ML20002D248
| ML20002D248 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/05/1981 |
| From: | Gilberts D NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-80-24, NUDOCS 8101200145 | |
| Download: ML20002D248 (8) | |
Text
Northern States Power Company 9-G J
414 &coliet Mall D.E.Gilberfs Minneapolis, Minnesota 55401 Senior vice President Telephone (612) 330-6071 Power Suppip" 5
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Mr. James G. Keppler Director, Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137
Dear :
- r. Keppler:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-292 and 50-306 In response to IE Bulletin No. 80-24, the following is offered. The response is numbered to correspond to Bulletin numbering.
1.a.
Cooling water use within containment is limited to the Fan Coil Units and the Control Rod Drive mechanism shroud cooling coils.
Four fan coil units and two CRDM Fans for each generating unit provide the necessary heat removal for normal operation.
During accident condi-tions the cooling water is isolated to the CR)M Fans a M flows only to the FCU's.
The redundancy requirement for this safeguards equip-ment is met in that there are two trains of cooling water for each containment vessel.
The design flow through the fan coil units during norel operation is 450 gpm.
The inlet and outlet flows are monitored in the control room for each fan coil unit, with an alarm for low flow.
Inlet and outlet flows for the CRDM shroud cooling coils are monitored in conjunction with the #13 and #14 (#23 and #24 for unit 2) FCU cooling water flow because the supply and return lines for each CRDM cooling coil ties into the respective FCU header.
For compliance with Technical Specification 4.1, the aforementioned equipment is checked monthly in the Post-Accident Monitoring Instruments Monthly Check, SP 1045 and SP 2045 for Units 1 and 2, respectively. The acceptance criterion for the flow indicators is such that the inlet and outlet flows of each fan coil unit. are to be within 150 gpm of each othe..
If inlet and outlet flows are found to differ by more than 150 gpm, steps are taken to determine the discrepancy. The necessary steps taken are:
- 1) Each containment S ump A pump (two per containment) elapsed time indicator is checked to determine if there has been an increase in pumping time.
2)
Containment humidity indication is checked to determine if there has been an increase in containment humidity.
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Mr. James G. Keppler Page 2 January 5,1981
- 3) The fan coil unit condensate flow instrumentation is checked for an increase in flow rate, and
- 4) Fan coil unit outlet pressure indicators are compared with each other to determine any inconsistencies. After these actions are taken, calibration is mandated and performed as necessary.
Conteinment fan coil condensate collection tanks exist for each of the fan coil units. The collection tanks measure the flow rate of con-densate and leakage (if any) from the containment fan coil cooling coils. Any flow present will flow into the inlet chamber of the tank and spill through the "V" notch in the partition into the outlet chamber.
Because of the restriction of the weir notch the water level in the inlet chamber will rise above the bottom of the notch and stabilize at some level dependent upon the flow-rate of the leakage. Therefore, the water level is utilized as a measure of the flow-rate.
Each weir tank is capable of measuring flow up to 30 gpm.
An alarm in the control room will annunciate when the flow exceeds b gpm (18 percent level in-dication). Operating procedure C19.3 Leakage Within Containment des-cribes how to verify proper operation of the containment fan coil unit collection tanks. In addition to this procedure, the collection tank level indicators are recalibrated at each refueling outage. The fan coil unit condensate collection tank levels are normally logged every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to insure that the level is known.
Leaks within the CRDM shroud cooling coil will leak to the refueling cavity and in time to containment Sump B through the refueling cavity drain.
Containment Sump B has two high level alarms for detection of leaks.
Sump B overflows into containment Sump A and is then pumped out of containment. Due to TMI Lessons Learned, additional level in-dication is being added to Sump B.
From this it is determined that this kind of leak cannot go undetected.
