ML17037C100
| ML17037C100 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/04/1972 |
| From: | Schneider F Niagara Mohawk Power Corp |
| To: | Skovholt D US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17037C100 (12) | |
Text
c AEC DISTRIBUTION ~
~ FOR
~
PART~0
. SOCKET-- -MATERIAL (TEMPORARY'ORM' CONTROL NO'::
FROMlgiagara Mohawk Power Corp.
- Syracuse, N. Y. 13202 DATE OF DOC::
DATE REC'D 2 LTR NEMO RPT OTHER 70:
Mr. Skovholt GRIG 1
PROP LNAA'0 XlcTPUT
.'0 CYS;e-.C' 50 cys rec'd.
DOCKET XO:
50>>220 DESCRXPTIOAN:
Ltr submitting description of New system for unidentified. 3.eak-rate detection for Nine Mile Point Nuclear Station Unit No. 1 W/Attachment-diagram of Nine Mile station Floor Drain Tanks Eh CLGSUR"'S l DO NOT REMOVE hCQCMBKD BUTLER(DRL)
W/
Copies CHITWOOD(DML)
W/
Copies CLARK(DRL)
W/
Copies H.
DLcCTON W/
Copies DICKER(DREP)
W/
Copies GOLLER(DRL)
W/
Copies KNIEL(Dar,)
W/
Copies KNIGHTON(DREP)
W/
Copies scarmu,(DRL)
W/
Copies SCHWENCER(DRL)
W/
Copies STOrz(DRL)
W/
Copies UASSALLO(DRL)
W/
Copies NIEMANN(DRL)
W/9 Copies W/
Copies W/
Copies W/
Copies W/
Copies W/
Copies W/
Copies W/
Copies Reg Fil gAEC PDR g Compliance (2)~
- OGC, Rm P 506A Q~Aiunc.sins 6c S tai A.
QMolris/Dubc/Wilson(DRL)
D Moxris/Sc'nxoeder (DRL)
Q Dube/Wilson (DRL)
Vollmer(DRL)
Q Sliger(DRL)
@Long(Dl?L) g Collins(DRL)
Tnompson(DRL)
Q 0.
E. Nunn(DRL)
D Benaroi a(DRj.)
lSE
~
G ~ Case(DRS)
Q Il. Fi tspa trio,((DRi!p) Q Q Kastner(DREP) g Lic, Asst(DR':P)
Q QilcC:eless(DR"'2),
. Q Q G.
Blanc(DREP)
Q j3 Pro'ec" Leader(DR"P) +
Q DcCaiP Fl.le Room CJ 13 A ~ Bral.c.macl(SLR)
Q tli Boyd (DRL)
~ DeYoung (DRL) g il. Den.'on(Di?L)(4)
~'l~lcckcr (l)RL)
D Grimes (DRL)
Q Gazmi ll(DRL)
QJt Tedesco( 0'?L) gfAiaccary(D'.S)
Sc.ello(D S) g V. Moorc{Di?S)
C3 Lanpc ( l)RS)
Q Smiley(D!'iL)
Q Aic Ropital s (DcxEP) 0 ~Liullcr (iP.,:-:P)
Q 5 a 1 c'.aliilan (SLR)
D Tremmcl (DrP)
Q i.ilornLOn(>c~ciM)
Knuxh(D:?S)
D Shao (D;;S) 0 P wlicki (DRS)
Skowclol 't.
(DPL Ci C3 LJ l~
1:.l Q
Q Local'DR
- DTIE(Laughiin) 1 - ASLB(Yore/Woodard 1
ItHII St )
gl6 1 - C. Miles, C-459, GT 1
9 - National Laboratories.
1
( A TNT. InTNRTT./Tucks. )
XTERNAL DISTRIBUTIO
- NSIC(Buchanan)
- R. Carroll OC, GT
<< Holding for ACRS
>> R. Catling A-170)
GT
- Consultant(Newmark/
Blum/ Agabian)
2 - Warren Nyer
f ]ggl:
1 i,,gll II
'egulatory File NIAGARA MOHAWK POWER CORPORATION
- tIt, ni~IUk NIAGARA~
MOHAWK BOO ERIK BOULEVARDWEST SYRACUSE, H.Y. IS202 yisY<@ 18%~
Mr. Donald J. Skovholt Assistant Director for Reactor Operations Division of Reactor Licensing United States Atomic Energy Commission Iltashington, D. C.
20545 May 4,,1972 g fj/p d
at~'e 'da 8
fop
+@4@/~~1 e~ 4(
Dear Mr. Skovholt:
Re:
Provisional Operating License:
DPR-17 Docket No.: 50-220 You requested that we provide the Commission with a description of the new system for unidentified leak-rate detection as installed on Nine'ile Point Nuclear Station - Unit ¹1.
Unidentified leakage detection has been greatly inhanced by the addition of new instruments.
These consist of two separate signal channels, installed to meet the single failure criteria.
This new system is a redundant one which consists of displacers located in the dry well floor drain tank and are attached to linear differential voltage transformers (L.V.D.T.).
The displacer is placed to cover the range of the sump pump float switches.
Analog signal from the L.V.D.T. is then fed thru an A.C. to D.C. converter, which in turn, feed two voltage sensitive strip chart recorders.
(sketch enclosed)
The sump and chart recorder scale are calibrated for a gallon-level relation-ship giving a gallons vs time on the recorder..
The -recorders are located in the control room on front panel location.
This, provides the plant opera-tor with the current trend of unidentified leakage.
Each indicate rate of rise of the floor drain tank level as water collects in the tank, which is proportional to inflow leakage.
Any change of leakage rate results in a recorded
~slo e change on the chart.
Using an overlay curve grid, the operator may quickly determine the'low rate or rate of change.
