ML20204H421

Application for Amends to Licenses NPF-37,NPF-66,NPF-72 & NPF-77,allowing Use of Gamma-Metrics post-accident Neutron Monitors to Provide Neutron Flux Info During Operational Mode 6

ML20204H421
Person / Time
Site:	Byron, Braidwood
Issue date:	03/22/1999
From:	Krich J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20204H427	List: ML20204H421 ML20204H429
References
NUDOCS 9903290072
Download: ML20204H421 (9)

Text

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g , - Caimmonmhh bbon Company 1400 Opus PLuc Dow ners Grove,11. MK l 5-5'01 March 22,1999 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-001 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. 50-454 and 50-455 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. 50-456 and 50-457

Subject:

Request for an Amendment to Appendix A, Technical Specifications, to Facility Operating Licenses to Support Use of Post Accident Neutron Moriitoring Source Range Detectors During Operational Mode 6 Pursuant to 10 CFR 50.90, Commonwealth Edison (Comed) Company is requesting a change to Appendix A, Technical Specifications (TS) of Facility Operating License Nos.

NPF-37, NPF-66, NPF-72, and NPF-77, for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, respectively.

The proposed change is to TS Section 3.9.3, " Nuclear Instrumentation." The change allows the use of the Gamma-Metrics Post Accident Neutron Monitors (PANMs) to provide neutron flux information during Operational Mode 6. The change revises TS Section 3.9.3, " Nuclear Instrumentation," to insert the word " required

• into Conditions A and B to address the allowance to use any combination of the Westinghouse and/or Gamma-Metrics PANMs as source range neutron flux monitors. We request approval of this amendment prior to the start of Byron Station Unit 2 refueling outage beginning October 23,1999, f

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March 22,1999 W. S. Nuclear Regulatory Commission Page 2 This amendment request is subdivided as follows.

1. Attachment A gives a description and safety analysis of the proposed change.

2. Attachment B includes the Technical Specifications pages with the proposed '

changes indicated. Corresponding changes to the Bases are also included.

3. Attachment C describes our evaluation performed using the criteria in 10 CFR 50.91(a)(1) which provides information supporting a finding of no significant hazards consideration using the standard in 10 CFR 50.92(c). j

4. Attachment D provides information supporting an Environmental Assessment.  !

The proposed change has been reviewed and approved in accordance with the  !

requirements of the Comed Quality Assurance Program.

l Comed is notifying the State of Illinois of this application for amendment by transmitting a copy of this letter and its attachments to the designated State Official. 1 i

Should you have any questions concerning this letter, please contact Mr. J. A. Bauer at (630) 663-7287.

Respectfully, R. M. Kric Vice President - Regulatory Services Attachments: Affidavit i A - Description and Safety Analysis for Proposed Change B Marked-up Pages of Proposed Change for Byron Station B Marked-up Pages of Proposed Change for Braidwood Station B Incorporated Proposed Change, Typed Pages, for Byron Station B Incorporated Proposed Change, Typed Pages, for Braidwood Station C - Information Supporting a Finding of No Significant Hazards Consideration D-Information Supporting Environmental Assessment cc: Regional Administrator- NRC Region Ill NRC Senior Resident inspector- Byron Station NRC Senior Resident inspector - Braidwood Station Office of Nuclear Facility Safety -IDNS f

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STATE OF ILLINOIS )

4 COUNTY OF DUPAGE )

IN THE MATTER OF )

COMMONWEALTH EDISON g)OMED) COMPANY ) Docket Nos.

BYRON STATION UNITS 1 and 2 ) STN 50-454 and STN 50-455 AND )

BRAIDWOOD STATION ljNITS 1 and 2 ) STN 50-456 and STN 50-457

SUBJECT:

Request for an Amendment to Appendix A, Technical Specifications, to Facility Operating Licenses to Support Use of Post Accident Neutron Monitoring Source Range Detectors During Operational Mode 6 AFFIDAVIT l affirm that the content of this transmittalis true and correct to the best of my knowledge, information and belief.

/

R. M. Krig/

Vice President - Regulatory Sery ces Subscribed and swom to before me, a Notary Public in and for the State above named, this LL day of b4 c.h .19 % .

