1CAN108607, Forwards Comparison of RCS Leak Detection Sys to Reg Guide 1.45 Guidelines,Per Rev to GDC 4.Util Intends to Remove Remaining Lateral Restraints Per GDC 4

Forwards Comparison of RCS Leak Detection Sys to Reg Guide 1.45 Guidelines,Per Rev to GDC 4.Util Intends to Remove Remaining Lateral Restraints Per GDC 4

ML20211D131
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/14/1986
From:	Enos J ARKANSAS POWER & LIGHT CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
RTR-REGGD-01.045, RTR-REGGD-1.045 1CAN108607, NUDOCS 8610220113
Download: ML20211D131 (6)

Text

ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501)3714000 October 14, 1986 1CAN108607 Mr. J. F. Stolz, Director PWR Project Directorate No. 6 Division of PWR Licensing - B U. S. Nuclear Regulatory Commission Washington, DC 20555

SUBJECT:

Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Information Submittal - Comparison of ANO-1 RCS Leak Detection Systems to Reg. Guide 1.45

Dear Mr. Stolz:

On May 12, 1986 the NRC made effective a revision to General Design Criteria 4 (GDC 4), which permitted the use of analyses that demonstrate the probability of rupturing PWR primary coolant loop piping is extremely low under design basis conditions (" leak-before-break" technology). Generic Letter 84-04, issued February 1,1984, stated the NRC staff's intent to proceed with the rulemaking, and the proposed modification to GDC 4 was published on July 1,1985.

AP&L actively participated in the Babcock & Wilcox Owners Group (B&WOG) Leak Before Break (LBB) Task Force activities, which resulted in submittal of B&W generic topical reports BAW-1847, Rev. 1 and BAW-1889P. The NRC concluded that an acceptable technical basis had been provided to eliminate, as a design basis, the dynamic effects of large ruptures in the main loop piping and issued a generic Safety Evaluation Report (SER) to the B&WOG on December 12, 1985. The SER was transmitted to AP&L by your letter dated February 18, 1986 (1CNA028604),

which stated that upon promulgation of the final rule (GDC 4), protection against large break dynamic loads would no longer be required. Your letter also stated that information should be submitted to demonstrate that leakage detection systems installed at our facility comply with Regulatory Guide 1.45.

During the IR7 refueling outage presently in progress, work in the area of the reactor coolant pumps (RCPs) will require removal of some existing wire rope RCP lateral restraints, described in Section 4.2.6.6 of the ANO-1 SAR. The only function of these restraints is to mitigate the dynamic effects of a postulated pipe rupture of the main primary loops. Therefore, the revised GDC 4 eliminates the requirements for these restraints. AP&L plans to remove the remaining restraints when convenient or required by inspection or maintenance activities in the future.

8610220113 861014 f PDR ADOCK 05000313 f p PDR E l

M8EMBEA MOOLE SOUTH UTIUTIES SYSTEM

Octobsr~14, 1986 The resolution of the LBB issue demonstrated that postulated thru-wall flaws based on conservative detectable leakage-rates result in either no flaw growth 3

or stable flaw growth when conservative bounding values of loads and material properties are used. In addition, these postulated leakage flaw sizes are much smaller than the critical flaw size which might lead to pipe failure.

The 10 gpm leakage rate postulated for the LBB studies is well in excess of the 1 gpm leakage rate detection sensitivity outlined by Regulatory Guide 1.45 and presently ~available at ANO-1.

Attached is a comparison of the leakage detection systems installed at ANO-1 to the individual items contained in the Regulatory Position of Regulatory Guide 1.45. This.information demonstrates that the ANO-1 leakage detection systems follow the guidelines of Regulatory Guide 1.45.

Very truly yo rs, M

J. Ted Enos, Manager Nuclear Engineering and Licensing JTE:RBT Attachment i

t t

COMPARISON OF ANO-1 RCS LEAK DETECTION SYSTEMS TO R.G. 1.45 The following discussion demonstrates that the RCS leakage detection systems installed at ANO-1 follow the guidelines of~ Regulatory Guide (R.G.) 1.45 by.

providing a comparison of the systems to the items listed under the Regulatory Position of R.G. 1.45.

~

R.G. 1.45, Regulatory-Position states: TPa 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:

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.

The leakage detection systems installed ~at ANO-1 are described in the Safety Analysis Report (SAR) Section 4.2.3.8. Identified leakage from the RCS through the RCP seals is collected and measured by a dedicated system, shown on SAR Figure 4-1, Sheet 1. This leakage is logged by the control room operators and~

accounted for in the daily RCS inventory balance (leak rate) calculation. This system therefore meets the requirements of Item 1.

2. Leakage to the primary reactor containment from unidentified sources should be collected and the flow rate monitored with an accuracy of one gallon per minute (gpm) or better.

The accuracy requirement of Item 2 is met by the inventory balance method of determining RCS leakage. This is described in SAR Section 4.2.3.8 (B),

and Technical Specification (TS) 3.1.6 Basis (b), and is performed daily per an approved station procedure. The accuracy of this method is 'significantly better than one gpm. Methods for determining and identifying unidentified RCS leakage are also provided in an approved station procedure.

