ML20149H629
| ML20149H629 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 07/17/1997 |
| From: | Jain S DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9707250086 | |
| Download: ML20149H629 (11) | |
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p SNppingport. PA '15077-0004 I
- SU$HILO.JAlH
. (412) 393 4 512 l
Fax (412) 64Mc69 DMeton vlos PresMent
..M y 17. 1997 Oggysen U; S. Nuclear Regulatory Commission
-l Attention:. Document Control Desk 1 Washington, DC '20555 0001'
Subject:
Beaver Valley Power Station, Unit No. I Docket No. 50 334, License No. DFR '
' Request for Reilef from ASME IH Code Requirements Pursuant to 10 CFR 50.55a(a)(3), Duquesne Light Company (DLC) is hereby requesting relief from the requirements _of ASME Section III as it applies to the
. applicable code requirements for overpressure rcUef protection for specified components.
j in Beaver Valley Power Station Unit L This request is similar to the request dated January 29,1996, and subsequently reviewed and approved by the NRC for the Joseph i
M. Farley Nuclear Plants. Approval of.this relief request will allow the use of a e
proposed altemative for DLC to retain locked open isolatiort valves:
- 1) downstream of a relief valve for the volume control tank,-
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- 2) upstream and downstream of the rupture discs and safety valves for the i
charcoal delay beds, and c
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- 3) upstream and downstream of the rupture discs for the gaseous waste surge tank and decay tanks.
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A complete description of the attemative method is provided in the Eclosure. DLC has Edetermined that the proposed attemative would provide an acceptable level of quality and safetyc In addition, we 'have concluded that compliance with.the specified requirements of ASME Section 'Ill, as detailed in the E.90sure, would resu or unusual difficulties without a compenung increase in the level of quality and ' safety.
LIfyou have any questions, pl< ase contact Mr. J. Arias at (412) 393-5203.
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_Bc4ver Valley Power Station, Unit No.1-Request for Relief from.
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' ASME111 Code Requirements-
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Mr. D. M. Kern, Sr. Resident Inspector i
Mr. H. J. Miller, NRC Region 1 Adrninistratot
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Mr. D. S. Drinkman, Sr. Project Manager i
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F ENCLOSURE l
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- Request for Relief from ASME Section III Requirements
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Isolatipp_. Valves in Series with Overoressure Prqlgtipn Devicet -
f Pursuant to 10 CFR 50.55a(a)(3), Duquesne Light Company (DLC) is hereby requesting j
f 1 authorization to use an' alternete method to meet the Code' requirements of ASME p
Section'III, e it applies to specific vessel overpressure protection for Beaver Valley.
' Power Station Unit 1.
n This is a request for relief from ASME Section III requirements which proposes an 4
' alternative to allow DLC to retain the installation of administratively contro'Jed locked open isolation valves in the following configurations:
downstream of a relief. valve from the vohime control tank-(VCT) in the Chemical 'and Volume Control System to the Boron Recovery (BR) System.
i degasifiers, j
i both upstream and downstream of rupture discs and safety valves for the charcoal delay beds in the Gaseous Waste Disposal System (GW),
'l both upstream and downstreara of rupture discs for the Gaseous Waste Disposal
. System surge tank and decay tanks.
These configurations are schematically shown in Figures 1 and 2.
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COMPONENTS FOR WHICH RELIEF IS REOUESTED j
2 The purpose of these valves is to provide an effective ineans to perfonn maintenance activities on componems such as the VCT, degasifiers and their associated piping and valves without creating the situation where entire systems, and possibly the plar.t would i
require shutdown for maintenance activities.
i The present anangement of the subject isolation valves allows isolation of one of the two degasifiers, as well as in the Gaseous Waste Disposal System two of the four charcoal j
delay beds, and one of the two overpressure discharge flow paths from the surge tank or individual decay tanks for maintem.nce or replacement of the gaseous waste rupture
. discs when required with the plant operating.
