ML20215G020
| ML20215G020 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/19/1987 |
| From: | Robert Williams PUBLIC SERVICE CO. OF COLORADO |
| To: | Calvo J NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| GL-87-06, GL-87-6, P-87212, NUDOCS 8706230095 | |
| Download: ML20215G020 (17) | |
Text
,
O Public Service ~
mh P.O. Box 840 conver, Co 802010840 June 19, 1987 i
Fort St. Vrain R.O. WILLIAMS, JR.
Unit No. 1 QP E$
EN R PE TIONS P-87212 1
U.S. Nuclear Regulatory Commission ATTN:
Dccument Control Desk Washington, D.C. 20555 Attention: Mr. Jose A. Calvo, Director Project Directorate IV Docket No. 50-267
SUBJECT:
Response to Generic Letter 87-06, dated March 13, 1987 (G-87089)
Dear Mr. Calvo:
NRC Generic Letter 87-06 is seeking to verify the methods by which PSC is assuring the leak-tight integrity of all pressure isolation v61ves (PIVs) as independent barriers against abnormal leakage, rapidly propagating failure, and t
gross rupture of the reactor coolant pressure boundary (RCPB). PIVs are defined for each interface as any two valves in series within the RCPB which separate the high pressure reactor coolant system (RCS) from an attached low pressure system.
PIVs are normally closed during power l
[
operation.
This letter contains PSC's response to NRC's Generic Letter I
87-06 which (PIVs) quested that a list of all pressure isolation re valves in the Fort St.
Vrain (FSV) plant, and associated test requirements, be submitted for NRC's assurance that the RCPB is being protected.
There are significant differences between the design concept of the FSV plant's reactor coolant system (RCS), which is mostly contained within the Prestressed Concrete Reactor Vessel (PCRV), and the RCS design in LWR plants.
PSC has performed research of applicable drawings in an attempt to identify any low pressure piping systems that are attached to and are isolated by PIV's from the high pressure reactor coolant system during normal operation of the FSV plant.
8706230095 B70619 0(O ADOCK0500g7 DR
- .P-87212 ~ June 19, 1987
'PSC has concluded that. FSV does not contain any PIVs, as defined in Generic Letter 87-06. Attachment A contains a general discussion of.FSV's Licensing Basis for assuring the integrity of the RCPB.- Attachment B is a summary of the results of PSC's investigation to identify valves which could be classified.as. normally closed isolation valves within the RCPB that. separate the high pressure RCS from attached low pressure systems.-
Ifl you have any questions about this response, please contact Mr. M. H. Holmes at (303) 480-6960..
Very truly yours, l
M R. O. Williams, Jr.
Vice President, Nuclear Operations R0W/AHW:bac Attachments.'(2) cc: Regional Administrator, Region IV
. ATTN:
Mr.- J. E. Gagliardo, Chief Reactor Projects Branch Mr. R. E. Farrell Senior Resident Inspector Fort St. Vrain'
P-87212 June 19, 1987 PSC has concluded that FSV does not contain any PIVs, as defined in Generic Letter 87-06. Attachment A contains a general discussion of FSV's Licensing Basis for assuring the integrity of the RCPB. Attachment B is a summary of the results of PSC's investigation to identify valves which could be classified as normally closed isolation valves within the RCPB that separate the high pressure RCS from attached low pressure systems.
If you have any questions about this response, please contact Mr. M. H. Holmes at (303) 480-6960.
Very truly yours, f
fik R. O. Williams, Jr.
Vice President, Nuclear Operations R0W/AHW:bac Attachments (2) cc: Regional Administrator, Region IV ATTN: Mr. -3. E. Gagliardo, Chief Reactor Projects Branch Mr. R. E. Farrell Senior Resident Inspector Fort St. Vrain f /ff87 WW Arm /lk0x hy /Oc.el G f
Reviewed By:
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION i
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Public Service Company of Colorado-
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Docket No. 50-267 Fort St. Vrain Unit No. 1
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AFFIDAVIT R.- 0. Williams, Jr., being first ' duly sworn,.' deposes and says: That he is Vice President, Nuclear Operations, of Public Service Company of Colorado, the Licensee herein, that he has' read the foregoing information and knows the contents thereof, and that the statements and matters set -
forth therein are true and. correct. to the best knowledge, information and belief.
