ML20079Q706

Monitoring of Electric Power to Reactor Protection Sys for Quad Cities Nuclear Power Station,Units 1 & 2, Technical Evaluation Rept

ML20079Q706
Person / Time
Site:	Quad Cities
Issue date:	05/18/1983
From:	Selan J LAWRENCE LIVERMORE NATIONAL LABORATORY
To:	NRC
Shared Package
ML20079N131	List: ML20079Q706
References
CON-FIN-A-0250, CON-FIN-A-250 UCID-19704, NUDOCS 8306140082
Download: ML20079Q706 (9)

Text

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TECHNICAL EVALUATION RBPORT ON THE MONITORING OF ELECTRIC POWER TO THE REACTOR PROTECTION SYSTEM FOR THE QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 (Docket Nos. 50-254, 50-265)

James C. Selan May 18, 1982

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ABSTRACT This report documents the technical evaluation of the monitoring of electric power to the reactor protection system (RPS) at the Quad Cities Nuclear Power Station, Units 1 and 2. The evaluation is to determine if the proposed design modification will protect the RPS from abnormal voltage and frequency conditions which could be supplied from the power supplies and will meet certain requirements set forth by the Nuclear Regulatory Commission. The proposed design modifications will protect the RPS from sustained abnorma? voltage and frequency conditions from the supplying sources.

FOREWORD This report is supplied as part of the Selected Operating Reactor Issues Program 11 being conducted for the U. S. Nuclear Regulatory Commission, Of fice of Nuclear Reactor Regulacion, Division of Licensing, by Lawrence Livermore National Laboratory.

The U. S. Nuclear. Regulatory Commission funded the work under the authorization entitled " Selected Operating Reactor Issues Program II,"

B &R 20 19 10 11 1, FIN No. A0250.

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TABLE OF CONTENTS Page *

1. INTRODUCTION . . . . . . . . . . . . . . . ]

2. DESIGN DESCRIPTION . . . . . . . . . . . . . 2

3. EVALUATION . . . . . . . . . . . . . . . 3

4. CONCLUSION . . . . . . . . . . . . . . . 5 REFERENCES . . . . . . . . . . . . . . . . 6 l

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TECHNICAL EVALUATION REPORT ON THE MONITORIFG OF ELECTRIC POWER TO THE REACTOR PROTECTION SYSTEM AT THE QUAD CITIES NUCLEAR POWER STATION UNITS 1 AND 2 l

(Docket Nos. 50-254, 50-265) '

James C. Selan Lawrence Livermore National Laboratory, Nevada

, 1. INTRODUCTION During the operating license review for Hatch 2, the Nuclear Regulatory Commission (NRC) staff raised a concern about the capability of the Class lE reactor protection system (RPS) to operate af ter suffering sustained, abnormal voltage or frequency conditions from a non-Class lE "

power supply. Abnormal voltage or frequency conditions could be produced as a result'of one of the followiag causes: combinations of undetected, random single f ailures of the power supply components, or multiple failures of the power supply components caused by external phenomena such as a ,

seismic event.

4 The concern for the RPS power supply integrity is generic to all

! General Electric (GE) boiling water reactors (BWR) MARK 3's, MARK 4's, and '

MARK 5's and all BWR MARK 6's that have not elected to use the solid state i RPS design. The staff therefore pursued a generic resolution. Accordingly,

GE proposed a revised design, in conceptual form, for resolution of this concern [Ref. 1}. The proposed modification consists of the addition of two Class 1E " protective packages" in series between each RPS motor generator (M-G) set and it's respective RPS bus, and the addition of two similar packages in series in the alternate power source circuit to the RPS buses.

Each-protective package would include a breaker and associated overvoltage, undervoltage and underfrequency' relaying. Each protective package would .

meet the testability requirements for Class lE equipment.

With the protective packages installed, any abnormal output type failure (undetectable random or seismically caused) in either of the two RP3' M-G sets (or the alternate supply) would result in a trip of either one or ,

, both of the two Class IE protective packages. This tripping would interrupt the power to'the effected RPS channel, thus producing a scram signal on that channel, while retaining full scram capability by means of the other channel.

Thus, fully redundant Class 1E protection is provided, bringing the overall

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RPS design into full conformance with General Design Criteria (GDC)-2 [Ref. 2],

and GDC-21 [Ref. 3] (including IEEE-279 [Ref. 4] and the standard review plan

[Ref. 5]). The NRC staff reviewed the proposed GE design and concluded that the modification was acceptable [Ref. 6], and should be implemented in conform-ance with the applicable criteria for Class lE systems.

