IR 05000295/1986024
| ML20211P339 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 12/08/1986 |
| From: | Baer R, Cortland P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML20211P317 | List: |
| References | |
| 50-295-86-24, 50-304-86-23, NUDOCS 8612190041 | |
| Download: ML20211P339 (8) | |
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U. S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT DIVISION OF EMERGENCY PREPAREDNESS AND ENGINEERING RESPONSE Report Nos. 50-295/86024(DRSS); 50-304/86023(DRSS)
Docket Nos. 50-295; 50-304 License Nos. DPR-39; DPR-48-Licensee:
Comonwealth Edison Company Post Office Box 767 Chicago, Illinois 60690 Facility Name: Zion Nuclear Power Station, Units 1 and 2 Inspection At:
Zion Site, Zion, Illinois Inspection Conducted: September 29 through November 7, 1986
@N Inspector:
P. Cortland Date Signed I
Accompanying Inspector:
M. M. Holzmer
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i N)bert L. Baer, Chief Approved by:
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Date Signed Engineering and Generic Communications Branch Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Inspection Sumary Inspection of September 29 - November 7,1986 (Report Nos. 50-295/86024(DRSS)
and 50-304/86023(DRSS))
Areas Inspected: Verification of implementation of an effective program for preventing overpressure transients at low temperatures from adversely affecting safety-related systems.
Results:
No violations or deviations were identified. Based on revised information supplied by the licensee, the low temperature overpressurization protection system provides for 10 minutes of operation in the event of the loss of the normal air supply.
8612190041 861216 PDR ADOCK 05000295 O
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DETAILS 1.
Persons Contacted Licensee Personnel
- J. Ballard, Quality Control Supervisor
- A. Bless, Regulatory Assurance
- R. N. Cascarano, Technical Staff Supervisor
- R. Lane, Primary Group Leader
- D. J. McHenamin, Quality Assurance Inspector
- G. Plim1, Station Manager
- T. Rieck, Superintendent, Technical Services
- J. Tiemann, Technical Staff Engineer R. Landrum, Operations Training Group Leader
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USNRC Personnel
- M. M. Holzmer, Senior Resident Inspector
- L. Kanter, Resident Inspector The inspector also interviewed other personnel during the course of the inspection including members of the licensee's technical, operating, and administration staff.
- Denotes persons attending the exit meeting of October 3, 1986.
2.
Inspection Scope and Objectives The objective of this inspection was to verify that Zion Nuclear Power Station, Units 1 and 2 has implemented an effective program for preventing overpressure transients at low temperatures from adversely affecting safety-related systems. To accomplish this objective, selected portions s
of the Safety Evaluation Report of February 28, 1980 and Amendments 54 (DPR-39) and 51 (DRP-48) to the Technical Specifications were reviewed for their implementation.
This inspection has been divided into several areas: design, administra-tive controls and procedures, training and equipment modification, and surveillance. The plan was to summarize the observations as follows:
a.
Items that have been verified.
b.
Items that have been verified using alternate methods.
c.
Items scheduled for implementation.
d.
Items not scheduled for implementation.
3.
Design i
a.
Design in accordance with the 10 CFR 50 Appendix G limits.
Documentation was found in the letter from Westinghouse Electric Corp. dated August 26, 1986.
This analysis selected a positive displacement charging pump rather than the safety injection pump identified in the SER as the most limiting mass input transient because the safety injection pumps switches are put into the
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PULL-TO-LOCK position and tagged out of service and then the circuit breakers are racked out.
b.
The system protects the vessel given a single failure in addition to a failure that initiated the pressure transient. Examples are loss of offsite power and loss of nomal air supply.
In the event of loss of offsite power, separate banks of DC batteries will operate the solenoids. Diesel generators 1A and 1B will supply the power for relief valves PRV 455C and PRV 456, respectively. A passive backup air supply is part of the system.
c.
