U-600176, Forwards Results of post-accident Containment Venting & Corresponding plant-specific Emergency Procedure Guidelines, Per 850301 Telcon.Info Fulfills Requirements of TMI Item I.C.1 & SER (NUREG-0853) Confirmatory Issue 41
| ML20128N968 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 07/24/1985 |
| From: | Spangenberg F ILLINOIS POWER CO. |
| To: | Butler W Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0853, RTR-NUREG-853, TASK-1.C.1, TASK-TM U-600176, NUDOCS 8507260309 | |
| Download: ML20128N968 (29) | |
Text
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U-600176 L30-85 (07-24 )-6 P04-85 (07-24 )-6 1A.120 ILLIN0/8 POWER 00MPANY IP CLINToN POWER STATION. P.o. Box 678. CLINToN. ILLINolS 61727 July 24, 1985 Docket No. 50-461 Director of Nuclear Reactor Regulation Attn: Mr. W. R. Butler, Chief Licensing Branch No. 2 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Clinton Power Station Post-Accident Containment Venting (PACV)
SER Confirmatory Issue #41
Dear Mr. Butler:
Illinois Power (IP) submitted to the NRC Staff the Clinton Power Station (CPS) Emergency Procedure Guidelines (EPGs) as part of the Emergency Operating Procedures Generation Package on May 1, 1984 in letter U-0708. IP contacted the Staff Reviewers of the package, Mr. W.
Kennedy and Mr. M. McCoy, on March 1, 1985 to discuss remaining concerns related to Post-Accident Containment Venting (PACV). IP considers the information provided in the attachment to this letter sufficient to resolve these concerns and thus fulfill requirements associated with the development of Emergency Operating Procedures as specified in TMI Action Plan Item I.C.1 and listed as Confirmatory Issue No. 41 in the Clinton Power Station Safety Evaluation Report (NUREG-0853).
The purpose of this letter is to submit the results of the CPS PACV evaluation along with the corresponding Clinton-specific EPG. Please find attached for your review the following information:
- Detailed description of the methodology used in determining the CPS vent pressure and the selected vent paths.
- Draf t PACV Emergency Procedure Guideline (CPS Procedure No.
1450.00, " Contingency #10, Emergency Containment Venting").
- EPG Appendix B Technical Basis for the Emergency Containment Venting Contingency #10.
The approach selected for Post-Accident Containment Venting at CPS
. is consistent with the guidelines established by the BWR Owners' Group and should therefore provide an acceptable basis for closure of Confirmatory Issue No. 41.
85072603K)9 850724 PDR F
ADOCK 05000461 PDR gl
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U-600176 L30-85 ( 07-24)-6 P04-85 ( 07-24)-6 1A.120 Please contact us if you have any questions regarding this submittal.
t Sincerely your .
(f F. A Sp genb g Director - Nuclear Licensing and Configuration Nuclear Station Engineering TLR/ lab Attachment cc: B. L. Siegel, NRC Clinton Licensing Project Manager NRC Resident Office Regional Administrator, Region III, USNRC Illinois Department of Nuclear Safety
Attachment 1 to Lettsr
. , U-600176 Clinton Power Station Post Accident Containment Venting (PACV)
Methodology and Selection of Vent Pressure and Vent Paths Summary The Primary Containment Control section of the Clinton-specific Emergency Procedure Guidelines (EPGs) directs the operator to vent the primary containment when excessive containment pressure jeopardizes the integrity of the containment structure. Veating is an emergency means of decay heat removal (DHR) that permits a controlled release of containment atmosphere to prevent indeterminate containment failures and the subsequent uncontrolled release of fission products to the environment.
Clinton's Mark III Containment has a 15 psig design pressure and an NRC accepted ultimate strength capability of 63 psig. The selected vent pressure limit, 45 psig, is three times greater than the containment design pressure but well within its ultimate structural capability. Limitations on safety / relief valve (SRV) operability above 45 psig impose the venting limit.
The CPS containment venting procedure incorporates the use of multiple vent paths and initiates venting in a progressive sequence from small to larger lines. All vent paths vent from the containment building atmosphere taking full advantage of suppression pool scrubbing and steam condensation to remove radioactivity from the effluent and reduce the radioactivity release fraction. A total of 6 paths have been selected for venting and provide individual flow capacities equivalent to containment penetrations ranging in diameter from 2 inches to 8 inches. Venting through small lines first limits the rate of containment depressurization and also minimizes the offsite dose rate. Larger paths are used last and have the capacity to remove decay heat associated with a generation rate at 10 minutes after shutdown as required by the Boiling Water Reactor Owners' Group (BWROG) Generic EPG Calculational Procedures.
Introduction Following the accident at the Three Mile Island Station, the Nuclear Regulatory Commission issued NUREG-0737, " Clarification of TMI Action Plan Requirements". In response to Action Plan Item I.C.1, Illinois Power Company (IP) developed Clinton-specific Emergency Operating Procedures (EOPs) from the symptom based BWROG Emergency Procedure Guidelines and committed to implementing Revision 3J of the Generic EPGs.
