ML20238E582

Application for Amends to Licenses NPF-11 & NPF-18, Permitting Use of Functioning Channels of Traversing Incore Probe (TIP) Sys W/One or More TIP Measurement Locations Inaccessible or Inoperable.Fee Paid

ML20238E582
Person / Time
Site:	LaSalle
Issue date:	09/04/1987
From:	Allen C COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20238E584	List: ML20238E582 ML20238E588
References
3442K, NUDOCS 8709150084
Download: ML20238E582 (7)

Text

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N Commonwealth Edison

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) One First N1ional Plaza Chicago, Illincis

'l Address Reply to: Pow Offic) Box 767

(_j Chicago, Illinois 60690 - 0767 September 4, 1987 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

LaSalle County Station Units 1 and 2 Proposed Amendment to Technical Specifications for Facility Operating License NPF-11 and NPF-18 NRC Docket No. 50-373 and 50-374 References (a): LaSalle County Station Updated Final Safety Analysis Report Subsection 7.7.6.2.3 (b): Federal Register Vol. 51 No. 44 dated March 6, 1986

Dear Sir:

Pursuant to 10 CFR 50.90 Commonwealth Edison proposes to amend Facility Operating License NPF-ll. This amendment is being submitted for your staff's review and approval and is in accordance with reference (b).

The proposed amendment will permit the use of functioning channels of the Traversing Incore Probe (TIP) System when one or more of the TIP measurement locations are inaccessible or inoperable. This will allow continued operation utilizing operable TIP measurement location data for required LpRM recalibrations and core thermal power monitoring. It will also allow use of substitute TIP data from symetric locations or from computer modeling to be used as an input to the station's process computer.

i Attachment A provides an introduction and discussion. Attachment B provides copies of the changes to be made to the Facility Licenses.

Commonwealth Edison has reviewed this document and finds that no significant hazards exist. This review is documented in Attachment C.

l Commonwealth Edison is notifying the State of Illinois of our request for this amendment by transmitting a copy of this letter and attachments to the designated state official.

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In accordance with 10 CFR 170, a fee remittance in the amount of

$150.00 is also enclosed.

The effective date of this amendment should be 45 days after the date of issuance. If you have any additional questions regarding this matter, please contact this office.

Very truly yours, ,

C. M. Allen Nuclear Licensing Administrator Attachments cc: Paul Shemanski - NRR Regional Administrator - RIII NRC Resident Inspector - LSCS M. C. Parker - IDNS SUBSCRIBED and a RN to befo e m th s day of L. , 1987 11 01Ah

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ATTACHMENT A TECHNICAL SPECIFICATION CHANGE REOUEST LASALLE COUNTY STATION UNITS 1 AND 2 l'

BACKGROUND AND DISCUSSION 1

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b BACKGROUND The TIP system provides a sufficiently precise signal proportional to axial neutron flux at 43 radial core locations. This signal provides the j following: I

a. reliable calibration of the LPRM flux amplifier gains to compensate 1 for changes in detector sensitivity which accompany prolonged neutron )

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b. accurate core wide flux shapes to the computer so power and exposure distributions can be calculated, and  !

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c. accurate fixed location inputs to the computer where Local Power Range Monitors (LPRMs) have failed.

The TIP system consists of five independent neutron detection units.

Each unit contains a miniature fission chamber which is driven from outside the primary containment by a motor drive mechanism. The detector is attached to the drive mechanism by means of a flexible drive cable. Operation of the drive mechanism causes the fission chamber to be inserted or retracted from ,

I the reactor core within individual TIP guide tubes. These tubes are an integral part of the LPRM detector assemblies. Each TIP unit uses an indexing l device to route the detector to the desired LPRM assembly. The 43 LPRM strings are divided between the five TIP machines with one common t#RM assembly connected to all five TIPS for cross channel calibration. The outuput signal from the TIP channel may be used to provide a flux signal into the process computer for calculation of LPRM gain adjustments. The TIPS provide the computer with a base flux distribution in the reactor core. This flux distribution is used to calculate and track power / exposure distribution in the fuel.