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ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOL 2D CHANGE A. ' SilMMARY OF PROPOSED CHANGES Pursuant to 10 CFR 50.90, Comed proposes changes to Appendix A, Technical Specifications, of Facility Operating Licenses NPF-37, NPF-66, NPF-72, and NPF-77. The proposed change allows the use of the Gamma-Metrics Post Accident Neutron Monitors (PANMs) to provide neutron flux information during Operational Mode 6, " Refueling." The change revises Technical Specifications Section 3.9.3, " Nuclear Instrumentation," to insert the j word " required"into Conditions A and 8 to address the allowance to use any combination of 1 the Westinghouse and/or Gamma-Metrics PANMs as source range neutron flux monitors. I The proposed changes are described in detailin Section E of this Attachment. The marked up Technical Specification (TS) pages are shown in Attachment B.

B. DESCRIPTION OF THE CURRENT REQUIREMENTS l l

TS Limiting Condition for Operation (LCO) 3.9.3 requires that two source range neutron flux l monitors be operable in Operational Mode 6, If one source range neutron flux monitor i

becomes inoperable all core alterations and positive reactivity additions must be suspended 1 immediately. When two source range neutron flux monitors are inoperable, action to restore  !

one monitor to operable status must be initiated immediately and Surveillance Requirement (SR) 3.9.1.1 must be performed once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

C. BASES FOR THE CURRENT REQUIREMENTS The Westinghouse source range neutron flux monitors are used during refueling operations to monitor the core reactivity condition. The installed source range neutron flux monitors are part of the Nuclear instrumentation System. The installed source range neutron flux monitors are boron trifluoride detectors operating in the proportional region of the gas filled detector characteristic curve. The detectors monitor the neutron flux in counts per second (cps) over a range that covers six decades (i.e.,1 to 1E06 cps). The detectors provide continuous visual indication in the Main Control Room (MCR) to alert operators to a possible dilution accident or

! an improperly loaded fuel assembly during the refueling operations. TS LCO 3.9.3 requires that two source range neutron flux monitors be operable to ensure that redundant monitoring ,

capability is available to detect changes in core reactivity. To be operable, each monitor must

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provide visualindication to the MCR. With one source range neutron flux monitor inoperable, j the required actions are to immediately suspend core alterations and positive reactivity I additions. With no source range neutron flux monitors operable, there is no direct means of I

detecting changes in core reactivity, and additional actions must be immediately initiated to restore a source range neutron flux monitor to operable status.

D. NEED FOR REVISION OF THE REQUIREMENT Comed is submitting this proposed change to allow for the use of the installed Gamma-Metrics PANMs as redundant source range neutron flux monitors available for the operator to monitor changes in core reactivity during Operational Mode 6. TS LCO 3.9.3 requires two source

range neutron flux monitors to be operable and does not allow credit for the use of the Gamma-Metrics PANMs. The Gamma-Metrics PANMs provide continuous visualindication in the MCR to alert the operators to any changes to core reactivity during the refueling i

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ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGE ope' rations. The Gamma-Metrics PANMs are currently installed and functional along with the Westinghouse source range neutron flux monitors. The two Westinghouse source range neutron flux monitor channels and the two Gamma-Metrics PANM channels are functionally equivalent and are both Safety Category I (Class 1E) systems. By taking credit for the Gamma-Metrics PANMs as source range neutron flux monitors, two additional channels of redundant source range neutron flux monitoring are available during Operational Mode 6.

Historically, during refueling operations, the Westinghouse source range neutron flux monitor channels have experienced noise interference (i.e., erratic indication) that has caused delays in the refueling outages. These channels are susceptible to electrical noise due to the low magnitude of the signal and the circuitry sensitivity to electrical noise inherent to the detector and cable design. In NUREG-0452, " Standard Technical Specifications for Westinghouse Pressurized Water Reactors," the source range neutron flux monitors were required to have continuous visual indication in the MCR and one detector was required to have audible indication in the containment and the control room. With the conversion to the improved Standard Technical Specifications (ISTS), the audible count indication was deleted as a requirement for the source range neutron flux monitors during Operational Mode 6. The conversion to the ISTS was approved in Amendment 106 for Byron Station, Units 1 and 2, and Amendment 98 for Braidwood Station, Units 1 and 2. As a result of this change, the use of the Gamma-Metrics PANMs can now be an acceptable alternative to the Westinghouse source range neutron flux monitors in Operational Mode 6.