Low flow.rates (up to 1.0i'pm) can be best displayed using a chart speed of 0.1 inch per hour.
Higher flow rates require a 1.0 "inch per hour chart travel.
This.selection can be made by the operator at the recorder.
~
~
~
~
~
~
0
~
~
0
~
Mr. Donald J. Skovholt May 4p 1972 CHART SPEED 0.1 in./hr.
FLOW RANGE 0 -'.0 GPM SENSITIVITY
+ 0.2 GPM TIME TO DETECTION
~ 40 min.
1.0 in./hr.
1.0 GPM 5 above
+ 0.5 GPM 8 min.
- Time required to record a flow rate change of sufficient detail to make an accurate measurement.
Previous to the installation of this system, sump accumulation rate was determined only by the timing of the interval between water contact with probes spaced vertically in the sump and by, integrating the total volume pumped over a twenty;four hour period.
Operators could detect a change in system leakage of approxi'mately 0.2 gpm within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
With the new system, the same change could be detected in 40 minutes using a chart speed'f 0.1.inches per hour.
This, is 'the normal operating condi-tion.
Increased leakage rates,would'require the operator to change the recorder speed to 1 inch per hour and thereby obtain a sensitivity of approximately 8 minutes change detection, time.
Therefore, the operator is provided with a tool whereby he may. determine change in leakage rate in a reasonable time period.
This is useful in allowing some investigation as to the source of the "unidentifiable" leakage which could come from one or more of the following:
a)
Dry well cooling system leakage from reactor building closed loop cooling (fresh water) into the dry well and hence to sump.
b)
Primary coolant leaks not identifiable as to source and therefore to be considered as coolant boundary failures.
c)
Primary. coolant leaks which can be identified by manipulation of valves, isolation of equipment, etc.
and therefore actually no longer "unidentifiable".
d)
Leakage of containment spray system.
Obviously, (a) and (d) are not pressure boundary oriented.
Leakage from these sources can readily be determined by isotopic analysis of the water being pumped from the floor drain sump.
ln as much as this amount now has been identified, it should not be assessed in the limitation of unidenti-fied leakage.
Likewise, by the manipulation of valves and shutdown of parts of systems, together with appraisal of rate change in sump pump-out rate as determined from the new recorders, it would be possible to determine if certain valve packings or pump seals are leaking.
bfith this ability to differentiate on various means of leakage into the
- sump, we propose the following program:
r K
)
Mr. Donald J. Skovholt May 4, 1972 1.
Should rate of change in "unidentifiedu leak-rate continuously increase at 1 gpm or greater per 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> day, the reactor will be started down before exceeding 3 gpm and be in a cold shut-down condition within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.
2.
Should rate of change in "unidentified" leak-rate change at less than 1 gpm per 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> day or in a stepwise
- manner, determinations will be made to determine what portion of the total may be identified.
This shall be subtracted from the total discharge from the floor drain'ump.
In no event will the total be allowed to exceed 5 gpm or an orderly shut-down of. the reactor will be started and be in cold shut-down,'n 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.
Other instxumentation would be used to assist in detecting leakage such as constant air monitoring. of,the dry,~cell atmosphexe, dew point determinate.on',
-and bakch pump-out of the sump.
However, the xate of rise recording, bei'ng the" most sensitive,'ill be the primary means of leak detection.
Over the period of operation'since August 1969, the background leakage has been in the order of 0.3 gpm into the floor drain sump.
Leakage into the equipment drain tank has been in the order of 4.2 gpm.
Obviously, these values have deviated depending on plant condition.
On three occasions totaling 10 days and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, it was necessary to take the plant off the line to investigate increases of leakage into the dry-
- well, 1.
Leakage to the equipment drain tank increased to 9.8 gpm in a six day period.
Two shut-off valves ie recirculating coolant loops were found to have stem packing leaks.
All ten similar valves stem packing was replaced.
2.
Leakage to the equipment drain tank incxeased to 12.6 gpm in twelve days.
This was again found to be recirculating loop valve packings.
3.
Leakage to the floor drain sump, "unidentified", increased to 3.7 gpm in a 13 day period.
Two 1" valves were blowing by the packing.
All small valves in the dry well were serviced.
The new rate-of-rise detection and recording instrumentation allows a
much improved sy'tem of appraising leakage into the dry well. It enhances the possibility of identifying the previously unidentified leakage and better appraises trends.
Leakage into the equipment drain tank has always been "identified" and therefoxe, present limits adequate.
lfe believe that with this knowledge, our approach to limiting operation with respect to primary coolant leakage is quite conservative.'
II Ir
Mr. Donald J. Skovholt May 4, 1972 Lower limits could well restrict plant operation at crucial power demand periods yet would not increase the safety to the general public as evidenced by the increased ability for leak detection analysis.
In the near future, as well as present, continuous reliable power is essential to the well being of the people.
Very truly yours,
~p 5'.
J. Schneider Vice President - Operations Enclosure
l l'1 ll
CONTROL PANEL (IN CONTROL ROOM)
RECORDERS-
.(2 Speed Chart) y ~
~POWER SOURCE "A" POWER SOURCE "8"~
DRYWELL AC TO DC CONVERTER AC TO DC CONVERTER WEST
- L.V.D.T.'s EAST DISPLACERS DRYWELL FLOOR DRAIN SUMP (unidentified leakage)
OPERATING RANGE UHPS
- L.V.D.T. (Linear Variable Differential Transformer)
"NINE MILE POINT NUCLEAR STATION FLOOR DRAIN TANK RATE-OF-RISE INSTRUMENTATION FOR UNIDENTIFIED LEAKAGE DETECTION
I q(~
l c
r g /
7/~
w ~ >
C J
~
r
~
~
~
'iv))i<r
"),gt I
t
(
V 4%~$ I