ML19308C351
| ML19308C351 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/19/1976 |
| From: | Brownwell R BURNS & ROE CO. |
| To: | |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001220811 | |
| Download: ML19308C351 (15) | |
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BURNS AND ROE,1NC.
RECORD OF TELEPHONE CONVERSATION 10/19/76 2:00 P.M.
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- gom, N.B. Godfrey B&R compoar or 0est ca,,,,,3,,gRilcy-Beaird 315-565-44,1 susJEcTt s) cascussto Specification 2555-37, Radwaste Evaporator HEC Originated FQs #832, 833 and 834 REMARKS Summary of questions asked:
1)
Q.
Will the replacement concentrator and gas stripper vacuum pumps have sufficient discharge pressure to discharge into the Waste Gas Header since it is maintained at 2.5 to 5.0 psig? (2.5 to 8.0 psig backup).
A.
Yes, even though the flow diagram (154-003-E009) shows service gas exhaust conditions as 2 psig at 150 F.
2)
Q.
Will this back pressure blow the loop seals on the air / water separators which are piped to 1.ocal floor drains?
A.
In all probabilit/ yes.
If Riley-Beaird sized the loop seals for the air / water separators they would have sized them for a 2 psig backpressure.
Recommended solution would be to increase size of loop seals; install back pressure /rertriction orifice upstream of 1000 seals or as was d ne in Unit I pipe to evanorntor feed tar.k.
t
'3)
Q.
Will the air /wat,e separators after initial filling per instruction manual pages 2;;
nd 2-6 maintain their normal water level during operation of the system?
A.
Yes, the =oisture carry over of the vacuum pumps should maintain the level and overflow throUgh the loop seal line.
Destrinution:
CC: File BR 0t05
Page 2 of 2 RECCR0 CF TELEPHONE CONVERSATION 10/19/76 2:00 P.M.
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Continued
,gm3 Note: MEC (E. Showalter - FQ 833) maintains that the air / moisture separators must have water added to them because seal water is lost throuch va2or carry over to the feed tank. Unit I evaporators are operating with Unit II vacuum pumps and air /=oisture separators.
4)
Q.
What would be your estimate of the frequency of chemical cleaning of the heating bundle when an evaporator is used exclusively for boric acid concentration of R.C. water?
A.
Probably never since pure boric acid solutions do not normally produce deposits that inhibit heat transfer.
(FQ 834 requests chemical addition line and tank be piped into feed tank).
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J The following write-up details a number of changes to flow diagram
.2028 which are necessitated to eliminate superfluous components (not yet purchased), to make the relief valve vent header perform its intended function and to bring the system design into conformancc
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with ASME Section VIII requirements (the 1968 ASME section III code refers back to Section VIII for overpressure requirements.)
This
, write-up gives the reasons and justifica tion for the changes outlined in the reference (1) memo.
Summa ry o f the Problem The system as it is presently constituted has three relief valves that contribute nothing to the overpressure protection of the radwas te gas disposal system and J.n one ins tance crea tes a code violation.
By means of some modifications to the existing system, positive overpressure protection can be a ttained and the three valves can be eliminated for a cavings of about $500,0.00 in capital costs.
Further discussions are provided for each of the relief valves.
Relief Valve WDG-R6 Located on the Relie f Valve Ven t Header This vent header is a manifold collection point for the relief valve discharges which emanate from the 11 radwaste disposal system storage tanks which are connected to this header.
The relief valve vent header has a design pressure of 150 psig while the highest design pressure of any of the~ tanks served by this header is 100 psig
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(mos t of the tanks have a 20 psig design pressure).
Thus, relief
-valve WDG-R6 is not provided to protect,the header from overpressure M M*
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Page 2
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11/18/74
~
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since the tanks that feed this header (and are the only sources of than the header.
have lower design pressures overpressure for it) relief valve WDG-R6 is provided as a means of meeting the
- Instead, that may exist will not reduce code requirement that the back pressure (see paragraph UG-134 the relieving capacity of the relief valvespressure of valve WDG-R6 provides of ASNZ Section VIII),
i.e.,
the set the limiting value of variable back pressure or superimposed back The valve can only pressure which the relief valves will see.
perform this function if its set press'ure is low enough to ensure in the relief valve vent header does not tha t the back pressure exceed the value established by the pressure relief device which has the lowest. backpressure limitation in the system.
Conventional style relief valves are capable of operating at while bellows backpressures of up to 10% of their set pressures, A
style relief valves can withstand.50% of the set pressure.
i.e.,
ropture disk is directly af tected by any backpressure, the vassel relief pressure will be equal to the rupture disk's Considering that there is (7 w) design pressure plus any backpressure.
fy' at least one conventional valve (WDS-Ra) set at 20 psig and that d
13 psig on the 15 psig design
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there is one rupture disk set at discharging into the relief pressure' reactor coolant evaporator,the set pressure of relie f valve WDG-R6 valve vent header, not be any higher than 2 psig if all the foregoing requirements the radwaste gas system will normally '
are to be met.