E. DESCRIPTION OF THE PROPOSED CHANGES The proposed change allows the use of the Gamma-Metrics PANMs to provide neutron flux information during Mode 6. The change revises TS LCO 3.9.3, " Nuclear Instrumentation," to insert the word " required"into Conditions A and B to address the allowance to use any combination of the Westinghouse and/or Gamma-Metrics PANMs as source range neutron flux monitors. Condition A will be revised to read;"One required source range neutron flux monitor inoperable." The Required Actions and Completion Times associated with Condition A will remain unchanged. Condition B will be revised to read; "Two required source range neutron flux monitors inoperable." The Required Actions and Completion Times associated with Condition B will also remain unchanged. The wording change (i.e., adding the word " required")

is an option allowed in Revision 1 of NUREG-1431, " Standard Technical Specifications Westinghouse Plants," for plants with more than the TS required number of source range neutron flux monitors.

For the Gamma-Metrics PANMs to be operable, they shall meet the TS surveillance requirements and have continuous visualindication in the MCR. The ability currently exists to satisfy all TS surveillance requirements and demonstrate operability of the Gamma-Metrics PANMs. The computer points are also available for trending the Gamma-Metrics PANMs source range neutron flux on a computer pen recorder at the Main Control Board and on the Human-Machine Interface display at the Nuclear Station Operator's console.

The Bases section, B 3.9.3, will be revised to include the allowance to use Camms Metrics PANMs as source ranpa neutron flux monitors for providing neutron flux information during Operational Mode 6. The bases will address the ability to use any combination of the Page 2 of 6

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ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGE detectors, including the use of a portable detector provided the detector can met the LCO requirements for operability. The revised bases section is provided forinformation.

F. SAFETY ANALYSIS OF THE PROPOSED CHANGES The proposed changes add the word " required" to TS Conditions A and B of TS 3.9.3,

" Nuclear Instrumentation." Tho use of the word " required" was a bracketed option identified in the NUREG-1431, Revision 1. Adding " required" to Conditions A and B will provide flexibility to the stations to use any two operable source range neutron flux monitors to satisfy the requirements of TS LCO 3.9.3 to allow core alterations and positive reactivity additions, in Operational Mode 6. As th'.sy are currently written, Technical Specifications do not allow credit for the Gamma-Metrics PANMs.

TECHNICAL COMPARISON BETWEEN GAMMA-METRICS PANMs AND WESTINGHOUSE AS SOURCE RANGE NEUTRON FLUX MONITORS Two separate sub-systems comprise the Neutron Monitoring (NR) System. The Westinghouse portion of the NR System consists of three instrumentation ranges: the Source Rann, Intermediate Range and the Power Range. Each portion consists of detectors, power supplies, signal processing equipment and indicators. In particular, in Operational Mode 6, the purpose of the Westinghouse source range neutron flux monitors is to monitor the neutron flux level. The Westinghouse source range neutron flux monitors provide audio and visual indications of neutron count rate. The audible output provides a warning of any potentially hazardous condition in the MCR and containment. With the conversion to the ISTS, the audible count indication was deleted as a requirement for the source range neutron flux monitors during Operational Mode 6.

As a result of this change, the use of the Gamma-Metrics PANMs can now be an acceptable alternative to the Westinghouse source range neutron flux monitors in Operational Mode 6.

The Westinghouse source range neutron flux monitors use a Safety Category I (Class 1E) detector (two per unit) filled with boron trifluoride (BF3), to detect ne Jtrons in the source range when a voltage potential is applied between the electrode and detector wall. The number of neutrons is represented as low-level current pulses. The Westinghouse source range neutron flux monitors are located in a detector well outside of the reactor vessel, and use a triaxial cable terminated with a moisture tight connector.

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l ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGE

' WESTINGHOUSE SOURCE RANGE NEUTRON FLUX MONITORS i Number of detectors: 2 (per unit)

. Location: One detector is located at 0 orientation about the reactor vessel, while the second detector is located at 180 orientation about the reactor

, vessel.

. 1 Def.ector Type: Boron Trifluoride (BF3 ) Proportional Counter j Detector Sensitivity: 13 cps / neutron-volt (nv) i Range: 10 to' 10' cps I l

Accuracy: 3% of full scale Designed Range of Detector Operating Temperatures: 175-310*F i

. The signal from the Westinghouse source range detector is input into the preamplifier assembly located in a mild environment outside of containment. The signalis amplified

and attenuated at the preamplifier before being input in the source range drawer in the

MCR where the signal is conditioned and processed for input to the ind' ation meters,

audio count rate drawer, comparator and rate drawer, and the plant coinputer.

Each portion of the Westinghouse source range neutron flux monitors has two trains, each is assigned to an independent engineered safeguards features (ESF) diision. ,

These trains are physically and electrically separated in accordance with applictble

, IEEE Standards.

