ML20141F509

Forwards Response to 970501 RAI Re Licensee Request to Extend Surveillance Interval for Calibr of APRM Flow Bias Instrumentation from 18 Months to 24 Months

ML20141F509
Person / Time
Site:	Peach Bottom
Issue date:	06/25/1997
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-91-04, GL-91-4, NUDOCS 9707030020
Download: ML20141F509 (5)

Text

~ ~ . - . ~ , . . . . - ~. _ . . . - . . - . . . .- , , ..-. ~ ~ .....~ . . .. - . . ~ . . . . . - -

I

( ,

Ct*. tion Support Depsrtment l

. t a

& 10CFR50.90 y #

PECO NUCLEAR etw t- c-965 Chestertwook Boulevard i A Unit of PECO Energy Wayne, PA 19087-5691 l 1

June 25,1997 i l

l Docket Nos. 50-277 50-278 License Nos. DPP.-44 f DPR-56 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk WasNngton, DC 20555

SUBJECT:

Peach Dottom Atomic Power Station, Units 2 and 3 l Respon9707030020 970625 ttagmifutmlite !!Eenulam PDR ADOCK 05000277 lllNlElI'lllll lllllllll P PDR 4

COMMONWEALTH OF PENNSYLVANIA:

SS l

COUNTY OF CHESTER  :

l J. B. Cotton, being first duly sworn, deposes and says:

l That he is Vice President of PECO Energy Company; the Applicant I herein; that he has read the Enclosed Response to the NRC Request for i l

4 Additional Information dated May 1,1997, related to a proposed extension of i

surveil'ance interval for calibration of APRM flow bias instrumentation, and knows the contents thereof; and that the statements and matters set forth therein

. are true and correct to the best of his knowledge, information and belief. l l

)

On/idL

/

. Vice President Subscribed and sworn to l before me this S day

~

of  % 1997.

r Notary Public

Notanat seal

% r y 990

1 4 l i

1

\

l Attachment 1 l

l l

l l

l

i

' ~

i '

Docket Nos. 50-277

, . 50-278 i

l'.

License Nos. DPR-44

. . DPR-56 i

I Response to Request for Additional Information l

Peach Bottom Atomic Power Station, Units 2 and 3

]

i-

)

i Question I

) (1) Generic Letter (GL) 91-04, " Changes in Technical Specification Surveillance j Intervals to Accommodate a 24-month Fuel Cycle," was issued April 2,1991.

i Enclosure 2 of GL 91-04 provides guidance for addressing the effect of

increased surveillance intervals on instrument drift and safety analysis assumptions. it states that licensees should address a number of issues to

[ provide an acceptable basis for increasing the calibration interval for instruments i that are used to perform safety functions. GL 91-04 gives actions that the

licensee should address for each issue.

2

! Please address each of the provisions of Enclosure 2 to GL 91-04 as they pertain to your request to extend the calibration interval for the APRM flow bias instrumentation.

Response

(1) As stated in our License Change Request dated March 31,1997, the APRM safety design basis does not require the flow biasing signal to fulfill its purpose.

Furthermore, the Updated Final Safety Analysis Report accident and transient analyses do not take credit for the flow bias function in the mitigation of any accidents or transients. Only the APRM clamped high neutron flux scram is credited for accident mitigation. This clamped high neutron flux scram is not impacted by the proposed changes and will be automatically enforced regardless of the status or accuracy of the APRM flow bias circuitry over a 24 month fuel cycle.

The intent of GL 91-04 was to provide guidance for evaluating the extension of surveillance intervals to 24 months for existing equipment. The subject APRM ,

flow bias instrumentation was recently replaced. The original equipment was not capable of supporting a 24-month calibration interval based on historical surveillance records. This equipment was replaced with a Moore Mycro 352 controller which is more accurate and reliable than the original equipment. This same model controller was first introduced in 1991 for reactor feedpump control. 1 The 24-month surveillance interval proposed for the APRM flow bias instrumentation is the identical calibration frequency for the same instruments l

used in High Pressure Coolant injection (HPCI), Reactor Core Isolation Cooling (RCIC), and Containment Air Dilution system applications since 1994. These

systems h va rclirbly opertt:d on a 24-month calibration int rval without any

- c' .- .. need for recalibration. This is b std on a revicw of 16 historical calibration surveillances and preventive maintenance activities on the above mentioned controllers where no recalibration was required ( i.e., as-found data was within specified tolerances).

The flow transmitters used in the APRM system for sensing recirculation flow are Rosemount 1151s which are used throughout Peach Bottom Atomic Power Station (PBAPS) and the nuclear industry. Their industry wide calibration experience support their current 24-month calibration interval employed at PBAPS.

l The equipment used to interface the controllers to each APRM channel are

f. Moore Industries current to voltage (1/E) signal converters. These converters l

are from the same line of components used in HPCI and RCIC control and indication applications. Although the HPCI and RCIC applications use current to current (1/l) converters, the internal design is the same as the 1/E design except that the l/l converter has an additional current driver in its output stage. A

! review of 13 historical 24-month calibration surveillances of HPCI and RCIC l . signal converters showed no recalibration was required (i.e., as-found data was -

l within specified tolerances).

l These data support the proposed change to a 24-month surveillance interval for l the APRM flow bias instrumentation.

l

{.  !

l l

l p

l l

4 i

,, ~