ML20118B052
| ML20118B052 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/21/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20118B049 | List: |
| References | |
| REF-GTECI-070, REF-GTECI-094, REF-GTECI-NI, TASK-070, TASK-094, TASK-70, TASK-94, TASK-OR GL-90-06, GL-90-6, NUDOCS 9209290335 | |
| Download: ML20118B052 (6) | |
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6,,s,,,s SAFETY 1VALVAT10fl BY THE Off]CE Of NVCLEAR REAC10R REGVULT10tj SUPPOR1]NG AMENDMENT NO. 16 TO FACLLl]Y OPERATLt4G llCEN1[l0 NPf-86 RQRTH ATLANilC [NERGY SERVICE (9_RP0 PAT 104
}1AjLRQQK ST ATION. UNIT _NO.1 ROCKET NO 50-443 1.0 ItLTROMJTlgt!
On June 25, 1990, the staff issued Generic Letter 90-06, " Resolution of Generic issue 70, " Power-Operated Relief Valve and Block Valve Reliability,"
and Generic Issue 94, " Additional Low-Temperature Overpressure Protection for Light later Reactors," Pursuant to 10 CFR 50.54(f)," The generic letter reptesented the lechnical resolution of the above mentioned generic issues.
Generic Issue 70, " Power-0perated Relief Valve and Block Valve Reliability,"
involves the evaluation of the reliability of pressurizer power operated relief valves (PORVs) and block valves and their safety significance in pressurized water reactor plants.
The generic letter discussed how PORVs are increasingly being relied on to perform safety related functions and the corresponding need to improve the raliability of both PORVs and their associated block valves.
Proposed staff positions and improvements to the plant's technical specifications were recommended to be implemented at all affected facilities.
This issue is applicable to all Westinghouse, hbcock &
Wilcox, and Combustion Engineering designed facilities with PORVs.
Generic issue 94, " Additional Low-lemperature Overpressure Protection for Light-Water Reactors," addresses concerns with the implementation of the requirements set forth in the resolution of Unresolved Safety Issue (USl)
A-26, "Reacter Vessel Pressure Transient Protection (0verpressure Protection)." The generic letter discussed the continuing occurrence of overpressure events and the need to further restrict the allowed outage time for a low temperature overpressure protection channel in operating MODES 4, 5, and 6.
This issue is only applicable to Westinghouse and Combustion Engineering facilities.
9209290335 920921 i
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2,0 1,R LtBLL BLSP@lk New llampshire Yankee (NilY), t he f ormer Seabrook licensee, responded to f4RL Generic let ter 90-06 by let ter nunher liiN 90217, dated December 21, 1990, for Seabrook Station, Unit 1.
In NYH-90211, fulY lndicated that two PORVs ami assot lated block valves are installed in Seabrook Station.
lhe Seabrook (t: tion PORVs are solenotd valvenontrolled, pressure attuated, poppet-type relief valves wht(h do not depend upon control air systems for their operation.
The block valves <,re flexible wedge, rising stem, motor-operated gate valves.
ihe Seabrook St at ion PORVs, blotk valves and associated components were designed to meet safety-grade requirements.
Mechanically, the PORVs and block valves ar e Saf ety Class I componcut s, llectrically, the PORV solenolds and the block valve motor-operators are destynated Llass 1[.
The PORV and block valve control switches, selettor switches and position indicat ions ;.re also designated Class 11.
Other ein trical components in the PORV and block valve (ircuitry including tables, (onnectors and splices that are located in harsh environments ate environmentally qualified, the PORV circuitry includes contracts from relays driven by non safety telated slynals associated with automatic control functions.
these relays are not qualified but are similar to Class il relays.
An analysis has been performed to demonstrate that no
< t edible f ailure of these relays can create a condition which degrades the fun (tlon of the Class 11 portion of the PORV circuitry, the PORVs and block valves at Seabrook Station are included within the scope of the IUIY (now NMSCO) Operational Quality Assuran 9 program and are, therefore, liste1 in Updated final Safety Analysis ihport (ISAR) lable 3.2 4.
Approved procedures implement maintcnance requirements for the PORVs and block valves in accordance with manufacturer's recommendations.
Maintenance is performed by trained maintenance personnel.
Complete replacement PORVs or block valves would be purchased, if needed, in accordance with the requirements of the original construction specification includthy applicable amendments.
Replacement parts fcr the PORVs or block valves woeld be purchased, is needed, by reference to the original manufacturer or supplier's part number.
Additionally, purchasing requirements have been pre-ostablished for specific valve parts based upon a review of the safety function of each part with input from the original manufacturer and/or supplier, lhese requirement s are imposed by the part s purchne order.