3. At 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,

b. monitoring of airborne gaseous radioactivity.

The three separate leak detection methods primarily employed at ANO-1 are described in SAR Section 4.2.3.8, and also in the Bases of TS 3.1.6. Two of these methods are sump level monitoring, which matches (1) above, and radiation monitoring, which matches (2) and 3.b above. The condensate flow from the reactor building (RB) air coolers (3.a, above) is returned to the RB sump, where it is included in sump level monitoring. ANO-1 employs two types of RB atmosphere radiation monitors, one designated as the RCS leak detector, which

.is sensitive to radioactive gas, and one designated as the RB airborne particulate monitor. In addition to these two process radioactivity monitors, several area radiation monitors, which have control room dose rate indication and alarm,'are located throughout the reactor building. Although not specifically identified by R.G. 1.45, ANO-1 employs a leakage detection method based on performing an RCS inventory balance and considers this-the primary and most accurate leak detection method. This method is capable of providing early indication of small (less than 1 gpm) RCS leaks.

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 affected area.

Intersystem leakage would show up in the Decay Heat (DH) System, Core Flood-Tanks (CFTs), Intermediate Cooling Water (ICW) or the Once-Through Steam Generators (OTSGs). DH suction pressure, pressure between the redundant DH suction isolation valves, and CFT level and pressure are logged once per each eight' hour shift by the control room operators. CFT high and low level and pressure control room alarms are also provided. ICW is a closed system, and ICW surge tank levels are logged twice per~ shift. Process radioactivity monitors are installed on each loop of the DH System and each of the ICW return lines and provide high radioactivity alarms. Service Water and ICW 1eakage considerations are also discussed in SAR Section 9.3.2.1. Process radioactivity monitors (designated N-16 monitors) are installed on the main steam lines from the OTSGs, and have control room alarms. Process monitor indications are logged hourly by the operators. These provisions and methods comply with Item 4.

5. The sunsitivity 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 one gpm in less than one hour.

Sump level: ANO-1 has redundant PB sump level instruments, each with control room indication. One of these indicates % level (26.6 gallons /%), and the other indicates level in inches. The surp contains 63.6 gallons per inch, therefore a 1 gpm leak would result in a 2% increase and a 1 inch increase on the respective indicators in one hour. The resolution of each indicator is such that a 1 gpm leak will be detectable in less than one hour.

Airborne particulate monitor: The RB airborne particulate monitor indication is logged hourly by control room operators. A significant increase.in count rate would therefore be noticed within one hour, and an increase above the alarm setpoint would annunciate immediately in the control room. The response time of this monitor is a function of coolant activity, and therefore the amount of failed fuel. ANO-1 operates with as little coolant activity as is reasonably achievable, which increases.the r.esponse time of this detection method.

Therefore, this method is considered a backup detection method to RB sump level, inventory balance and RB airborne gaseous radioactivity monitoring.

Condensate flow rate from the air coolers: Although not individually measured, RB air cooler condensate flows to the RB sump where it is included in the sump level monitoring, described above.

Airborne gaseous radioactivity monitoring: This indication, as with other area and process radioactivity monitors, is logged hourly. The response time for the RB radioactive gas detector is a function of the percentage of failed fuel.

Response times for various levels of failed fuel are given on page 4.2-14a of the ANO-1 SAR. Example: For 0.01% failed fuel, response time = 200 seconds.

An increase above the alarm setpoint would annunciate immediately.

Inventory balance: A leak rate of a fraction of a gpm results in a noticeable downward trend on the Makeup Tank level stripchart recorder, and would be noticed by the control room operators within one hour.

The sensitivity and response times of these systems comply with Item 5.

6. 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 functional when subjected to the SSE.

Valid indication of a " Design Earthquake" (0.lg) requires a plant shutdown.

The radiation monitoring' system and one of the redundant RB sump level indicators are Q components and were qualified to the response spectra of the SSE for ANO-1, described in Section 5.1.2 of the SAR. Although not seismically qualified, Makeup Tank level indication, used to perform an RCS inventory balance, should remain operable following minor seismic events.

These systems meet the criteria of Item 6.

7. 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.

Control room indicators are provided for the redundant RB sump level instruments. The RB airborne particulate and gaseous radioactivity monitors both have indication and high alarm in the control room.

Makeup Tank level indication and high or low level alarm are provided in the control room for the inventory balance method of leakage detection. An RCS leak rate of a fraction of a gpm results in a noticeable downward trend on the Makeup. Tank level strip chart recorder. The inventory balance (RCS leak rate) procedure provides the method for converting various indications to a common leakage equivalent. This complies with Item 7.

8. The leakage detection systems should be equipped with provisions to readily permit testing for operability and calibration during plant operation.

l Testing and calibration are routinely performed by approved station procedures on the ANO-1 leakage detection systems, and are required for various system components per TS Surveillance Requirements 4.5.1.1.2, 4.5.1.1.3 and Table 4.1-1.

This complies with Item 8.

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.

ANO-1 TS 3.1.6 complies with Item 9.

The above comparisons demonstrate that the ANO-1 leakage detection systems follow the guidelines of R.G. 1.45.

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