The Primary Containment Control section of the generic guideline specifies action for controlling containment pressure to prevent an overpressurization that may result in an unpredicted breach of the primary containment and an uncontrollable release of radioactivity to the environment. The preferred method of pressure control utilizes the emergency cooling and heat removal systems to process decay heat and control primary containment pressure. If pressure continues to increase, containment sprays '
are used when the appropriate E0P conditions are reached. If primary containment ;
pressure cannot be maintained below established limits using emergency pressure
, control systems and containment sprays, other actions are specified to minimize i further pressurization of the primary containment from reactor decay heat. These actions are taken at progressively higher containment pressures and include, in sequence, depressurizing the reactor pressure vessel (RPV), flooding the RPV, and I spraying the containment irrespective of adequate core cooling. As a last resort, the primary containment is vented to the atmosphere when the series of operator actions to reduce pressure have failed and the containment pressure approaches the 1
Attachm:nt 1 to Latter
. , U-600176 limit at which vent path operability or core cooling-related equipment operability can no longer be assured.
This attachment identifies the methodology used in determining the containment vent pressure limit, the methodology for selecting the vent paths,and a description of the selected vent paths.
Methodology for Selecting the Containment Vent Pressure The primary function of the containment venting procedure is to provide a predetermined capability of removing containment atmosphere at a rate that will prevent damaging the containment due to over-pressurization. Containment pressure is directly dependent on the amount of energy added to the containment atmosphere from residual heat in the reactor core. Reactor core decay heat generation following a reactor shutdown is well defined and serves as the basis for determining the required relief capability of the vent paths. Although the venting procedure provides an emergency means of removing RPV decay heat to control the rate of containment pressurization, DHR intentions do not overshadow venting for other reasons based on path operability problems, etructural integrity limitations, or limiting the release using small lines first.
Illustrated in Figure 1 are the required vent path relief capacities as a function of containment pressure for times ranging from 10 minutes to 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> after reactor shutdown. A " perfect" penetration is defined as an ideal nozzle penetration containment having negligible flow losses. The 10 minute decay heat curve in the figure indicates that a 12-inch perfect penetration has enough flow capacity to exhaust decay heat from the containment for pressures greater than 27 psig as required by the 10-minute DHR criterion established by the generic EPG calculational procedure.
The philosophy used for selecting a vent pressure limit was to vent the containment at a pressure "as high as possible" while still maintaining the integrity of the structure and insuring operability of the vent path and core cooling systems. This approach will delay post-accident containment venting until after all other pressure reducing responses have been tried and no alternatives remain.
Shown in Figure 2 are the Vent Pressure Limiting Conditions identified during the vent pressure selection process. The uppermost limiting condition is the 95 psig structural integrity limit calculated as the structural failure pressure causing excessive plastic deformation in the knuckle region of the containment dome. From the structural analysis performed by Illinois Power on the CPS Containment, 76 psig was conservatively estimated as the containment ultimate strength based on the stress capacity of the weakest element in the primary containment boundary (spherical equipment hatch). To resolve NRC Staff concerns, IP applied a safety factor of 1.2 to the 76 psig limit thereby reducing the ultimate strength to the 63 psig limit as referenced in the figure.
Based on SRV operability, a more restrictive condition for the vent pressure selection is the 45 psig Automatic Depressurization System (ADS) Operating Pressure Limit determined by the differential pressure requirements across the SRV pneumatic actuator. The minimum ambient-to-supply differential pressure across the actuator required to open and hold open an SRV is 95 psid for the most conservative caae when the RPV is depressurized. Higher reactor pressures assist in lif ting the valve disc from its seat, thus a smaller actuator differential will open the valve. Air supply pressure to the ADS valve actuator was conservatively chosen at the 140 psig main control room low pressure alarm set-point. Ambient actuator pressure 2
Attachmtnt I to Latter U-600176 is assumed to be the containment pressure if effects of the containment-to-drywell vacuum breakers are ignored. The 95 psid SRV differential opening pressure is conservatively approximated as the difference in the 140 psig actuator supply pressure and the ambient actuator pressure. Therefore, the upper limiting condition for venting with respect to SRV operability is 45 psig (differential (95 psid) =
supply (140 psig) - ambient (45 psig)). Venting at or below the ADS operability limit assures SRV performance so that control of the ADS function is maintained.
In Figure 2, the lowest limiting condition to be considered is the 8.76 psig calculated peak LOCA pressure for a design basis accident (DBA). Venting should not be initiated at such a low pressure since the containment is designed for 15 psig.
From the specified limiting conditions a " desired range for PACV" is established and the bounding conditions are the lower 15 psig CPS Mark III Containment Design Pressure Limit and the upper 45 psig ADS Operability Limit. Within this range is the EPG Target Pressure Limit defined by the NRC Staff in their Safety Evaluation Report as twice the containment design pressure.
Selected Containment Vent Pressure Based on the concept of venting at a pressure as high as achievable, 45 psig was selected as the Primary Containment Pressure Limit (PCPL) to be used for Post-Accident Containment Venting.
The selected vent pressure limit is three times greater than the containment design pressure but well within its ultimate structural capability. Limitations on SRV operability imposed the venting limit. The value of 45 psig was determined to be the maximum vent pressure at which SRV performance and therefore ADS operation can be assured. Conservatism used in calculating the ADS Operability Limit justified this selection.
To meet the 10-minute DHR criterion, the CPS containment can be vented by combining multiple paths to achieve a capacity that approximates a 12-inch perfect penetration.
