ML19209A690
| ML19209A690 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/01/1979 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Rubenstein L Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7910050211 | |
| Download: ML19209A690 (16) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANCOG A. TENN ESsEE 374o t 400 Chestnut Street Tower II October 1, 1979 Director of Nuclear Reactor Regulation Attention:
Mr. L. S. Rubenstein, Acting Chief Light Water Reactors Branch No. 4 Division of Project Management U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Rubenstein:
In the !btter of the Application of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 On September 10, 1979, a telephone conference call was held with TVA, Lambros Lois of the NRC Reactor Systems Branch, and Stan Bruske, an NRC consultant from Idaho National Laboratories.
The topic of discus-sion was NRC cor.. carn with TVA compliance with IEEE-279 for interlocks for Reactor Coolant System (RCS) Pressure Control during low temperature operation.
As a result of this discussion, TVA agreed to provide the following information.
l.
Logic and wiring diagrams 2.
Expanded general description of the RCS overpressure mitigation system and its operation 3.
An amended Final Safety Analysis Report (FSAR) section 7.6.7 4.
An evaluation of a design problem which occurred at North Anna Nuclear Plant where a failure in a power supply could cause both an overpressure transient and partially disable the RCS mitigation system Enclosed is one copy each of the following logic and wiring diagrams.
47W610-68-1 through 6 47W611-68-1 through 3 45N668 s
45N765-10 and 13 Two copies of each of these drawings are being sent concorrently with this letter to Lambros Lois.
O\\
b #s #
1110 258
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. Director of Nuclear Reactor Regulation October 1, 1979 Also enclosed is the information requested in item 2.
Section 7.6.7.1 of the FSAR will be revised to accurately reflect the degree of TVA's compliance with IEEE-279.
This revision will be provided by October 12, 1979.
With respect to item 4, TVA has reviewed the power supply to the letdown portion of the Chemical and Volume Control System (CVCS) and the Power Operated Relief Valves (PORV).
The power supply arrangement at Sequoyah Nuclear Plant is designed so that a single event cannot initiate an over-pressurization transient, disable part of the mitigation system, or make the system vulnerable to a single consequential failure.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure 1i10 259
9 SEQUOYAH AND WAITS RAR NUCLEAR PLANTS COLD OVERPRESSURE PROTECTION SYSTEM g
trhe cald overprecoure protection cyctem for CQH and WHi ic decigacd to encure 2.ti.tigation capability for RC3 proccure trancienic for the full rance of RC3 operating temperatures. The :sCS ccfety vaJvac provide overproccure protection (i.e., they vill 2.:aintain RC3 preccure holov the pend i.: G liinitc) for all RCG opere. ting conditionc Tith temperaturec
- e. Love 350 F (thic van determined from the technical crocification proccure-teraporatura li altation curvoc).
During normal pouer operation, the proccurizer poucr-operated relief va.!.vec (pCRV'c) provide additional otection an diceucced in FSAR coetion > '.2.
The cold overproccure
-Lc etion cycten vill une the FORV'c to encure redundant trainir d relief y-the
>r proccure trancient uhich occur below appron.:.ately 450 F (note that the exact value of thic permiccive interloch has nct beca ized).
For cach train, the cyctem vill (1) monitor actual RC3
- 2..
temperai,ure and proccure; (2) generate a temperature dependent proccure point for each PORV; (3) compare tne c.ctual preccure to the cetr> int mcure; (4) clarm when the actual proccure apprcaches the cetroint; and i
(9) actual;c the IOR7 when tht. actual proccure in greater bhan e equal
- n the cetpoint picccure.
Additionally, the c/c tc:s uill ir
'.u'..
temperaturc interlocks to autombically am the.'yctem ac RCS temperature dacrec.ucc.
A discuccion of the protection cycteu component and their operation ic provided below:
1.
RC3 Tennerature - The RC3 vide rcnge temperature inctrumnts vill provide ini ut to the train A FORV (PCV-68-340A) actu,. tion logic. Tne fove int leg inctruments vill provide in;ut to the train 3 TC'lY
( ICV-8--335 ).
For each case, the four to:qnrature signalc vill be auctioneered lou (1.c., tha loucct indicate 'calue will be Colcebed) to provide a concervative input to the cetpoint Cor.crator.
Additionally, thece aur tJoncered tcmperaturec vill be used to pro 7ide interlocks to autombically arm the PEV'c on decreasing RC3 temperattre (cc.-
iI en 5 be.!mr).
2.
Punction Omernier
'6e Uectir(:houcc-curplied function generator 2:, proprci~n:c:cd to to'
- the aw l.loneered temperature input (from 1) and concrate a pr. nre : e' Nt for the accociated PC M.
'i'he prt cccJr.cd cetpolnL curve 10 nuffit.icntly lecc then the technical crccificaticn li:d.t to allow for overchoot above the cetpcin, without erece! ins the liz.h.
1110 260
3.
RCf; prermrce The trained RC3 trido range preccurn incbruir.cnts (0-3000 pcic) provide proccure input to their accaciated comparatcr.
(I!ote that the actuation cignals for the POIl7'c durin; normal power operation are tahen fro:a the proccurizer narrcw renco preccure inctrrccnts )
h.
Co:npurn. hor The cc:t.parator roccivec nignala frora the function Concrator (colpoint proccuro) and the RCS ulde rance proccure inctrunc h:
(actual 1,rea:ntre ).
If tb' e.ctual proccure approc.chen within.
(Inte that thic valuu ic not yet finaliced pc of the cetpoint preccure an annimeir. tor rnd alarn vill aln t the er rator.
3 If the actual proccure ic Cre Scr than or equal to thic cetpoint preccure an actuation sic;ncl will be t, cub to the PM;V.
Te:nocrature Tntechru Fach IORV actuation circuit is provided with temperature interloc.
fro the oppoc i tu treined ar tiencored tc:a..rature cignal hhen m HCS teuperature in above thic pc_ nic -1. ; interloch the cold 3
.arprec.:ure cclustic n logic for thal ICRV is no L fract nal.
l' hic utcrloch is includel to mini:dce the potenti.nl for a npurious ci gnal operuting Lhe IU;1V during normal cpcration.
An annuncic;bor in the main control room aln.t ec when the intcclocP ic : >.de up to indierto tha e the overpreccura logic ic Amational, l!ote that the tc.speraf,nce inntru:tants, a-ciencering circuitc, function concratorc, tride r re,e prescure inctrume:.33, and ccy. c tor.. provido indc/ pendent acta allon cicula to their ac;;ociated iC;il.
'ih a:cr : cnd mnrnciator o rnt oC the bro ec.4c.rabora c.re rirec to a c in the s'an couLrol roo,
o::. :n ; larm (or baffer) rel.1/c to encure lhe indcycudenac of bl c M o tr
^
t on v.i d tted.
lnc cre not The permi:,,;l'ae iu. pere.vure interlockc beateen trainc I
ancociated nmnmaiahlon cir,'ui Lc, also use ceparatton rcJnyc
, cud their i
Thus, the call overprennure actuat lon circults fer the PGIV'c c.rc indepen.ient failure proof.
una cin-lc Av e,.Un:e the cycter:
i v
tabion (due to the fant thL t icting inct:rcn'aut.;cc cene control gracle inctruman-i l
thic backfit), T/A ciu:nat ctu.te full complicnce rith Is'Z 279
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