t Ogicous Waste Disposal System.i.Decav Tanks The components for which relief is being regrested are manual locked open isolation vales located both upstream end downstream of rupture discs (RD-GW-103A1, A2, B1,
'B2, C1, and C2) for the decay tanks:
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Enclosure Request for Relief from ASME III Code Requirements Page 2l Decay Tank GW-TK-1 A; Isolation valves GW-97f103,100, and 106 4
Decay Tank GW-TK-1B; Isolation valves GW-98,104,101, and 107 Decay Tank GW-TK-IC; Isolation valves GW-99,105,102, and.108 The rupture discs provide overpressure protection for the Gaseous Waste Disposal System decay tanks and ultiraately discharge to the process vent.
OggLous Waste Disposal Svstem: Charsg.nlyelav Bqd_g The components for which relief is being requested are manual locked open isolation -
valves located both upstream and downstream of rupture discs (RD-GW-100,101) and safety valves (SV-GW-100,101) for the charcoal delay beds:
Delay Beds GW-TK-3A and 3B; Isolation valves GW-227,228 Delay Beds GW-TK-3C and 3D; Isolation valves GW-229, 230 The safety valves provide overpressure protectian for the Gaseous Waste Disposal System charcoal delay beds and ultimately discharge to the process vent, Daseous Waste Disr>osal Systept Surgg_T..ad The components for which relief is being requested are manual locked open isolation valves located both upstream and downstream of rupture discs (RD-GW-102-1,102-2) for the surge tank:
Surge Tank GW-TK '2; Isolation valves GW-91, 92, 93, and 94 '
e The rupture discs provide overpressure protection for the Gaseous Waste Disposal System surge tank and ultimately discharge to the process vent.
Chemical amLVolume Control Syste_mL olume Control Tad V
The components for which relief is being requested are manual locked open isolation valves located downstream of relief valve (RV-CH-257) for the volume control tard in the Chemical aml Volume Control System flow path to the Boron Recovery System
'degasifiers:
Volume Control Tank CH-TK-2; Isolation valves BR 16,17 The relief valve prmides overpressure protection for the Chemical and Volume Control System vohane control tank' and ultimately discharges to the process vent.
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L Enclosure L Request for Relief from ASME III Code Requirements Page 3 Qaseous Waste Disposal System: Dischame Flow Path The flow path to the process vent downstream of the equipment described above.
includes common discharge isolatioh valves installed in series. These valves are also maintained locked open in a manner simila-to the isolation valves above. Reliefis being reqmsted for manual locked open isoladon valves:
Gaseous Waste Disposal System;Isolatiorvalves GW-131,192
.The system flow paths are shown in Figures 1 and 2. The VCT relief valve discharges to
' the degasifiers which in turn discharge to the charcoal delay beds. The overpressure protection flow path on the chaccoal deley beds leads directly to the process vent through
.h loop seal which prohibits the build up of flammable mixtures in the discharge heeder.
Isolation valve GW.192 provides for isolation of the relief flow path from the normal release flow path to support maintenance dating power operation. The normal flow path for gaseous waste is through the compressor to the surge tank. The compressors operate automatically in response to the suction pressure thus maintaining the degasifier's overhead components at' a pressure between established limits.
The overpressure protection flow path for the smge tank is through the rupture discs, the loop seal and to 4
the process vent. Gas which is to be normally discharged is then transferred from the l
surge tank to the decay tanks. Normally one tank receives while one bleeds to the waste disposal blower which is the normal flow path to the process vent (release point), and the j
t third tank is held for decay. The overpressure protection flow path for the decay tanks is through the rupture discs, the loop seal and to the process vent. Isolation valve GW 131 provides for the isolation of the Gaseous Waste Disposal System hom the outside atmosphere during performance of maintenance activities while the pint is operating.
For each of the flow paths discussed above, replacing the isolation valves with automatic valves using positive controls and interlocks would require the procurement and installation of new ccatrol valves, additional pressure sensing instrumentation and associated controls, and power and control cabling. This would result in a significant cost without a compensating increase in the level of quality and saefty.
