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 ORIGINAL SSINS No.: 6835 IN 86-48 UNITED STATES RECEIVED NUCLEAR REGULATORY

COMMISSION

Bart D. Withers OFFICE OF INSPECTION

AND ENFORCEMEN

Vice President, Nuclear WASHINGTON, D.C. 20555 IJL!N, 3 1986 Route To: , June 13, 1986 ________IE INFORMATION

NOTICE NO. 86-48: INADEQUATE

TESTING OF BORON SOLUTION CONCENTRATION

IN THE STANDBY LIQUID CONTROL SYSTEM

Addressees

All boiling water reactor (BWR) nuclear power facilities

holding an operating license (OL) or a construction

permit (CP).

Purpose

This notice is to alert recipients

to a potentially

significant

problem that has been observed with the sampling and testing of the sodium pentaborate

solution concentration

in the standby liquid control system (SLC) at several BWR nuclear power plants. It is expected that recipients

will review the information

for applicability

to their facilities

and consider action, if appropriate, 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 indicates continuing

problems in maintaining

volume and concentration

of the solution within Technical

Specification (TS) limits. Inspections

have also revealed inadequate

preoperational

testing which failed to prevent operational

problems with concentration.

Several of the problems caused plants to initiate shut-downs as required by TS limits. Usually, the proper level and concentration

was 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 that time. Values both lower and higher than the TS requirements

were reported.Low boron concentration

or low tank level reduces protection

against an anticipated-transient-without-scram (ATWS) event due to reduced negative reactivity

worth of the boron solution.

High boron concentration

increases

the risk of forming crystals of boron that could render the system inoperable.

However, none of the LERs or inspections

reported situations

in which the SLC would 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 94 percent to 99 percent of the TS limit) while 6 reported concentration

too high Copies 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 86-48 PGE OAR Action -M. H. Malmros-, -A "No OAR to be issued -Applicable

to BWR's only"

IN 86-48 June 13, 1986 (ranging from 100.1 percent to 106 percent of the TS limit). The causes reported included incorrect

tank levels, inadequate

accounting

for system leakage, inadequate

accounting

for the specific gravity of sodium pentaborate, inferred loss of boron, and increased

water evaporation

rate with increased solution temperature.

The problems of tank level measurement

and mixing and testing procedures

are discussed

below in more detail.Storage Tank Level At LaSalle 2, NRC inspection

revealed that the operations

group and the chemistry

group used 3 different

methods to measure the tank level and results were in frequent disagreement.

In some instances, the disagreement

was as large as 200 gallons (about 4 percent).

The 3 methods involved level meter readings, sight glass readings, and readings of a measuring tape attached to a plumb bob. As a corrective

measure, the licensee is sr-cifying

the use of tne last m because it is apparently

the most reliable method.At Susquehanna

2, level was reported to be 8 percent less than the TS requirement (about 17 percent error in volume). Level was measured using a steel tube from which air bubbles continuously

exited near the bottom of the tank and tank level was inferred from the air pressure.

This approach was rendered inaccurate

by tube blockage built up by the alternate

wetting and drying of the tip of the tube. The licensee modified this system for periodically

cleaning the tube with a brush and Is establishing

an addi-tional alternative

method of level measurement

using an ultrasonic

device.Mixing Over the course of 3 inspections

of preoperational

testing of the SLC at LaSalle, Perry, and Clinton, the NRC has identified

apparent noncompliance

related to whether the SLC can generate a uniform solution.

The involved licensees

did not adequately

meet their commitment

to implement

Regulatory

Guide 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 the liquid 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 Regulatory

Guide 1.68 gives in part: (3) Standby Liquid Control System Tests. Demonstrate

proper operation of the system with demineralized

water. Verify proper mixing of solution 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 86-48 June 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 sparging time 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 well mixed at the time of the test. If the solution is not adequately

mixed, a sample will be unrepresentative

of the tank's contents.

This may lead to accepting

the inferred concentration

erroneously

or diluting or strength-ening the solution erroneously

and thus allowing the concentration

to be outside the TS requirement.

The licensees

at LaSalle, Perry, and Clinton have found that an adequate way 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 to the maximum allowed time between surveillances, and apply air sparging of the solution at a given rate with periodic axial sampling until the difference

in concentration

between the axial samples is within a prede-termined variance (e.g., twice the sampling accuracy).

The cumulative

sparging time that yields this variance then is the minimum sparging time to 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 original testing performed

on the SLC air sparger subsystem

was inadequate, the TS surveillance

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 Regional Administrator

of the appropriate

regional office or this office.Jdwaorn D r Division of Emergency

Preparedness

and E gineering

Response Office of Inspection

and Enforcement

Technical

Contacts:

Vernon Hodge, IE (301) 492-7275 Roger D. Lanksbury, RIII (312) 790-5579 Attachment:

List of Recently Issued IE Information

Notices

I t 4.Attachment

1 IN 86-48 June 13, 1986 LIST OF RECENTLY ISSUED IE INFORMATION

NOTICES Information

Date of Notice No. Subject Issue Issued to 86-47 86-46 Feedwater

Transient

With Partial Failure Of The Reactor Scram System Improper Cleaning And Decon-tamination

Of Respiratory

Protection

Equipment Potential

Falsification

Of Test Reports On Flanges Manufactured

By Golden Gate Forge And Flange, Inc.6/9/86 6/12/86 6/10/86 86-45 86-44 86-43 86-42 86-41 86-32 Sup. 1 Failure To Follow Procedures

6/10/86 When Working In High Radiation Areas All BWRs and PWRs facilities

holding an OL or CP All power reactor facilities

holding an OL or CP and fuel fabrication

facilities

All power reactor facilities

holding an OL or CP and research and test facilities

All power reactor facilities

holding an OL or CP and research and test reactors All power reactor facilities

holding an OL or CP All power rector facilities

holding an OL or CP All byproduct material licensees All power reactor facilities

holding an OL or CP Problems With Silver Zeolite Sampling Of Airborne Radio-iodine Improper Maintenance

Radiation

Monitoring

Of Systems 6/10/86 6/9/86 6/9/86 6/6/86.Evaluation

Of Questionable

Exposure Readings Of Licensee Personnel

Dosimeters

Request For Collection

Of Licensee Radioactivity

Measurements

Attributed

To The Chernobyl

Nuclear Plant Accident OL = Operating

License CP = Construction

Permit