In addition to the aforementioned operating rode, there is presently under construction a closed chilled water system for the containment vessels and the auxiliary building. The system is designed for normal operation and will not operate during accident situations. The plant will have the capability of monitoring a fixed volume, detecting leaka e c
~3v an inventory decrease.
the cooling water system response (in containment) to a LOCA is essen-tially the same as in normal operations. The major difference is that the flow through each fan coil unit is increased to approximately 900 gpm by the automatic opening of the valves on the discharge of the fan l
coil units in the header for each train of cooling water.
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Radiation monitors R-16 and R-38 monitor the containment fan coil cooling water following a loss of coolant accident for radiation indicative of a leak from the containment atmosphere into the cooling water system.
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Mr. James G. Keppler Page 3 January 5,1981 R-16 monitors #12, #14, #22, and #24 fan coil unit flow while R-38 monitors #11, #13, #23, and #21 fan coil unit flow. Upon indication of high radiation level, the affected fan coil units may be individually taken out of service to determine which unit is leaking. Solenoid valves located in the sampling lines to monitors R-16 and R-38 are normally closed.
Solenoid valves for the affected unit open automati-cally or a safety injection signal, allowing cooling water samples to pass through the monitor and discharge to the Auxiliary Building stand-pipe.
1.b.
The source of water for the cooling water system is the Mississippi River Water. A typical chemical content analysis of the water is shown below.
Analysis in ppm Solids Total 320 Dissolved 300 Suspended 20 Hardness Total, CACO 3 204 Calcium, CACO 3 136 Magnesium, CACO 3 68 Alkalinity Total, CACO 3 155 Phenolphthalein, CACO 3 0
Cases Free Carbon Dioxide, CO2 N/A Dissolved Oxygen, 02 12.8 Ammonia Nitrogen, N 0.61 Anions Carbonate, C03 0
Bicarbonate, HCO3 189 Hydroxide, OH N/A Chloride, Cl 15 Fluoride, F N/A Nitrate Nitrogen, N 1.10 Sulfate, SO4 60 Total Soluble Phosphorus, P 0.112 Orthophosphate, PO4 N/A N/A Polyphosphate, PO4 Silica, SiO2 14.0 Cations Calcium, Ca 54.5 Magnesium, Mg 16.5 Sodium, Na 12.5 Potassium, K 3.5 Total Iron, Fe
.43 Total Manganese, Mn N/A Miscellaneous Color, APHA Units 60 Biochemical Oxygen Demand, BOD 1.1 Temperature, C 0.0 Turbidity, NTU 2.6 Ryznar Index @ 25 C 7.0 Conductivity, umhos/cm @ 25 C 444 pH 8.0
Mr. James C. Keppler Page 4 January 5, 1981 1.c.
The cooling water system component materials are as follows:
- 1) Fan Coil Units:
Tubes: Copper ASTM B-280 Fins: Copper ASTM B-152 Coil Header: ASTM A53 schedule 40 Tube to Header Bond:
High Temperature Braze Fin to Tube Bond: Mechanical Expansion
- 2) Piping:
2" nominal and smaller: ASTM A-106 Grade B Schedule 80 2 " nominal to 10" nominal: ASTM A-106 Grade B Schedule 40 12" to 24" nominal: ASIM A-106 Grade B Standard 3/8" wall All pipe is seamless 3)
Fit cir.gs :
2" nominal and smaller: ASTM A-181 Grade 1 or A-105 Grade 2 2h" nominal and larger: ASTM A-234 Grade WPB
- 4) Valves:
2h" and larger: ASTM A-216 Grade WCB 2" and smaller: ASTM A-105 Grade 2 1.d.
There have been only two cases of leaks on the cooling water system within containment, both of which were small. The first instance was located during a routine containment entry in March, 1975.
The leak was detected on #12 Fan Coil Unit in a tube end plug fitting. The fitting leak was caused by overtightening of the end plug at the manufacturer's shop which in turn cracked the fitting. This was a very minor leak and the repair was performed during the April,1975 refueling outage.
The second cooling water leak was on #13 Fan Coil Unit Cooling Water Relief Valve CL-57-5, occurring in February, 1978. Again, this leak was found during a routine containment entry. Again, the leak was very minor, in that the valve leaked slightly by the seat. The repair was performed during the March,1978 refueling outage.