.of his F
R. O. Williams, Jr. '
Vice President Nuclear Operations STATE OF Ceder.edo COUNTY OF Ms
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Subscribed and sworn to before me, a Notary Public on this
/M day of Sw
, 1987.
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My commission expires r/ey J /9 198 7.
Attachment A P-87212 Page 1 FSVs LICENSING BASIS FOR ASSURING THE INTEGRITY OF THE REACTOR COOLANT PRESSURE BOUNDARY (RCPB)
FSV is a High Temperature Gas-Cooled Reactor (HTGR) whose reactor coolant system is doubly contained within the Prestressed Concrete ' Reactor Vessel (PCRV). The vessel's i
steel liner, steam generator tubing and penetration primary closures constitute the RCPB.
Secondary closures on the PCRV penetrations and the PCRV concrete structure constitute the containment.
To further confine and process any accidental radioactive releases, the PCRV and reactor plant associated systems are located in a " reactor building". The reactor building is a vented tertiary confinement containing.
continuously operating ventilation system, including high a
efficiency particulate air filters (HEPAs) and charcoal adsorbers that process any radioactive gaseous releases in the ventilation system's exhaust stack.
I The only normally uncontained extensions of the RCS through the PCRV are the helium sampling lines, the helium circulator differential pressure instrumentation tubing, and several capped test lines which penetrate PCRV containment and connect directly to instrument lines containing reactor coolant helium (e.g. moisture sample rake test connection, reactor pressure sensortestconnection). These lines are designed for PCRV reference pressure.
The helium sampling lines and helium circulator differential pressure instrumentation tubing are 1/4 inch OD.
The capped test lines are 3/8 inch OD or smaller. These lines include redundant isolation valves necessary to meet general design criterion 53 in Appendix C of the Updated FSAR.
Buffer helium lines to and from the helium circulators, purge helium lines to each of the control rod drive penetrations and purge helium lines to the PCRV pressure relief system all connect indirectly to the RCS. These are all small diameter pipes designed for PCRV reference pressure and provided with isolation valves and backflow check valves where possible.
i Containment isolation relative to potential leakage down the helium circulator shaft is provided, when the circulator is operating, by the buffer helium purged double labyrinth shaft seal, buffer helium seal, and bearing water seal.
l
i Attachment A P-87212 Page 2 When.the helium circulator is shut down, there is a static mechanical shutdown seal. 'As a back-up, bearing water can be used to prevent' helium leakage.
Lastly, all connections to the helium circulator contain positive isolation valves and are designed for the pressure and temperature associated with reactor coolant.
In the FSAR accident analyses (Section 14.7), a study was made of all the possible leakage sources from the PCRV.
This study shows that the maximum credible primary coolant leakage would result from a failure involving the helium purification system regeneration line.
Therefore, this i
accident has been identified as the Maximum Credible Accident for the Fort St.
Vrain plant, and all other credible reactor coolant leakage rates result in substantially less significant environmental consequences.
The points of significant potential accidental leakage from the RCS are all related to PCRV penetrations, where -the double barriers to leakage are welded or bolted-and-gasketed seals.
Hypothetical PCRV liner cracks of significant size are also a potential source of reactor coolant leakage, but such leakage.is much less than for penetration failures due to the tortuous leakage flow path through the PCRV concrete.
The PCRV penetration primary and secondary closures are i
virtually leak tight, as demonstrated by continuous monitoring, and quarterly surveillance tests. Technical l
Specification LC0 4.2.7 requires that the penetration interspaces between primary and secondary closures are pressurized during normal operation with purified helium to a pressure slightly higher than PCRV main cavity pressure, such that any primary closure leakage would be purified helium inwards.
This also minimizes the differential pressure across the primary closure, thereby limiting the flow of helium through any leak path that might be present in the primary closure. An exception is the group of steam generator penetrations that have a small helium leak into the cold reheat piping.
This penetration group may be 1
pressurized with purified helium at a pressure below reactor coolant pressure, but slightly above cold reheat steam pressure, per Technical Specification LCO 4.2.7.
