ML18144A043
| ML18144A043 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/30/1985 |
| From: | VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | |
| Shared Package | |
| ML18144A041 | List: |
| References | |
| TAC-59821, TAC-59822, NUDOCS 8512110276 | |
| Download: ML18144A043 (17) | |
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VIRGINIA ELECTRIC AND POWER COMPANY SURRY UNITS I AND 2 REACTOR COOLANT SYSTEM LEAKAGE DETECTION ASSESSMENT FOR ELIMINATION OF REACTOR COOLANT SYSTEM MAIN LOOP PIPE BREAK PROTECTIVE DEVICES NOVEMBER 1985 I
, 8512110276 851203 PDR ADOCK 05000280 P
PDR 11-RKM-OIOX-l ATTACHMENT 2
I.
I I.
III.
IV.
'--")
11-RKM-OlOX-2 TABLE OF CONTENTS INTRODUCTION REGULATORY POSITION
SUMMARY
REFERENCE i
PAGE 1
2 11 14
)
I.
INTRODUCTION This report is submitted in support of Virginia Electric and Power Company's request for partial exemption to General (GDC-4) as applicable to Surry Units 1 and Design Criterion 4 2, to the extent that protection against the dynamic effects of postulated pipe rupture on primary system components/supports and piping may be eliminated.
The technical basis for the exemption request is based upon the fracture mechanics analyses referred to as "leak-before-break."
Generic Letter 84-04 provided the NRC safety evaluation concluding that an acceptable technical basis exists so that the blowdown loads resulting from double-ended pipe breaks in the RCS primary loop need not be considered as a design basis, provided that certain conditions can be met for the reviewed plants, including Surry Units 1 and 2.
One condition is that an acceptable capability exist for detection of reactor coolant system leakage.
An assessment of the Surry Units 1 and 2 reactor coolant leakage detection system is the subject of the report.
It contains a comparison of the Surry leakage detection systems with respect to the nine Regulatory Guide 1.45 design guidelines, taking into account the exceptions given in NRC Generic Letter 84-04.
This evaluation demonstrates that these systems are capable, with margin, of detecting the leakage from the postulated through-wall flaws.
11-RKM-OlOX Page 1
II. REGULATORY POSITION Per NRC Generic Letter 84-04, 11 Leakage detection systems should be sufficient to provide adequate margin to detect the leakage from the postulated circumferential through-wall flaw utilizing the guidance of Regulatory Guide
- 1. 45, "Reactor Cool ant Pressure Boundary Leakage Detection Systems, 11 with the exception that the seismic qualification of the airborne particulate radiation monitor is not necessary.
At least one leakage detection system with a sensitivity capable of detecting 1 gallon per minute (gpm) in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> must be operable.
11 Regulatory Guide 1.45 states:
11 the source of reactor coolant leakage should be identifiable to the extent practical.
Reactor coolant pressure boundary leakage detection and collection systems should be selected and designed to include the following 11 Design Guideline 1:
"Leakage to the primary reactor containment from identified sources should be collected or otherwise isolated so that:
- a.
the flow rates are monitored separately from unidentified leakage, and
- b.
the total flow rate can be established and monitored.
11 11-RKM-OlOX Page 2
Assessment Identified sources of primary system leakage are collected in the Reactor Containment in the primary drain transfer tank (POTT) and pressurizer relief tank (PRT).
The POTT receives leakoff from various primary valve packings, #2 and #3 RCP seal leakoff, and leakage from the reactor vessel flange leakage detection system.
The PRT receives leakage from the pressurizer PORV 1s.
Flow rates from identified leakage sources are determined by the PRT and POTT level changes over time as a part of procedure PT-10 (RCS Leak Rate Determination). Additionally, these tanks are provided with High level alarms to enhance the ability to detect a sudden increase in identified leakage.
Design Guideline 2:
11Leakage to the primary reactor containment from unidentified sources should be collected and the flow rate monitored with an accuracy of one ga 11 on per minute ( gpm) or better.
11 Assessment Leakage to the primary containment from unidentified sources is collected in a common sump within the containment.
A narrow range sump level instrument is provided which has a loop accuracy of
+ 2% over a range of 100% (300 gallons).