1.e.
These two leaks in the cooling water system were repaired as follows:
For the cracked fitting, the fan coil unit was isolated and the cracked fitting removed. A new fitting was brazed in place and the plug re-inserted to the proper depth. The fitting was then pressure tested and found satisfactory.
For the leaking relief valve, the valve was rebuilt and the valve seats lapped. The valve was then set to 150 psi and bench tested to this value. The pressure test results were satisfactory.
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Mr. James G.- Keppler Page 5 January 5, 1981 1.f.
It is possible to isolate cooling water to each fan coil unit indivi-dually. 1Nue supply to each fan coil unit has an isolation valve and a redundant isolation valve which would isolate that entire train of cooling water. The discharge lines of each fan coil unit contain re-dundant isolation capabilities.
1.g.
Cooling water penetration for Unit 1 and Unit 2 meet the requirements of 10CFR50 Appendix J for testing containment isolation valves. However, it is not common practice to test these valves because:
- 1) The system is'normally filled with water and operates under post-accident conditions, and
- 2) The Technical Specification designations for these penetrations are " sealed"; that is, the pipes are sealed by water in the space between the isolation barriers.
1.h.
The instrumentation to detect leakage consists of the following:
- 1) Containment fan coil unit flow in (1 for each FCU)
- 2) Containment fan coil unit flow out (1 for each FCU)
- 3) Containment fan coil unit low flow alarm (100 gpm) (1 for each FCU)
- 4) Containment humidity indicator (1 for each unit)
- 5) Containment fan coil unit pressure out (1 for each FCU) 6)
Containment fan coil unit temperature out (1 for each FCU)
- 7) Containment Sump A pump run time (1 for each pump)
- 8) Containment fan coil unit condensate collection tank level alarm (18 percent level - h gpm leakage) 9)
Containment activity monitors
- 10) Cooling water activity after an accident R-16 and R-38, and
- 11) Waste holdup tank level to account for water.
r Procedures for detecting leakage are part of the Post Accident Monitoring Instrument Monthly Check, the operating procedure C19.3, and the Monthly Containment Fan Coil Unit Check. Logs are provided for daily checks and four times daily checks. These log entries are incorporated into the operator's routine operation schedule.
1.1.
As stated previously, radiation monitors R-16 and R-38 provide the necessary detection of contamination in the cooling water discharge from both contain-ment vessels. These two monitors function during accident conditions only.
It is felt that continuous monitoring of the containment cooling water i
discharge is not needed during normal operation because a leak in containment coinciding with high containment activity would be neces-sary for contamination of the water.- Also, the Prairie Island cooling water system would need leaks in two heat exchangers at the same time to allow for contamination to enter the system. This is considered a nonplausible event without detection by another means.
Mr. James G. Keppler Page 6 January 5, 1981 2.a.
Of the three sumps in containment, all are equipped with level alar,s.
Sump A has a level alarm which annunciates in the control room. Sump B has two redundant level alarms which are powered by separate electrical power supplies. Each level alarm has two status lights each for hi-hi and lo-lo level of Sump B in the control room. The train B level alarm of Sump B will alarm in the control room. Sump C, which is below the thimble chase area (reactor vessel pit), is equipped with a level alarm that will alarm in the control room.
2.b.
Presently Sump A is the only sump to be pumped out of containment.
Sump C pumps its contents to Sump A.
Sump B is where the RHR pumps take suction for long-term recirculation following a LOCA.
There are no flow indica-ting elements located on Sump A's lines out of containment, but there are timers on the Sump A pump breakers. The timer readings are logged daily by plant operators. This gives a good indication of the amount of water coming out of containment, since when the pumps run, they run at full capacity and when multiplied by the running time of the pump give the daily flow from containment.
Containment Sump A pumps into the waste holdup tank which has a level recorder. The operators monitor the waste holdup tank recorder frequently for unusual level changes.
2.c.