As indicated in Figure 1, total flow from the paths at the PCPL is capable of removing residual heat at a rate greater than the heat production at 10 minutes after reactor shutdown.
Methodology For Selecting The Containment Vent Paths The use of multiple vent paths initiated in a progressive sequence from small to larger lines limits the rate of containment depressurization so that the magnitude of the induced containment and suppression pool structural loads from depressurization and/or suppression pool flashing due to venting remain relatively small. A thermodynamic investigation considered pressure effects on building loading as a function of vent size and vent pressure for varying steam flow rates, depressurization rates, and suppression pool flashing rates. The analysis verified that induced loads in the suppression pool and the containment structure caused by flashing or depressurization during venting are not significant and will not challenge structural integrity.
8 Dynamic loads resulting from safety / relief valve actuation at the Primary Containment Pressure Limit were also considered. In the existing CPS EPCs, this problem is explicitly addressed. The Emergency Operating Procedures are written to assure that suppression pool design basis loads are not exceeded during SRV actuation by specifying operator actions to depressurize the reactor vessel before significant containment pressurization occurs. In addition, a venting limit is established that ensures ADS operability.
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Attachm nt 1 to Letter
. . U-600176 The multiple vent path scheme also allows greater control over fission product releases by limiting the rate of radioactive discharge to the environment. The CPS venting procedure uses smaller lines first with the fundamental intention of minimizing the off-site dose rate. However, if containment pressure continues to rise, larger paths are available and may be required to maintain pressure below the specified limit although the radioactive release will be more significant. Other considerations for determining the sequence of vent path use were the discharge location, the release point elevation, and the degree of filtering or scrubbing available.
Ideally, vent paths should relieve pressure from the containment air-space above the suppression pool to take full advantage of suppression pool scrubbing and steam condensation to remove radioactivity from the effluent prior to venting. The location of the release should be as remote from the control room as possible to maintain control room habitability during emergency operation. Discharge points within plant areas where personnel access is required for emergency maintenance should be avoided. If a radioactive release is anticipated, the path should provide a means of radiologically monitoring the effluent to assess the severity of the release. The discharge point should be at the highest plant elevations, typically the HVAC stack or the standby gas treatment (SBGT) stack, to ensure optimum dispersion of the radioactive material. Additional effluent processing or filtration that can be provided by the vent path is highly desirable.
A final selection criterion for determining the vent path sequence is the relative ease with which one or more vent paths can be established. Complex alignment procedures are avoided in part by limiting the number of integrated boundary systems requiring operator action to align the vent path. Candidate paths requiring excessive hardware modifications to existing plant equipment to define the vent path should not be used.
Selected Containment Vent Paths The generic guideline for primary containment pressure control instructs the operator to vent the containment with available systems according to the emergency venting procedure when primary containment pressure cannot be maintained below the containment pressure limit. The systems listed in detail in Table 1 have been selected as the CPS containment vent paths. Venting will be initiated at the 45 psig pressure limit using the following systems in the indicated order of preference:
Path A - 2" Containment Spray Header "B" to Condenser.
B - 4" Containment Spray Header "B" to Condenser.
C - 6" Containment Spray Header "B" to Spent Fuel Pool and Condenser.
D - 6" Containment Spray Header "A" to Spent Fuel Pool.
E - 2" Containment Ventilation to Fuel Building.
F - 8" Containment Vent / Purge to atmosphere.
A simplified schematic of Paths A, B, C, and D from the containment spray headers is shown in Figure 3. Figure 4 is a schematic of vent Paths E and F, ori,inating from the containment ventilation system.
All vent path sizes specified herein are conservatively defined as the diameter of a
" perfect" containment penetration having a flow capacity equivalent to the actual vent path flow capacity with all line losses considered.
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Attacharnt I to Latter
. . U-600176 i
All 6 vent paths listed in Table 1 relieve containment overpressure from the free volume above the suppression pool. If drywell by-pass scenarios are neglected, the remaining venting scenarios ensure steam condensation and radioactive scrubbing by 1 the suppression pool since structural integrity of the suppression pool is
- unchallenged and SRV operability is assured at the Primary Containment Pressure Limit. Suppression pool water is lost only by boil-off, and therefore will be j available to perform its intended function well into the accident progression and long after venting is initiated.
] The first two vent paths, A and B, selected for use in the vent procedure have
- maximum flow capacities equivalent to 2-inch and 4-inch diameter perfect penetrations, respectively. The smallest path can be remotely operated from the main control room and can be throttled from 0-2 inches. Path B, used in conjunction with Path A, can be partially throttled. As shown in Figure 3, these paths use essentially the same flow line. The inlet point for both paths is the containment spray header in the containment dome. Flow is through penetration 16 exhausting into the main condenser shell. Further steam condensation and plate-out occur in the condenser providing an additional reduction of radioactivity in the effluent. The main condenser vacuum pumps take suction from the condenser shell and are capable of processing full flow while venting to the condenser from paths A and B simultan-eously. The vacuum pumps exhaust to the plant HVAC stack where radiological monitor-ing of the effluent is performed. As indicated in the first foot note of Table 1, the HVAC stack and the SBGT stack are the highest release points at the plant and provide the best dispersion of radioactivity to the environment to further minimize off-site exposure.
