Information Notice 1986-48, Inadequate Testing of Boron Solution Concentration in the Standby Liquid Control System

Inadequate Testing of Boron Solution Concentration in the Standby Liquid Control System

ML031220694
Person / Time
Issue date:	06/13/1986
From:	Jordan E L NRC/IE
To:
References
IN-86-048
Download: ML031220694 (4)

118 ORIGINALSSINS No.: 6835IN 86-48UNITED STATES RECEIVEDNUCLEAR REGULATORY COMMISSION Bart D. WithersOFFICE OF INSPECTION AND ENFORCEMEN Vice President, NuclearWASHINGTON, D.C. 20555 IJL!N, 3 1986Route To: ,June 13, 1986 ________IE INFORMATION NOTICE NO. 86-48: INADEQUATE TESTING OF BORON SOLUTIONCONCENTRATION IN THE STANDBY LIQUIDCONTROL SYSTEM

Addressees

All boiling water reactor (BWR) nuclear power facilities holding an operatinglicense (OL) or a construction permit (CP).

Purpose

This notice is to alert recipients to a potentially significant problem thathas been observed with the sampling and testing of the sodium pentaboratesolution concentration in the standby liquid control system (SLC) at severalBWR nuclear power plants. It is expected that recipients will review theinformation for applicability to their facilities and consider action, ifappropriate, to preclude a similar problem at their facilities. However,suggestions contained in this information notice do not constitute NRC require-ments; therefore, no specific action or written response is required.