Though not directly 11-RKM-OlOX Page 3
monitored, flow rate is easily calculated to within the required accuracy by observing level change over a fixed time interval.
Again, sump high level alarms are provided to detect a sudden change in unidentified leakage.
Normally, at Surry Power Station, unidentified leakage is calculated by subtracting identified leakages (POTT and PRT) from total leakage (VCT).
Design Guideline 3:
11At least three separate detection methods should be employed and two of these methods should be (1) sump level and flow monitoring, and (2) airborne particulate radioactivity monitoring.
The third method may be selected from the following:
- a.
monitoring of condensate flow rate from air coolers, and
- b.
monitoring of airborne gaseous activity.
Humidity, temperature, or pressure monitoring of the containment atmosphere should be considered as alarms or indirect indication of 1 eakage to the containment.
11 11-RKM-OlOX Page 4
I Assessment Leakage from the Reactor Coolant System to the containment is indicated in the control room by one or more of the following methods:
- 1.
The containment air particulate monitoring system is indicated, recorded, and alarmed in the control room.
- 2.
The containment gas monitor is indicated, recorded, and alarmed in the control room.
- 3.
Abnormal makeup water requirements to maintain normal level in the pressurizer are an indication of a leak.
The primary-grade water and concentrated boric acid makeup flow rates are both recorded and alarmed in the control room.
- 4.
The instrumentation for containment pressure, partial pressure, temperature, dew point and sump level, all indicate in the control room.
This instrumentation provides an indirect indication of leakage into the containment.
- 5.
Reactor vessel leak-off through the reactor vessel head flange is collected and will cause a high temperature in the drain line, which actuates an alarm in the control room.
11-RKM-OlOX Page 5
Design Guideline 4:
"Provisions should be made to monitor systems connected to the RCPB for signs of intersystem leakage.
Methods should include radioactivity monitoring and indicators to show abnormal water levels or flow in the unaffected area.
11 Assessment The condenser air ejector monitor, the component cooling water monitor, and the steam generator blowdown monitors are utilized to indicate primary system leakage into interconnected systems.
Leakage into the low head safety injection system (Event V) is precluded by redundant check valves which are subject to routine surveillance.
Leakage into this system would ultimately be detected by the Refueling Water Storage Tank (RWST) level detection system and ventilation vent gross and particulate activity monitoring system.
Design Guideline 5:
11 The sensitivity and response time of each leakage detection system in regulatory position 3 above employed for unidentified leakage should be adequate to detect a leakage rate, or its equivalent, of 1 gpm in less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
11 11-RKM-OlOX Page 6
Assessment Generic Letter 84-04 allows an exception to the Regulatory Guide 1.45 by requiring "at least one leakage detection system with a sensitivity capable of detecting 1 gpm in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> must be operable." The sensitivity and response time of the methods described for detection of RCS leakage are dependent on RCS activity, previous leakage rate which can increase steady state count rates on the gross and particulate radiation monitoring system, frequency of surveillance, etc.
Different detection methods would be effective over a broad range of operating conditions.
Given the depth and redundancy of leakage detection methods described above, we are confident a 1 gpm leak rate would be detected within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> during steady state operation.
Additionally, upon indication of primary plant leakage, using the methods previously listed, Surry Power Station Abnormal Procedure AP-16 provides guidance for response to increased leakage and guidance for determining the cause of the leakage and the leak rate.
Periodic Test Procedure PT-10 is used to determine the leak rate. The indicating parameters are normally monitored every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
In addition, the contatnment particulate and gas monitors also provide indication of leakage.
11-RKM-OlOX Page 7
Design Guideline 6:
11 The leakage detection systems should be capable of performing their functions following seismic events that do not require plant shutdown.
The airborne particulate radioactivity monitoring system should remain functi ona 1 when subjected to the SSE.
11 Assessment Generic Letter 84-04 allows an exception to Regulatory Guide 1.45 by stating that 11 the seismic qualification of the airborne particulate radiation monitor is not necessary.
11 The containment pressure and sump level instrumentation at Surry Units 1 and 2 are seismically qualified per Regulatory Guide 1.97.
Design Guideline 7:
11 Indicators and alarms for each leakage detection system should be provided in the main control room.
Procedures for converting various indications to a common leakage equivalent should be available to the operators.