- However, be maintained at a pressure of 3 psig via,the radwaste gas Since the relief valve vent header is separated compressors.
from the rest of the radwaste gas system by a single check valve there is a good probability that 3 psig can exist (WDG-V130),
in the relief valve vent header due to leakage across the check The existance of any valve or whenever a relief valve operates.
pressure greater than, 2 psig in the relief valve header nullifies i.e.,
creates the overpressure protection of some of the equipment, a code violation.
it in felt that the Bearing in mind the above problem areas, following system modifications o;ffer the most expedient remedy and the most economical solution:
)
- 1) Relief valve WDG-R6 shall be eliminated and the spool piece m(J where WDG-R6 was formerly located shall be permanently connected to the relief valve vent header, i.e.,
relief O
valve WDG-R6 will be replaced with piping.
(
Page 3
~
11/18/74 from the relief valve vent header' The 2" piping which runs shall be
- 2) to a point just downstream of check valve WDG-V130 deleted.
Pipe line drainers similar to the one,s,that already exist on the WDC system must be added to the low points of the line tha t 3) station vent.
connects the relie f valve vent header to the to determine
- 4) An investigation and calculation must be done if the built-up backpressure in the relief valve vent header is suff'i'ciently high to necessitate balanced-bellows style valves on all of the equipment whose overpressure protection devices discharge into this header.
If built-up backpressure turns out to be too high, some new relief valves will have to be bought.
the relief valve vent header
"'NAs a result of the above changes, the present
,)will become an open discharge system rather thanclosed discha s
,)
ve n,t.
for different tanks which The only connon. source of overpressure the nitrogen sys tem.
discharge into the relief valve vent header is this danger has been eliminated by proper. design of the
- However, tha t high pressure nitrogen system's pressure relief sta tions so Thus, the nitrogen is relieved via a nitrogen system relief valve.
is elimina ted.
The only tanks' overpressuriza tion due to N2 remaining plausible way of overpressurizing any of these tanks tank's relief valves to open would be when a tank's and causing the from the vent gas system vent line has been inadvertently isolated the to.'k is being used.
Adequately' vented tanks do not need while relief valves ur;less the vent line can be closed of f, e.g.,
by forcing a check means of an isolation valve or a high backpressurelines of all of these tanks we If the vent valve shut. the possibility of operation of the relief valves would be keeping all the vents open would cause a high left opan, fur ther reduced.
- But, consumption of nitrogen; consequently only the vents from the these three three bleed holdup tanks will be kept normally open since
{}/ tanks are the ones most likely to contain radioactive gases.
- Thus, operation of any of the relief. valves on ecuicment whose vents are not
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be precipitated by an opera tor error and,1f o f f
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normally coen must no concern since they should have low or nil activity ano,the Ipossibili ty o f opera tion or the relic: valves on the tanks which
- h. un hinh ac tivity is further reduced bv keenina their
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Page 4 11/18/74 The addition of automatic liquid drainers in the relief valve discharge system is necessary since the discharge of any of the relief valves could contain liquid.
Also, the built-up backpressure must b'e investigated to determine if it has any ef fect on the set pressures of any of the relief valves connected to this manifold cystem.
'Relie f Valve WDG-R7 Loca ted Near Radwa s tb Ga s Comores sor Inlets Each of the radwaste gas compressors have a sensor which monitors the lobe pressure in the compressors.
In a telephone conversation with Mr. B~utner of the Nash Engineering Conpany (the compressor vendor),
I learned that the above sensor activates the gas unloader valve when the lobe pressure reaches about 85 psig.
On conventional opplications, the gas unloader valve would discharge to a tmosphere thereby reducing the internal ecmpressor pressure.
Since the gas unloader also operates when the compressor shuts down so tha t the compressor will not.have to start against full discharge pressure T
,_x thereby enabling it to start easily and smoothly, the TMI Unit 2
/(
' pplication of these compressors has the gas unloader discharge j
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/ piped back to the inlet header ups tream of pressure reducing s-valve WDG-V59.
The pressure in the compressor is reduced using this method because the volume of high pressure gas is much smaller than the volume of the inlet header.
The only time relief valve WDG-R7 would serve any purpose is when the discharge from the unloader ended up right back at the inlet to the ccmpressor, i.e.,
control valve WDG-V59 fails open or its bypass is left open.
In this case, the unloader cannot reduce the internal pressure below 85 psig and relief valve WDG-R7 would take over this task.
If,WpG-R7 were elimina ted, the only way any compressor damage co'uld result from the inability to unload the gas pressure is if all of the following items occurred:
- 1) A pressure equal to or greater than 85 psig would have to exist in the vent header system; this is unlikely since the only normally open vents exist on 20 psig tanks (see discussion on relief valve WDG-R6).
1 p s2) Either pressure reducing valve WDG-V59 (this valve controls the l
compressor inlet pressure) must fail open or its bypass must be
'd l
left open.