The PORVs and block valves are included within the scope of the Inserv',ce lesting Program for
- valves, lhe block valves are included within the scope of the Motor Operated Valve lesting Program being developed in response to NRC Generic letter 8910.
New Hampshire Yankee submitted a propose.1 amendment to Seabrook Station lechnical Specifications (lS) implementing the guidanc.e of NRC Generic letter 90-06 by let ter number NYN-91167, dat ed October 16, 1991, tor Seabrook Station, Unit 1.
In NYN-91167, NilY indicated that the proposed changes regarding PORV operability are based upon the model technical specification',
provided as Attachment A-1 of inclosure A to Generic letter 90-06.
The proposed changes regarding low temperature overpressure protection are based l
l upon the model technical specifications provided as Attachment B-1 to inclosure B of Generic letter 90-06, but reflect the fact that either the PORVs or the Residual Heat Removal (RHR; System suction relief valves can provide the required low temperature overpressure protection.
New Hampshire Yankee has developed the Seabrook Station 15 changes pertaining tc Generic letter 90-06 in association with the licensees of Braidwood, Byron, Callaway, Comanche Peak, Millstone 3. Vogtle and Wolf Creek.
This common approach is facilitated by the similarity er plar,t types and technical specifications.
All the plants in this group are Westinghouse pressurized water reactors (PWR) which utilize the PORVs and RHR System suction relief valves for low temperature overpressure protection.
3.O LMLVAILQH,JELS((l[R[{_. [51VL]LI G I - 7 OJ 1he actions proposed by the NRC staff to improve the reliability of PORVs and block valves represent a substantial increase in overall protection of the public health and safety and a determination has been made that the attendant costs are justified in view of this increasad protection.
The technical findings and the regulatory analysis related to Generic issue 70 are discussed in N'JREG-1316. " Technical findings and Regulatory Analysis Related to Generic issue 70 - Evaluation of Power-Operated Relief Valve Reliability in PWR Nuclear Power Plants."
3.1 Eenrhlion of PrppagiCitanges (Gl-701 The proposed changes to Seabrook Station Technical Specification 3/4.4.4
- Relief Valves" and its associated Bases increases the availability of the PORVs for Reactor Coolant System (RCS) pressure transient mitigation.
These changes require that P Ner be maintained to block valves which are closed to isolate PORVs which are exhibiting excessive seat leakage because removal of power would render the block valves inoperable.
By maintaining power to closed binck valves when the PORVs are exhibiting excessive seat leakage, the block valves can be readily opened to allow the PORVs to be used to control RCS pressure transients.
Closure of block valves establishes RCS pressure boundary integrity for PORVs which are exhibiting excessive seat leakage.
if the block valves are inoperable, the changes preclude the potential for having a stuck-open PORV that could not be isolated because of an inoperable block valve, yet maintains the ibility to use the p0RVs for RCS pressure transient control by placing the associated PORV in tranual control (i.e., the control switch in the "CLOSl'" position).
The proposed changes require that PORVs be cycled only during MODES 3 and 4 and not during power operation to simulate the temperature and environmer tal effects on the PORVs.
i The proposed changes do not reduce the margin of safety defined in its Bases, l
The changes do not affect the functions of the PORVs and their block valves in l
MODES 1, 2, or 3.
The changes require that if one PORV is inoperable due to causes other than excessive seat leakage, within one hour the PORY must be t
. restored to operable status or the associated block va've must be closed with its power removed.
No credit for automatic PORV operation is taken in the ISAR analysis for MODES 1, 2 and 3 transients, and the PORVs can be considered OPERABLE in either the manual or automatic mode, lhere is no change proposed to the PORV actuation circuitry or to the PORV or block valve power supply configuration, lhe proposed changes will increase the availability of the PORVs to mitigate RCS pressure transients and will, therefoie, enhance safe operation.
4.O LYAltJM10N fORJiGMKJ1WL2U01-10 The actions proposed by the NRC staf f to improve the availability of the low temperature overpressure protection (L10P) system represents a substantial increase in the overall protection of the public health and safety and a determination has been made that the attendant costs are justified in view of this increased protection, lhe technical findings and the regulatory analysis related to Generic issue 94 are discussed in NUREG-1326, " Regulatory Analysis Overpressure Protectton for Light-Water Reactors."
4.i DMcriplign_pf PrgnoM Changu,JGI-941 The proposed changes to Seabrook Station lechnical Specification 3/4.4.9.3
" Overpressure protection Systems" and its associated Bases provide enhanced operational flexibility through the use of a PORV in combination with an RHR suction relief valve for low temperature overpressurization protection.
