ML20210A426

Application to Amend License DPR-3,extending Present in-core Instrumentation Sys Tech Specs Applicable for Cycle 18 to Include Cycle 19 as Listed.Mods Would Only Be Utilized If Further Neutron Detector Thimble Failures Occur.Fee Paid

ML20210A426
Person / Time
Site:	Yankee Rowe
Issue date:	01/29/1987
From:	Heider L YANKEE ATOMIC ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20210A431	List: ML20210A426 ML20210A504
References
FYR-87-11, NUDOCS 8702060471
Download: ML20210A426 (5)

Text

___,

se 'a YANKEE ATOMIC ELECTRIC COMPANY wig"l,(o*.Wo*,'o ,~*,'

_ . :> - 'j- ,.;, .

~

< x ^ ^ '1 b 1671 Worcester Road, Framingham, Massachusetts 01701 2.C2.1 A- '.L:. ]

D.rJKEE,/ " *

. - ~ _ _ .

January 29, 1987 PC 205 FYR 87-11 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

References:

(a) License No. DPR-3 (Docket No. 50-29)

(b) YAEC Letter to USNRC, dated July 31, 1986 (FYR 86-071)

(c) USNRC Letter to YAEC, dated December 1, 1986 (NYR 86-270)

(d) YAEC Letter to USNRC, dated October 8, 1986 (FYR 86-097)

(e) USNRC Letter to YAEC, dated December 3, 1986 (NYR 86-269)

Subject:

Incore Instrumentation System Technical Specifications

Dear Sir:

Pursuant to Section 50.59 of the Commission's Rules and Regulations, the Yankee Atomic Electric Company (YAEC) hereby requests the authorization to make the following changes:

Proposed Change Reference is made to the Technical Specifications of License No. DPR-3 of the Yankee Nuclear Power Station. We propose to extend the present Technical Specifications applicable for Cycle 18 to include Cycle 19 as follows:

1. Continue Specification 3.3.3.2 to allow for a change in the number of operable incore neutron detector thimbles required for operability for Cycle 19 operation.

2. Continue Specifications 4.2.1.2, 4.2.2.1, 4.2.2.2, and 4.2.3.2 to allow for increased uncertainty when less than 12 of the incore neutron detector thimbles are operable.

3. Continue Page B3/4 2-2 to reflect the chango in uncertainty to be applied to the measured kW/ft values where less than 12 of the neutron detector thimbles are operable.

/ko (

'(

8702060471 870129 W CSfcl< W DR 4 lgo,o ADOCK0500g9

United Stctra Nuclcir RIgulatory Commissicn J;nuary 29, 1987 Attention: Office of' Nuclear Reactor Regulation Page 2 FYR 87-11 Description of Channe The current Technical Specification (3.3.3.2) governing operability of the Incore Instrumentation System requires that a minimum of 12 neutron detector thimbles be operable with at least two per core quadrant whenever the system is used for core power distribution measurements. An exception to this requirement which allowed a minimum of nine neutron detector thimbles available for operability was recently approved (Reference (c)) for the portion of cycle 18 operation exceeding a cycle average burnup of 4,000 mwd /Mtu. That change also lowered the two per core quadrant requirement to one per core quadrant. This proposed change is an extension of the Reference (b) submittal to include Cycle 19 operation. In addition, the system measurement uncertainties applied to the measured power distribution parameters would remain the same as previously approved by the Commission.

Reason and Basis for Change This change would allow an increase in plant operating flexibility while maintaining sufficient data collection capability to ensure that the operation of the Yankee core is within licensed limits. A concurrent increase in the measurement uncertainty with fewer than 12 available neutron detector thimbles is also included as part of this proposed change. These Technical Specification modifications would be utilized only if further failures of the neutron detector thimbles occur prior to or during Cycle 19 operation. A similar proposal (Reference (b)) was submitted and approved by the Commission for the portion of Cycle 18 operation exceeding 4,000 mwd /Mtu. This proposal is an extension of that proposed change for Cycle 19 operation.

The Incore Instrumentation System is used to perform power distribution measurements so that compliance to the power distribution limits of F ,

FAH, and LHGR (kW/ft) can be verified. Powerdistributionmeasuremenks are made approximately every 1,000 EFPH while at full power, steady-state conditions, and also as part of our power ascension startup test program, previously, in cycles 15 and 18. Technical Specification approval with a minimum of nine available neutron detector thimbles and one per core quadrant was granted once cycle operation was well established and the core. power distribution characteristics well defined. Yankee believes that this reduced complement of available thimbles is also sufficient for power distribution monitoring during Cycle 19 startup and subsequent Cycle 19 full power operation, and as such, the technical evaluation provided in Reference (d) is also applicable to this proposed change.

The Yankee core is a small core which contains only 76 assemblies and employs a simple two-batch fuel management scheme. The loading pattern for Cycle 19 is similar to previous core loadings which results in similar core power distribution and peak power distribution parameter values.

Illustrations of this can be found in Attachment A. The assembly design and initial enrichment has changed only slightly from the previous cycles.

Furthermore, the consistency and accuracy of our analytical models versus measurement, shown in the previous cycles, provides additional assurance of our ability to determine the core power distribution properly.