The next larger paths, C and D, in the indicated order of preference have 6-inch equivalent pipe flow capacities. Flow from both paths can be combined outside of containment for an 8-inch total flow capability. The simplified schematic in Figure 3 shows that Path C, through penetration 16, discharges into the condenser and into the spent fuel pool through a fill line located 20 feet below the water surface.
Path D, from penetration 15, flows through the Residual Heat Removal (RHR) System and through Spent Fuel Pool Cooling and Clean-up (FC) lines, then into the spent fuel
< pool via the fill line. The steam-air mixture percolates through the pool water further removing condensables from the effluent. Plate-out in the Fuel Building also reduces airborne radioactivity. The Fuel Building atmosphere is processed by the Stand-by Gas Treatment System (SGTS) through a series of filters, and then exhausts out the SBGT stack past detection instrumentation that monitors the release. Pool J scrubbing, SGTS filtering, and high point dispersion significantly reduce exposure and provide maximum public protection when venting through these larger paths.
Vent Paths A, B, C, and D from the containment spray headers to the main condenser and/or the spent fuel pool are designed as pressurized water systems and are I constructed entirely of pipe. The feedwater, RHR, and FC systems are rated at
, working pressures greater than 200 psig. The 45 psig venting limit is far below their system design pressures. Structural integrity of the piping and valve performance at the designated PCPL imposes no restrictions on venting with these systems.
The CPS inboard motor-operated containment isolation valves in Paths A, B, C, and D are remotely operated from the main control room and powered by a Class IE power supply. As previously stated, the valves and actuators are designed for use in pressurized systems. Actuator torques and mechanical stresses developed in the valves while venting at the specified limits are not restraining conditions. The motor-control mechanisms and motor-operators for the inboard valves are environmentally qualified for operation at a peak containment temperature and 5
1 Attachmsnt 1 to Letter 2 . . U-600176 pressure of 185'F and 15 psig, respectively. Due to built-in conservatism in the i environmental qualification of the actuating mechanism, there is reasonable assurance I that during an isolated venting incident, actuators will remain operable for approximately 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> at the 45 psig containment pressure limit and the attendant 293*F saturation temperature. If it is determined that venting may be required after i
the 9 hour1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> period when containment design conditions have been exceeded, then the inboard isolation valve should be opened. At this point, control over the vent path l initiation and termination functions will be maintained with the outboard isolation valve. It should be noted that other valves downstream of the isolation valve having remote flow regulating capabilities can be used as redundant or back-up isolation '
valves so that primary containment isolation and vent path operability will be
, maintained. Actuator performance for the outboard motor-operated isolation valves
- can be assured since the motor-control mechanisms are outside of the containment l where environmental qualification is not a limiting condition.
- The last 2 vent paths, E and F, in the preferred sequence provide additional back-up venting capabilities but do not have as many of the inherent advantages provided by the other paths. As shown in Figure 4, these paths are part of the containment HVAC system and are constructed of pipe from the inboard isolation valves to the discharge point outside of the containment. Both paths utilize the general area HVAC ductwork inside of the containment. Structural integrity of the containment ductwork is not a
- concern during venting since the internal and external ductwork pressures are nearly j equivalent and the resultant net differential pressure is negligible. Path E, I through penetration 101, is equivalent to only a 2-inch perfect penetration and 4 discharges directly into the Fuel Building atmosphere where secondary effluent
! scrubbing by the spent fuel pool cannot be accomplished, although processing through l SGTS is still provided. Path F is to be used as a last alternative for venting and l was specifically included among the final vent path selections to meet the 10-minute :
DHR criterion. This path uses a section of the Containment Vent and Purge System that is fabricated of pipe outside of the containment. The disadvantages when i venting through this path are as follows:
i 1 - Modification is required prior to venting.
l - No additional radiological scrubbing or filtering can be performed.
- Radioactivity in the effluent can not be monitored, j - Release point does not provide optimum dispersion. ,
From Table 1, five of the six vent paths selected for use in the CPS emergency i procedure require no major hardware modifications. Path F requires the removal of a j small section of pipe prior to venting. Valve alignment in all the paths can be 2
readily accomplished. Few interconnected systems border the vent paths, so isolating i a path from other systems is relatively simple. Also, the selected paths have few
] valves, the majority of which are operable from the main control room for most j venting scenarios. Valves requiring manual operation are easily accessed. Paths ,
I with the shortest pipe runs were chosen to reduce line losses and also to reduce line-up times and personnel exposure by permitting faster walk-downs when aligning systems in a potentially radioactive environment.
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Attachm:nt I to Letter
. . U-600176 Listed in Flow Chart 1 is the preferred sequence of path use when the main condenser is available for venting and an alternate venting sequence when the condenser is unavailable. Highlighting this flow chart is the Total Vent Size which represents the total flow capacity when paths are combined in the indicated order. Total flow from the containment can be regulated (increased or decreased) in 2-inch vent size increments when each successive path in the sequence is used. This progression provides the operator with substantial containment pressure control capability during an accident.
Conclusion The previous discussion provides detailed information on the determination of the containment venting pressure and the vent paths to be utilized for containment pressure control. The rationale for the progression of use of these vent paths has also been described. Based on the above information, a Clinton EPG for Post-Accident Containment Venting has been developed and is provided in Attachment 2. The technical basis for this portion of the CPS-EPG is provided in Attachment 3.
