United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9803190268

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  LaSalle County Station, Unit 1            PAGE: 1 OF 4



DOCKET NUMBER:  05000373



TITLE:  Abnormal Startup of Idle Reactor Recirculation Loop

        Analysis (UFSAR Ch. 15) Not Bounding Due To Vendor

        Inadequate Calculation



EVENT DATE:  02/10/98   LER #:  98-003-00   REPORT DATE:  03/12/98



OTHER FACILITIES INVOLVED:  LaSalle County          DOCKET NO:  05000374

                            Station, Unit 2



OPERATING MODE:  4/N POWER LEVEL:  000



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

OTHER (Voluntary Report)



LICENSEE CONTACT FOR THIS LER:

NAME:  Dave Henry, System Engineering       TELEPHONE:  (815) 357-6761

                                                        Extension 2250



COMPONENT FAILURE DESCRIPTION:

CAUSE:      SYSTEM:       COMPONENT:       MANUFACTURER:

REPORTABLE NPRDS:



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



On February 10, 1998, while analyzing a potential setpoint change,

General Electric (GE) discovered that the LaSalle UFSAR Chapter 15

analysis for "Abnormal Startup of an Idle Reactor Recirculation Pump" is

not bounding.  Preliminary results from a GE analysis for a revised Flow

Control Valve (FCV) position for recirculation pump upshift indicated

that the current transient initial conditions are not the most severe.

In addition, using LaSalle's current approved setpoint of 15 percent FCV

position and the most limiting initial conditions, the thermal limits

acceptance criteria are not met.  The plant was never in a condition to

challenge plant safety.  LaSalle has never violated the procedural and

Technical Specification (3/4.4.1.4.b) requirements that govern idle

recirculation loop startup, thus maintaining thermal limits and fuel

cladding integrity.  Previous GE analyses were insufficient, since the GE

analysis of this UFSAR transient did not properly identify the bounding

conditions.  Events leading to this cannot be identified by ComEd, and

are being investigated by GE through the 10 CFR Part 21 process.

Bounding parameters and conditions will be established prior to restart

of either unit.  These results, when obtained, will be incorporated into

the UFSAR and applicable procedures.  There are no previous occurrences

of this event.  The event is being reported voluntarily.



END OF ABSTRACT



TEXT                                                          PAGE 2 OF 4



PLANT AND SYSTEM IDENTIFICATION



     General Electric - Boiling Water Reactor 3323 Megawatts Thermal

     Rated Core Power



     Energy Industry Identification System (EIIS) codes are identified in

     the text as [XX].



A.   CONDITION PRIOR TO EVENT



     Unit(s): 1/2             Event Date: 02/10/98     Event Time: 15:45

                                                                 Hours

     Reactor Mode(s): 4/N     Power Level(s):       RCS [AB] Temperature:

                              000/000            Unit 1 </= 200 Degrees F

                                                 Unit 2 </= 140 Degrees F

     Mode(s) Name: Cold                          RCS [AB] Pressure:

     Shutdown/Defueled                           14.7 psia (Unit 1/2)



B.   DESCRIPTION OF EVENT



     On February 10, 1998, while performing an analysis to support a

     setpoint change, vendor personnel discovered that the LaSalle UFSAR

     Chapter 15 analysis for "Abnormal Startup of an Idle Reactor

     Recirculation Pump" (section 15.4.4) is not bounding.  Preliminary

     results from the General Electric (GE) analysis regarding a revised

     Flow Control Valve (FCV) position for Reactor Recirculation System

     (RR) [AD] pump upshift indicated that the current Chapter 15

     transient initial conditions are not the most severe.  There is an

     increased rigor on the part of all fuel vendors to find the most

     limiting conditions for transients.  They are now reviewing areas of

     the power to flow map that were previously not explored due to the

     belief that the areas were non-limiting.  In doing so, GE discovered

     that initiating this transient at a lower power level than was

     previously assumed creates a more severe transient with respect to

     thermal limits.  In addition, using LaSalle's current approved

     setpoint of 15 percent FCV position and the most limiting initial

     conditions, the thermal limits acceptance criteria [maximum Average

     Planar Linear Heat Generation Rate (MAPLHGR) and Minimum Critical

     Power Ratio (MCPR)] are not met.  There were no equipment failures

     that contributed to this event.



