ML20070L998
| ML20070L998 | |
| Person / Time | |
|---|---|
| Site: | Clinch River |
| Issue date: | 01/07/1983 |
| From: | Longenecker J ENERGY, DEPT. OF, CLINCH RIVER BREEDER REACTOR PLANT |
| To: | Check P Office of Nuclear Reactor Regulation |
| References | |
| HQ:S:83:171, NUDOCS 8301120188 | |
| Download: ML20070L998 (49) | |
Text
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Department of Energy Washington, D.C. 20545 Docket No. 50-537 HQ:S:83:171 g 1983 Mr. Paul S._ Check, Director CRBR Program Office Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commissioa Washington, D.C.
20555
Dear Mr. Check:
NUCLEAR REGULATORY STAFF COMMENTS REGARDING PRELIMINARY SAFETY ANALYSIS REPORT (PSAR) SECTIONS 9.3 AND 9.13 FOR THE CLINCH RIVER BREEDER REACTOR PLANT In accordance with agreements between our respective staffs, enclosed are responses to questions concerning PSAR Section 9.3, " Auxiliary Liquid Metal Systems," Section 9.13, " Plant Fire Protection System," and other related sections. Enclosure 1 responds to questions f om the Chapter 9 working meeting held on December 14 and 15,1982; Enclosure 2 responds to additional Chapter 9 questions discussed in the Florek, King, et al, telecon of December 20, 1982; Enclosure 3 is the proposed PSAR amended pages that will be submitted in the January amendment reflecting the above responses; and Enclosure 4 is an additional response requested in another Florek, King, et al, December 20, 1982, telecon.
Questions regarding this submittal may be addressed to either Mr. D. Robinson (FTS 626-6098) or Mr. D. Hornstra (FTS 626-6110) of the Project Office Oak Ridge staff.
Sincerely, b.
JdknR.Longen ker Acting Director, Office of Breeder Demonstration Projects Office of Nuclear Energy 4 Enclosures DOOl cc: Service List Standard Distribution g
f Licensing Distribution i
8301120188 830107 PDR ADOCK 05000537 A
4 4
Enclo0ura I i
(2,128)
PSAR.SECTION 9.3 ITEMS 1.
Question:
The design conditions (temperature and pressure) should be specified for each subsystem.
Response
Design temperatures and pressures are provided for each subsystem on amended PSAR pages 9.1-26, 9.3-la, 7a, 11, 14, 20d.
2.
Question:
The PSAR should identify the materials of construction of the sodium and NaK receiving stations.
Response
See amended PSAR page 9.3-la.
3.
Question:
Appropriate emergency plans should be implemented during receiving and loading of sodium.
Response
PSAR page 9.3-2 has been amended to say that appropriate and necessary emergency planning with local officials will be taken to consider the possibility of an outside sodium fire during the initial loading of sodium.
PSAR page 9.3-2 also states that precautions will be taken during liquid metal loading conditions to limit aerosols efects to plant components prior to plant operation.
4.
Question:
What procedure is planned for replacement of cold traps?
Response
Amended PSAR pages 9.3-5, 13, and 9.1-21 discusses cold trap removal and storage.
5.
Question:
What procedure is used for maintaining NaK purity and what has been experience with other plants using NaK?
Response
As discussed in amended PSAR pages 9.1-21, NaK has been successfully used without impurity problems and no monitoring of NaK impurities are scheduled based upon anticipated maintenance activities of the NaK loops and the capacities of the diffusion traps.
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6.
Question:
Can a leak in the EVS cooling circuits disable cooling of the EVST?
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Responses As discussed on PSAR pages 9.1-27, no leak in the EVS system can~ disable more than one loop.
Discussion of the EVST anti-syphon features are provided.
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PSAR SECTION 9.13 QUESTIONS 9.13-1) During cooldown of the cell atmosphere after a liquid metal fire, a negative pressure could result due to.the depletion of the oxygen. The PSAR does not state that the pressure differential resulting across the liner is less than the 5 psig design value in this instance. Therefore, the resulting negative pressure in an;inerted cell due to cooldown after a sodium spill should be calculated and documented in the PSAR.