The CPS " Containment Control-Emergency" procedure No. 4402.01 will contain or refe-rence the detailed operating procedures necessary to use the multiple containment vent paths.
GJS/ lab 1
7
TABLE #1 DESCRIPTION OF SELECTED VENT PATHS-CONTAINMENT PATH INLET / VENT
- DISCHARGE DESIGNATION PENETRATION SIZE SYSTEM LOCATION A) Containment Spray header 0"-2" RHR Loop "B" Supply Main condenser to (Penetration 16) (Throttled) in Containment Spray HVAC stack #
Mode /Feedwater flushing by-pass line to main
. condenser.
B) Containment Spray header 4" RHR Loop "B" Supply Main condenser to (Penetration 16) in Containment Spray HVAC stack #
Mode /Feedwater flushing and by-pass lines to main condenser.
C) Containment Spray header 6" RHR Loop "B" Supply in Main condenser to (Penetration 16) Containment Spray Mode / Spray HVAC stack and Header Cross-tie /Feedwater Spent fuel pool in flushing and bypass lines . Fuel Building'to to condenser / Fuel Pool SBGT stack #
Cooling and Clean-up spent fuel pool fill line D) Containment Spray header 6" MIR Loop "A" Supply in Spent fuel pool in (Penetration 15) Containment Spray Mode / Fuel Building to Fuel Pool Cooling and SBGT stacki Clean-up spent fuel pool fill line E) Containment HVAC duct 2" Containment Building Vent- Fuel Building to (Penetration 101) ilation Supply (duct) by-pass SBCT stack #
line F) Containment HVAC duct 8" Continuous Containment Purge Roof of Diesel-(Penetration 113) Supply (pipe) Generator Bldg after removal of pipe section
- The highest plant elevation release points are 198'6" above grade level at the top of the HVAC stack and SBGT stack.
OThe Vent path size is conservatively specified as the diameter of a " perfect" containment penetration having a flow capacity equivalent to the actual vent path capacity with all line losses considered.
POST-ACCIDENT CONTAINMENT VENTING FLOW CHART #1
~
Decide To Vent Preferred Sequence Alternate Sequence Is Condenser Vacuum Available?
Yes Total Vent Size No Open 2" Open Path Path A (2") E (2")
IF Inadequate 4" Open Path B (4")
IF Inadequate 6"' IF Inadequate Open Path C (6") Open Path D Close Path E (6")
IF Inadequate 8" IF Inadequate Open Path D (6") Open Path C (8")
Isolate Condenser IF Inadequate 8+" IF Inadequate Open Path E (2") Open Path E (2")
IF Inadequate 12" IF Inadequate Modify and Open Modify and Open Path F (8") Path F (8")
FIGb1E #1 Flow for Air-Steam Mixture Through " Perfect" Penetrations
- 120
, Total Capacity at CPS Vent Limit + - - - --
12-inch .
10-incb 100 - I I
Minimum Capacity <
- - ~ _ ~ '
_ _ _ - - - - - --- - - - ~ ~ _ _ _ _ _ .10-Min. DHR~
'and Pressure . 80 i Criterion For 10-Min. DHR For Generic o EPG. .
e l
- tt)
E
.o c 60 -
l ta i '
1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> g __ __'___ _ _ - - - . _ - - - - - - - - - - - - -
3 O
~
40 -
tn i 6-inch m a i l
._._ _ _ _. 10 hours 20 ----- *-~~
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_:. b ttr 3 - - 6 1 n c h -
t 0-15' 27 $0 45 6'O 73 CO!! TAIT!ME 1T PRESSURE (psig) -
Choked flow for indicated pipe diameter.
Steam production from decay heat for indicated time af ter SCRM1.
- "negligible Perfect" Penetration flow resistance. - ideal nozzle penetrating containment having Vent path size is defined as the diameter of a " perfect" penetration having a flow capacity equivalent to the vent path flow capacity with all line losses considered.
FIGURE #2 Vent Pressure Limiting Conditions 100 *-
(
95.0 Calculated Structural failure in the knuckle region 90 -
80 - '
- 76.0 Calculated Equipment Hatch Failure 3
g 70 -
m e
63 0 NRC Defined Ultimate Strength (Safety Factor =1.2)
E 60 - -
n n.
4J C 50 -
.,4 45.0 ADS o eratin ressure g g ;
30 -
N30.0 EPG SER Target Pressure (2 x design) -
g 20 _
h 15.0 Design pressures (%\ jr 10
~
~ 8.75 tiaximum Calculated pressure following DBA 0
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FIGURE #3 SCHEMATIC FOR VENT PATHS A,B,C, AND D FROM CONTAINMENT SPRAYS THROUGH PENETRATIONS 15 and 16 PATH (SIZE) FLOW .
, (FROM-TO) -
1,' 2 & 1,3,4 LJ C(6") 1,2,4 & 1,3,4 Ll1
^
' ' f 1 & 1,5,7 F1 ~' " ' ' ' ^
~ '
Containment D(6") 6,7 Spray Containment
. Loop A . Spray Loop B Inside co'n t a in me- n- -t 15 ~~~~~~~~~~~~~-~~~~-- - - - - - - - - - - -
Outside Containment 16 MO '
MS z
7 A_]
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K is
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To Atmosphere -
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-] 4 1
SB6 T stack E h To i
' #
- Atmosphere H' Via l .=
4 Melin -
~ HVAC stack
! Fuel Spent Condenser Fuel i Building ygg -
Atmosphore - PO
FIGUPS #4 SCHEMATIC FOR VENT PATHS E AND F FROM -
CONTAINMENT HVAC THROUGH PENETRATIONS 101 AND 113 .