This limits purified helium flow to the main condenser.
i
'e Attachment A P-87212-Page 3 LC0 4.2.9 prohibits operation if helium leakage through any group of primary closure seals exceeds 400 lbs/ day at a differential pressure'of 10 psi or if total leakage through all the secondary closure seals exceeds 400 lbs/ day at a differential pressure of 688 psi.
These limits provide assurance that the maximum. leak rate that would occur upon i
failure of either closure would not result in a release in-excess of that evaluated for the Maximum Credible Accident.
-The maximum resultant dose rate, assuming failure of the secondary closure and " Design" reactor coolant activity, is at least an order of magnitude less than 10 CFR 100 guidelines at the exclusion area boundary (EAB).
Due to a leak path between some of the, steam generator penetration interspaces and the cold reheat steam piping internal to the penetrations, the interspace pressurization system was modified and_ Technical Specification LC0 4.2.7 was revised to permit the affected steam generator 1
penetrations to be pressurized below reactor coolant pressure but above cold reheat pressure.
This modification reduces purified helium leakage to the reheat system, but also creates a potential flow path for reactor coolant to the cold reheat system.
When operating in this mode, Technical Specification LC0 4.2.9 requires monitoring of the interspaces for reactor coolant activity and prohibits operation if the reactor coolant. leakage via the cold reheat system exceeds 1.4 ' curies per day, an amount which represents 10 percent of the plant's design objective for radioactive gas releases, l
b
Attachment B P-87212 Page 1 GENERIC LETTER 87-06 CONSIDERATIONS FOR FSV's REACTOR COOLANT PRESSURE BOUNDARY (RCPB) ISOLATION i
While FSV's high pressure RCS is not attached to any low pressure piping system that is isolated by PIVs, as stated in the FSV Licensing Basis of Attachment A, there are a 4
number of low pressure piping systems that are attached to high pressure piping systems that in turn may be attached to the RCS during normal operation of the plant.
Even though outside of the scope of the Generic Letter's request, these high/ low isolated by normally closed valve (s) pressure interfaces have been evaluated.
The high pressure piping systems evaluated are:
1.
Helium Purification 2.
Helium Circulator Auxiliaries 3.
Analytical Instrumentation 4.
PCRV Auxiliary Piping
{
5.
In-Reactor Instrumentation The results of the evaluation of these systems are summarized in the following paragraphs.
HELIUM PURIFICATION SYSTEM (PI-23-1 thru 5),
In order to maintain a low level of impurities and radioactivity in the reactor coolant that is circulating within the PCRV, the helium purification system (System
- 23) is designed to continuously draw off a fraction of the circulating reactor coolant, purify it, and return it to the PCRV. This system consists of a purification
The entire helium purification system is designed for PCRV reference pressure (845 psig) and normally operates at reactor coolant pressure.
The purification system is entirely contained within the secondary closures of the PCRV with the exception of the purified helium, hydrogen removal and regeneration section and the connected analytical instrumentation.
i There are two separate purification trains:
one train is normally in service while the other is in standby (except when undergoing regeneration).
While the regeneration section of the purification system is also designed for PCRV pressure, it normally operates or is maintained in standby condition at about 88 psig by pressure controller PC-2352,
1 Attachment B.
P-87212 Page 2 The regeneration section is normally isolated from PCRV I
~
pressure by'a normally closed boundary valve for both i
the in' service _and the standby purification trains.
For the in service purification train, the regeneration i
section is normally isolatedby(2308),
separate regeneration valves HV-2305 -(2306),
HV-2307 and HV-2309 (2310).
During regeneration, the standby train of the purification system is isolated from reactor coolant l
pressure by inlet valve HV-2301 (2302) and return valve HV-2303(2304).. The regeneration section's isolation valves are interlocked with the purification section's isolation valves so that the regeneration of a
purification train cannot be performed unless it is isolated from the RCS. The boundaries for both the in service and the standby purification trains provide at least a single valve pressure boundary for the regeneration section.
The regeneration section interfaces with several other systems with lower design pressures. These systems are as follows:
Radioactive Gas Waste (PI-63-1)
This system collects and disposes of radioactive gases discharged from the plant's potentially radioactive
- systems, including the System 23 regeneration section.