If need be, a change to the cell design con'dition for negative pressure should be made.
Response: The Project has done a 'very conservative analysis of the PHTS cell cooldown pressure effects following a sodium spill.
The analysis assumed that the postulated spill pressurizes the cell to 30 psig (approximately twice more than calculated)' with a corresponding gas temperature of 1500 F (also twice more than calculated). The 0
analysis assumed that the cell leaks outward at the design leak rate increased for pressure effects. With no inward leakage assumed, the maximum negative pressure with sodium cooling until freezing is 4.5 psi which is still within the cell liner design limits.
9.13-2) The functional design and evaluation of the catch pan system is based on the sodium /NaK leak rates and spill volumes listed in Table 9.13-9.
In all cases, except the case in Cell No. 211A for the storage vessel valve gallery, the total postulated spill volume is identical to the potential spill volume.
Since it is stated that no operator action is taken to terminate the leak, it is not obvious why the larger potential soill volume of 69,000 gallons would not also be the total postulated spill volume.
If
the spill volume of 69,000 gallons was used it would constitute a much more severe fire potential than the 3400 gallons considered.
Provide justification as to why the larger spill volume was not used or change the PSAR and perform the analysis to be consistent with the larger volume.
Response
The maximum potential Na spill volume in either Cell No. 211A or 211 is' presently 50,000 gallons, assuming no credit for operator action to mitigate the spill.
The analysis and conclusions on PSAR Section 15.6.1.3 for a 45,000 gallon spill are still applicable, since an' additional 5000 gallons of sodium do not present any significant additional heat load to the building structures.
Appropriate change pages to the PSAR t
t (9.13-45B, 15.6-8) are attached to this response.
l 9.13-3)
Not all cells with catch pans have fire suppression decks.
Some have drains that allow the spilled sodium /NaK to go to catch pans with fire suppression decks and others allow open pool burning as long as no safety-related equipment or building structures are affected (generally limited to cells with only small spill i
i potential).
However, there are two cells (nos. 211 and 22B) which have the potential for large sodium spills for which no fire suppression decks are provided.-
Lack of fire suppression decks in these cells have not been justified.
It should be noted l
that the plant design has similar cells to Cell No. 228 (IHTS loop 2 pipe cell) for loops 1 and 3 which have fire suppression decks.
Fire suppression decks should be added to Cell Nos. 211 l
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4 and 228 or justification should be provided as to why the decks are not needed.-
Response
Cell No. 211 will be inerted whenever sodium is present-in-4 the storage tanks (in excess of the heel) in this cell.
- Hence,
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no fire suppression deck is required since the inerted gas precludes any significant' burning from a postulated sodium spill accident.
Drains are provided between Cell Nos. 228 and 225 and to cell No. 208 which is provided with a fire suppression deck.
Drainage of sodium from Cell No. 228 is required since the free volume of
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j the cell is not sufficient _to contain the potential volume of leaked sodium.
9.13-5) The free volume of the catch pans was provided only for the catch pans in Ce-1 Nos. 207, 208, and 209 - the reaction product tank cells for IHTS loops 1, 2, and 3.
The volumes given were 5251 ft3,4279 ft3, and 5835 ft3, respectively, and represent approximately 11 percent excess capacity over the maximum postulated spill volume.
i The catch pans are; however, in cells which are approximately 73 ft x 73 ft which means the catch pan walls are only approximately I
one foot high.
Since according to the applicant's criteria, the catch pans must provide roor 2 the fire suppression decks to sit above the liquid metal pool (minimum 4" above pool is design value) and since the sides of the catch pans are to extend at least one foot above the top of the pool, the volumes of these catch pans do not seem large enough to meet the criteria'.
To verify that the above criteria are met in all cases the volumes of each catch pan without i
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a drain should be provided along with its approximate surface area.