PATH (SIZE) FLOW (FROM-TO)
E(2") 1,2' F(8") 1,3 CONTAIID1ENT GENERAL AREAS bEST WEST WEST EAST EAST EAST DOME 755'-0" 303'-3" 778'-O' .
303'-3" 7 5 0 ' '- 0 " 778'-0" I
F >
[$
- 2::S ,
m A0
[ -
A0 MO -
[fg Incide Containment
- 101 ----
Outside Containment 1
1.
/ -
A0
_y Hj g (D '
Fuel y Duilding Roof of Diesel
. Atmosphere Generator Bldn.
To Atmosphere After Piping Section is Removed
- pipe
\v/ Ductwork To Atmosphere Via SBGT Stack
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Attachment 2 To letter U-600176 l
Contingency #10, EMERGENCY CONTAINMENT VENTING
! in the t
Primary Containment Pressure Control Section I of the Emergency Procedure Guideline (CPS No. 1450.00)
Page 32,and Pages 64 to 68
.- .Attcchment 2, to CPS No. 1450.00
'Lottar U-600176 i PC/P-5 IF
~~
Containment pressure cannot be maintained below the Primary Containment Design Pressure THEN RPV Flooding is' required. Enter Contingency
- 2,-EMERGENCY RPV DEPRESSURIZATION, and Contingency #6, RPV FLOODING, and execute them concurrently with this procedure.
NOTE IF Containment Pressure decreases to 0 psig (Mark III containment apray termination pressure for plants without external vacuum breakers)
THEN Terminate containment spray PC/P-6 IF Containment pressure cannot be maintained below the Primary Containment Pressure Limit THEN Initiate containment spray, irrespective of whether adequate core cooling is assured, to maintain pressure below the Primary Containment Pressure Limit.
Caution #22 PC/P-7 IF Containment pressure exceeds the Primary Containment Pressure Limit THEN Vent the containment to reduce and maintain pressure below the Primary Containment Pressure Limit. Enter Contingency #10, EMERGENCY CONTAINMENT VENTING.
SLA37 Page No. 32 of 138 Rev. No. O j
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. . Attachment 2, to CPS No. 1450.00 Letter U-600176 C10 Contingency #10, EMERGENCY CONTAINMENT VENTING NOTE If either condenser vacuum pump is available for operation, enter section C10-1, VENTING WITH CONDENSER.
If the vacuum pumps cannot be run, enter C10-2, VENTING WITHOUT CONDENSER.
C10-1 VENTING WITH CONDENSER C10-1.1 Operate at least one condenser mechanical vacuum j pump taking suction on the condenser.
1 C10-1.2 IF Circulating Water is available THEN Operate at least one circulating pump to establish flow through the condenser.
C10-1.3 IF
~-
At any time condenser pressure cannot be maintained below 0 psig THEN Throttle and/or isolate vent paths to the condeaser until condenser vacuum is restored AND IF Containment pressure is increasing THEN Enter section C10-2, VENTING WITHOUT CONDENSER C10-1.4 Initiate venting from the RHR loop B containment spray sparger to the condenser.
C10-1.5 IF Containment pressure continues to increase THEN, Provide additional vent capacity by opening 1FWO21.
C10-1.6 IF Containment pressure continues to increase THEN Operate both trains of SGTS taking suction from the Fuel Building AND Initiate venting from RHR loop B to the spent fuel pool in addition to the main condenser.
SLA37 Page No. 64 of 138 Rev. No. O
Attachn.ent 2, to CPS No. 1450.00 L3ttor U-600176 C10-1.7 )); Containment pressure continues to increase THEN Initiate venting from RHR loop A to the spent fuel pool.
C10-1.8 IF Containment pressure continues to increase
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THEN Initiate venting from the Containment Building Ventilation System to discharge to the Fuel Building.
C10-1.9 ))[ Containment pressure continues to increase THEN Modify the Continuous Containment Purge System and initiate venting from the Continuous Containment Purge System to discharge at the Diesel Building roof.
C10-1.10 WHEN Containment pressure is decreasing / stable THEN Enter section C10-3, VENTING AND RECOVERY.
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SLA37 Page No. 65 of 138 Rev. No. O s . . - - . .
. [. Attachment 2, to CPS No. 1450.00
-Lstter U-600176 C10-2 VENTING WITHOUT CONDENSER
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C10-2.1 Operate both trains of SGTS taking suction on the Fuel Building C10-2,2 Initiate venting from the Containment Building HVAC System to discharge to the Fuel Building.
C10.'2.3 IJ Containment pressure continues to increase THEN Initiate venting from the RHR loop A containment spray sparger to the spent fuel pool AND '
Isolate the vent from the Containment Building Ventilation System.
C10-2.4 IF Containment pressure continues to increase THEN Initiate venting from the RHR loop B containment spray sparger to the spent fuel pool.
C10-2.5 IF Containment pressure continues to increase THEN Reopen the vent from the Containment Building Ventilation System to discharge to the Fuel Building.