In addition to the RCS/ regeneration section boundary valves identified above, the gas waste piping is protected from overpressure by isolation valve HV-2342-5 and pressure control valve PV-2352. The off-gas piping is connected to the gas waste vacuum tank T-6301 which is designed for 15 psig and is protected from overpressure by relief valve V63102 that is set at 10 psig.
This valve relieves the waste gas to the reactor building's ventilation exhauste filters.
High vacuum tank pressure is alarmed by PSH-6363, providing warning to the plant operators of excessively
- leaking, inadvertently actuated or mispositioned isolation valves.
Radioactive Licuid Waste (PI-62)
This system collects and cisposes of radioactive liquids removed from the plant's systems, including the regeneration section.
In addition to the RCS/ regeneration section boundary valves identified above, the liquid waste piping is isolated by valves HV-2347 and V2350 and helium purification cooler drain valves HV-2381 and HV-2382.
These valves isolate water from the regeneration process in the helium purification section from the liquid waste receivers, T-6202 or T-6203.
The receivers are designed for 15 psig p'ressure and are protected from overpressure by 3 relief valves, V6254 or V6256.
The relief valves discharge to the
Attachment B P-87212 Page 3 radioactive liquid waste sump via the column M-5
)
standpipe. Leakage past the regeneration system radioactive liquid waste system isolation valves would be alarmed by LAH-6206, providing warning to the plant operators of excessively leaking, inadvertently actuated or mispositioned isolation valves.
Reactor Plant Ventilation (PI-73-1)
This low pressure system is connected to the higher pressure systems by relief valves which could open during an abnormal condition in the regeneration section of the purification system.
The ventilation system is designed for receiving the full capacity of the relief valves discharged into its ducting.
It is noted that most helium gas relief valves in the FSV plant are protected from seat leakage by an upstream rupture disk.
Reactor Plant Cooling Water (PI-46-1) - While this 150 psig system is referred to on PI-23-3, the water supplied for establishing the water level in the regeneration section's knock-out pot, T-2301, is from the condensate system's (515 psig design pressure) supply piping.
The condensate supply is isolated from the regeneration section piping by normally closed valve HV-2386.
During regeneration of a
helium purification train, the helium purification section is isolated from the RCS by HV-2301 and HV-2303 (loop 1) or HV-2302 and HV-2304 (loop 2). The regeneration section pressure, which operates at about 88 psig during regeneration or standby conditions, is controlled via PC-2352 by i
discharging potentially contaminated helium to the gas waste system. Since the regeneration section is controlled at about 88 psig, there is no hazard to the condensate or reactor plant cooling water systems caused by excessively leaking check valve V23108 or inadvertent actuation or mispositioning of valve HV-2386.
J CIRCULATOR AUXILIARY SYSTEMS (PI 21-1 thru 15)
During normal operation, the reactor coolant is prevented from escaping down the helium circulator shaft (thus entering the circulator auxiliary systems) by a labyrinth seal and an upflow of higher pressure purified helium supplied by the buffer helium system.
Therefore during normal operation when all the systems are functioning properly, reactor coolant is isolated from the circulator auxiliary systems by differential fluid pressure rather than isolation valves.
i Attachment B 1
P-87212 Page 4 The ' buffer helium system could become contaminated with reactor coolant helium leaking down a circulator shaft under transient conditions, although it normally operates at pressures above reactor coolant pressure to prevent such leakage.
In _the event reactor coolant
' leaks past the upper labyrinth seal and down a
circulator shaft, differential pressure sensors in the Plant Protective SystemLfunction to detect the abnormal
. buf fe r-mi d-bu f fer. differential pressure and initiate a circulator trip.
This trip results in the circulator seal being automatically actuated and any reactor coolant leakage down the circulator shaft terminated.
For the scenario of a loss of the buffer helium system pressure and failure of -the helium circulator shaft seals to be set, if reactor coolant helium leaks through check valves V211485 and V211771 (typical for each circulator) reactor coolant would enter the buffer
-helium system.
However, there is no concern about the high pressure reactor coolant leakage overpressurizing the buffer helium system since-the buffer helium system is designed for a pressure of 845 psig. This is above the setpoints of rupture disks and safety valves in the PCRV pressure relief system, so the maximum pressure of the reactor coolant will not exceed this value and will not overpressurize the buffer helium system even in the worst case scenario.
In this case, reactor coolant would 'also flow into the helium / water drains and enter the high pressure separators.