C.   CAUSE OF EVENT



     The root cause of this event lies within General Electric, and

     cannot be determined by ComEd.  GE is investigating this event for

     10 CFR Part 21 applicability.  Resolution of this issue will be

     addressed by GE's internal Corrective Action Program.



TEXT                                                          PAGE 3 OF 4





     This transient has been considered a non-limiting event, as

     determined in the original FSAR.  Therefore, it did not need to be

     reanalyzed every cycle.  Therefore, this transient has only been

     analyzed for the initial FSAR, and in 1988, as the result of a plant

     modification.  Although the results from these analyses were shown

     to be acceptable for the conditions stated in the FSAR, the analyses

     failed to identify that different conditions (ie., lower power

     levels) would result in more severe results.  Additionally, the

     ComEd review process for vendor analyses that existed at that time

     did not effectively result in recognition of the error in the

     determination of initial limiting conditions.



D.   SAFETY ANALYSIS



     The plant was never in a condition to challenge any thermal limits

     as a result of this event.  Plant operation is bounded by procedures

     and Technical Specifications (3/4.4.1.4.b) which govern idle

     recirculation loop startup.  According to those sources, an idle

     recirculation loop shall not be started unless the temperature

     differential between the reactor coolant within the idle and

     operating recirculation loops is less than or equal to 50 degrees

     Fahrenheit and the operating loop flow rate is less than or equal to

     50 percent of rated loop flow.  The GE analyses that have shown

     existing thermal limits to be non-bounding assumed a 100 degree

     Fahrenheit idle loop temperature.  If the Technical Specification

     constraints are credited, the existing thermal limits remain

     adequate.  Since LaSalle has never violated the Technical

     Specification requirements, thermal limits and fuel cladding

     integrity have been maintained.  This notification is being made

     voluntarily.



E.   CORRECTIVE ACTIONS



     1.   Bounding parameters and conditions will be established prior to

          restart of either unit.  These results, when obtained, will be

          incorporated into the UFSAR, Core Operating Limits Report, and

          applicable procedures.  (NTS# 373-180-98-SCAQ00003.01 and NTS#

          373-180-98-SCAQ00003.02)



     2.   LaSalle Station will perform a review of other UFSAR Chapter 15

          transients for similar inconsistencies.  (NTS

          #373-180-98-SCAQ00003.03)



     3.   Current ComEd procedure (NEP-16-32 Control Management and

          Review of Controlled Work) requires that in depth acceptance

          reviews of vendor transient and accident analysis be performed

          in order to ensure input assumptions and results are valid and

          reasonable.  These controls were not in place at the time of

          the original analysis of this transient.



     4.   Resolution of this issue will be addressed by GE's internal

          Corrective Action Program.  ComEd will track this item.  (NTS#

          373-180-98-SCAQ00003.04)



TEXT                                                          PAGE 4 OF 4



F.   PREVIOUS OCCURRENCES



     LER NUMBER          TITLE



     None.



G.   COMPONENT FAILURE DATA



     Since no component failure occurred, this section is not applicable.



ATTACHMENT TO 9803190268                                      PAGE 1 OF 1



Commonwealth Edison Company

LaSalle Generating Station

2601 North 21st Road

Marseilles, IL 61341-9757

Tel 815 357-6761



                                                                    ComEd



March 12, 1998



United States Nuclear Regulatory Commission

Attention: Document Control Desk

Washington, D.C.  20555



Licensee Event Report #98-003-00, Docket #050-373 is being submitted to

your office.  This event does not meet any reportability criteria but is

being reported voluntarily for your information.



If there are any questions or comments concerning this letter, please

refer them to Perry Barnes, Regulatory Assurance Manager, at (815)

357-6761, extension 2383.



Respectfully,



Fred Dacimo

Site Vice President

LaSalle County Station



Enclosure



cc:  A.  B.  Beach, NRC Region III Administrator

     M.  P.  Huber, NRC Senior Resident Inspector - LaSalle

     C.  H.  Mathews, IDNS Resident Inspector - LaSalle

     F.  Niziolek, IDNS Senior Reactor Analyst

     INPO - Records Center



A Unicom Company



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