l DISCUSSION Technical Specification (T.S.) 3.3.7.7 for both units currently requires that all five TIP units and their associated hardware (TIP detector, drive, readout equipment and indexing mechanism) be operable. Furthermore, it also requires that all five detectors be calibrated in a common location. If these requirements are not met for each TIP unit, then the TIP system, in accordance with T.S. 3.3.7.7, is inoperable and cannot be used for recalibration of any LPRM detectors and for monitoring core thermal limits (APLHGR, LHGR, or MCPR) and fuel exposure. CECO believes that the intent of l

this specification is to prevent the use of the TIP system in one of the 43

! channels if all the equipment associated with that channel is not operable or l accessible. Other operable channels can still be used for LPRM recalibrations and thermal limit monitoring. This specification is being revised to clarify that all channels are not required to be operable for the TIP system to be considered operable. The applicability is revised to include the footnote that only the required channel (s) are needed tor LPRM recalibration(s). This enables calibration of a single LPRM without an entire TIP set as is desirable after returning a failed or drifted LPRM to service.

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l l Procedures currently exist at LaSalle (and most other BWRs) Which utilize the TIP system for recalibration of individual LPRMs and core monitoring functions without the performance of a full core TIP set (all 43 channels). The computer calculates machine normalization constants for each desired channel using values that were ultimately derived from the most recent full core TIP set. Consequently, the TIP machnine normalization constants determined by Process Compu*er Program OD-2 are ultimately derived through calibration of the TIP mach L*s in a common location and the intent of T.S.

3.3.7.7.b is satisfied. L'se of Program OD-2 allows the recalibration of LPRMs that are served by operab'.e TIP units when one or more other TIP un';2 and/or associated equipment are inoperable. The use of this program is an accepted practice at most BWRs and is a valuable tool in maintaining accuracy in core monitoring functions.

The proposed amendments will also allow the utilization of substitute TIP data from symmetric TIP channels in lieu of inaccessible channels under certain core conditions. The Action Statement of T.S. 3.3.7.7 is modified to allow substitute LPRM string TIP data to be copied into an inaccessible string's data area in the computer memory. If the reactor is operating in an octant symmetric (type "A") sequence, certain LPRM strings will have symmetric counterparts which have comparable readings due to the symmetry of the core loading and the control rod pattern. The symmetric TIP data from accessible channels may be substituted for inaccessible channels provided the core is octant symmetric and the total core TIP uncertainty for the present cycle has been measured to be less than 8.7 percent. Certain TIP channels which lie on the axis of symmetry do not have symmetric counterparts. Should these channels be inaccessible, TTP data will be generated by computer modeling of the core conditions using a 3-dimensional core simulator, with the calculated data normalized to the available real data, The proposed amendments do not limit use of the computer modeling method to only the channels which lie on the axis of symmetry. The computer modeling method may be used to generate substitute TIP date for any TIP channel. Analysis supports the use of this method for the generation of subsititute TIP data for all channels of a single TIP machine or for up to five channels if more than one TIP machine is involved. Since uncertainty could be introduced by the simulation and normalization process, an evaluation of the specific rod pattern and core operating state must be performed to ensure that adequate margin to core operating limits is maintained. This is consistent with Updated FSAR Bubsection 7.7.6.2.3 which currently states that a substitute reading for a failed chamber (LPRM) can be derived from an octant symmetric chamber.

The Action Statement additions are intended to prevent shutdown required by certain inoperable TIP equipment which can only be repaired with the reactor shutdown. The two proposed methods (using symmetric counterparts and/or a computer modeling method using a 3-dimensional core simulator) of using substitute data are not new innovations. Previous problems at Peach Bottom, Washington Public Power Supply and Caorso (Spain) have necessitated substitution for inaccessible TIP channels. This work was supported by General Electric Fuel Management services.

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The proposed amendments also include a revision to T.S. Table 4.3.1.1-1 footnote (f) and to Bases 3/4.3.7.7 for both Units 1 and 2. Table l 4.3.1.1-1 footnote (f) is being revised to reflect the changes to T.S.  !

3 . 3 . ~1.*7 . The words using the TIP system" are being deleted to allow the use !

of symmetric counterparts or a computer modeling method for LPRM i recalibrations. A paragraph is being added to Bases 3/4.3.7.7 to explain the use of substituted TIP data from symmetric channels or a computer modeling method as inputs to the Process Computer.

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4 ATTACHMENT B PROPOSED CHANGES TO THE TECHNICAL SPECIFICATIONS FOR OPERATING LICENSES NPF-Il AND NPF-18 REVISED PAGES:

NPF-11 NPF-18 3/4 3-8 3/4 3-8 3/4 3-73 3/4 3-73 B 3/4 3-5 B 3/4 3-5 i

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