Radiation monitors (RAH-21585, typical) located at the high pressure separator will alarm if reactor coolant leaks into the buffer helium system and this will warn the control room operator that an upset in the buffer helium system has occurred.
Helium exiting each high pressure separator remains in the buffer helium system and bearing water draining from each high pressure separator is directed to that loop's bearing water surge tank.
Both the
' buffer helium and the bearing water systems are designed for PCRV reference pressure so there is no danger of overpressurizing these systems.
For the scenario of loss of helium circulator bearing water, the PPS system automatically shuts down the circulator and actuates the circulator shaft seal to isolate all the systems, including bearing water, from the reactor coolant system.
Since the bearing water system is designed for PCRV reference pressure, there is no concern for overpressure,due to leakage of reactor coolant past the shaft seals.
There is a remote possibility that if the shaft seals leak and both buffer helium and bearing water pressure is lost, reactor coolant could flow to the low pressure separator, T-2111. This tank is designed for 50 psig,
Attachment B P-87212 Page 5 but it is protected by a full capacity relief valve, V21345, preventing overpressurization. The low pressure 2
separator is also equipped with a radiation monitor,
(
RAH 93267 that would alarm and warn the operator of i
reactor coolant leakage into this system.
)
ANALYTICAL INSTRUMENTATION SYSTEM (IC-93-2)
This system samples reactor coolant continuously from 1
the PCRV via the process and moisture instrument penetrations.
This system also samples gas from other points in the helium purification and radioactive gas waste systems.
The system is aligned during normal operation of the plant to directly sample reactor coolant via instrument penetrations B-1 and B-6, continuously. All other sample points are isolated during normal operation of the plant (except when samples are required) by two normally shut isolation valves. The 1/8" 0D tubing upstream of pressure control valves, PCV-93490 (Penetration B-1) or PCV-93491 (Penetration B-6),
is designed to withstand full PCRV pressure.
While the 1/8" 0D lower pressure tubing portion of the Primary Coolant Depressurizing box can withstand RCS pressure, components _in this piping are protected by pressure control valves PCV-93490 (Penetration B-1) or PCV-93491 (Penetration B-6) which are set to reduce reactor coolant pressure to 200 psig for each RCS sample line.
In the event that a pressure control valve fails wide open, a relief valve V93872 (Penetration B-1) or V93783 (Penetration B-6) set at 275 psig, is located immediately downstream of PCV-93490 or PCV-93491 to protect downstream components.
Each relief valve relieves to the Gas Waste System Vacuum Tank (T-6301).
This tank has a design capacity of 500 cubic feet and a design pressure ranging from full vacuum to 15 psig.
Two safety valves set at 10 psig prevent an overpressure condition in the vacuum tank.
These safety valves discharge to atmosphere via the filtered Reactor Building's ventilation exhaust system.
Additionally, in the event of a failure of the pressure boundary of this piping in the analytical instrumentation room, radiation monitor RIS-7312 will detect a release of radiation.
Upon high radiation, the RCS sample lines upstream of the pressure control valves are automatically isolated from the RCS by isolation valves HV-93256 (Penetration B-1) and HV-9316 (Penetration B-6), restoring the integrity of the RCPB.
Valves upstream and downstream of these automatic valves may be manually closed as a further protective measure.
Attachment B P-87212 Page 6 PCRV AUXILIARY PIPING (PI-11-1 through 5) - This piping system provides a supply of purified helium for pressurizing the interspace of each PCRV penetration i
(with the exception of the steam generator penetrations as -discussed in attachment A) to a pressure slightly above PCRV pressure, pressurizing the reserve shutdown hoppers to insert reserve shutdown. material when necessary, purging Control Rod Drive and Orifice Assembly (CRD0A) penetrations to inhibit reactor coolant i
flow into the CRDOA cavity and to add. helium to the PCRV via the PCRV safety valves' inlet piping. Only the CRD0A purge and PCRV safety valve inlet piping is open to the reactor coolant system during normal operation of the plant.
CRD0A Purge Piping (PI-11-1) - The purified helium header (PI-23-4), designed for PCRV pressure, is the normal supply of purified helium to the 37 CRD0As. An alternative supply of pure helium is a helium tube trailer which is normally isolated by two normally shut manual valves, V11190 and V111198 and check valve V111197. The tube trailer piping is designed for full RCS pressure and is protected by relief valve, V111193, which is set at 900 psig.
