seals from the reactor s
coolant system.
The RCP is designed to accommodate the loss of support systems for one minute following loss of off-site power.
Under best estimate conditions, the RCP design should preclude hot water from entering the seal area for at least several minutes.
Loss of off-site AC power without SI. Upon loss of off-site AC power, two emergency diesel generators will automat!.cally start, come up to speed and voltage, and energize the safeguards buses A05, A06, B03, and B04 within ten seconds.
There is sufficient fuel oil on site to allow one diesel to operate continuously for more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
In response to a low-pressure signal, both CCW pumps will automatically start.
The CCW system alone has sufficient cooling capacity to provide adequate seal cooling.
In addition, service water is also available to cool the CCW.
The service water pumps are part of the engineered safety features equipment and three service water pumps will automatically start within 35 seconds of the start of the diesels.
In addition to the normal mode of seal cooling, the emergency diesels have sufficient capacity to allow manual start of a charging pump to provide cool seal water injection to the RCP seals.
Loss of off-site AC power with SI.
As described in the above case, the emergency diesels will start and three service water pumps will automatically start within 35 seconds.
However, because l
of the SI signal, the CCW pumps will not automatically start.
In l
the immediate action steps of Point Beach Nuclear Plant Emergency Operating Procedure 7A, Loss of Outside AC Power, a CCW pump is to be manually started, thus providing seal cooling.
The seal injection system is also available to provide seal cooling but without injection water leak-off because the RCP seal return lines must be closed for containment isolation purposes until the SI signal is reset.
i C \\
NRC Position 2:
RCP seals should be designed such that they are cooled by means of two independent supplies, e.g.
seal injection (charging pumps) and thermal barrier heat exchangers (Reactor Building Closed Cooling Water [RBCCW) System).
If plant design consists of only one cooling method, provide detailed design information to demonstrate that seal integrity is still maintained in the event of a loss-of-offsite power event for two hours.
RESPONSE
Under normal operating conditions, the RCP controlled leakage seal system is cooled by two independent and redundant cooling systems.
Adequate cooling for continued RCP operation can be provided by either high-pressure seal injection flow or low-pressure CCW flow circulated through the RCP thermal barrier.
A brief description of these two systems is given below.
Injection and seal leak-off system.
A high-pressure injection pump supplies injection water from the volume control tank (VCT) to the controlled leakage reactor coolant pump seal at a rate of approximately 8 gpm.
The seal injection water enters the area adjacent to the pump bearing assembly through a flanged connection in the therma 2 barrier with approximately 5 gpm flowing downward through the thermal barrier heat exchanger and into the reactor coolant system (RCS).
The remaining 3 gpm flows upward through and around the pump bearing, which is cooled and lubricated, and through the No. 1 seal.
The No. 1 seal reduces the pressure from approximately 2250 psia to the pressure of the VCT which is normally between 15-75 psig.
The No. 1 seal leakage of approximately 3 gpm flows out the flanged No. 1 leak-off line to the VCT.
A leak rate of approximately 3 gph flows through the No. 2 seal where the pressure is further reduced to approximately seven feet of water.
This leakage flows through the flanged No. 2 leak-off connection to the waste disposal drain tank.
A very small leakage (100 cc/ hour nominal) flows through the No. 3 seal and into the No. 3 seal reservoir, then to the containment sump.
Component cooling water system.
On the controlled leakage reactor coolant pump there are three heat exchangers which utilize CCW:
the thermal barrier, motor lower bearing, and motor upper bearing heat exchangers.
Only the thermal barrier heat exchanger is of interest for this response.
The thermal barrier is designed to reduce heat transfer from the 550 F primary coolant system to the 150 F bearing and seal environment and to cool the primary system water if seal injection flow is lost.
Low-pressure component cooling water enters the thermal barrier heat exchanger, flows downward through a vertical inlet header which feeds six parallel cooling coils, and then flows upward through the exit header.
. -. J
- NRC Position 3:
It is currently our position that automatic loading of the cooling water pumps onto the emergency buses is desirable and should be pursued.
The cooling water pumps should be automatically (requiring no operator action) started and sequentially loaded onto the diesel generators.
RESPONSE
As stated above, upon loss of off-site AC power, one CCW pump j
and three service water pumps are automatically loaded onto the emergency buses provided a SI signal is not present.
When a SI signal is present the CCW pumps must be manually started.
Although some field experience exists wherein both seal injection flow and thermal barrier CCW flow have been lost, it is of such limited nature that RCP seal behavior cannot be accurately predicted on the basis of only this field experience.
- However, general conclusions by the Westinghouse Owners Group (WOG) indicate that loss of seal cooling for up to ten minutes may be reasonably assumed without affecting RCP seal integrity.
Following the guidelines of the draft ANSI N660, " Proposed American National Standard Criteria for Safety-Related Operator Actions",
an evaluation of Point Beach Nuclear Plant's Emergency Operating Procedures was made to estimate the amount of time required to procedurally initiate seal cooling.
Emergency Operating Procedure (EOP)-1A, " Loss of Reactor Coolant", which is currently in use, calls ror starting the charging pumps in one of the first steps of the subsequent action section.
The operator response of starting the charging pumps is estimated to occur seven minutes after the initiation of the SI signal.
Wisconsin Electric is currently in the process of revising its procedures using the new format proposed by the WOG.
The estimated response time of an operator using the draft of the new EOP-0, "Reector Trip or Safety Injection",
is five and one-half minutes.
Both of these estimates are conservative.
Therefore, it is our belief that the combination of automatic actions, manual operations, and emergency procedures are adequate to assure the integrity of the RCP seals upon loss of off-site AC power.