The system is not vulnerable to an event which both causes a pressure transient and a failure of equipment needed to terminate the tran-sient. Examples are loss of a single power-operated relief valve, block valve, solenoid or air supply.
Redundant electrical circuits are shown by drawings 22E-1-4840 and 22E-2-4840, pages RC45 and RC46. There are two independent relief valves and each is capable of handling the flow of one charging pump.
Each PORY line includes a separate and independent solenoid, blocking valve, and air supply.
d.
Plant-specific analysis for PORV setpoints.
The setpoint selection is based on the maximum pressure allowed (520 psig) at a given temperature (100 F) minus the pressure rise in the system until the PORVs are fully opened. At temperatures of 250 F or lower, the system will activate when the reactor coolant system pressure is greater than 435 psig, e.
10 CFR 50.59 eval.uation.
The licensee has completed the evaluation.
f.
IEEE 279 design and redundancy in actuation controls.
Separate electrical circuits and air systems were verified by a physical inspection.
g.
Findings No violations or deviations were identified.
4.
Administrative Controls and Procedures a.
Minimize the time in a water-solid condition.
Depending on the nature of the outage, the reactor operator may place the RCS in a water-solid condition per step 65 of G0P-4, Plant Shutdown and Cooldown and add a nitrogen bubble per step 72. The procedure requires drawing a bubble in the pressurizer prior to starting a reactor coclant pump. On startup, the pressurizer goes water-solid from step 14 of GOP-1, Plant Heatup until a bubble is drawn prior to the startup of a reactor coolant pump in step 20.
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b.
Minimize temperature differentials between the steam generator and the reactor vessel while water-solid.
By procedure a bubble must exist in the pressurizer before a reactor coolant pump may be operated.
c.
Restrict the number of safety injection charging pumps.
Both safety injection pumps and two of the three charging pumps are disconnected before the unit cools to 250 F.
The switches are put into the PULL-TO-LOCK position and the circuit breakers are racked out per step 48 of G0P-4, Plant Shutdown and Cooldown.
d.
Installation in accordance with the FSAR.
The system is in accordance with the FSAR.
e.
Alert operators about the automatic operation of the system.
The operators are instructed in the automatic operation of the systent and the actuators in the control room indicate system operation.
f.
Manually align the system for operation using verification.
In procedure GOP-4, Plant Shutdown and Cooldown, step 43 establishes operability of the low temperature overprotection system; step 45A turns off the pressurizer heaters; step 48 deenergizes both safety injection pumps and two charging pumps and closes the accumulator discharge isolation valves; and step 54 places the low temperature overpressurization protection system in service.
g.
Verify that equipment is deenergized.
In procedure GOP-4, Plant Shutdown and Cooldown, step 48 deenergizes both safety injection pumps and two charging pumps and closes the accumulator discharge isolation valves. Verification was found for the shutdown of Unit 2 dated September 15, 1985.
h.
Maintain a bubble in the primary system during shutdown.
There may be a bubble in the pressurizer based on the nature and length of the shutdcwn. For extended outages, a bubble is drawn in the pressurizer per step 72 of G0P-4, Plant Shutdown and Cooldown.
i.
Remove the low temperature overpressure protection system on tempera-ture increase to prevent inadvertent actuation.
In step 37 of GOP-1, Plant Heatup, the control switches are returned to the AUTO position from the AUTO L0 TEMP position. The block valves may also be closed at this time. The system can be manually actuated when the block valves are open and the control switch is held in the OPEN position. The latter position is spring loaded and will return to AUTO when released.
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Findings No violations or deviations were identified.
5.
Training and Equipment Modification a.
Causes of reactor coolant system low temperature overpressure events, operation and maintenance of the system that mitigates the events, and the consequences of inadvertent actuation.
The operators have received training in the operation of the system that mitigates overpressurization. LO-PSC-3C Pressurizer System Operation covers the basics of the subject and the step in the shutdown procedure which makes the pressurizer water-solid is taught as an administrative option. LO-TAA-3 Miscellaneous Pressure Con-cerns is 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> long and covers the consequences of inadvertent actuation. LO-TAA-5 Plant Mode Changes covers other operational steps, technical specs and limiting conditions for operation.