The valves in the purified helium purge supply piping to the CRD0As are all normally open.
In the event of simultaneous loss of helium purge pressure and the failure of helium supply check valves (valve "F"
on PI-11-1 typical for 37 CRD0As) to close during the resulting back flow condition, reactor coolant would flow into the CRD0A cavity and then into the purified helium purge supply piping.
This condition would be alarmed in the control room by an orifice plate type flow switch (FSL-11268-1 typical). Upon a low flow (back flow) alarm in the control room, the reactor operator would stop reactor coolant back flow by remote manual closing of valve HV-11260, regaining the integrity of the RCPB.
PCRV Safety Valves (PI-11-5) - The purified helium makeup line attached to the PCRV safety valve inlet piping is designed for PCRV reference pressure.
In the ovent purified helium is lost, this normally open line is automatically protected from reactor coolant flow into the purified helium header by two check valves, V11703 and V11749.
Normally open valve HV-1196 can be closed remotely from the control room to backup the check valves and isolate the reactor coolant from the purified helium header.
I Attachment B
=P-87212 Page 7 f
Each of-the two PCRV safety valves is protected
.from excessive reactor coolant leakage by'a rupture 1
disk which is installed upstream.
Each PCRV safety
-valve train is relieved to the atmosphere via a l
full flow sintered metal filter F-1101.
Pressure switches, PS-1148 and PS-11209, are set to alarm at 5 psig pressure in the interspace between the rupture disk and its downstream safety valve, warning the plant operators of a failed rupture-disk;- The rupture disk and safety valve in.each relief train provide double isolation of the RCS t
from the atmosphere. Therefore, they do not meet the criteria for PIVs.
Core Support Floor (CSF) Vent Piping (PI-11-5) -
This system is normally separated from the RCS by the CSF's steel casing..Since a crack exists in i
the steel casing, reactor coolant leaks at varying rates (depending upon the self sealing conditon of the crack and the reactor coolant system temperatureandpressure)intotheCSFventpiping.
While this vent piping is designed for PCRV
- pressure, it is connected to the low pressure radioactive gas waste system via normally open valve HV-1195.
The radioactive gas waste system has PIC-6364 set at 60 psig to control the pressure in the CSF vent line. The CSF vent piping is also attached to the low ' pressure radioactive liquid drain tank, T-6302, but is normally isolated from.
1 the drain tank by V111062. As discussed previously these two low pressure waste systems are designed for receiving radioactive gas and liquid and are protected from over-pressure by full flow relief l
valves.
l l
I I
Attachment B.
P-87212
~Page'8-l IN-REACTOR INSTRUMENTATION (IC-11-2, 3 and 7) i Thissystemisdesignedforhighpressure,consistingof small diameter (1/4 to 3/8" 0.D.)
instrument tubing that contains reactor coolant for sampling, pressure and pressure differential measurements and moisture monitoring.
Only the sample piping 1.s attached to. low pressure systems. These low pressure sampling systems are:
1.
Analytical Instrumentation 2.
Fast Gas 3.
Iodine There are twenty helium circulator differential pressure sensing elements mounted outside the PCRV; five per circulator.
There are four pressure sensing lines associated with each circulator which supply the differential pressure sensing elements and which l
penetrate primary, secondary and tertiary closures of PCRV circulator instrument penetrations C-1 and C-4 and contain reactor coolant helium.
Each line is rated for PCRV reference pressure and has two manual isolation i
valves inside the PCRV penetration tertiary closure and a manual isolation valve and remotely operated valve 1
outside the PCRV penetration tertiary closure.
All of i
these valves are open when the helium circulator differential pressure sensing elements are in service.
Therefore, none of these valves meet the criteria for PIVs.
Each of these four sensing elements has two associated capped tube stubs, one on each side of the differential pressure sensing element.
These tube stubs 1
are for maintenance and include a normally closed valve and cap at the stub end.
Since these tube stubs vent to atmosphere during maintenance and not to an attached low pressure system, the isolation valves and the tube stubs do not meet the criteria for PIVs.
