ML18043B116
| ML18043B116 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 10/04/1979 |
| From: | Diianni D Office of Nuclear Reactor Regulation |
| To: | Reid R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18043B117 | List: |
| References | |
| NUDOCS 7910250341 | |
| Download: ML18043B116 (2) | |
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Chief, O?erating Reactors Sranch f4, DOR FRO~~:-
. SUSJECT:
. S?*URlOUS REACTOR SC?w!.M F:OST *Tt;H *:*
L*ice;;sees of the Babcock &. l-i 1i1cox (B&W) designed Ci*crating reactor p1ants
~ere ~sked to present their operating experiences reg~rding feedwater tra~sients resulting in reactor scracs (meeting held S/23/79).
As an attendee at this meeting, l f-ee1 obliged to express ~' views on this ;;.atter~
Recent operating experi enc:e shows that instabi1 ity in the secondary systems cawscd spurious* reactor scrams by the actuation of the high pressure trip 5 et point in. the primary system.
As a resu1 t of T~I, this high pressure irip setpoint ~as 1owered from 2450 to 23DO psig and the pcwar-operated re1i~f va1~e (?ORV) setting was raised ~bove the ~igh pressure trip settinef (2300 psig).
Lowering the pre.s.sure trip resulted in reducing the* pres.sure Spread.bet~~en the normal operat~~g pressure ~nd the high ¢ressure trip
,... t6.ap;:iroxi'fr.at:1yTOD *psi. *-This change res-u1ted,in* negating an imp-Ottant....... :.~.*-
fwnction of t=-:e ?O~V ";hi ch 'is. to pn:vent spurious r~~ctor _.sc1ams d.uring.
- ~plant transients.
It is r.ecoru.,~:"l6ed that *these changes in the pressure "t:ri_p* set.ting and the s~tting of ?O~V be considared as an interim ~easure*and the settin~s sh6u1d
."be returned to pre-TM! conditions_ after upgrading the reli abi1 ity 'of--the.
FGRV.
Upg*r:.cing the reliability* of tbe PORV should be =~peoited in* order that these und:sirable pressure settings are eliminated.
Experience shows that re~ctors ar~ more susceptible to spurio~s scra~s when scram settings*
c.:-e set.cicse to the noriiia1 open.ting pararaeter (Li.P~OO psi). This ex~!~~ence ~~s broug~t to the staff's attention by the 1icensees during the
~~=tine bf A~:ust 23, 1979. Furthermore. one could expect that the B&W
~~a~ts*a~e ~:~e susceptib1e.t6 spurious scrams than th~ other two P~R ~eactor
- v~nC:ors* becawse of the faster response of the E&Ws pdrr.a*ry system to changes i,,
- t~*e s eco:-ida ry system.
The transient* condi ti ens d.uri ng
~ spurious scram deies iT*?.ke piant equipjj.ent (i.e.,* va1ves, pipe vibra_tion, control system, etc.)
- prone to ~aifwnction decreasing scffi; of the ~afety margins during trarysie~t
- periods.* The present-pressure setpo'\\nt cond1tion a1s.o *p1aces an exces?ive * **
stress on the reactbr operator since the operating margin is r~duce~ r~quiring i~~ediate action by the operator to avoid reactor scrams.
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or ~ *. e fer revt~w from the three NSS vendor$ the engineering specifi~ations
?OKV that was issued-to the va1ve manufacturers.
- 2.
- The va 1 ve *manufacturer s hou1 d be consu1 tea as. t: meeting.the requi re.m:nts of the specifications. Discussions with the vt :ve manufacturer should inc1:.i.:e a review of the va1ve*design, qua1ity *.ssurance/qua1ity control d
- a~ 1.es1.1ng.
Iniori71ation from !terns 1 and 2 abo*,re wou1d assist the staff in dete:nnining area's of design, fabri ca ti on, qua 1i ty assurance/qua 1 i ty control and testi.ng that wou1d require upgrading.
- 3.* '.. Ev: iuc. te-the e leva ti on of this va 1 ve typ_e to a safety grade va 1 ve.-meeti ng the requ~re~ent of ASME Code,Section III. The ASME Code addresses pow~r actuated re1ief va1ves which are f'equired for over pressure protection
- p:.:r;:i:ises. but whether. these requir~iiients are adequate for the ?ORV having
- the ft.::'"ictfon ;of:~ -press:ure- -co~tro1 *valva :is.ope.r:a-tc qu.est1ori._ -.*"-....
- 4.
V!1v~ b~nch testino criterion shou1d be estab1ished which wou1d i~c1ude design {1ow rates *or fluids in all three phases (i.e., liquid, two ph~se
&: *steam).. !t appears _that a f1 ui d supp1y system for tesfing shou1 d not
.present a ~rob1ern because of the 1ow~cap~city of the PORV ~s compared. to~
the saf:ty valves (i.e.* ?ORV l x 10~ ~/hr V.S. safety.valves. 3.117.*x 10~
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Vaive c~ntro1s inc1ud'ing contro1 circuitry, power supp1ies, pane1 'indications sh:~1~ be rgviewed wit~ the objective of meeting the requirements IEEE 279.
IM conc1~sio~ thi objective of this rnem~randurn is~to bring to your attention th:: i:-:-::-:~::e n::d for U?grading the. reiiabi1ity of the ?ORV for which adequate p~iority shou1d be given and to give in approach in t~e reso1ution of.this.
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.::r11!1eS D. C. Di!anni, ~reject Manager Operating Reactors Branch ~4 Division of Operating Reactors
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