CQD}LREOUJREMENTS q
i The ASME Code years prior to the 1971 Edition of Sectien III for Class C def'med the design requirements for vessels to be in accordance with ASME Section VIII except for protection against overpressure conditions and nameplate stamping requirements.
l ASME lll semained the Code of reference for overpressme protection in these instances.
There requirements were fmther defined in Code. Articles referenced in the Code year applied.to the fabrication of the respective vessels. The 1968 ASME Section Ih Code u.
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Enclocure i
i Request for Nicf f uu ASME III Code Requirements Page 4 i
contains the requiremenn for overpressure protection in Article 9 ef that Code. The 1971 ASME 111 Code comains the requirements in Article NC-7000 of that Code. These Articles require that any~ stop ulves in the pressure relief path or pressure relief discharge path he equipped with positive intedocks and controls.
The current 4
configuration with manually operated locked open stop valves in the paths are not compliant with this ASME Code requirement.
The applicable Codes for the ves;cis in question are as follows:
I GW-TK-1 A,1B, and 1C; ASME 111, Class C,1968, W70A GW-TK-3A,3B,3C, and 3D; ASME III, Class 3,1971, S i2A GW-TK-2; ASME 11I, Class C,1968, W69A CH-TK-2; ASME Ill, Class C,1968, W69A DLC used a systems apprcach to provide for overpressure protection through the u.se of j
prudent and conservative procedures which lock open and verify the open position of the isolation valves.
The requirements for positive controls and interlocks on relief valve isolation valves were not explicitly defined until ASME Code Interpretation III-1-80-67R (March 1, 1989), which nded that " operating procedures governing the use and application of the system" were not acceptable as the " controls." Interpretation 1111-89-25 (March 3, 1989) restated that an arrangement such as described in this request does not meet die Code requirements. Therefore, a deviation exists betv'een the relief systems for the volume comrol tank and Gaseous Waste Disposal System components and the latest interpretations of the applicable Code.
CODE REQQI_REMFNTS FOR WHiCH RELIEF IS REOUESTED.
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DLC is tequesting relief from the " control and interlock" requirements of 1968 ASME Section III,.Atticle 9, Section N-910.8, and 1971 ASME Sectica III, Article NC-7000, Paragraph NC-7153 which state the following-
"Any stop valve or similar device on the inlet or discharge side of a protective device provided in conformity with N-910.7 shall be so constructed, positively controlled and iatedocked that the requirements of N-910.1 will be complied with under all conditions of operation of the system." (1968 ASME Section III)
"No stop valve or other device shall be placed relative to a pressure-relief device so that it cmdd reduce the overpres,sure protectior, below that required by tnese rules, unless such stop valves are constracted and installed with positive controls and interlocks so that the relieving-capacity requirements of NB-7400 are met under all conditions of o
Enclosure Request for R elief from ASME Ill Code Requirements Page5 operation of both the system and the stop valves. Means shall be provided such that the operability of controls and interlocks can be verified by test." (1971 ASME Section III)
PROPO_ SED ALTERNATIVE TO CODE RF_QlllREMENTS A.s an altemative to the ASME Section III requirements, DLC proposes to maintain the current, as built configuration with the following administrative controls.
Administrative controls are in place to ensure the manual valves in the overpressure protection discharge flow path remain in the locked open position. The locking device consists of either a chain and lock or a locking device and lock specifically designed for the valve. The valves are periodically reviewed to verify their loc'ked open position.
These measures assure a pressure relief path is always available.
The BVPS-1 operating procedures for the Boron Recovery and Gaseous Waste Disposal Systens contain valve position verifications and checklist sign-offs. Any maintenance activity that may result in valve configuration changes would result in verification that the isolation valves are returned to their nonnal open and locked position. In the case that one of the valves is closed (for maintenance purposes), the position of the redundant uain valve would be locked open by the norma' mtem arrangement. Restoration of components following maintenance activities -
valve position verifications and appropriate sign-offs.
