Information Notice 1986-48, 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 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
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