Page 5
./
11/18/74 e.
- 3) The compressor inlet pressure alarm WDG-PAH-1504 (indica tes high pressure in vent gas system) would have to fail or be ignored.
- 4) The radwaste gas compressor motors' overload protection as per elect'rical elementary 3075, sheet 41, failed to trip the motors (see also* reference 2).
Considering tha t the probability of all 'four of the above independent items occurring simultaneously is extremely small, and that the compressors have a design pressure of 150 psig which is equal to or higher than any of the pressures tha t exist in the vent header
- cystem, i.e., the code overpressure requirements are met by virtue of the compressors' design pressure, it is clear that even if the four above items did occur simultaneously, there is still no hazard to opera ting personnel or the sur rounding equipmen t.
, consequently, relief valve WDG-R7 is superfluous and shall be deleted since it is not yet purchased.
)
"elief valve wDG-R1 Located on the Vent Gac S /ctem Header Th purpo'se of this valve is to protect the vent gas system piping and the equipment a ttached to it from the effects of any high pressure systems that. interface with this system.
Since the lowest pressure of any item which is normally open to this system has a d3 sign pressure of 20 psig (see discussion on relief valve WDG-R6),
the maximum that this valve can be set for is 20 psig.
At a set pressure of 20 psig, relief valve WDG-R1 would protect the tanks which have normally open vents from the effects of one of the 4
150 psig class system's normally closed vents being inadvertently opened and it would protect the radwaste gas system's 150 psig class piping from the effects of connecting the possibly high pre:sure rsactor building rad' aste gas disposal piping (the set pressure of 700 psig on relief valve WDG-R3 permits high pressure to develop in this piping) to the low pressure radwaste gas disposa~1 piping whenever the containment isolation valves are opened.
Tho relief valve mentioned in the previous paragraph, WDG-R,3, is on a 700 psig design pressure system and is set at 700 psig.
All of tha sys tems tha t are connected to this header are normally connected or valved off from the header.
'Op era ting pressures this header can never exceed 150 psig since whenever this header o in operation it will be connected to the 150 psig portion of e
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Page 6 11/18/74
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the only way a high
- Thus, the radwaste gas disposal system.this header is if the vents of a normally
' pressure could develop in valved of f high pressure system, e.g., the core flooding tanks, should time while the isolation valves are Joak over a long period of if reliefH.Mr.
closed.
This leakage pressurization can be eliminated its set pressure reduced to 150,psig with the
_ valve WDG-R3 h_as the only
.odded benefit that..this change in set oressure elimina teswiththeradwas't'e'ga$;si
~
Tiigh pressure system that interfaces
- - ~ ~ ~
If in addition to the above change, a check valve is placed the three bleed hold-up inmediately downstream of the point where tie into the vent gas system, then these tanks' normally open vents tanks will,be protected from the possibility of a normally closed, With this change, high pressure vent being inadvertently opened.func tion for relief valve the last all equipment upstream of this j
the valve could be deleted (Note:
to pressIrize
' check valve is of insuf ficient capacity or pressure the bleed hold-up tanks).
Examination of flow diagram 2028 reveals that check valve WDG-Vll3 is a redundant check valve, i.e., check valves already exist in all of the lines tha t are ups tream of this.
relief valve WDG-R1 can safely be deleted by
- Thus,
- c. heck vcive.
changing the set pressure of relief valve WDG.R3 and relocating i
check valve WDG-V113, thereby making the vent gas system work as foll~:-
than 150 psig)
- 1) All pressures above 3 psig (but always less that may develop in thic system's piping will be reduced below 3 psig by the radwaste gas compressors.
- 2) If a tank's vent is prevented from discharging due to a high backpressure on the vent's check valve, i.e.,
during the infrequent the header pressure periods when the compressors have not reduced below 20 psig, th'e n the tank's relief valve will discharge into
. the relief valve vent header.
A check valve One final change is required in the vent gas system.
should be added to the concentrat.ed waste tank's vent to provide isolation of this tank from the bleed hold-up tanks which will be This check valve supplies the concentrated normally open now.
waste tank with pcs itive b a ck-flow-protec tion from the bleed
/
') hold-up tanks (NOTE :
All other eqtiipment in.the system already isolate them from the bleed hold-up tu.ks), whichj h(Jhavecheckvalvesto is required to prevent radioactive gases from flowing into the tank when the vent is opened for purging.
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Page 7 11/18/74
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t-This change can be accomplished by using check valve WDG-V130 to the changes discussed which became surplus (spared) due Also, due to this change it
. for relie f valve WDG-R6.the vent normally open on the concentrated to leave ii is possibletank if gas space sampics should indicate high gas act v ty
- tank, if there are high activity levels in the waste relief valve can be reduced
. levels,. i.e.,
potential operation of the tank's (NOTE': The same thing can be tank's vent line.
by opening thedone on the reclaimed boric acid tank and the spent re tank ~'
the concentrated waste same sys tem as which belong to the they also have isolating check valves.
and since t
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