ML20118B919

Safety Evaluation Supporting Amend 22 to License NPF-85

ML20118B919
Person / Time
Site:	Limerick
Issue date:	09/28/1992
From:	Office of Nuclear Reactor Regulation
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ML20118B917	List: ML20118B916 ML20118B919
References
NUDOCS 9210080114
Download: ML20118B919 (7)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED AMENDMENT NO. m TO FACILITY OPERATING LICENSE NO. NPF-85 PHILADELPHIA ELECTRIC COMPANY LIMER[CK GENFRATLN[G STATION. UNIT 2 DOCKET NO. 50-353 i

1.0 INTRODUCTION

By letter dated July 7, 1992, the Philadelphia Electric Company (PEco or the licensee) submitted a request for changes to the Limerick Generating Station, Unit 2, Technical Specifications (TS).

The requested changes would revise the TSs to add new isolation valves to the table of primary containment isolation valves that must be operable and to delete the presently designated valves on the same lines.

Limerick, Unit 2, is_ scheduled to shutdown for the second refueling outage on January 23, 1993.

During the refueling outage, the licensee plans to install eight new check valves (four pairs of valves) on the control rod drive (CRD) supply headers to the hydraulic control units (HCUs).

These new valves will constitute a new isolation boundary for the Integrated Leak Rate Test (ILRT), replacing the existing HCU isolation boundary valves.

The proposed changes to the TS are to include the new valves in Table 3.6.3-1, "Part A - Primary Containment Isolation Valves" and to remove the current HCU valves as boundaries.

The same change was approved for Limerick, Unit 1, by Amendment No. 42, dated August 16, 1990. The safety evaluation supporting Amendment No. 42 is incorporated herein by reference.

2.0 DISCUSSION The ILRT is a pressurization of primary containment and measurement of total leakage from all isolation boundaries.

The current method of testing the isolation boundaries of the CR0 system is to collect leakage th ough the HCUs at the vent valves on each of four supply headers during an ILRT.

If the total leakage exceeds specified limits, approximately 1300 individual check valves. or solenoid valves must be examined to find and repair leak paths.

To minimize critical path outage time, new check valves will be installed in the CRD supply headers in four locations, effectively extending the isolation boundary from the HCOs to these new valves.

These eight new valves (4 pairs) sill reduce the number of testable CRD penetrations from approximately 1300 to four.

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i e The licensee included a sketch of the proposed arrangement which is enclosed (At tachmerit 1).

As shown, the licensee proposes to install two lift check valves, a manually controlled block valve and two test connections on each of the four CRD headers to the HCUs (drive, cooling, charging and exhaust).

The general process diagram for the CRD hydraulic system is shown in figure 4.6.7 in the Limerick Updated final Safety Analysis Report (UFSAR), which is also enclosed (Attachment 2).

The

'w valves will be installed between the main control station and the exist,ag vent valve shown in Attachment 1.

In a BWR 4 such as Limerick, Units 1 and 2, there are 185 control rods, each of which has an HCU.

As shown on figure 4.6.8 in the UFSAR (Attachment 3),

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and in Attachment 1, there are 3 check valves and 4 directional control valves on each HCU for a total of 1295 valves.

The ILRT is a pressurization of primary containment and measurement of total leakage from all isolation boundaries.

The current method of testing the isolation boundary of the CRD system is to place a bucket under the vent valves shown in Attachment 1 and to collect leakage through the HCUs at the vent valves on each of the four supply headers during an ILRT.

If the total leakage exceeds specified limits, approximately 1300 individual check valves or solenoid valves must be examined to find and repair leak paths.

Expeeience has shown that the total leakage is usually due to a drop or two of water leakage from many of the ball check valves rather than failure of one or two valves.

To avoid these problems, the licensee proposes to relocate the isolation boundary on the headers to and from the HCUs rather than on the HCUs.

Although a TS change is not required prior to installation of the new valves, a TS change is required to take credit for these new isolation boundaries, and also to remove the current HCU valve boundaries from the TS.

