ML20151A017
| ML20151A017 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 07/12/1988 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20151A022 | List: |
| References | |
| NUDOCS 8807190208 | |
| Download: ML20151A017 (6) | |
Text
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ENCLOSURE SAFETY EVALUATION OF REQUEST FOR RELIEF FROM REQUIREMENTS OF ASME SECTION XI MCGUIRE UNITS 1 AND 2 OUKE POWER COMPANY Occket Nos. 50-369 and 50-370
1.0 INTRODUCTION
By letter dated February 9,1987, as modified by letter dated February 16, 1987, Duke Power Company (the licensee) requested relief from the ASME Boiler and Pressure Vessel (B&PV) Code,Section XI, hydrostatic testing requirements for portions of modifications on the Nuclear Service Water (RN) System for McGuire Nuclear Station, Units 1 and 2.
The reason for the request is that the licensee has determined that conformance with Code hydrostatic test require-ments is impractical.
The licensee requested this relief because of the difficulty of performing the hydrostatic tests and the time constraints imposed by Technical Specifications for other systems that would be inoperable during modification to the RN system.
The relief request, as modified, states that the alternate examina-tions are as good as testing required by the code for detecting weld defects and ensuring safe operation of the system.
2.0 EVALUATION The staff has evaluated the licensee's written relief requests as detailed
- below, a.
ASME Code Section XI Requirement for which Relief is Requested.
The ASME B&PV Code,Section XI,1980 Edition through Winter 1980 Addenda, IWA-4400 and IWA-5000, recuires a hydrostatic test fellowing repair or replacement ey welding.
The relief request involves portions of modifications to the RN systems including changing small diameter carbon steel piping to stainle*,s steel piping going to a numcer of coolers for safety-related pumps.
The major modifications are to reduce problems associated with fouling
$o in the RN system.
The licensee requested relief f rom hydrostatic g
testing of welds performed as part of modifications to large diameter g
RN piping and for welds tying the small diameter pump cooling systems
$n to the large diameter RN system piping.
The welds in the small C0 0 diameter pump cooling systems are to be hydrostatic tested between (o r isolation valves in the cooling systems. Only the welds that cannot 88 be isolated from the large diameter piping are covered by the relief requests.
b The modifications were scheduled to be implemented during the 1987 gg and 1988 refueling outages.
t Enclosure 2
MC Insoection Report No.
50-369, 370/87-44 documented the review of weld records and coservation of actual configurations for welds for whicn relief. was requested.
The licensee was recuested to provice additional information relative to justification for alternate testin and succort of impracticability of performirg coce reovired tests. Additional information was provided by licenseeis letter datec Maren 25, 1988.
b.
Components for Whien Relief is Requested (1) The various components for which relief is requested are identified by modification (MG) numbers as follows:
(a) MG-1-1887:
All welds associated with the replacement of Valves 1RN137A and 1RN238B.
Two aew slip-on flanges per valve will be installed on this modification.
(b) MG-2-0666: All welds associated with the replacement of Valves 2RN137A and 2RN2388.
Two new slip-on flanges per valve will be installed tn this modification.
(c) MG-1-0351: Welds associated with final tie-in to process header on check valve bypass lines and welds associated with final tie-in to process header on high point bypass loop. The final tie-in weld are the welds that connect the new piping to the existing piping. All other welds within the new piping will be hydrostatically tested.
(d) MG-1-1836, MG-1-1888, MG-1-1889, MG-1-18 90, MG-1891, MG-1-1892, MG-2-0667, MG-2-0663,, MG-2-0669, MG-2-0670, MG-2-0671, MG-2-0672:
All welds between the supply /
discharge header and the first isolation valve. All welds between the isolation valves will be hycrostatically tested.
(2) Materials (Base and Weld)
Carbon Steel Piping Materials - A-106, GR B or equivalent l
Stainless Steel Piping Materials - SA-312, TP 304 Welding Materials
- Caroon Steel to Carbon Steel:
E-7018 or E705-2
- Stainless Steel to Stainless Steel:
E308-16 or ER-308 l
f Enclosure 3
- Stainless Steel to Carbon Steel:
E309-16 or ER309 c.
ASME Code Class:
Equivalenc co Section III Class 3 d.
Function The Nuclear Service Water System is a Nuclear Safety-Related open cooling system that provides cooling wster from Lake Norman or the Standby Nuclear Service Water Pond (SNSWP) to various station heat exchangers during all modes of operation. In addition, the system acts as an assured source of makeup water for various requirements and is the normal supply water for the Containment Ventilation Cooling Water System (RV).
In addition to these general functions, the following specific functions as related to the above listed modifications are applicable:
(1)
MG-1-1887 and MG-2-0666 - Containment Spray (NS) heat exchanger downsteam isolation valves (1RN157A, 1RN2388, 2RN137A, and 2RN2388) on the RN system will be replaced.
Valves are being replaced to support a wet-layup system for each heat exchanger.
The purpose of the wet-layup system is to keep the shell side (RN side) of the heat exchangers in a chemically controlled anytronment.
(2) MG-1-1888 and MG-2-0668 - Replace small diameter carbon steel piping going to the NI (Safety injection System) pump motor coolers and the NV (Chemical Volume Control System) pump motor coolers with stainless steel piping.
