ML20151H304
| ML20151H304 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/14/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20151H299 | List: |
| References | |
| NUDOCS 8808010225 | |
| Download: ML20151H304 (5) | |
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ff .y m'o, UNITED STATES NUCLE AR REGULATORY COMMISSION i wasmuo ton. o.c. nom t
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$AFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULAT!0N RELATED TO AMENDPENT NO.148 TO FACILITY OPERATING LICENSE N0. NPF-1 i i
PORTLAND GENERAL ELECTRIC COMPANY l THE CITY OF EUGENE. OREGON ;
PACIFIC POWER AND LIGHT COMPANY TROJAN NUCLEAR PLANT i DOCKET NO. 50 344 l
i 1.0 INTR 00VCT!0N By letter dated January 20, 1987 Portland General Electric Company j (PGE) requested a che' ige to the Trojan Nuclear Plant Technical Specifications with regard to the surveillance requirements for removal j of power from the accumulator isolation valves. Supplemental information ;
pertaining to the no significant hazards discussion was provided in a letter dated July 2,1987. By letters dated October 2 1987 and February 19, 1988 PGEprovidedsupplementaltechnicalInformationonthis t subject. The supplemental information provided by these letters did not alter the action noticed in the Federal Register on October 7, 1987 or '
affect the staff's initial determination of the proposed action. The j following evaluation addresses the proposed technical specification i change as well as the hardware modifications that accompany it. ,
2.0 DISCUS $10h AND EVALUATION l
Trojan Technical Specification Section 4.5.1.c presently requires that !
each accumulator be demonstrated operable at least once per 31 days when tre reactor coolant system (RCS) pressure is above 2000 psig, by verif ing !
that power to the isolaticn valve s operator is disconnected by remova l of the breaker from the circuit. This requirement, together with the requirement in Section 4.5.1.a.2 to verify that the accumulater isolation ,
t valve is open, ensures that power is removed from the valve operator to (
that a single electrical failure cannot spuriously close the valve. The I proposed technical specification change would delete the words 'by l rermal of the breaker f ree the circuit" from Section 4.5.1.c. This ;
would then allow power to be renoved from the isolation valve operator by l sore neans other than reroval of the circuit breaker. PGE is proposing '
that the pcwer be rensved by de energizing the control power to the accurulator isolatten valve rioter operator control circuit.
6808010225 880714 DR ADOCK0500g4 i
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l l The PGE letter dated October 2.1987 provided an electrical schematic of the power lockout circuit modification provided for the accumulator i isolation valves. The modification consists of a combination valve .
l control / lockout switch located in the control room. The switch has a normal, open, and close position with a spring return to normal. The switch handle is rotated clockwise to open the accumulator isolation i valve and counterclockwise to close the valve. The valve switch is placed in lockout by pulling out on the handle when in the,nomal position.
Once in lockout, the handle cannot be rotated in either direct,1on.
One contact of the combination valve control / lockout switchhsElecated '
in the neutral leg of the power supply feeding the motor starter coils and auxiliary control relays of the acccoulator isolation val e. Another '
contact of the switch is located in the power supply hot leg feeding the auxiliary relays only. The contacts in the hot legs and neutral legs open when the combination valve control / lock switch is in the pull to-lock position. This removes control power frou the motor contactor coils and auxiliary relays of the accueulator isolation valve.
Because the contacts which operate the accumulator isolation valve are located on the same switch with the contacts that provide the lockout feature, the staff questioned the electrical and mechanical independence between the operating contacts and lockout contacts. In a letter dated February 19, 1988 Put responded that rotary contacts provide normal control of valve motion while lateral contacts provide lockout of the valve control circuit. The two types of contacts are located in different ,
contact stages and are electrically and mechanically isolated from one '
another via a glass / polyester barrier. A cossmon actuating shaft causes the various contacts to change state according to the predetemined ,
switch contact configuration. The discussion of the switch in the PGE letter then goes on to describe switch operation and potential mechanical .
and electrical failures. I No single mechanical failure of the switch was identified which could cause both the rotary and lateral contacts to change state other than ;
gross mechanical deformation which is not considered a credible event for this installation. No signal electrical fatlure we 'dentified which i could simultaneously cause the lockout contacts and operating contacts l to close or remain closed when the switch is in the lockout position. A .
simultaneous electrical failure of both types of contacts was identified !
for the switch in the Mn lockout position. The failure that was identified was an uncleared fault on the control circuit while the valve was being closed that might cause both the operating and lockout contacts to weld shut. This failure however would have to result from the failure of the overcurrent protection to operate and would not be different if the lockout contacts were on a switch separate from the valve operating switch. PGE also states that the manufacturer's operating experience and failure history with similar switches does not indicate any comon-noce failure rechanism which could cause simultaneous failure of both lateral ard rotary contacts. Based on PGE's discussion of the independence t,etween the cperating centacts and lockout contacts, the staff concludes trat the use cf the single corbined control / lockout is sufficiently reliable.