The eight Plant Protective System Dew Point Moisture Monitors (DPMMs) are continually supplied reactor coolant helium from process lines at the outlet of each circulator. The helium exiting the DPMMs returns to the PCRV at the circulator inlets.
The supply and return process tubing is all rated for PCRV reference pressure.
All DPMMs are contained within the PCRV tertiary closures of Process and Moisture Instrument Penetrations B-1 through B-6.
These tertiary closures are rated for PCRV reference pressure and will contain reactor coolant which could-leak out of the DPMM system.
However, these tertiary closures are removed at times during normal operation of the plant to permit maintenance on the DPMM
w.
Attachment B P-87212:
Page 9 system. There are manual isolation valves in both the DPMM. supply and return lines. These valves are.normally open whenever.the DPMM is in service and therefore do not meet. the criteria for PIVs.
Each DPMM has'two associated. capped tube stubs, one on each side of the DPMM, which can be used to vent a supply or. return line to atmosphere during-maintenance.
These tube stubs-contain a normally closed valve which is not considered a PIV since the tube stub can only vent to atmosphere and not to an attached low pressure system.
There are.six reactor. pressure elements which are contained in Process.
and Moisture Instrument Penetrations B-1 through B-6 and continually sense reactor coolant pressure.
Each pressure element is-connected directly to the RCS by a single sensing'line
{
which contains two manual isolation valves.
Each sensing line is' rated for PCRV reference pressure. Any reactor coolant leakage from a' reactor pressure element I
or its sensing line would be contained by the tertiary closure, except when this closure is removed for maintenance on,the-instrumentation.within a penetration.
The isolation valves in the sensing lines are normally open, so they do not meet the criteria for PIVs.
Each-
. reactor pressure element has one associated pressure sensor test connection line which exits the tertiary closure.
This test line includes a normally' shut isolation valve, 'a check valve and a cap all located outside the tertiary containment in a " horn box".
Since this sensor test line would be open to' atmosphere, and not an attached low pressure system, during reactor pressure element testing, the isolation valve and check valve in each line do not meet the criteria for PIVs.
Analytical Instrumentation (IC-93-2) - This system f
has been discussed above.
Fast Gas Sample (IC-11-7) - Two sample lines which penetrate the primary and secondary closures of the PCRV's Process and Moisture Instrument Penetrations B-2 and B-5, direct the reactor coolant helium sample to the fast gas sampling manifolds at panel I-9374 (loop 1) and I-9375 (loop 2).
The high reactor coolant pressure is reduced to 5 psig by normally(open high pressurereducing valves PCV-11272 loop 1) and PCV-11274 (loop 2).
The reduced pressure fast gas helium sample is then discharged to the low pressure radioactive gas waste system's vacuum tank, T-6301.
The 5 psig pressure portion of the fast gas tubing is protected from overpressure by relief valves (set at 26 psig), V11901-20 (loop 1) and V11901-27 (loop 2). These relief valves also discharge to T-6301.
l
l Attachment B P-87212 Page 10.
l The gas waste vacuum tank. is protected from-overpressure as discussed previously.
The high pressure : section of the fast gas sample l
line in each loop has three isolation valves (in series) 'that could separate the high pressure RCS from the fast' gas manifold's high pressure reducing
-. valve PCV-11274..These loop isolation valves would be shut when the other loop is-being used for sampling the RCS.
These isolation valves do not meet the PIV criteria because they would isolate the high pressure RCS from-the high pressure section of the fast gas; sampling manifold.
Excessive leakage or mispositioning of these shut isolation valves would not jeopardize the fast gas manifold's-integrity. The low pressure section of the manifold is protected by its high pressure reducing valve and/or its relief valve.
Iodine Sam)1e- (IC-11-7)
The iodine gas sample line from tie RCS penetrates the primary, secondary and ' tertiary closures of the spare instrument penetration C-4 of the PCRV and is attached to the high pressure inlet end of the fast gas' sampling manifold.
Two normally shut manual valves, V11901-10 and V11901-16,. isolate the RCS from the high pressure section of the fast gas manifold.
As discussed for the loop 2 fast gas. isolation, excessively leaking or mispositioned valves do not jeopardize the integrity of the low pressure section of.the fast gas sampling manifold.
l 0
)