C10-2.6 1]; Containment pressure continues to increase l THEN Modify the Continuous Containment Purge l System AND
' Initiate venting from the Continuous Containment Purge System to discharge at the Diesel Building roof._
C10-2.7 WHEN Containment pressure is decreasing / stable THEN Enter section C10-3, VENTING AND RECOVERY.
l SLA37 Page No. 66 of 138 Rev. No. O
.Attachm:nt 2 CPS No. 1450.00
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To lotter U-600176 C10-3 VENTING AND RECOVERY NOTE IF At any time containment pressure exceeds the Primary Containment Pressure Limit AND Containment pressure is increasing THEN Return to the beginning of Contingency #10, EMERGENCY CONTAINMENT VENTING.
C10-3.1 Continue venting until containment pressure is less than the Primary Containment Pressure Limit.
C10-3.2 WHEN Containment pressure is less than the Primary Containment Pressure Limit THEN Throttle and/or isolate the containment vent path (s) in an order which will minimize the release to the environment and will maintain containment presse';e as high as possible but below the Prima;.y Containment Pressure Limit.
C10-3.3 WHEN All of the emergency vent paths have been isolated THEN Monitor the containment depressurization rate and control cooling sources (cool water injecting into the RPV or containment, suppression pool cooling, or containment or drywell coolers) to prevent containment pressure from rapidly going negative.
C10-3.4 ]g[ The Containment Spray Initiation Pressure Limit is exceeded THEN Isolate and prevent automatic initiation of containment sprays.
SLA37 Page No. 67 of 138 Rev. No. 1
. . Attechment 2 To letter U-600176 C10-3.5 IF
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Containment pressure decreases to 0 psig (Mark III containment spray termination aressure for plants without external vacuum areakers)
THEN Terminate containment spray C10-3.6 IF Containment pressure decreases below 0 psig THEN Initiate vacuum relief to the Containment Building using either or both of the following systems:
- a. The main condensor vacuum breaker through feedwater to any RHR containment spray sparger,
- b. The supply half of the Post-LOCA-Purge portion of the Containment Building HVAC System.
C10-3.7 IF
~ Containment pressure cannot be maintained above the Containment Negative Pressure Design Limit THEN Before containment pressure exceeds the maximum Containment Negative Pressure Limit, initiate vacuum relief to the Containment Building from the supply side of the Continuous Containment Purge System.
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l Attachment 3 To letter U-600176 CPS-EPG Appendix B Technical Basis for .
Contingency #10 EMERGENCY CONTAINMENT VENTING Pages 133 to 138
a.Attechm:nt 3 1R) 1stter.U-600176 APPENDIX B CONTINGENCY #10
' Contingency #10 has been developed to provide a method of venting the containment where excessive containment pressure jeopardizes the primary containment integrity as per step PC/P-7. This. contingency incorporates the use of a multiple path venting sequence that initiates, venting through small lines first to limit the rate of containment depressurization and minimize the off-site dose rate.
The first note directs the operator to perform section C10-1 if either condenser vacuum pump is available for operation. Venting through the. condenser is preferred because internal building-releases are avoided.
C10-1.1 [None]
Operating the condenser vacuum pumps will move the vent mixture from the condenser to the plant HVAC stack. This stack is the highest release point in the plant and provides the best dispersion of radioactivity to the environment. One pump should.
be able to handle the vent flow since these pumps are designed for high moisture applications.
C10-1.2 [None] l Steam condensation and plate-out in the condenser !
will-reduce the radioactivity levels of the .
effluent. If circulating water flow is maintained, then continued steam condensation is assured. This will reduce the mass flow rate and radioactivity released out the HVAC stack.
C10-1.3 [None]
If condenser vacuum cannot be maintained then one or more of the following conditions exist:
- 1. The condenser vacuum pumps or support systems are not operating at expected capacity,
- 2. The vent path flow is higher than expected, or
- 3. There exists significant air in-leakage into the condenser.
SLA37 Page No. 133 of 138 Rev. No. 1
. .Attechm:nt 3 CPS No. 1450.00 To lottar U-600176 When condenser pressure is positive, the potential exists for an unmonitored, ground-level release through the Turbine Building. Although this is preferable to containment failure, other vent paths exist which provide a monitored, high-point release.
Therefore, the operator is directed to throttle and/or isolate vent paths to the condenser until condenser vacuum is restored. If this new vent rate is unable to arevent containment pressure from increasing, t aen section C10-2, VENTING WITHOUT CONDENSER, should be used to determine the adt.cional vent paths needed.
C10-1.4 (None]
This vent path has approximately the equivalent flow capacity of a 2" ideal nozzle and contains a throttlable globe valve. It was chosen first because of its small size, steam condensing abilities, radiation monitoring capabilities, and high release point. Using this vent path still allows loop A of RHR to be used for containment sprays.
C10-1.5 [None]
If containment pressure is increasing then the vent path is too small to control containment pressure.
Oaening this valve in conjunction with the t:1rottlable globe valve provides approximately 4" ideal nozzle capability.
C10-1.6 [None]
At this point, additional venting capacity is required and all paths to the main condenser have been used. This path vents simultaneously to the main condenser and the spent fuel pool. The SGTS is operated to remove non-condensables from the Fuel Building providing a filtered, monitored, high-point release. Flow is still directed to the condenser to minimize the challenge to secondary containment.
