ML20037D571
| ML20037D571 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 08/04/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20037D570 | List: |
| References | |
| GL-81-14, TAC-43660, NUDOCS 8108270582 | |
| Download: ML20037D571 (2) | |
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SAFETY EVALUATION REPORT TROJAN NUCLEAR PLANT SEISMIC OUALIFICATION OF THE AUXILIARY FEEDWATER SYSTEM Introduction and Background On August 8,1980, the Division of Safety Technology (DST) transmitted the results of a study on the seismic capability of decay heat removal systems to the Division of Licensing (DL).
That study included a simplified probabilistic risk analysis and recommendation for action by D L.
Since August 1980, this. subject has been that topic of acditional correspondence relative to NUREG-0667, " Transient Response of Babcock and Wilcox-Desicned Reactors," and has been discussed at several ACRS r.eetings and at planning sessions with DL and the Of fice of Nuclear Pegulatory Research (RES).
As a result of these concerns, and to assure conformance of each plant with General Design Criteria 2 and 34 of Appendix A to 10 CFR Part 50, "Multiplant Action Plan C-14:
Seismic Qualification of Auxiliary Feeddater Systems" was formulated.
The pu. pose of this plan is to determine th6 extent of the seismic qualification of the auxiliary feeddater ( AFW) system for all cperating Fressurized Water Reactcrs (PWRs). For plants with AFW systems that are not seismically qualified. either in whole or in part, this plan ultimately involves increasing the seismic resistance of the systems in c timel;. s):tematic marnt e, w".ere necessar,.
U;;rading of tne
!Ji systems will bc required to the extent thct is apprcpriate to
- <ovice re?
nable ass"rance that they are able to function following the c:currence cf ca rthc:. abs up to cnd inclMing the design Safe
[ hut docq E a rth u-.L e ( $5E ) f or t r c p l 6 r.t.
-o identify it ese plants witncut AFh systems. c; ;crticns thereof, which na,'e been cesi;ned, constructed end maintaincd (ana incicced witnin
- ne scope of seismic related IE Euiletir.s 79-02, 79-04, 79-07, 79-14, and 50-11, end :E Inf c>rmati:n Nctice 50-21: as seismically qualified systems in c;cordance with the criteria f cr ciner safety-grece systems at the fccility, LRC Ger.eric Letter El-14, " Seismic Cualification of Auxiliary Feedwater Systems," dated February 10, 1961, was issued under 10 CFR 50.54(f) to all operating PWR licensees.
This letter also requtsted walk-downs of the eq;ipment, components and piping comprising those portions of tne AFW system which werc not designed, constructed and meintained as seismically cualified systems in accor-dance with the criteria for other safety-grade systems at the facility.
8108270582 810804 PDR ADOCK 05000344 P
A T These walk-dovins were to be perf ormed by personnel experienced in the analysis, design and evaluations of structures, systems and compon-ents sinilar to those comprising the non-seismically qualified portions of the AFW system to identify any readily recognized deficiencies in scisric resistance and to reconnend any apprnpriate remedial modifica-tions. Any corrective actions taken, or pl-nned, sere to be described, and a schedule for the planned corrective actions provided.
Similar considerations as those described above were to be given to alternate decay beat remaval paths in those cases where portions of the AFW system are not seismically cualified.
The bounds to be considered for these systems were defined as follows:
1,i responding to this letter, tne \\FW system boundary from suction to discharge (including the water source and heat sink) shall include those portions of the system required to accorplish the AFW system function and connected branch piping up to and including the second valve which is normally closed or capable of automatic closure when the saf ety f unction is required.
The AFW system boundary shall also include any portion of branch piping that is structurally coupled to the AFW system boundary such that the seismic response of the branch piping transmits loads to the AFW system. As a minimJm, this includes the branch lines outside the AFW system boundary to a point ef three orthogonal restraints.
All mechanical ar.d electrical equi, ment. piping (e.g., instrument air), conduits and cd i. itays, unish cr._
rece sary c, ccntain iters which are r c :e s t o ry. ice tie c,erctico cf the 7 i cy5t(r shall also be consin. n d.
In
'qition. tw s tructu' s housing these systens i r. d c eo at s < N.11 oc inclue 1.
S-il a r cen:i cerations shall te u;,;li,o *Nn w,or n: 'I t t et.<: t c r a s o f de c ay N. c t rca> val.
) '-S_s]i O n it,e Portland unerel Li t tu i.. ' t m;'a n
( PM ) tub::itted the inf orm3 tion ir<;w sted 1ar the i-u, U n h r Plant i n I:RC Generic Letter 81-14 via T ttter froc ;6rt L.,Jit k rt te Farrtil G. Eistnhut, dattd June 9, 1081.
