ML20210L161
| ML20210L161 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/30/1999 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9908090048 | |
| Download: ML20210L161 (6) | |
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t Tennessee Valley Authonty Post Othce Bon 20(X) Soddy-Daisy Tennessee 37379 July 30,,1999 10 CFR 50.50a (a) (3) (i)
U.
S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.
C.
20555 Gentleman:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT (SQN) - BEQUEST FOR APPROVAL OF RELIEF FROM AMERICAN SOCIETY OF MECH 7NICAL ENGINEERS (ASME) CODE REQUIREMENTS - REQUzb! 5'OR RELIEF RV PRESSURE RELIEF VALVE TESTING
Reference:
NRC latter to TVA dated October 23, 1987,
" Request for Relle' from ASME Boi'er and Pressure Vessel Code,Section XI, Inservice scsting Program (TAC 61835, 61836)"
Enclosed is Request for Relief RV-4 for SQN's Second 10-Year Inservice Test Program.
The proposed request for relief is 3
applicable to ASME Class 1, 2, and 3 pressure relief valves j
and is associated with the 10-minute hvid time between valve j
openings.
The applicable sections of the ASME Code are J
contained in Operations and Maintenanc. Standard, Part 1 I
(OM-1), Paragraphs 8.1.1.8, 8.1.2.8 and v.1.3.7.
I j
/
This request.for relief is similar to a TVA request that was approved by the staff in the referenced letter for SQN's g) first 10-year inservice test time interval.
The approved relief request relaxed hold time from 10 minutes to 3 to 5 minutes for SQN's main steam and' pressurizer safetv valves and no hold time for all other relief valves.
TVA is submitting RV-4 pursua-to 10 CFR 50.55a (a) (3) (i) as a proposed alternative that wo 4 provide an acceptable level of quality =and safety.
. 9908090048 990730 PDR-ADOCK 05000327 P
PM j
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1 U.S.: Nuclear Regulatory Commission Pa'ge 2*
July 30, 1999 TVA is requesting NRC review'and approval of RV-4 to support SON's Unit 1 Cycle'10 refueling outage.
This refueling outage is currently' scheduled'to start on February 13, 2000.
If you have any questions regarding this response, please contact megat exronsion (423) 843-7071 or Jim Smith at extension-(423) 843-6672.
Sincerely, j
~
Peute,salas Licensing and Industry Affairs Manager
-Enclosure cc (Enclosure):
Mr.
R. W. Hernan, Project Manager Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike
.Rockville, Maryland 20852-2739 NRC Resident Inspector Seguryah Nuclear-Plant 2600 Igou Ferry Road-j Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region II.
Atlanta Federal Center 61LForsyth Street, SW, Suite 23T85 Atlante, Georgia 30303-3415
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ENCLOSURE TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN)
UNITS 1 AND 2 2"d 10-YEAR INTERVAL REQUEST FOR RELIEF NO. RV-4 Executive:
TVA performs testing of safety relief valves in Summary accordance with American Society of Mechanical Engineers (ASME) Code, which endorses operations and Maintenance Standard, Part 1 (OM-1).
The provisions of OM-1 require a minimum of 10 minutes between successive openings when testing a pressure relief valve to determine the set pressure of the valve.
TVA's proposed request for relief relaxes the hold time from 10 minutes to 5 minutes for SON's pressurizar and main steam system pressure relief valves.
In addition, TVA is prop,osing relaxation from 10 minutes to no hold time for SON's air and i
water system pressure relief valves.
This is based on the steady-state thermal conditions that SON's pressure relief valves experience during testing.
I This request for relief is submitted for SON's second 10-year inservice test (IST) interval.
This relief request is provided for NRC review and approval in accordance with 10CFR50.55a (a) (3) (i).
A similar relief request for relaxing hold time from 10 minutes to 3 to 5 minutes for main steam and pressurizer safety valves and no hold time for all other relief valves was approved by the staff for SON's first 10-year IST interval, i
Unit Affected:
Units 1 and 2 System:
ASME Class 1, 2, and 3 systems with pressure relief valves Components:
System Pressure Relief Valves Code Class:
ASME Code Class 1, 2, and 3 Component Function:
Pressure relief valves provide overpressure protection for une system piping and vessels within the safety system.
E-1
Code Requirement:
The 1989 Edition of the ASME Code endorses OM-1 for testing pressure relief devices in pressurized water reactors.
Section 8 of OM-1 contains test methods for steam service, compressible fluid services other than steam, and liquid service valves.
Paragraphs 8.1.1.8, 8.1.2.8, and 9.1.3.7 provide the requirement associated with the time between valve openings.
The requirement from these paragraphs states:
A minimum of 10 min shall elapse between successive openings.
Code Requirement From Which Relief is Requested:
Relief is requested from the 10 minute time between successive openings as contained in Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7 of OM-1.
