ML20029B374

Safety Evaluation Granting Request for Relief from ASME Code Requirements Re Visual Exam Requirements for Valve Body Internal Surfaces

ML20029B374
Person / Time
Site:	Millstone
Issue date:	03/05/1991
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20029B372	List: ML20029B371 ML20029B374
References
NUDOCS 9103070132
Download: ML20029B374 (4)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUEST FOR RELIEF FROM ASME CODE REQUIREMENTS YlSUAL EXAMINATION REti!REMENTS F0P VALVE BODY INTERNAL SURFACES t

NORTHEAST NUCLEAR ENERGY COMPANY. ET AL MILLSTONE NUCLEAP, POWER STATION, UNIT NO. 1 DOCKET NO.50-24S

1.0 BACKGROUND

TheCommission'sRegulationsin10CFR50.65a(g)requireexaminationsandtests of nuclear power facility piping and components to be performed in accordance with the requirements of the applicable ASME Section XI Code edition and

addenda, if it is impractical to meet the requirements, the licensee of the facility is required to notify the Commission and submit information in support of the determination that a requirement is impractical to perform. TDe Northeast Nuclear Energy Company (the licensee) has requested relief from the American Society for Mechanical Engineers Code (the ASME Code),Section XI, concerning visual examination requirements for valvft body internal surfaces, Code Category B-M-2.

Code Requirement:

Section XI, Table IWB-2500-1, Examination Category B-M-2, Item B12.50 reliuires a 100% visual (VT-3) examination of the internal surfaces of Class 1 valve bodies exceeding 4 inches nominal pipe size.

Examinations are limited to one valve that is of the same constructural design and manufacturing method, and that performs similar functions in the system.

Licensee's Code Relief Request:

Relief is reouested from performing the tode-required visual examination (VT-3) of the internal surfaces of the valve bodies in Table 1.

Licensee's Proposed Alternative Examination: The licensee states that if a valve is disassembled for maintenance, the Code-required visual examination (VT-3) will be performed, in the event valves within certain groups of this code category are not disassembled during this inspection interval, this fact shall be reported in the ISI Summary Report at the end of the interval.

Licensee's Basis for Requesting Relief:

The licensee states that the alternative of performing a visual examination on valve body internal surfaces when any valve of this category is disassembled for maintenance has been an ongoing r m tice at Millstone Unit No. 1.

The attached table lists all Category 6-ri-2 valves and identifies when 151 Section XI examinations were performed as a result of disassembly because of maintenance.

To date, there t

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2 has been no observed degradation of valve body internal surfaces due to erosion, corrosion or crackin at Hillstone Unit No. 1.

The code requirement to disassembleanoperabevalveforthesolepurposeofan151visualexamination provides a very small potential for increasing plant safety margins while increasing expenditures, radiation exposure, critical path outage time, and manpower resources.

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?.0 EVALVATION The Code requires one valve in each group of valves to be visually examined internally.

Visual examination of the valve's internal surfaces is performed to deternine if significant degradation of the valve body material is occurring in service due to phenomena such as erosion, corrosion, or cracking.

In order to accomplish the Code requirement, each valve subject to examination must be disassembled, in niany instances, disassembly of the valves would require that either the water level in the reactor coolant system be lowered below the core or removal of the core from the reactor vessel.

The forter case would create an unsafe condition for plant personnel and the letter case would create a burden on the licenste that would not be compensated by the increetc in saftty gained by the examination. The requirement, therefore, is impractical to perform at Millstone Station, Unit 1.

Inservice cyperience of valves in this examination category indicates that the valve body materials have performed to design specifications and the mechanisms likely to cause degradation of the valve body materials have had little or no effect on their structural integrity. The licensee has proposed to eran.ine the valves when they are disastembled for maintenance and the staff finds this ecceptable for detection of any valve body degradation if it occurs.

3.0 CONCLUSION

S Based on the above evaluation, it is concluded that the Code requirement is impractical. Therefore, it is recenmended that relief be granted provided that:

(a) the visual examination (VT-3) of the internal surf aces of the valve bodies is performed whenever the internal surfaces are made accessible due to disassembly for maintenance, and (b) if the valves have not been disassembled, this f act should be reported by the licensee in the 151 Summary P,eport at the end of the interval.

The relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Principal Contributor:

D. Jaffe Date:

March 5, 1991 l

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Page 1 of 2 Table 1 CATEGORY B.M 2 VALVES DESIGN MATERIAL VALVE SIZE 10 VEAR INTERVAL Skl &

GROUP 1 Angle Globe Carbon Steel 1MS!A 20" 1.MS.1 B 20' 1.MS lC 20' 1 hts lb 20" 1.MS.2 A 20' 1 MS 2B 20*

1987 1 MS 2C 20" 1984 l MS 2D 20*

1973 ftRD1T 2

'R elie f Carbon Steel 1 MS.3 A 6"

1 hts 3B 6'

1 MS 3C 6"

1.MS 3D 6"

1 MS 3E 6'

• 1980 L

l MS.3F 6"

GROUP 3 Check Carbon Steel 1.FW.9 A 18*

1980 l FW.9B 18" 1980 1 FW 10A 18" 1980 1982 1.FW 10B 18" 1980 GROl!P 4 Check Stainless Steel 1 LP 11 A 16" 1 LP 11B 16" 1980 l CS 6A 10" 1980 1.CS 6B 10" 1980 l CU 29 8"

1980 GR ot!P s Gate Stainless Steel 1.CS 7A 10" 1980 l CS 7B 10" '

1980 1 LP 12 A 18" l LP.12B 18*

1974 l LP 10A 18*

1984 l LP 10B 18*

1980 1985 1 SD 1 14*

1973 11C 1 14*

1973 11C 2 14" 1973 1.lC 3 10*

1973 1978 1984 l IC 4 10" 1

1

l Page 2 of 2 DERIG N' M ATTRI AI V AI Vr Ef 7r 10 Vr AR INTERVAI.

Ist 2nd GkOUP 1 (Cont'd)

Oste Stainless Steel 1.CS 5A 10*

1979 1985 1.CS.5 B 10*

1984 1.CU l 8'

1.CU 2 8'

1.CU.3 8*

1985 1989 1005 8'

1973 10028 8*

1.CU.30 8'

1.RR.l A 28' 1.RR.1 B 28*

1984 1.RR 2 A 28' 1.RR.2 B 28" 1.RR 4 A 22*

1.R R.4 B 22' GROUP 6 Gate Carbon Steel 1.FW.ll A 18" 1980 1.FW.11 B 18*

1.SD 2A 12*

1973 1.SD 2B 12*.

1.S D.5 12*

1973

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