A separate Gamma-Metrics PANMs System is installed to satisfy 1he requirements (J Regulatory Guide 1.97, " Instrumentation For Light-Watered-Cooled Nuclear Power Plants To Assess Plant And Environs Conditions During And Following An Accident."

. The PANM System monitors neutron flux from the source range through 200% Rated Thermal Power (RTP) during all Modes of plant operation.' The PANMs System utilizes two separate Safety Category I (Class 1E) fission chamber neutron detectors for all ranges of neutron flux indication. A voltage potentialis applied to the detector electrode and outside wall. The signal from the detector is composed of a series of charged pulses that are input into an amplifier assembly that contains signal conditioning circuitry, DC power supplies and the high voltage power supply to the detector. The output from the amplifier assembly goes to the signal processing assembly to further process the detector signalinto signals which are a measure of the log count rate and the log of the reactor power. These values are displayed in the MCRi i

i s

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ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS

, FOR PROPOSED CHANGE

' GAMMA-METRICS PANMs INSTRUMENTATION Number of detectors: 2 (per unit)

Location: One detector.is located at 90 orientation about the reactor vessel, while the second detector is located at 270 orientation about the reactor vessel.

Detector Type: Enriched U-235 Fission Chamber Detector Sensitivity: 4 cps /nv(thermal) and 2 cps /nv(fast) 5 Range: 0.1 to 10 cps (source range) 1E-08 to 200% RTP (wide range)

Accuracy: 2% of full scale Designed Range of Detector Operating Temperatures: 32-300 F (Normal Conditions) 32 430 F (Design Basis Event)

(Steam)

Each portion of the Gamma-Metrics PANM instrumentation has two trains, each assigned to an engineered safeguards features (ESF) division. These trains are physically and electrically separated in accordance with applicable IEEE Standards.

The detector for each Westinghouse and Gamma-Metrics PANM source range neutron flux monitor instrumentation channel is installed in the same type of detector well, equidistant to the reactor vessel. For each Gamma-Metrics PANM channel, its neutron detector is 90 apart from its corresponding Westinghouse source range neutron flux monitor channel with respect to the detector's orientation about the reactor vessel.

Based on the previous discussions, both the Westinghouse and Gamma-Metrics PANM source range neutron flux monitors are functionally equivalent and both are Safety

. Category I (Class 1E) systems.

Therefore, the Gamma-Metrics PANMs are functionally equivalent to the Westinghouse source range neutron flux hionitors for providing neutron flux indication to satisfy the requirements of TS LCO 3.9.3.

UFSAR/TS BASES ACCIDENTS ASSOCIATED WITH NEUTRON FLUX MONITORS The primary function of the source range neutron flux monitors is to provide a visual signal to alert the operator to unexpected changes in core reactivity such as boron dilution accident or an improperly loaded fuel assembly.

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The uncontrolled boron dilution transient, as documented in UFSAR 15.4.6, is prevented in Operational Mode 6 by administrative controls that isolate the Reactor Coolant System (RCS) from potential sources of unborated water. TS LCO 3.9.2, Page 5 of 6

ATTACHMENT A DESCRIPTICN AND SAFETY ANALYSIS FOR PROPOSED CHANGE "Unborated Water Source Isolation Valves," requires valves used to isolate unborated water sources to be secured in the closed position thus ensuring the uncontrolled boron dilution transient can not occur. l Improperly loaded fuel assembly errors, as documented in UFSAR 15.4.7, are prevented by administrative procedures (i.e., nuclear component transfer lists, core inventory verification, etc.) implemented during core loading. In the unlikely event that a fuel loading error occurs, analyses confirm that result;ng power distribution effects will either be readily detected by the incore moveable detector system or will cause a sufficiantly small perturbation to be acceptable within the uncertainties allowed between nominal and design power shapes. No credit is provided for the source range neutron flux monitors.

Summarizing, source range neutron flux monitors have no safety function in Operational Mode 6 and are not assumed to function during any UFSAR design basis accident or transient. The source range neutron flux monitors provide the only on-scale monitoring of neutron flux level during refueling. Therefore, they are being retained in Technical Specifications.

G. IMPACT ON PREVIOUS SUBMITTALS This license amendment request does not impact any other licensing submittals H. SCHEDULE REQUIREMENTS This change to ine TS is consistent with the wording provided in NUREG-1431, Revision 1.

Therefore, we request approval of this amendment prior to the start of the Byron Station Unit 2 l refueling outage beginning October 23,1999.

1. REFERENCES None.

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