Description of Circumstances

Review of licensee event reports (LERs) over the past several years indicatescontinuing problems in maintaining volume and concentration of the solutionwithin Technical Specification (TS) limits. Inspections have also revealedinadequate preoperational testing which failed to prevent operational problemswith concentration. Several of the problems caused plants to initiate shut-downs as required by TS limits. Usually, the proper level and concentrationwas recovered in less than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> but in one case recovery took twice thattime. Values both lower and higher than the TS requirements were reported.Low boron concentration or low tank level reduces protection against ananticipated-transient-without-scram (ATWS) event due to reduced negativereactivity worth of the boron solution. High boron concentration increases therisk of forming crystals of boron that could render the system inoperable.However, none of the LERs or inspections reported situations in which the SLCwould be rendered inoperable by boron crystallization or not capable of shut-ting down the reactor as required.Discussion:Eight LERs reported boron solution concentration too low (ranging from 94percent to 99 percent of the TS limit) while 6 reported concentration too highCopies to: Withers, Yundt, Lentsch, Orser, Steele, E. Burton, E. Jordan, A. Holm,LIS, C. A. Olmstead, S. Hoag, S. Sautter, TNP:GOV REL F:NRC CHRONO,TNP:GOV REL F:NRC IE Information Notice 86-48PGE OAR Action -M. H. Malmros-, -A "No OAR to be issued -Applicable to BWR's only" IN 86-48June 13, 1986 (ranging from 100.1 percent to 106 percent of the TS limit). The causesreported included incorrect tank levels, inadequate accounting for systemleakage, inadequate accounting for the specific gravity of sodium pentaborate,inferred loss of boron, and increased water evaporation rate with increasedsolution temperature. The problems of tank level measurement and mixing andtesting procedures are discussed below in more detail.Storage Tank LevelAt LaSalle 2, NRC inspection revealed that the operations group and thechemistry group used 3 different methods to measure the tank level andresults were in frequent disagreement. In some instances, the disagreementwas as large as 200 gallons (about 4 percent). The 3 methods involvedlevel meter readings, sight glass readings, and readings of a measuringtape attached to a plumb bob. As a corrective measure, the licensee issr-cifying the use of tne last m because it is apparently the mostreliable method.At Susquehanna 2, level was reported to be 8 percent less than the TSrequirement (about 17 percent error in volume). Level was measured usinga steel tube from which air bubbles continuously exited near the bottom ofthe tank and tank level was inferred from the air pressure. This approachwas rendered inaccurate by tube blockage built up by the alternate wettingand drying of the tip of the tube. The licensee modified this system forperiodically cleaning the tube with a brush and Is establishing an addi-tional alternative method of level measurement using an ultrasonic device.MixingOver the course of 3 inspections of preoperational testing of the SLC atLaSalle, Perry, and Clinton, the NRC has identified apparent noncompliancerelated to whether the SLC can generate a uniform solution. The involvedlicensees did not adequately meet their commitment to implement RegulatoryGuide 1.68, "Initial Test Programs for Water-Cooled Nuclear Power Plants."In particular, the air sparger subsystem was not tested properly. Also,the sampling methodology (dip samples were or might be taken from near theliquid surface at these plants) necessary to satisfy surveillance require-ments of TS was not demonstrated to yield valid results.Concerning preoperational testing of the SLC, Appendix A of RegulatoryGuide 1.68 gives in part:(3) Standby Liquid Control System Tests. Demonstrate proper operationof the system with demineralized water. Verify proper mixing ofsolution and adequacy of sampling system. ...Verify operability of. ..air spargers. ..The testing observed consisted of filling the solution tank with deminer-alized water, commencing air flow through the sparger, and verifying that IN 86-48June 13, 1986 the distribution of air bubbles was even. This procedure does not demon-strate uniform mixing of the solution and it does not determine what spargingtime is required to ensure that dip samples represent the tank's contents.The sodium pentaborate solution stratifies over time. Because TS surveil-lance tests are performed on a monthly basis, the solution may not be wellmixed at the time of the test. If the solution is not adequately mixed, asample will be unrepresentative of the tank's contents. This may lead toaccepting the inferred concentration erroneously or diluting or strength-ening the solution erroneously and thus allowing the concentration to beoutside the TS requirement.The licensees at LaSalle, Perry, and Clinton have found that an adequateway to verify proper mixing is to initially fill the tank to the concen-tration required by the facility's TS, allow a settling period equal tothe maximum allowed time between surveillances, and apply air sparging ofthe solution at a given rate with periodic axial sampling until thedifference in concentration between the axial samples is within a prede-termined variance (e.g., twice the sampling accuracy). The cumulativesparging time that yields this variance then is the minimum sparging timeto be used for all future surveillances for the specified sparging rate.Any decrease from the sparging rate used in the above test would necessi-tate retesting to determine an acceptable sparging time.For those plants past the preoperational test phase, if the originaltesting performed on the SLC air sparger subsystem was inadequate, the TSsurveillance tests may not be yielding valid results.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact the RegionalAdministrator of the appropriate regional office or this office.Jdwaorn D rDivision of Emergency Preparednessand E gineering ResponseOffice of Inspection and EnforcementTechnical Contacts: Vernon Hodge, IE(301) 492-7275Roger D. Lanksbury, RIII(312) 790-5579

Attachment:

List of Recently Issued IE Information Notices It4.Attachment 1IN 86-48June 13, 1986LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to86-4786-46Feedwater Transient WithPartial Failure Of TheReactor Scram SystemImproper Cleaning And Decon-tamination Of RespiratoryProtection EquipmentPotential Falsification OfTest Reports On FlangesManufactured By Golden GateForge And Flange, Inc.6/9/866/12/866/10/8686-4586-4486-4386-4286-4186-32Sup. 1Failure To Follow Procedures 6/10/86When Working In High RadiationAreasAll BWRs and PWRsfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CP andfuel fabricationfacilitiesAll power reactorfacilities holdingan OL or CP andresearch and testfacilitiesAll power reactorfacilities holdingan OL or CP andresearch and testreactorsAll power reactorfacilities holdingan OL or CPAll power rectorfacilities holdingan OL or CPAll byproductmaterial licenseesAll power reactorfacilities holdingan OL or CPProblems With Silver ZeoliteSampling Of Airborne Radio-iodineImproper MaintenanceRadiation MonitoringOfSystems6/10/866/9/866/9/866/6/86.Evaluation Of QuestionableExposure Readings Of LicenseePersonnel DosimetersRequest For Collection OfLicensee RadioactivityMeasurements Attributed ToThe Chernobyl Nuclear PlantAccidentOL = Operating LicenseCP = Construction Permit