Secondary containment pressure may rise to approximately atmospheric pressure depending on the percentage of non-condensables in the containment atmosphere at the time of the venting. This path is limited by the containment spray sparger which is approximately equal to a 6" ideal nozzle.
C10-1.7 [None]
This step provides additional venting capability to the spent fuel pool and continues to increase the vent size making its total capacity approximately equal to an 8" ideal nozzle.
SLA37 Page No. 134 of 138 Rev. No. 1
. Attachment 3 CPS No. 1450.00 To letter U-600176 C10-1.8 [None]
The path from the Containment Building Ventilation System supply is used last because it discharges directly into the Fuel Building airspace and does not provide steam condensing. Adding this vent path makes the total vent path slightly larger than an 8" ideal nozzle.
C10-1.9
[None]
At this point, all efforts to control containment pressure were inadequate and the largest and least desirable vent path is required. A section of the supply pipe is removed from the Continuous Containment Purge System. The containment is vented to the roof of the Diesel Building providing an unmonitored, unfiltered release. Combined with the other vent paths this provides approximately the venting capability of a 12" ideal nozzle and satisfies the BWROG requirement for removing the energy of decay heat 10 minutes after shutdown.
C10-1.10 (None]
When vent capability is sufficient to control containment pressure, this step directs the operator to the venting and recovery section of this contingency.
I SLA37 Page No. 135 of 138 Rev. No. 1
. ,Attcchm:nt 3 CPS No. 1450.00 To letter U-600176 C10-2.1 [None]
This step is performed to remove the non-condensables which will be vented into the Fuel Building and to provide a monitored, filtered, high-point release.
C10-2.2 [None]
This path was chosen first because of its small size. Vent flow will be within the capability of SGTS, therefore secondary containment integrity will not be challenged. Although this path does not provide any steam condensing, it is assumed the containment atmosphere will initially be largely non-condensables anyway. This vent path has approximately the capacity of a 2" ideal nozzle.
C10-2.3 [None]
Performing this step increases the vent size to approximately the capability of a 6" ioeal nozzle.
This vent path also discharges below the surface of the spent fuel pool providing steam suppression.
This path may cause a temporary: rise in secondary containment pressure to approximately atmospheric pressure depending on the amount of non-condensables in the vent mixture. It is assumed that the initial vent mixture contains a large percentage of air and as venting continues, the percentage of steam gradually increases. The smaller vent path to the Fuel Building atmosphere is closed here to reduce the steam content in the Fuel Building and provide gradually increasing vent sizes.
C10-2.4 [Nonel Because the spray sparger is the limiting component in this path, venting through both containment spray spargers increases the vent size to approximately an 8" ideal nozzle.
C10-2.5 [None]
At this point re-opening this vent path will discharge steam into the Fuel Building atmosphere and will only slightly increase the vent pati capacity. However, it is the last-remaining vent path prior to performing step C10-2.6.
SLA37 Page No. 136 of 138 Rev. No. 1
..- ,Attechm:nt 3 CPS No. 1450.00 To letter U-600176 C10-2.6 -[None]
At this step all previous efforts to control containment pressure were inadequate, therefore the largest and least desirable vent path is required.
A section of pipe is removed from the Continuous Containment Purge System and the containment is vented.from the roof of the Diesel Building. This would be an unmonitored, unfiltered release.
Combined with the other vent paths this provides approximately the venting capability of a 12" ideal
-nozzle and satisfies the BWROG requirement of removing the energy of decay heat 10 minutes after shutdown.
C10-2.7 [None]
When vent capability is sufficient to control containment pressure, this step directs the operator to the venting and recovery section of this contingency.
j< C10-3.1 [None]
This step is the common exit point for sections C10-1 and C10-2. If containment pressure is not increasing then the vent size is adequate and no further action is needed until_ containment pressure is below the Primary Containment Pressure Limit.
The note above this step applies at any time. If containment pressure is above the Primary Containment Pressure Limit and increasing, then additional vent capacity in required and it is appropriate to return to the beginning of contingency #10.
C10-3.2 [None]
In order to minimize the release and protect the containment, containment pressure should be maintained as high as possible below the Primary Containment Pressure Limit. Also, the fewer non-condensables that are vented, the less severe
-the containment negative pressure transient will be.
C10-3.3 [None]
( This step provides the operator with guidance on how to control the containment depressurization rate in an attempt to minimize the negative pressure transient.
C10-3.4 [None]
The Containment Spray Initiation Pressure Limit is calculated to prevent the containment from reaching its negative design pressure. It is just as appropriate to observe this limit with decreasing containment pressures as it is with increasing containment pressures.
SLA37 Page No. 137 of 138 Rev. No. 1
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.Attechment 3 CPS No. 1450.00 To letter U-600176 C10-3.5 (None]
This step is included in an attempt to prevent containment pressure from exceeding Negative Pressure Design Limit.
C10-3.6 INone]
The normal Containment Building HVAC System is not used here because of the potential for continued offsite release. Although these systems are small, they are designed to handle these pressures and they can be operated.from the control room. The wording allows the operator to chose which path (s) would be more appropriate based on the accident scenario.
C10-3.7 (None]
This system was not used initially for vacuum relief because it requires bypassing some interlocks.
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