The NRC requires that the components of the RPS not be exposed to unacceptable electric power of any sustained' abnormal quality that could damage the RPS. This involves providing means to detect any overvoltage, undervoltage, or underfrequency condition that is outside the design limits of the RPS equipment and to disconnect the RPS from such abnormal electric power before damage to the RPS can occur. The equipment which performs these functions must satisfy the single failure criterion and be seismically qualified. The NRC issued a generic letter [Ref. 7] to all operating BWR's requesting the licensees to submit design modification details and Technical Specifications for post implementation review.

By letters dated January 12, 1982 [Ref. 8], April 19, 1982 [Ref. 9],

July 23,1982 [Ref.10], February 4,1983 [Ref.12], April 20,1983 [Ref.13),

May 6, 1983 [Ref. 14], and a telephone conference on August 20, 1982 [Ref. 11]

Commonwealth Edison (CE), the licensee, submitted design modification details and Technical Specifications changes regarding the monitoring of electrical power to the RPS at the Quad Cities Nuclear Power Station, Units 1 and 2.

The purpose of this report is to evaluate the licensee's submittal with respect to the NRC criteria and present the reviewer's conclusion on the adequacy of the design modifications to protect the RPS f rom abnormal voltage and frequency conditions.

. 2. DESIGN DESCRIPTION The licensee has proposed to install the GE designed " electrical l protection assembly" (CE No. 914E175) to monitor the electric power in each of the six sources of power (two RPS M-G sets, and one alternate source per each unit) to the RPS. Each assembly (EPA) consists of two identical and

, redundant packages. Each package includes a circuit breaker and a monitoring module. When abnormal electric power is detected by either module, the respec-tive circuit breaker will trip and disconnect the RPS from the abnormal power -

source.

The monitoring module detects. overvoltage, undervoltage, and under-frequency conditions and provides a time-delayed trip when a setpoint is exceeded.

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3. EVALUATION The NRC stated several requirements that the licensee must meet in their design modification to monitor the power to the R?S. A statement of these requirements fo' lowed by an evaluation of the licensee's submittals is as follows:

(1) "The components of the RPS shall not be exposed to unaccept-able electric power of any sustained abnormal quality that could damage the RPS."

The monitoring module will detect overvoltage, undervoltage, and underfrequency conditions with the following setpoints.

Nominal voltage 115 volts, 60 Hz nominal Condition Setpoint Time Delay Overvoltage 126.5 volts 3.0 seconds Tolerance + 2.5% Tolers.nce + 5%

l Undervoltage 108.0 volts 3.0 seconds Tolerance + 2.5%

Tolerance + 5%

Underfrequency 56 Hz 3.0 seconds Tolerance + 1% Tolerance + 5% ,

GE certified RPS component (relays and contactors) operating capability is + 10% of 115 volts and - 5% of 60 Hz on its terminal, resulting in a voltage range of 126.5 to 103.5 vcits I and a frequency range of 60 to 57 Hz. Based on these values,

} the GE recommended setpoints for a system of 60 Hz and 120-I volt nominal are 132 volts - 2.5% of nominal for overvoltage, 108 volts + 2.5% of nominal for undervoltage, and 57 Hz + 2%

of nominal for underfrequency.

, The licensee'. proposed setpoints, specifically the tolerances, i

are evidently outside the GE recommended values. However, based on the results of RPS component testing (two HFA relays and one ASCO solenoid) performed by the licensee, the following is concluded:

(a) For the proposed undervoltage setpoint, the minimum terminal voltage at the downstream RPS components, considering the maximum cable voltage drop of 3.2 volts, will be 102.1 volts (1.4 volts below the above GE value).

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t (b) Similarly, for the proposed overvoltage and underfrequency setpoints, the respective maximum terminal voltage will be 126.5 volts and the minimum frequency will be 55.4 Hz (1.6 Hz below the GE value).

These abnormal voltages and frequency may be sustained for a maximum time of 3.15 seconds before the EPA trips.

Projecting these voltage (frequency)/ time points onto the temperature / voltage (frequency) test curves, it is found that a 2

negligible rise in coil temperature would result. Also shown in the test results was a negligible effect on the components' pickup and dropout voltages as the frequency varied. In addi-tion to these tests which generated the test curves compared above, a combined test of overvoltage, underfrequency, and high ambient temperature for a long period of time was performed.

The test was conducted for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> at 130 volts, 55 Hz, and in an ambient temperature of 55 *C.