The training program requires employee signatures at the time of taking a class. Two employees were contacted and they verified taking the courses, b.
Permanent modifications and procedure changes The control switches, b17ck valve switches and annunciators for this system are in the control room. Unit I was in an outage and the two backup air supply tanks were not accessible. Seen in the containment were PORVs PCV 455C and 456, 3 Safety Valves, and 2 power relief isolation valves.
In the electrical area, the circuit breakers for the safety injection pumps and 2 charging pumps were tagged out of service (005).
Since the system is Seismic Class I and the control air to contain-ment is isolated on a containment isolation signal, a backup air supply tank was installed for each PORV. The backup air supply tank i
is connected to the normal air supply and the pressure is in excess of 100 psig. A pressure regulator was installed in each line to reduce the pressure to the PORVs to 85 psig.
The cooldown and startup procedures have been modified to accommodate the overpressure mitigating system. Step 45A of G0P-4 turns off the pressurizer heaters and step 48 deenergizes both safety injection pumps, two charging pumps, and the accumulator discharge isolation valves. When the RCS temperature decreases to 250 F, a control panel light indicates that the protective system is not in service. At this point the operator verifies that both block valves are open and places the relief valve switches in the low temperature position.
This action places the system into service.
If the pressure exceeds a preset value, the relief valves will open and reduce the RCS pressure. Annunciators will light to indicate the opening of the PORVs and an increase in temperature in the PORV drain lines.
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c.
Modification placing equipment out of the original design basis.
There were not any modifications to the PORVs.
d.
Annunciators to alert the reactor operator to a transient.
Annunciator 10B on Panel 9 alerts the reactor operator to high pressure in the pressurizer at low temperature and impending motion of the PORVs. Annunciators 9E and 10A on Panel 9 alert the reactor operator to lifting of the PORVs and high temperature in the PORV relief lines.
e.
Backup air supply sufficient for 10 minutes of operation.
Based on calculations initially furnished by the licensee, there is not sufficient air for 10 minutes of operation at the qualified air pressure when the ncrmal air supply is not available. The system was qualified for 85 psig by the procedure, Special Test of Low Tempera-ture Overpressurization Protection Installed Under Modifications M-22-1-76-88 and H-22-2-76-88, but the 51 cubic foot air tank cannot supply air for the required 10 minutes (100 actuations) of the PORV at 85 psig when the initial tank pressure is only 100 psig.
The equation used for calculating the size of the backup air supply tanks incorrectly assumed that the air arriving at the PORV from the pressure regulator would be a higher pressure (85 psig) than the air leaving the *,upply tanks and going to the regulator (55 psig).
The pressure regulator was set at 85 psig and at lower pressures, it is fully open and becomes a pressure-reducing flow restrictor.
It is not known if the stroke time of the PORVs is adequate at a lower pressure. According to the data furnished, the PORVs will operate at pressures as low as 55 psig.
On November 7,1986, the licensee reported the results of the PORV tests. First, the valves were Copes-Vulcan and not Masoneillan and the diaphragm diameter and stroke were smaller; second, the air line was 3/8 in diameter and not 3/4 in, diameter; and third, the minimum air pressure for full actua* ion was 80 psig, not 55 psig. Air use was recalculated and showed that there would be sufficient air for 10 minutes of operation event with a pressure regulator setting of 85 psig.
In this case, the regulator would first reduce pressure and then act as a flow restrictor and 100 actuations would occur before the tank pressure dropped to 80 psig.
f.
Findings Based on the test data and revised information furnished by the licensee, the system has 10 minutes of backup air supply available.
No violations or deviations were identified.
6.
Surveillance a.
Periodic verification of PORV electronics and setpoints.
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The integrity of the air system is tested every 31 days while in a condition that requires the PORVs to be operable per PT-2T, "PORV Accumulator Check Valve Leakage Test". The data sheets for the most recent test of Unit 1 on September 7, 1986 were reviewed.
b.