Basis for Relief:
At SON, pressure relief valves from various plant systems are tested in accordance with the provisions of OM-1.
Two consecutive valve actuations are measured to determine the set pressure of the valve.
Under the provisions of OM-1, the amount of time between valve openings is required to be 10 minutes.
Any reduction in the 10-minute hold time between valve actuations would minimize test performance and system outage times.
A reduction in system outage time facilitates plant safety by the timely return of plant systems to service.
SON's main steam safety valves are tested during operation (on-line testing) at full system pressures and temperatures.
This test method exposes test personnel to a high humidity and high temperature environment.
TVA's proposed alternative would minimize the time between valve actuations and reduce the risk associated with personnel exposure to these test conditions.
I Alternative Testing:
The main steam safety valves and the pressurizer safety valves will require a minimum time of five minutes between actuations.
For all other air and water system relief valves, no minimum time between actuations will be required.
4 E-2 a.
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j Justification for the Grinting of Relief:
At SQN, pressure relief valves in ASME Class 2 and 3 water systems are bench testad at ambient conditions using water as the test medium.
Testing of these valves is conducted at ambient conditions in a shop environment.
The test medium and the valve in this environment are in thermal equilibrium.
The valve is placed on a stand and a pump is used to achieve test pressure.
There is no chermal source introduced during the test, which would result in a thermal imbalance or skew the accuracy of the test.
Repeated valve actuations are conducted in a coultviled environment under steady-state conditions.
Consequently, accurate and repeatable test results are achieved when measuring the set pressure of the water system pressure relief valves.
Pressure relief valves in SON's ASME Class 2 and 3 air systems are bench tested at ambient conditions using compressed gas as the test medium.
Testing of these valves is conducted at ambient conditions in a shop similar to the fluid medium safety valves.
The test medium and the valves in this environment are in thermal equi]ibrium.
The valves are placed on a stand and gas pressure is applied to achieve the valve lift setpoint.
There is no thermal source introduced during the test, which would result in a thermal imbalance or skew the accuracy of the test.
Test control methods prevent prolonged blowdown in order to minimize any cooling effect from gas expansion.
Repeated valve actuations are conducted in a controlled environment under steac'v-state conditions.
Consequently, accurate ano repeatable test re.=ults are achieved when measuring the set pressure of the air system pressure relief valves.
SON's main steam system safety valves are ASME Class 2 valves and are tested in place with an assist device during power operation just prior to removing a unit from service for a refueling outage.
A j
hydraulic assist device measures the force required 1
to lift the valve disc to the relief setpoint.
At l
the point at which the valve lifts, the hydraulic
]
force is removed allowing the valve to close.
This
]
evolution occurs in less than one second which I
minimizes the steam flow through the valve as it actuates.
This also minimizes any change in j
temperature that is experienced by the valve and the l
test medium (steam) curing testir.g.
Typically, there is some amount of time which elapses between E-3
p
. < ~ *'
r-i actuations due to data. recording,. inspection, and verification of test conditions.
These. test j
- onditions provide thermal stability of the valve and i
.the test medium.
Consequently, accurate and repeatable test results are achieved when measuring the set pressure of the main steam system relief valves.
j SON's pressurizer safety valves are ASME Class'1 valves that are removed from service during a unit refueling outage and are shipped to an independent test laboratory for-testing.
The laboratory tests L
limit valve disc lift time, which limits flow through the valve.
This minimizes temperature transients that occur during the disc lift.
The valves are tested at simulated operating conditions.
Thermal stabilization is achieved prior to.the start of testing as required by OM-1.
Typically there is some amount of time which elapses between actuations due to data recording, _ inspection, and verification of l
test conditions.
Consequently, these conditions i
provide thermal stability of the valve-and the test medium and provide accurate and repeatable results for measuring the set pressure of the pressurizer relief valves.
The 1997 ASME OMB Code contains a relaxation of the hold time. requirement to decrease the time delay between actuations from 10 minutes to 5 minutes.
This relaxation is applicable to the proposed relief request for SQN's main steam and pressurizer relief valves.
Accordingly, the proposed relief request is consistent with later ASME Code requirements.
==
Conclusion:==
TVA's proposed request for relief from the provisions of OM-1 provides an alternative methodology for.
testing SON's ASME Class 1, 2 and 3 pressure relief valves.
Alternative testing would shorten the time between valve openings from 10 minutes to 5 minutes
)
'for SON's pressurizer and main steam relief valves and from 10 minutes'to no hold time for all other water and air system relief valves.
TVA's proposed alternative would demonatrate satisfactory repeatability and accuracy for determining set pressures of relief valves and would provide an acceptable level of quality and safety.
Implementation of the proposed alternative is requested for SON's second 10-year IST Program
. interval.
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