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Response
The net catch pan floor area for cell Nos. 207, 208, and 209 is approximately 2334 f t 3.
Postulated spill volumes in these cells are 4700, 3800, and 5300 ft3, respectively, resulting in corresponding maximum sodium pool depths of 2.0, 1.6, and 2.3 test.
The bottom of the fire suppression deck is constrained to 4 inches above each of these sodium pool depths.
The sides of the catch pans are a minimum of 22 inches above the bottom of the fire suppression deck-in each of these cells.
Similar type design considerations also apply to other cells containing fire suppression decks, namely Cell Nos. 227, 230, 231, 232, 350, 354, and 355.
9.13-6) Cell Nos. 332, 352A, and 353A contain the EVST natural draft heat exchanger and air blast heat exchangers, respectively.
These cells do not have fire suppression decks in their catch pans and do not have automatic exhaust damper controls.
The postulated spill volumes and release paths in these cells have the potential for generating and releasing more than the 630 lbs. of aerosol allowed from spills in the SGB.
The rational needs to be provided as to why aerosol releases in excess of 630 lbs from spills in these locations are acceptable or protective measures provided to close off the exhaust paths or extinguish the fire.
e Response: See attached change to PSAR page 15.6-2 9.13-8) The accident analysis of the failure of an ex-containment primary sodium storage tank, reported in Section 15.6.1.3 of the PSAR, uses a postulated spill of 45,000 gallons of sodium in the accident conditions. Table 9-13.9 indicated that the total spillable volume of the tank is 50,000 gallons. There appears to be a discrepancy in the amount of sodium which is considered in the analysis,' which needs to be corrected, Response: The PSAR has been corrected as discussed in response to item 2 above.
9.13-9) There is no indication that the SFPS detectors and instrumentation provide local audible alarms in the fire area served by the detectors.
For normally accessible areas this should be provided for the safety of personnel that may be in the area.
Response: The Project will include local audible alarms in sodium fire areas as required to ensure the safety of personnel.
that may be in these areas..
9.13-10)
Paragraph 5.0 of Attachment B to Section 3.8-C indicates that the Project is presently developing non-destructive examination (NDE) requirements for the catch pans and fire suppression decks.
It is expected that the NDE requirements will be analogous to those specified for cell liners. The NDE program and requirements should be defined in the PSAR.
Response: The NDE requirements for catch pans are provided by PSAR Section 3.8C, Amendment 74 (attached).
The NDE requirement for the fire suppression deck is visual inspectionI The confirmation that these NDE requirements are acceptable will be obtained as a result of the Large Scale Sodium Spray Fire Test described in PSAR Section 1.5.
9.13-11)
No design methods are listed in the PSAR for the catch pan and fire suppression deck design. As discussed in Section 6.5 of the PSAR these methods will be incorporated in a new section of the PSAR to be added in the future (Section 3A.9). This section will require our review.
Response
Prcposed PSAR Section 3A.9 is attached.
9.13-12)
Features should be provided in the design of those cells which contain both sodium and water piping to minimize the potential for water leaks impinging on sodium piping and for sodium leaks impinging on water piping. The affects of any impingement should be evaluated in the fire hazards analysis report.
- Visual inspection for the first suppression deck is considered to be adequate since the fire suppression deck has no normal structural support function to perform other than its own weight.
In addition, the fire suppression deck is a non-pressure retaining device.
Response: The Project has provided jet impingement shields to minimize the potential for steam / water leaks impinging on sodium piping / components. Conversely, plant features will be provided as required to protect steam / water components from potential sodium jet impingements.
9.13-13)
The slope of the catch pan floors with drains was stated to be 1/4" to 1/8" per foot. This corresponds to an angle of 0.60 to 1.20.
It is not clear that this is adequate to ensure complete drainage of the spilled liquid metal.
(See report PWAC-347 " Liquid Metal Fire Control," dated 6/15/61). Therefore, the slope of the catch pans should be increased to 70 or the liquid metal spill analysis should account for retention and burning of some sodium in the drainable catch pans.