Since high coil temperature is the most significant contributing f actor affecting component operation, these tests demonstrated that no adverse effects resulted on the ability of the RPS compo-nents to perform their safety function. Therefore, all the above trip setpoints and time delays ensure adequate RPS component component protection from sustained abnormal power. .

(2) " Disconnecting the RPS from the abnormal power source shall be .

automatic."

The monitoring modula will automatically disconnect the RPS buses from the abnormal power supply af ter the set time delay

! should the parameters setpoints be exceeded.

(3) "The power monitoring system shall meet the requirements of IEEE 279-1971, GDC-2 and GDC-21."

The monitoring packages meet the Class 1E requirements of IEEE 279, the single failure criteria of GDC-21, and the scismic qualifications of GDC-2.

(4) " Technical Specifications shall. include limiting conditions of operation, surveillance requirements, and trip setpoints."

The monitoring packages are installed at Unit 1 and are planned for installation at Unit 2 in December, 1983. In accordance with the Standard Technical Specifications, the licensee has i submitted [Ref s.13 and 14] Technical specification changes l which inclodes limiting conditions for operation when the l number of operable monitoring systems is less than required f and surveillance requirements which included a functional test, channel calibration, and verification of the trip

! setpoints.

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4. CONCLUSION Based on the information submitted by Commonwealth Edison for the Quad Cities Nuclear Power Station, Units 1 and 2, it is concluded that:

(1) The proposed setpoints of the relays in the two protective packages to be installed in series, in each of the power sources to the RPS buses, will automatically protect the RPS components from sustained abnormal overvoltage, under-voltage, and underfrequency conditions outside the design limits of the RPS components.

(2) The protective packages meet the requirements of Class lE equipment (IEEE 279), single failure criteria (GDC-21), and seismic qualification (GDC-2).

! (3) The proposed time delay before circuit breaker tripping will not result in damage to components of the RPS or prevent the RPS from performing its safety function.

(4) The following minimum and maximum limits to the trip setpoints, limiting conditions for operation (LCO), and surveillance requirements (as outlined in the Standard Technical Specifica-tions), to be incorporated in the plant's Technical Specifica-

, tions, will protect the RPS components from sustained abnormal power:

(a) Overvoltage j[129.6 volts, time delay j[ 3.15 seconds Undervoltage > 105.3 volts, time delay j[3.15 seconds Underfrequency > 55.4 Hz, time delay j[ 3.15 seconds (b) With one RPS electric power monitoring channel for an inservice RPS MG set or alternate power supply inoperable, restore the it. operable channel to operable status within  ;

72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or remove the associated RPS MG set or alternate i power supply from service.

l (c) With both RPS electric power monitoring channels for an

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l inservice RPS MG' set or alternate power supply inoperable, l l restore at least one to operable status within 30 minutes or remove the associated RPS MG set .or alternate power supply from service.

(d) A functional test at least once per 6 months and a channel calibration once per operating cycle to determine the oper-ability of the protective instrumentation including simulated automatic actuation, tripping logic, output circuit breaker tripping, and verification of the setpoints.

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REFERENCES

1. General Electric Company letter, MFN 408-78 (G. G. Sherwood) to NRC (R. S. Boyd), dated October 31, 1978.

2. General Design Criteria-2 (GDC-2), " Design Bases for Protection Against Natural Phenomena," of Appendix A, " General Design Criteria for Nuclear Power Plants," in the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50).

3. General Design Criteria-21 (GDC-21), " Protection System Reliability and Testability," of Appendix A, " General Design Criteria for Nuclear Power Plants," in the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50).

4 IEEE Std. 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations."

5. NUREG-75/087, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants."

6. NRC memorandum f rom Faust Rosa to J. Stolz, T. Ippolito, and G. Lainas, dated February 19, 1979.

7. NRC letter to Operating BWR's, dated September 24, 1980.

8. CE letter (T. J. Rausch) to the NRC (T. A. Ippolito), dated January 12, 1982.

9. CE letter (T. J. Rausch) to the NRC (T. A. Ippolito), dated April 19, 1982. ,

10. CE letter (T. J. Rausch) to the NRC (T. A. Ippolito), dated July 23, 1982.

11. Telecon, T. J. Rausch and B. Fancher (CE), J. VanVliet (NRC), J. Selan (LLNL),

dated August 20, 1982,

12. CE letter (T. J. Raush) to the NRC (H. R. Denton), dated February 4,1983.

13. CE letter (B. Rybak) to the NRC (H. R. Denton), dated April 20 1983.

14 CE letter (B. Rybak) to the NRC (H. R. Denton), dated May 6, 1983.

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