(3) MG-1-1890 and MG-2-0670 - Replace small diameter carbon steel piping going to the RN (Nuclear Service Water) pump motor coolers with stainless steel piping.
(4) MG-1-1891 and MG-2-06671 - Replace small diameter carbon steel piping going to the CA (Aux. Feedwater) pump motor coolers with stainless steel piping.
(5) MG-1-1886 and MG-2-0667 - Replace small diameter carbon steel piping going to the KC (Component Cooling Water) pump motor coolers with stainless steel piping.
(6) MG-1-1889 and MG-2-0669 - Replace small diareter carbon steel piping going to the ND (Residual Heat Removal) air handling units, NS (containment spray) pump air handling unit with stainless steel piping.
(7) MG-1-1892 and MG-2-0672 - Replace small diameter carbon steel piping going to the KF (Spent Fuel Cooling) air handling unit with stainless steel piping.
___A__.__
(nclosure 4
(8) MG-1-0351 Rev. 0 - Add drains and bypass lines to the RN system to improve system draining capability.
(e) Basis for Requesting Relief The modification work (see b.
above), for which relief is recuested, will be performed during refueling outages.
During refueling outages, there are certain periods of time each t: 2 train of RN can be drained.
RN System cools the ND (Residual Heat Removal System) and the XF System (Sper.t Fuel Pool Cooling System) both of which are needed for the magority of the outage.
Based on a typical outage schedule, the RN supply and disenarge l
neader for either "A" or "B" Train can be drained and available for work for about ten days on Unit 2 and six days on Unit 1.
I Unit 1 is more restricted due to the fact that the VC/YC (Control Area Ventilation System / Chilled Water System)
Chillers discharge to Unit'l discharge header only; thus when Unit 1 dischurge header is drained, it makes VC/YC inoparable which places Unit 2 in a seven-day Technical Specification operability constraint (per TS 3.7.6).
These time' periods allow barely enough time to accomplish the actual physical l' abo'r involved in implementing the modifications to the RN System.
Attempting a hydro on the entire RN supply and discharge header would involve significant plannihg, manpower and equipment (high capacity, high head pump). A mydro on this large of a section of piping woulc add days to : e outage schedule even if the psmo was staged ahead of time. Most of the time needed would be comprised of valve alignments to fill and vent the system.
Sections of piping containing subject welds cannot be adequately isolated for hydrostatic testing.
Isolation valves are large butterfly valves ranging from 10" to 36" which are not designed to be leak tight and have a history of leakage.
Even with a high capacity hydro pump, there is still a good possibility that pressure cannot be maintained due to leakage past vaives.
Repair of the large diameter valves would be a major. undertaking since the valves are welded into the system rather than flanged.
The alternate testing identified in paragraph (f) below invclves Nondestructive Examination (NDE) in excess of that required by Code and an inservice leakage inspection. The alternate testing is considered ecunalent to hydro testing for detecting weld defects to ensure safe and consistent operationi reliability of system without any undue risk to the health and safety of the public based on the following:
l The RN System is a low temperature, low pressure (135 psig design pres sure)' systeir..
Hydro pressure on the system would be 110*. of design pressure or approximately 150 psig.
I I
l l
t
. Enclosure 5
The additional MT or PT examination re.* ement compensates for the dif f erence in hydro pressure r
' service leak inspection pressure (30-90 psig).
Tra
'lity of discovering additional weld defects by pres.
- 1 to 150 psig is low to none.
( f) Alternate Testing The applicable Code for the modifications, ASME B&PV Code,Section III, ', lass 3, requires that welds >
1" NPS receive a final weld liquid penetrant (PT) or magnetic particle (MT) examination.
The welds for which relief from hydrostatic testing has been requested will receive the following tests and inspections:
Fitup Root Pass P1 or MT (Welds > 4" itPS)
Final Weld PT or MT VT-2 Inservice Leakage Test 3.0. CONCLUSION The relief request are granted as requested based on the following considerations:
The staf f has determined that it is impractical to perform the required hydrostatic tests because, (1) sections of piping containing subject welds cannot be adequately isolated because either there are no isolation valves between the welds and a major component (heat exchanger) or the valves needed for isolation are large diameter butterfly valves not duigned to be leak tight and having a history of leakage, (2) thf short me period the RN system is available for modificatior, work during an outage, and (3) the time and ef fort requiied to parform the hydro test considering the high Orabability of leakage [;ast the isolation valves.
The alternate <xaminations and tests proposed by the licensee will provide an acceptable level of structural integrity for the welds in question and prov>Je reasonable assurance of opertional read' ness.
Paragraph 10 CFR 50.5Ea(g)(4) requires that components (including supports) which are classified as ASME Code Classes 1, 2 and.3 meet the requireraents, except design and access provisions and preservice T
requirements, set forth iri applicable editions of ASME Section X. to the extent practical within the limitation; of design, geometry and t
Enclosure 6
/
A materials of construction of the components.
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee determined that cont'rmance with o
certain Code requirements are impractical for this f acility and submitted supporting information, in accordarce with 10 CFR 50.55a(g)(6)(i), the staf f concludes that relief may be granted fcr the issues described in the Relief Request.
This relief is authorized by law, will not endanger life or property or the common defense and security, and is otherwi se in the public interest given due consideration to the burden upon the licensee that could result if the req.irement were imposed.
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