The calibration of the indicators should account for needed independent variables.
11 11-RKM-OlOX Page 8
Assessment Indicators and alarms are provided in the control room for all five leakage detection systems, with the exception of containment dew point and temperature.
Operator curves are used to convert leakage to vessels and sumps to a flow rate value, and Periodic Test Procedure PT-10 is used to quantify identified and unidentified RCS leakage.
Design Guideline 8:
"The leakage detection systems should be equipped with provisions to readily permit testing for operability and calibration during plant operation.
11 Assessment The instrumentation used for leakage detection at Surry Units 1 and 2 can be calibrated or tested for operability at any time.
Design Guideline 9:
"The technical specifications should include the limiting conditions for identified and unidentified leakage and address the availability of various types of instruments to assure adequate coverage at all times.
11 11-RKM-OlOX Page 9
I I
~'
Assessment Technical Specification 3.1 gives limiting conditions for both identified and unidentified leakage.
Also, it requires that "at least two means shall be available to detect reactor coolant system leakage.
One of those means must depend on the detection of radionuclides in containment."
11-RKM-OlOX Page 10
__ )
III.
SUMMARY
The following is a summary for each regulatory position design guideline:
- 1.
Surry Units 1 and 2 satisfy the regulatory position of detecting identified and unidentified leakage.
- 2.
Periodic Test Procedure PT-10, 11 Reactor Coolant Leakage,"
is capable of measuring flow rates with an accuracy better than 1 gpm.
- 3.
Surry has five methods which are available for leakage detection:
11-RKM-OlOX Containment air particulate monitors Containment gas monitors Abnormal makeup water Measurement of containment pressure, temperature, dew point, and sump level Reactor vessel flange leak-off detection system Page 11
- 4.
Surry utilizes the following monitors for detection of intersystem leakage:
Condenser air ejector monitor Component cooling water monitor Steam generator blowdown monitor
- 5.
Surry is capable of detecting a leakage rate of I gpm in less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
- 6.
NRC Generic Letter 84-04 does not require the airborne particulate monitors to be seismically qualified.
The containment pressure and sump level instrumentation are seismically qualified.
- 7.
Indicators for all the leakage detection systems are provided in the control room.
The containment temperature and dew point indicators do not alarm.
All others have alarms.
Various parameters used to determine leakage rate are converted using operator curves and Surveillance Procedure PT-10 to quantify RCS leakage (total, identified, and unidentified).
11-RKM-OIOX Page 12
- 8.
The instrumentation used for leakage detection can be calibrated or tested for operability at any time.
- 9.
Surry Technical Specification 3.1 gives limiting conditions for both identified and unidentified leakage.
Based on this evaluation, Surry Units 1 and 2 have systems which are capable, with margin, of detecting the leakage from the postulated through-wall flaws.
11-RKM-OlOX Page 13
IV. REFERENCES
- 1.
Regulatory Guide 1.45, 11 Reactor Coolant Pressure Boundary Leakage Detection Systems.
11
- 2.
NRC Generic Letter 84-04, 11Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks in PWR Primary Main Loops.
11
- 3.
Surry UFSAR Section 4.1.2.6, 11Monitoring Reactor Coolant Leakage.
11
- 4.
Surry UFSAR Section 4.2.7, 11 Leakage.
11
- 5.
Surry Technical Specification 3.1, 11 Reactor Coolant
- System, 11 Section C, 11 Leakage.
11
- 6.
Surry Power Station Periodic Test Procedure PT-10, 11 Reactor Coolant Leakage.
11
- 7.
Surry Power Station Abnormal Procedure AP-16, 11 Excessive Primary Plant Leakage.
11
- 8.
Alarm response procedure A-3, Annunciator 18-3, Containment Sump High Level - 80 percent.
11-RKM-OlOX Page 14
- 9.
Alarm response procedure 8-7, Annunciator 18-15, Containment Partial Pressure, +0.1 PSI, Ch. 2.
- 10.
Alarm response procedure C-6, Annunciator 18-22, Containment Partial Pressure, +0.25 PSI, Ch. 1.
- 11.
Alarm response procedure E-3, Annunciator 18-35, Incore Instrument Room Sump Hi Level, > 18 11 11-RKM-OlOX Page 15