Each of these relief valves, alone, is capable of mitigating a design basis mass or heat addition transient, lhe proposed 15 changes require that at least two overpressure protection devices; that is, two PORVs, or two RUR suction relief valves, or ;/e PORV and one RHR suction relief valve, must be OPERABLE when low temperature overpressure protection is required.
The NRC found acceptable the use of the RHR suction relief valves for low temperature overpressure protectica in NUREG-0896, " Safety Evaluation Report -lated to the operation of Seabrook Station, Units 1 and 2."
Seabrook Station overpressure protection analyses demonstrate that each RHR suction relief valve provides sufficient relief capacity to prevent exceeding 10 CFR 50, Appendix G limits during the overpressurization design bases mass addition event of one charging pump or one safety injection pump operating at tull flow with the RCS water solid and loss of letdown capability.
The analyses also show that each RHR suction relief valve will prevent exceeding the Appendix G limits during the overpressurization design bases heat addition event of a reactor coolant pump start with the steam generator secondary temperature 50' warmer than RCS temperature.
Seabrook Station facility Operating License Amendment No. 3, issued July 15, 1991, included the removal of the Residual Heat Removal System suction / isolation valves autoclosure interlock (ACl) function.
The RHR ACI removal design change was implemented during the first refueling outage (July 1991 to October 1991).
This plant modification enhances RHR system
reliability and overpressure protection system availability by precluding spurious kliR suttion valve closures caused by potential malfunctions of the All circuit.
lhe combination of PORVs and IUIR suction relief valves provides an equivalent level of overpressure protection with no degradation in the level of safety.
While low temperature overpre'.sure protectton is required for all shutdown modes, the most vulnerable perlod of time was found to be MODI 5 with the reat tor coolant temperature leu than or equal to 200'l,
especially when water '.olid, based on the detailed evaluation of operating reactor experiences performed in support of Generic issue 94.
lhe staff concluded that the t10P systems perform a safety-related function and inoperable overprenure protect ion equipment should be restored to an operable status in a shorter period of time, lhe current 7-day allowed outage time (A01) is considered to be too long under certain conditions and should be reduced to 74 hours8.564815e-4 days <br />0.0206 hours <br />1.223545e-4 weeks <br />2.8157e-5 months <br /> when operating in MODI 5 or MOOL 6 when the potential for an overpressure transient is most likely to occur.
Ihus, added assurance of overpressure protection system availability is provided in the 15 change by reducing the A01 for one of the two required overpressure protection devices (p0RV or idlR suction relief valve) f rom 7 days to 24 L ui s to MODI 5 and MODI 6, thereby providing a greater level of safety.
lhe proposed changes to 1S Surveillance Requirements include the performance of an ANALOG CHANNil OPIRA110NAL ILSI (ACOT) on the PORV actuat ion charynel to demonstrate that the PORV is OPlRAllti. w i i.he PORV is being used f or low temperature overpressure protection, lhe proposed TS (hanges do not reduce the margin of safety defined in its Dases.
lhe changes do not affect the functions of the PORVs or the Overpressure protection Systems required in MODt 4 below M9*l, MODI S and MODI 6.
lhere is no change to the PORV actuallon circuitry or to their PORV power supply configuratton and no reduction in surveillance testing of the PORVs or Overpres'. ore Protection Systems.
1he proposed changes wiIl increase the availability of the PORVs and Overpressure Protection Systems to mitio G RCS pressure transients and will, therefore, enhance safe operation.
5.0 OVL M L L M 01(G 10N 1he proposed changes to Seabrook Station lechnical Specificatir,ns included in New ilampshire Yankee letter number NYN-91167, dated October ro, 1991, are consistent with that proposed in Generic letter 90-06.
The staff has reviewed New ilampshire Yankee' proposed changes to the Seabrook Station lechnical Specifications.
S ii.
the proposed changes are consistent with the staff's position previously stated in Generic letter 90-06 ci found to be justified in the above mentioned regulatory analysis, the statf finds the proposed amendment to be acceptable, 6.0 51MLl0NSULlM10N in accordance with the Commission's regulations, the New ilampshire and Massachusetts State officials were notified of the proposed is'.uance of the amendment, lhe State officials had to comments.
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7.0 ENVIRONMENTAL CONSIDERATION
This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is ra 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 7815).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(C)(9).
Pursuant to 10 CFR SI.22(b) no environmental impact statement or environmental assessment need oe prepared in connection with the issuance of the amendt.ent.
8.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the 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 Commission's regulatior s, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
Gordon E. Edison Richard J. Jolliffe Date: September 21, 1992
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