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3 The staff was also concerned that there is no direct indication of the status of the contacts that provide the lockout function. With no periodic surveillance of the contacts this could result in the contacts :
being inoperable (eg. welded closed) with no means of ever detecting the condition. In a February 19, 1988 letter PGE committed to verify :
correct operation of the switch lockout contacts at least once every 18 '
months during shutdown. PGE also conunitted to include the requirement ,
for this verification in the Trojan Technical Specifications. However, ,
in accordance with the Cosnission's interim Policy Statement on Technical Specifications Improvement, dated February 6,1987, the requirement need ,
not be contained in the technical specifications but may be contained ;
instead in plant procedures. This is appropriate since failure to ver!fy the inoperability of the contacts, by themselves, will not prevent the i system from fulfilling its intended safety function. Therefore this ;
surveillance requirement does not fall under any of the three categories i as defined in the interim Policy Statement as requiring inclusion in the l TS. In a telephone call on June 2,1988. PGE stated that this requirement would be included in Periodic Operating Test (POT) 25-2, "Safepards Test ;
Panel Actuating Tests and Tests of Manual Initiation Switches. These i provisions will provide adequate assurance that the switch lockout .
contacts will remain operable. !
- In order to ensure that the combinetion control /inckout switch .emains in the lockout position when required, a blocking collar is installed under
, the switch to prevent inadvertent insertion of the switch handle. The '
staff inquired about the administrative procedures used to control the removal of the blocking collar. In the February 19, 1988 letter PGE referenced Administrative Order 3-13 for the control of this type of switch. They stated that this order s >ecifically requires the permission of the Shift Supervisor or Assistant Siift Supervisor prior to changing I the position of any administrative 1y controlled switch when the reactor l is in Modes 1, 2, 3 and 4. These provisions will provide assurance that l
the switch is in the correct position.
, in addition to the above provisions for locking out control power to the accumulator isolation valves, position indications and alams exist in the control room to alert the operator to an accumulator isolation valve that is not in the open position. An alam will occur when a valve is i not fully npen and the system is under pressure. This condition is sensed by a can switch in the motor operator and an externally mounted stem-operated switch that are connected in parallel to provide redundant alam initiation. Valve position indication is provided by separate cam switches in the motor operator. Presently, valve position indication is
, lost when the circuit breaker is removed from the valve operator circuit.
With the proposed configuration of locking out power to the controi circuit i of the valve operator, valve position indication will be retained to the accumulator isolation valves. These position indications together with the existing alams provide additional assurance that the accumulator isolation valves will be in the correct position.
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Based upon the above review, we conclude the following: l
, a. The use of the single combined contro?/ lockout switch is j sufficently reliable and is therefore acceptable; l
- b. Verification of correct operation of the switch lockout contacts at least once every 18 months during shutdown will provide adequate assurance that the lockout feature of the switch is operable and is therefore acceptable; ,
- c. The use of a blocking collar on the control / lockout switch together with the administrative procedures for controlling i operation of the switch will provide adequate assurance that the switch is in the correct position and are therefore acceptable; and ;
- d. Yalve position indications, which are presently lost when removing power from the valves, will be retained when locking out power to the valves with the aro>osed modification. These '
position indications together wit) tie existing alams provide )
additional assurance that the accumulator isolation valves will be in the correct position.
3.0 CONTACT WITH STATE OFFICIAL The NRC staff has notified the Oregon Department of Energy of the proposed issuance of this amendment along with the proposed determination of no significant hazards consideration. No comments were received.
4.0 ENVIRONMENTAL CONSIDERATION
l This amendment involves a change in the installation or use cf a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to surveillance requirements. The 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 j
offsite, and that there is no significant increase in individual or '
cumulative occupational radiation exposure. The Commission has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public conenent on such finding. l Accordingly, the amen exclusion set forth 6nent in 10 CFR meets the 651.22(c)(9 elig)ibility
. Pursuant to criteria 10 CFR for 65122(b),categorical l no environmental impact statement or environmental assessment need be l prepared in connection with the issuance of the amendment. l l
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5.0 CONCLUSION
We have 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, and (2) such ,
activities will be conducted in compliance with the Cessnissions's '
regulations, and (3) the issuance of the amenhnt will not be inimical i to the coanon defense and security or to the health and safety of the public.
PRINCIPAL CONTRIBUTOR: J. Lazevnick Dated: July 14, 1988 ,
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