Response: During IHTS design basis sodium spill scenarios, both spray and pool fire evaluations are performed.
For the spill durations, an instantaneous pool is assumed to exist in the drainable catch L
pans. These assumptions are considered to be conservative in assessing i
the design adequacy of the SGB structures to accommodate postulated sodium spill events.
9.13-14)
A description of the insulation to be used on the Na and NaK piping and its compatibility with Na and NaK needs to be provided.
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l Response: The insulation design for all CRBRP NSSS Na/NaK wetted components and piping includes both metallic and non-metallic materials. All of the metallic parts are either 304 or 316 stainless steel, i.e., the same material as the component or piping being insulated. The thermal insulating material is a refractory fiber blanket, elumine silica, insulation. Both literature searches and physical testing have been accomplished to demonstrate that the material selected does not react with Na/NaK or support combustion.
In addition, the material meets the requirements of Regulatory Guide 1.36, Nonmetallic Thermal Insulation for Austinetic Stainless Steel.
I The description of the insulation design is as follows:
I Immediately adjacent to the component surface, a continuous annulus is formed utilizing stainless steel strapping, stand-offs, and
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sheathling. The purpose of the annulus is to house the trace heaters and control / monitor thermocouples as required. The thermal insulation blanket material is then added and retained by stainless steel tie-wires. A stainless steel outer sheath is then added, completely encapsulating the thermal insulation. On irregular configurations, fiberglass cloth is used as the outer sheath. The only locations that the thermal insulating material actually comes in contact with the surface being insulated is where convection barriers ara required.
In most cases, the convection barriers are encapsulated
in fiberglass cloth.
It should be noted that this material also does not react with Na/NaK or support combustion.
9.13-15)
The seismic category of the fire detection instrumentatica should be specified and'should be at least Seismic 11.
Response
The seismic class of the non-safety-related sodium /NaK fire detection instrumentation is Category III as is the non-sodium fire detection instrumentation.'
In the event of an earthquake, a fire watch will be posted until the instrumentation is verified as operable.
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1 ADDITIONAL ITEMS IDENTIFIED IN THE FLOREK, KING, ET AL. TELECON OF DECEMBER 20, 1982 i
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1)
The in-service inspection plan for cell liner welds should call for inspection of those welds which have the highest stress during normal operation and those that have the highest stress during postulated spill conditions. Access to the welds should be provided in the design. 'In addition, the in-service inspection plans for the catch pans should be developed in a similar fashion with the design allowing sufficient access for performance of this inspection.
Response
In-service inspection plans for cell liners were provided in the response to Q760.170. Similar in-service inspection plans will be developed for catch pans.
2)
The final design analysis for the inerted cells should include a duty cycle of loss of cell cooling. This will lead to cell heatup and eventual reactor shutdown. Realistic assumptions on the duration of the cooling loss and on the number of times the event occurs should be made. The liners should be confirmed to be able to withstand this event.
Response: Section 3.8-B of the PSAR addresses the requirements for cell liners integrity under the anticipated plant duty cycle. The plant duty cycle shown in Section 3.8-B is being updated per recent design feature changes. The cell liner criteria will be revised to reflect the changes in the plant duty cycle, ensuring cell liner integrity for both nonnal and off-normal plant events.
1 3)
The catch pans are free floating and are supported above the concrete floor of the cells by a continuous layer of insulating material (Mg0 aggregate) and by steel beams. The aggregate being loose and not a solid mass would be subject to settling and have the possibility of producing bending stress in the steel catch pan if the aggregate had settled between the steel beams when a full load of sodium were to occur during an accident condition. Measures should be taken to insure that the aggregate will not settle below the level of the steel support beams or a structural analysis should indicate that the catch pan strength is adequate.
Response
The Project will specify compaction criteria for the 3/8" Mg0 aggregate to ensure that the height of the Mg0 bed is adequately maintained in conjunction with a postulated liquid metal spill event.