Water level indication instruments are not used in any of the sumps; only level alarms are used. Sumps A and C have only one level alarm each.
Plans are in motion to add a second level alarm to both sumps. The final design would be for Sump A and B to each have two level switches connected to one annunciator in the control room. Sumps A and B are each equipped with two pumps while Sump C has a single pump.
(Note:
the two RHR pumps can take suction from Sump B and in this case are counted as " Sump B's pumps".) It is not intended at this time to put another pump in Sump C.
In the event the Sump C pump fails to run, a portable pump can be in-serted into the thimble chase area from above.
The monthly surveillance procedures will consist of testing contaminated sump pumps and Sump C by use of local test buttons or moving the level alarms and switches and seeing that their individual contact functions perform as they should (i.e., that lifting a level switch will start a pump and that moving a level alarm will set off an annunciator in the control room).
NOTE: The local test push button for the Sump C pump is located in an area that is not accessible to plant personnel while the unit is at power. A local test button will have to be moved to allow personnel access. A test design for the alarm will be developed and installed in upcoming refueling outages.
In the interim, the routine containment inspection will verify no water on the Sump C floor.
2.d.
The monitoring of containment for water leakage during plant operation is as follows:
The Sump A pumps each have their own separate running tLner. The readings from the timer are logged daily by plant operators. This gives an indi-l cation of the amount of water pumped out of containment, since when the j
pumps run, they run at full capacity.
I
o Mr. James G. Keppler Page 7 January 5,1981 Monthly a containment entry is normally made into each unit for in-spection and routine maintenance. Among the things checked are:
fan coil units for Icakage, fan coil relief valves, local verification of sump operation. The thimble chase area (Sump C) will be checked for water on future entries.
During refueling outages, Sumps A, B, and C's level switches are tested and calibrated using SP 1030.
The fan coil collection, which measure condensate and leakage flow from the fan coil cooling coils, have an annunciator in the control room which will alarm when the flow to the pots exceeds gpm, The pot levels are normally recorded every four hours.
The containment atmosphere is monitored by radiation monitors R11/12, R-2, and R-7.
If a leak from a radioactive system occurs, an increase in readings in the above monitors will be observed and appropriate measures will be initiated to find the Icak. The humidity in containment is measured by various instruments that will pick up an increase in humidity which would be caused by a water leak in containment.
Underneath the reactor in the incore seal area a leakage detection system is provided to detect leakage into the ten-path transfer units. Ten-path transfer units drain to a drain header.
On high pressure in the drain header a switch actuates an alarm in the control room and also opens a solenoid valve so the liquid can drain to Sump C.
2.e.
Periodic containment inspections at power have been done since plant startup.
2.f.
Procedures for notification of NRC of cooling water system leaks within containment are in place.
The closed cooling water system inside containment which is now under construc-tion shares the cooling water piping in containment. Therefore, leakage exper-ience is as described in paragraph 1.d.
About 120 manhours were expended in review and preparation of the response.
Another 500 manhours will be required for implementation of corrective action.
Yours truly, D. E. Gilberts Senior Vice President Power Supply cc:
Mr. G. Charnoff Mr. C. D. Feierabend
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Director, U. S. Nucicar Regulatory Commission J0ffice of Inspection and Enforcement Washington, D. C.
20555 Enclosure DEC:nk
O UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 and 50-306 LETTER DATED JANUARY 5, 1981 RESPONDING TO NRC REQUEST FOR INFORMATION IN IE BULLETIN NO. 80-24 Northern States Power Company, a Minnesota corporation, by this letter dated January 5,1981, hereby submits information in response to NRC request for information concerning IE Bulletin No. 80-24.
This request contains no restricted or other defense information.
NORTHERN STATES POWER COMPANY By:
D. E. Gilberts Senior Vice President Power Supply On this day of 612M4
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, before me a notary public in and for said Coun't'y, personally appeared D. E. Gilberts, Senior Vice President Power Supply, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information and belief, the statements made in it are true and that it is not interposed for delay.
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