Therefore, the licensee is proposing that TS Table 3.6.3-1, "Part A-Primary Containment isolation Valves," be revised to remove the existing HCU isolation boundary valves and replace them with the newly installed isolation boundary valves.

Note 12 of that table also has to be revised to reflect the addition of the new valves.

Also since the affected CRD lines are water filled and would remain water filled for a minimum of 30 days after a loss of Coolant Accident (LOCA), Note 22 applies to these isolation valves.

3.0 EVALUATION The proposed TS change will take credit for the new valves installed in each of the CRD headers to the HCus (drive, coeling, charging, exhaust) between the main control station and the vent valve.

These valves constitute a new isolation boundary.

Each check valve station consists of two check valves, a block valve and two test connections.

This enables each check valve to be tested individually instead of during the criti:al path ILRT.

The change will move the isolation boundary out on the CRD headers.

A new access platform has been installed in order to facilitate local testing of the added check valves.

The new platform was designed to the American Institute of Steel Construction (AISC) and Category I requirements.

' The licensee has provided analyses to demonstrate that the new design does not change the design criteria pr siously approved in the staf f's Safety Evaluation (SE), NUREG-0991, Section 6.2.4.1.

The present method of leakage monitoring was accepted by the staff in Section 6.2.6.3 of the SE.

The piping to be included within the new isolation boundary complies with the same standards and specifications as the original boundary.

The number of active components making up the boundary will be reduced from approximately 1300 to four.

The current CRD isolation boundary includes the insert and withdraw lines, the scram discharge volume and the HCOs.

The relocation of the boundary will add some of the supply headee piping but will not affect the existing equipment.

The added piping is small diameter (2" or less) comparable to the previously analyzed scram discharge drain line.

The consequences of a pipe failure inside the isolation boundary remain within the envelope analyzed in NUREG-0803.

An analysis has been performed on the piping being upgraded for inclusion in the extended ILR1 boundary.

The piping and related pipe supports are designed to meet the criteria of Seismic Category I and American Society of Mechanical Engineers (ASME) Boiler and Pressure vessel Code,Section III, Class 2 or 3 as appropriate.

Analysis has shown that the existing piping and the modified piping is within the ASME Code allowables.

Piping supports have been evaluated and modified as necessary to accommodate the newly analyzed loads.

The licensee has evaluated the hydraulic effect of the new valves The additional pressure drop will not introduce significant line loss and is well within the CRD pamp capacity.

The calculations and test performed by the licensee show that there will be adequate flow in each of the headers to meet required design flows.

The performance of the CRD system is well within the system capability for normal operat on, and ccatrol rod scram performance is unaffected.

As discussed in the Safety Evaluation supporting Amendment No. 42 for Limerick, Unit 1, the NRC staff evaluated the potential impact if one or more of the new check valves were to fail closed.

The assessment concluded even if one of the new or existing check valves were to fail closed, it would not affect the ability to scram the reactor.

Based on uur evaluation, we have concluded that the new isolation boundaries will continue to meet all design requirements and will not adversely affect safety.

The proposed changes to the TSs are acceptabla.

4.0 STATE CONSULTATION

In accordance with the Comrission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendment.

The State official had no comments.

_4-5.0 My_LRJONMENTAL CONSIDERATION l

The amendment changes a requirement with respect to installation or use of a l

facility component located within the restricted area as defined in 10 CFR Part 20.

The NRC staff has determined that the amendment involves no I

significant increase in the amounts, and no significant change in tne types, of any effluents that mav be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.

The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (57 FR 34589).

Accordingly, the amendment meets the eligibility criteria for categorical exclusio,1 set forth in 10 CFR Sl.22(c)(9).

Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

6.0 CONCLUSi0B The Commissiori has concluded, based on the considerations discussed above, j

that:

(1) there is reasonable assurance that 'he health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Comr ission's regulations, l

and (3) the issuance of the amendment will not be inimical to the common defense and security cr to the health and safety of the public.

I Frincipal Contributor R. Clark Date: %ptember 28, 1992 Attachments:

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