Perform tests prior to shutdown.
The setpoints and electrical functions are verified prior to cold shutdown per FT-36.1, " Overpressure Protection Setpoint and Function-al Operation Verification Hot Shutdown Only". The data sheets for the most recent shutdown of Unit 1 on September 4,1986 were re-viewed.
In addition, the stroke time of the power operated relief valves is tested during shutdown per PT-27, " Miscellaneous Valve Tests". The data sheets for a recent test of Unit 1 on May 13, 1986 were reviewed.
c.
Perform tests after maintenance and modifications.
The function of power relief valves 2PCV-RC-455C 'and 2PCV-RC-456 for Unit 2 were verified after fire protection modifications per TSSP 74-85, " Fire Protection Transfer Panel Test" on December 20, 1985, d.
Findings No violations or deviations were identified.
7.
Commonwealth Edison Deviation Report 22-1-86-082, PORV Stroke Time The PORV stroke time used for the design analysis was 2.5 seconds and the actual time was less than that during the initial qualification tests.
Recent tests have measured stroking timet, as long as 8 seconds, with many readings in excess of 2.5 seconds. A licensee event report (LER) h being prepared and it is expected to discuss the valve opening times needed to prevent overpressurization. This LER will be reviewed by the NRC Region III Office.
8.
Exit Interview The inspector met with licensee representatives (denoted in Paragraph 1)
on October 3, 1986. The inspector sumarized the scope oad findings of the inspection, noting that the system design is based on a charging pump while the SER identified a safety injection pump as the critical element and that there did not appear to be sufficient backup air based on the information supplied. These items were to be discussed with the Office of Nuclear Reactor Regulation. The inspector noted that Region III is reviewing the licensee's response about the extended PORY stroke times.
The licensee acknowledged the statements made by the inspector.
The inspector also discussed the likely information content of the inspection report with the regard to documents or processes reviewed by the inspector during the inspection. The licensee did not identify any such documents / processes as proprietary.
Subsequent to the interview, the inspector reviewed the administrative procedure for deenergizing the safety injection pumps and found it to be sufficient, thus making the charging pumps the limiting items for causing l
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a pressure transient.
In addition, the corrected information furnished by the licensee on November 7,1986 led to a recalculation of the capacity of the backup air supply and the inspector concluded that the backup air supply is sufficient.
9.
Documents Reviewed.
Drawings 22E-1-4840 Schematic Diagram Page RC18 Power Relief Isolation Valve 8000A, Unit 1 Page P,C19 Power Relief Isolation Yalve 8000B, Unit 1 Page RC45 Power Relief Valve 455C, Unit 1 Page RC46 Power Relief Valve 456 Unit 1 22E-2-4840 Schematic Diagram Page RC45 Power Relief Valve 455C, Unit 2 Page RC46 Power Relief Valve 456, Unit 2 Procedures FT-36.1 Overpressure Protection Setpoint and Fun:tional Operation Verifi-cation Hot Shutdown Only, Rev.11. May 19,1986 GOP-1 Plant Heatup, Rev. 14, June 11, 1986 GOP-4 Plant Shutdown and Cooldown, Rev. 20, August 13, 1986 PT-2T PORY Accumulator Check Valve Leakage Test, Rev. 1. August 13, 1986 PT-27 Miscellaneous Valve Tests, Rev. 11. March 20, 1986 Special Test of Low Pressure Overpressurization Protection Installed Under Modifications M-22-1-76-88 and M-22-2-76-88, November 17, 1977 TSSP 74-85 Fire Protection Transfer Panel Test October 15, 1985 Correspondence RC-1 Calculations for Air Supply to Pressurizer Relief Modification, Rev. O, May 23, 1977 Westinghouse Electric Corp. to G. J. Plim1, August 25,1986,subj: Low Temperature Overpressure Protection System Setpoint Analysis 8