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 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 wella

mixed at the time of the test. If the solution is not adequately mixed, sample will be unrepresentative of the tank's contents. This may lead to

accepting the inferred concentration erroneously or diluting or strength- be

ening the solution erroneously and thus allowing the concentration to

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 toof

the maximum allowed time between surveillances, and apply air sparging

the solution at a given rate with periodic axial sampling until theprede- difference in concentration between the axial samples is within a

termined variance (e.g., twice the sampling accuracy). The cumulative

time

sparging time that yields this variance then is the minimum spargingrate.

to be used for all future surveillances for the specified sparging

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 TS

testing performed on the SLC air sparger subsystem was inadequate, the

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

t I

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 Feedwater Transient With 6/9/86 All BWRs and PWRs

Partial Failure Of The facilities holding

Reactor Scram System an OL or CP

86-46 Improper Cleaning And Decon- 6/12/86 All power reactor

tamination Of Respiratory facilities holding

Protection Equipment an OL or CP and

fuel fabrication

facilities

86-45 Potential Falsification Of 6/10/86 All power reactor

Test Reports On Flanges facilities holding

Manufactured By Golden Gate an OL or CP and

Forge And Flange, Inc. research and test

facilities

86-44 Failure To Follow Procedures 6/10/86 All power reactor

When Working In High Radiation facilities holding

Areas an OL or CP and

research and test

reactors

86-43 Problems With Silver Zeolite 6/10/86 All power reactor

Sampling Of Airborne Radio- facilities holding

iodine an OL or CP

86-42 Improper Maintenance Of 6/9/86 All power rector

Radiation Monitoring Systems facilities holding

an OL or CP

86-41 . Evaluation Of Questionable 6/9/86 All byproduct

Exposure Readings Of Licensee material licensees

Personnel Dosimeters

86-32 Request For Collection Of 6/6/86 All power reactor

Sup. 1 Licensee Radioactivity facilities holding

Measurements Attributed To an OL or CP

The Chernobyl Nuclear Plant

Accident

OL = Operating License

CP = Construction Permit