4)
For those liquid metal spills in the RSB or SGB which are adjacent to the containment shell, the impact of the spill on containment integrity should be analyzed.
Response: The Project analyzes the impact of postulated liquid metal spills on plant structures, including any effects on containment / confinement.
5)
Location of the fire detection instrumentation within an area is not specified.
In choosing the locations the flow patterns of the cell atmosphere should be considered so as not to locate the detector in a stagnant area.
Response: The Project will locate fire detection instrumentation 1 1n locations considering the flow patterns of individual cell atmospheres.
6)
How is the operability of the SGB aerosol mitigating damper assured for the sodium-environment it will see?
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Response: The subject damper will be tested as discussed in amended PSAR pages 1.5-46 and 46a.
7)
Although summary information has been provided on the Integrity of the 1
cell liner and catch pan / fire suppression deck systems under postulated l
t spill conditions, little was provided on the effect of those spills on other plant safety-related equipment. A comprehensive fire hazard l
L analysis needs to be performed and reviewed by the staff to determine r
the effect of the postulated spills on the ability to shutdown and
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maintain the plant in a safe condition. The applicant has committed to perform such an analysis, in a letter, J. R. Longenecker to P. Check, 4
"CRBRP/NRC Sodium Fire Protection Meeting," dated June 29, 1982. This l
evaluation should as a minimum address:
(a) the effect of the fire and combustion product release on the plant safety equipment and the operators ability to safely shutdown and remove plant decay heat, (b) the effect t
of vent steam from behind the cell liners (to non-inerted areas of the plant) on other plant safety-related equipment, (c) the justification for i
why the release of 630 pounds of combustion products from those acceptable, i
and (d) the possibility of water collecting in the catch pans due to l
condensation or small leaks in other piping systems within the cell.
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RESPONSE
A. comprehensive analysis was performed to determine that postulated sodium spills will not affect the ability to shutdown and maintain'the plant in a safe condition. The current fire hazard analyses included only part of this evaluation which traditionally were included in the fire hazard analysis report.
Other parts of this evaluation are included in various parts of the PSAR and will be consolidated into the final fire hazard analysis report.
Specifically:
a) The effect of the sodium fire on the safety related equipment and structures located in the cell where the fire occurs is described in Chapter 15.6.1 of the PSAR.
The effect of the sodium combustion release on the plant safety equipment and the operator's ability to safely shutdown and remove decay heat is described in Chapter 6.2.7 of the PSAR.
b) An evaluation has been perforned on the effect of steam vented behind the liner. This analysis indicated that the steam vented from behind the cell liners into non-inerted areas will not affect the plant safety related equipment qualification levels. Thus, safe shutdown is assured, c) The justification forrthe acceptance for the release of 630 lbs.. sodium combustion products is included in Chapter 6.2.7 of the PSAR. Th~e project will provide features to assure that unacceptable quantities of water do not accumulate in catch pans as a result of condensation or small leaks in other piping systems within the cell. The specific features will be discussed in the PSAR l
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1.5.2.8 Sodlum Fires Test Procram 1.5.2.8.1 Puroose The purpose of the ' sodium. fires test program is to verify that plant design -
features for accommodation of sodium /NaK spilIs in air-f11 led celIs w11l result in acceptable cell pressures and structural concrete temperatures..in addition, this test program will be used to demonstrate that the codes used in sodium fire analyses conservatively predict cell accident conditions.
1.5.2.8.2 Procrams The sodium fire experiments have been or will be performed at the Atomics International test f acilities in Santa Susana, California.
