2CAN059804, Provides Clarification to Info Provided in 960223, Correspondence Based Upon New Info Re Reactor Coolant Sys Leakage Detection

Provides Clarification to Info Provided in 960223, Correspondence Based Upon New Info Re Reactor Coolant Sys Leakage Detection

ML20247P279
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/15/1998
From:	James D ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2CAN059804, 2CAN59804, NUDOCS 9805270384
Download: ML20247P279 (3)

Text

!

e Entergy operations,Inc.

N{j 1448 SA 333 RuraMie, AR 72801

'.

• Tel501858 5000 May 15,1998 2CAN059804 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station OPI-17 Washington, DC 20555

Subject:

Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Reactor Coolant System Leakage Detection Gentlemen:

l By letter dated September 16, 1994 (2CAN099402), Entergy Operations provided information which demonstrated that the Arkansas Nuclear One, Unit 2 (ANO-2) leakage 1 detection systems met the reconunendations of Regulatory Guide 1.45, " Reactor Coolant l Pressure Boundary Leakage Detection Systems." By letter dated February 29, 1996  ;

(2CAN029602), Entergy Operations supplied additional information to support this position.  !

In the February 29,1996, correspondence, Entergy Operations committed to having an alarm which would assist the operator in detecting a one gpm sump increase within one hour. Based on the information in these submittals, the Staffissued a safety evaluation dated June 18,1996  !

(2CNA069601).

During s' recent design review of the ANO-2 sump level instrumentation, additional

( information concerning the operation of the sump level sensor was discovered. The purpose of this submittal is to provide a clarification to the information provided in the February 23, 1996, correspondence based upon this new information. Specifically, in a certain cirm==*ence, a one gpm increase in leskrate into the sump could require up to 70 minutes to

! be detected.

l The sump level sensor uses a vertical series of switches spaced at one 'mch increments which  !

! are magnetically actuated by a ball float. The float causes the switches to close in a sequence

! .which gives an effective reading for every halfincrement oflevel variation. The sump level E

sensor response time is dW. upon the existing sump level at the time that a one gpm increase in leakrate is initiated.

9805270304 990515 h i O PDR ADOCK 05000368 '

P PDR a OOd]; DD

U. S. NRC May 15,1998 2CAN059804 Page 2 in the, worst case scenario, if the indicated sump level is stagnant and at the bottom of a half

, " inch increment immediately above a closed switch when a one gpm leak into the sump is initiated, the second switch needed to indicate the one gpm leakrate within an hour may not actuate until approximately 70 minutes instead of the desired one hour. This scenario is unkkely because normal leakagei 'nto the munp prevents the sump level from stagnating in the lower portion of a switch increment and enhances the detection capability. Upon initiation of a one gpm leakrate into the sump, normal leakage into the sump of greater than 0.17 gpm would cause the alarm to be generated within one hour. Normal leakrates of this magnitude are not uncommon. Thus, a one gpm increase in leakage to the sump would usually be detected within one hour. However, during the described specific circumstance, with exactly a one gpm increase in leakage initiated just above a switch increment, and with no previously existing leakage, a one gpm sump increase could take up to 70 minutes to be detected.

Regulatory Guide 1.45 states that prudent selection of detection methods should include sufficient systems to assure effective monitoring during periods when some detection systems may be ineffective or inoperable. Containment sump monitoring was one of four methods described in the September 16,1994, correspondence for detecting leakage of one gpm in less than one hour. The three other methods utilized are the airborne particulate monitor, the airborne radiogas monitor, and the inventory balance procedure. These three other methods are available when the situation discussed above exists.

Due to the reasoning presented above, Entergy Operations believes that the ANO-2 leakage detection systems continue to meet the intent of Regulatory Guide 1.45, and therefore, the basis for which the Staff granted the safety evaluation remains valid. Should you have any questions, please contact me.

Very truly yours, Y Y ale E.

Acting or, Nuclear Safety DEJ/nbm

U. S. NRC May 15,1998 2CAN059804 Page 3

• 'cc': Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Rv1=*=y Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Mr. William D. Reckley NRR Project Manager Region IV/ANO-1 & 2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville rike Rockville, MD 20852 i

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