Thoi r res po ir e indicated th it; 1)
The saf ecy-related portion of the AFW system (the portion recessary for safe *hutdown of the plant) is designed, constructed and maittained (and includ( j within the scope of IE Pulletins 79-02, 79-04, 79-07, 79-14, and W-11, and '.; Inf ormatien Motice E0-21) in accordance with Seimic Category 1 nqui,ements including Regulatcry Guide 1.29.
The seisnic qualificetion is consistent with that of other safety-related sy* tems at T ro,ian.
k e 2) The primar water supply path (the candensate storage tank and the piping from the condensate storage tank to the single Category I check valve in each pump's suction line) is not seismically qualified.
However. the secondary water supply from the Service Water System to the 2 saf ety-related AFW pumps is seismically qualified.
Procedures exist which provide for this switchover from the main control room.
- 3) The recirculation lines from the safety-related pumps to the conden-sate storage tank are not seismically qualified downstream of the pressure reducing orifices and locked opec valves.
However, a break in the recirculation liner would not jeopardize the operation of the safety-related AFW pumps.
- 4) All other electrical and mechanical tvapcnents required for operation of the safety-related AFW pumps are safety -grade.
- 5) The recently installed (third) non-scfety-related motor-driven AFW pump and associated piping are not seismically qualified.
This pump is not required for plant safe shutdown as the safety-related portion of the AFW system includes two redundant ICO-percent capacity pumps.
Evaluation The NRC staff has reviewed the information in the June 9,1981 PGE response to Generic Letter El-14 concerning the seismic qualification on the Trojan Nuclear lant au xili ary fu ec.. ster sy ste-Ecsed on this review we have deterrained that:
i) ine scfety-related ;crtien of the Trcjan AFW syste-has been ccsiened, CcnstrJCtCC and ~;#".tained in aCd6f ddnce With the Seismic Eateg0ry I require':nts a;plicable tc cther safcty-related systers at the facility, ana theref re, is seis ically qualified.
- ) The prir.ary water supply path is not seismically cualified.
- However, the !ccendary water supply patn is seismically qualified.
Procedures are es t;blished to accen?lish the s.eitchover f rom.he prinary to the secondary supply in the event of the loss of the prir3ry supply. These have been found to be acceptable to the NRC in its review for the implementation of NUREG-061' recomnendations for Trojan under TMI Action Plan Item II.E.1.1 (See the SER transmitted to PGE via letter from Robert A. Clark to Charles Goodwin, J r., dated October 23, 1980).
o Sk
_4 Generic Letter 81-14 required that seismic qualification should be considered to the "second valve which is normally closed or capable of automatic closure when the safety function is required." Trojan incorporates a single Seismic Category I check valve in each of the two pump suction lines to the condensate storage tank (primary supply source).
Should an earthquake cause loss of the primary Source and o
one of these vc Lves f ail to function upon the switch from the primary to secondary supply, the other 100-percent capacity safety related AFW pump would still be available to maintain AFW s/ stem function.
Therefore, this arrangement is acceptable.
In adoition, the seismic event may not cause loss of the capability to rcstore service water supply by f ailing the Seismic Category 11 valve and piping in its vicinity.
The Seismic Category 11 locked open valve could be manually closed to restcre flow to the pump which is protected from failure due to loss cf suction pressure by a safety-grade low suction pressure trip.
Therefore, loss of one of the safety-related AFW trains may only be temporary.
- 3) Failure of the non-seismically qualified portion of the recirculation lines for the safety-related AFW pumps would not adversely affect the operation of the pumpr.
4)
The classification of the recently installed (third) motor-driven AFW pump and associated piping as non-safety-related has been found to be acceptacle to the NRC in its review for the implementation of
' be.S-Cfil recr ur daticns for Treiar, undar TMI Action rian Item
- I.i.1.1 (See -he EER transmitted to TSE via letter fren Robert A.
Clark to Eart :. n'i thc rs, dat ed F e brua ry 15, 1981).
_Cen:li si cn_
We finn in2t toe 'scisnic cualificaticn cf the a;;rc;riate pcrtions cf Trejen Naciaar Picnt auxiliary feed.ater system is ;onsistent with that of otner saf ety-crace systens at the facility.
Theref ore, t!.ere is rcascnable assurance that it will functicn foliching the cccurrence of earthqun:es up to a-d inclucing the SSE for the plant.
On this basis, the Det response tc Ge';eric Letter 81-14 is acctptable.
No further actions are required on th-part of PGE for Trojan, pending the outcome of the long-term studies discussed in "M. Itiplant Action Plan C-14:
Seisnic Qualification of.uxiliary Feedwate, Systems."