The following small scale tests have been completed:
- 1) A f ast spill (approximately 15 gal / min) of 1000 F sodium onto the fire suppression deck surface 2)
A slow spill (approximately 1.5 gal / min) of 1000 F sodium onto the fire suppression deck surface
- 3) A spray (approximately 15 gal / min) of 1000 F sodium onto the surf ace of the fire suppression deck 0
4)
A f ast spill (approximately 15 gal / min) of 1000 F sodium directly into the catch pan beneath the fire suppression deck ft 5)
A spray (approximately 15 gal / min) of 1000 F sodium, ento the surf ace of the fire suppression deck, through a walk grating above the deck
- 6) A spray (approximately 15 gal / min) of 600 F sodium onto the surf ace of the fire suppression deck, through a walk grating above the deck The results of the above snall scele tests will be documented as the test reports become avail able.
In addition to smalI tests, a Iarge scale test wIlI be performed using a large-scale model of the CRBRP catch-pan fire suppression deck system to collect spilied sodium under simulated spilI conditions.
Tne test f acti lty is designed to acco.T.modate a volume gas as large as 6600 gallons of 1000 F sodium with a sodium dischargo flowrate of approximately 70 GPM.
This test will verify the operability of SGB aerosol mitigating dampers by testing under prototypic aerosol conditions.
1.5.2.8.3 Schedule The small scalo tests have been completed. The large scale test is planned to be perf orned'In the last quarter of 1982.
Amend. 73 Nov. 1982 1.5-46
3 1.5.2.8.4 Success criteria l
The small scale tests successfully demonstrated fire suppression deck design features to ensure drainage capabil.Ity and fire-suppression of factivenesst o
No blockage of drain pipes during spill.
Post-spilI suppression of sod!um burning by control of oxygen Ingress to o
sodlum pool via oxide plugging of drain pipes and closure of vent Iids on vent pipes.
o No leakage of sodium from catch pan.
The success criteria for the large scale test are that the catch pan shall contain the spilled sodium precluding soditm concrete interactionsjnd that resulting test consequences are enveloped by those calcuiated wIth the 4~
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1.5.2.8.5 Fallback Position e
)s%wf If the ef fectiveness of the fire-suppression deck / catch pan system /[not demonstrated, alternative techniques to accommodate design basis lIquid metal spill events will be considered and/or prediction of plant design basis accident consequences wIlI be made wIth alternative methods.
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Amend. 73 1.5-46a Nov. 1982
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' Attachment tos-IAP-82-1059 P ge 1 of 2 All welding repairs shall be made in accordance with.a written welding
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4.3 STORAGE COND1TfDNfNG AND MANDf_fNG OF WFlniNG MATERIAL 1 4.3.1 Filler materials shall be. stored, conditioned and handled in accordance l
with the appendices of ASE Code - Section ll, Part C which are mandatory parts of this spectfIcation.
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3.8-C.15 Jan. 1982 i
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7 The catch pan. system is part of th] Sodium Fire Protection System
. gsres) which provides a passive fire suppression system for sodium fires in air filled cells. The overall Sodium Fire Protection System is described.
in Secticn 9.13.2.2.
The catch pan - fire suppression system is an Engineered Safety Feature f
. located in non-radioactive Na and NaK cells.
It's pur ose is to prevent sodium-concrete reactions between the liquid metal poo and concrete following an accidental spill, to reduce pool burning, to limit the tem-perature imposed on the structural concrete, and to limit the amount of sodium aerosols generated during a sodium-NaK spill accident.
4 3A.9.1 Design Description 3A.9.1.1 Catch Pan Types There are two basic types of catch pans located in the air filled cells:
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- 1), Catch Fans with Fire Suppression Deck - This catch pan type is located in PG sodium-NaWcells where the consequences of unmiti-gated sadium-NaK burning would have a significaiit impact on the struc-4 [
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tures or safety related systems.
In these areas the liquid as:?hwan forms a pool in ~the catch pan below a fire suppressi'on deck.
The fire J suppresien deck is designed to limit the oxygen supply available to the pq),,a doodia::t pool for tha continued burning of the - "
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In this nner the con-sequences of/%e =d'a spill are f tigated.
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2)
Doen Catch Pans - This catch pan type is 1ocatehn fe wial sodium-NaK e; RPM cells where the volume of--W:_= spill is small and
/WM *"]~TUllTurHing of'tW'W will not have significant effects.on the b
structures or safety related equipment! The sodium is collected in open catch pans to prevent sodium-concrete reactions with the liquid metal pool.