BASIS FOR RELIEF Compliance with 1968 ASME Section III, Article 9, Section N-910.8 and 1971 ASME Section 111, Article NC-7000, Paragraph NC-7153 is impractical for the subject isolation velves. This relief request is justified in accordance with 10 CFR $0.55a(a)(3)(i) and (ii).
Administrative controls are in place that specify and verify that the appropriate isolation valves are locked open. These administrative controls provide an acceptable alternative to the requirements of ASME Section III and provide an acceptable level of quality and safety meeting the intent of those requirements.
Compliance with Code requirements would result in hardship or unusual difficulties without a compenssting increase in the level of quality and safety. Denial of the relief request and ccmpliance with Code requirements would result in costly backfit design modifications to install controls and interlocks for the subject isolation valves.
The current configuration provides an acceptabb level of quality and safety.
Mispositioning of these isolation valves, although not desirable, would not impair the capability of plant shutdown or operation of the emergency core cooling system.
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. Encl::sure j
d Request for Relief from ASME III Code Requirements y
Page.6 -
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SAFETY ASSESSMENT-a iThe ;VCTJ provides surge capacity to accommodate programmed pressurizer level l
changes. The relief valve on the VCT does not have an active safety function' and is_ not
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required.to' actively operate during or following an accident to perform a nuclear safety 1
, function. JThe Chemical:and Volume Control System is isolated from the Reactor
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Coolant System (RCS) during'a design basis accident.
O The Gaseous Waste Disposal System Processes and monitors all waste gas stream's prior F
- to discharge to the atmosphere in accordance with the controls established in the Offsite.
. Dose Calculation Manual. The rupture discs do not have an' active safety function'and are not required to actively operate during or following an accident to perform a nuclear '
j isafety function. This system is isolated from the RCS during a design basis accident, j
F There are ~no credible failure modes associated with this design configuration.
Mispositioning of a valve to the closed position is precluded by positive locking devices-and administrative controls such that manipulation of any valve would require positive I
- and deliberate' action. ' Such action would occur only as the result of a recognized h
evolution and as suchs impact on the affected component would be operationally 1
evaluated prior to such manipulation.
a The' concentration of radioactive waste gases. in the RCS and auxiliary systems-is a 1
function of the rate of fission gas release to the coolant from defective fuel and the rate of removal via the auxiliary systems. The areas which retain significant concentrations
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- of radioactive gases are the volume control tank and the ' waste gas surge tank. The
. accidental release of waste gases, relating to the volume control tank and the gaseous waste surge tank, are evaluated in the Updated Final Safety Analysis Report, Section
' 14.2.3. The rupture of either tank will produce site boundary dose values much less than t
F the dose limits in 10 CFR 100 as described in the Unit No.1 UFSAR,' Section 14.2.3.2.
The consequences of a mispositioned valve resulting in tank overpressurization are F
bounded by the accident analysis which assumes tank rupture.
5 CONCLUSION It is the position of DLC that 1) the administrative control progra.m and the verification n
- requirements of the operating procedurcs are positive controls that provide a high-level j
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'of confidence that the relief valve discharge path will not be blocked during system 9
/ operation and 2) the present arrangement provides an acceptable alternative that meets the iment of the code requirements.
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Encl:sure -
JRequest for Relief from ASME III Code Requirements
. Page 7-4 Therefore, the present ' design provides an acceptable' level of quality and safety. The :
o removal of the isolation valves would result in operational hardship and a potential for increased airborne radiation and personnel radiation exposure that cannot be justified by any marginally small increase in the level of ovegressurization safety. The existing arrangement provides a sound design, is safe for maintenance personnel, and provides operational flexibility and efficiency. Therefore, compliance.with the specified Code.
rules would result in hardship without a compensating increase in the level of quality and safety.
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