+-

i.

United States Nuclear Regulatory Commission. January 29, 1987 Attention: Office of Nuclear Reactor Regulation Page 3 FYR 87-11 The ability to detect core misloading prior to core startup is not jeopardized given this proposed change. The possibility for a core misloading is very unlikely given the physical nature of the Yankee core and a program which provides for a complete videotaping of the reactor core. Physically, there are only two fuel batches; recycled fuel is positioned in the core interior and fresh fuel on the core periphery. From a gross detection standpoint, the periphery of this core is shiny, while the interior is dull.

In addition, the unique Yankee assembly geometries of Types A and B cannot be interchanged, and no assembly rotations are possible during core shuffling maneuvers. Verification of each assembly serial number identification is performed for each assembly location prior to vessel reassembly and core startup by an independent review of the core videotaping.

Yankee's capability to detect anomalies in the core during core startup and initial full power operation is also maintained for this proposed change.

A reduced number of available thimbles does not significantly change the ability of the Incore Instrumentation System to determine the core power distribution. A small increase in uncertainty for fewer available thimbles provides conservative peak power distribution parameters with very little change in the predicted core power distribution. Sufficient alternate means are available which provide assurance against any anomaly which might be present in the core. As part of startup physics testing, three out of four of the control rod group reactivity worths are measured. This provides an indirect yet accurate indication of the core power distribution since the three control rod groups cover a large portion of the core's geometry. The measurement of critical boron concentrations and reactivity coefficients for both unrodded and rodded reactor configurations provides an excellent indication of the core reactivity status and serves as the means to detect any possible reactivity anomaly in the core. Power distribution measurements at power levels of approximately 25, 60, 75, and 90 percent power provide step-by-step indications of the core power distribution as part of our power ascension program. The verification of acceptable values of gross quadrant tilt and measured to analytical reaction rates provides the assurance that no power distribution anomalies exist in the core. Given any indication of a possible anomaly, the use of incore thermocouple data, excore detector signals, and loop temperature indications are available as further protection from startup with any core anomalies.

As discussed in our previous meeting (Reference (e)), Yankee feels that this proposed change is interim in that cycle 19 is a transition period to convert the moveable detector locations to fixed detector locations.

Initially, eight of the 22 possible thimble locations are expected to contain fixed detector strings. A belef description of the initial program and the location of the fixed detectors is provided in Attachment B. During cycle 19 startup and approximately the first six months of power operation, data from the fixed detectors will be collected and cross-correlated with the moveable detector data to develop normalization factors and appropriate system measurement uncertainties. Given success of the fixed system, Technical Specification changes based on a combination system will be proposed in the near future, with a total conversion to fixed detectors being the ultimate goal.

United States Nuclear Regulatory Commission January 29, 1987 Attention: Office of Nuclear Reactor Regulation page 4 FYR 87-11 Safety Consideration i This change is requested in order to provide flexibility in plant Loperation with sufficient data gathering capability to ensure operation within licensed limits. As such, this proposed change would not:

1. Involve a significant increase in the probability or consequences of an accident previously evaluated. This change merely increases the measurement uncertainty for a reduced complement of operable incore neutron detector thimbles. Therefore, the change cannot increase the probability or consequences of an accident, as the core will continue to be adequately monitored.

2. Create the possibility of a new or different kind of accident from any previously analyzed. This modification only increases the measurement uncertainty for a reduced complement of operable incore neutron detector thimbles. Therefore, it does not create the possibility of a new or different kind of accident since it does not modify plant operation or components.

3. Involve a significant reduction in a margin of safety. This modification of increasing the measurement uncertainty for a reduced ,

complement of operable incore neutron detector thimbles will add I sufficient additional margin to the power distribution measurements such that this change does not impact the safety margins which currently exist. Thus, this change does not involve a significant reduction in a margin of safety.

Based on the consideration contained herein, it is concluded that there is reasonable assurance that operation of the Yankee plant, consistent with the proposed Technical Specifications, will not endanger the health and safety of the public. This proposed change has been reviewed by the Nuclear Safety Audit and Review Committee.

Fee An application fee of $150.00 is enclosed in accordance with 10CFR170.21.

Schedule of Channe These changes to the Yankee Technical Specifications will be implemented upon Commission approval. A timely review and approval of this submittal would be appreciated.

United StatOc Nucl00r Rigulctcry Commiccien Janunry 29, 1987 Attention: Office of Nuclear Reactor Regulation Page 5 FYR 87-11 We trust that you will find this submittal satisfactory; however, should you desire additional information, please contact us.

Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY L. H. Heider Vice President / Manager of Operations LHH/dps Attachments COMMONWEALTH OF MASSACHUSETTS)

)ss MIDDLESEX COUNTY )

Then personally appeared before me, L. H. Heider, who, being duly sworn, did state that he is Vice President of Yankee Atomic Electric Company, that he is duly authorized to execute and file the foregoing document in the name and on the behalf of Yankee Atomic Electric Company and that the statements therein are true to the best of his knowledge and belief, b

Robert H. Croce Notary Public My Commission Expires August 29, 1991 cc: USNRC Region I USNRC Resident Inspector, YNPS