Open catch pans are also used in cells with substantial sedium leak vol umes.
In these cells, a pool is not allowed to form.
The sodium collects in an open catch pan and drains,into a catch pan cell equipped by gravity, through drain pipes or large openings in the catch pan with a fire suppression deck.
The flow can be lateral or vertical.
One exception is Cell 211A which drains into ' Cell 211 which does not have a fire suppression deck.
Both cells have a common atmosphere and contain the Ex-Containment Primary Sodium Storage Tanks and associated SpecimimM piping.
These cells are inerted prior to the introduction of sodium.
- Further descriptions and catch pan arrangements are presented in 4
PSAR Section 9.13.2.2.
Figures 9.13-3 and 9.13-4 present typical arrange-ments of the two catch pan types described above.
b 3A.9-1 y
- o. w. p,r; uru h cacea in thu e Steam Ganerator and Reactor Service Buildings. Table 9.13-10 of Section 9.13 lists the RSB and SGB cells having each type of catch pan. The con-figurati n of th:s2 cells is shown in PSAR Section 1.2.
3A.9.1.2 Structural Features
, 3A.9.1.2.1 Catch Pan with Fire Suppression Deck The components of a Catch Pan with Fire Suppression Deck are shown on Figure 3A.9-1 and consist of the following:
1)
Catch Pan 2)
Fire Suppression Deck and Structural Support Beams and Columns 3)' Fire Suppresion Deck Drains i
4)
Fire Suppression Deck Vents 3:
5)
Insulation 6)
Catch Pan Lip Plate
\\
3A.9.1.2.1.1 Catch Pan - The Catch Pan consists of 3/8 inch thick carbon steel plate constructed using full penetration welds and foming a leak tight boundary to catch and contain a potential sodium-NaK spill.
In general, the catch pan is "floa. ting", i.et, it' is allowed free themal expansion to minimize themal stresses. Gaps are provided between the concrete structures and the catch pan side walls to pemit the themal expansion of the catch pan.
Around embedments, penetrations, fire suppression deck support columns or other elements attached directly to the concrete structure, a vertical sidewall catch pan plate is provided to per-mit the free floating catch pan to expand or translate relative to the fixed embedment location without imposing additional load on the catch pan (Figure 3A.9-F).
I 3A.9.1.2.1.2 Fire Suporession Deck and Structural Supports - The Fire Suppression System consists of standard metal deck panels, 4-1/2 inches deep, supported on steel framing composed of wide flange beams. The steel f raming is supported above the catch pan plate by stub columns with base plates anchored directly to the concrete floor slab.
At the perimeter of the catch pan cell, the support beams are attached to steel brackets anchored to the concrete walls.
The deck and beam ' structural connections are designed to allow for themal expansion thereby' minimizing themal st resses.
l 3A.9-2 l
,,dIII as a walkway for maintenance ac, cess. The steel grating is not a dt of the catch pan system and does not have a fire suppression function.
, f. pit is. supported by the, fire suppression deck support framing.
3A.9.1.2.1.3 Fire Suopression Deck Drains - As liquid sodium spills onto th'e fire suppression deck it flows through small diameter drain pipes in
, the fire suppression deck and into the catch pan.
These carbon steel drain pipes are welded to the deck and extended downward to a point 1/2 inch nominal above,the catch pan.
The drain pipes are spaced to fom a unifom array over the catch pan.
As the liquid sodium drains into the catch pans, hg the. level of Na in the drain pipe rises, thus limiting the effective sur-4
\\p I.
face burning area of the resulting liquid metal pool to the cross sectional area of the drain pipes.
Burning is teminated when following the Na spill the drain pipes become plugged with combustion products and air is pre-
% P(,
vented from reaching the liquid metal surface within the pipes.
3A.9.1.2.1.4 Fire Suppression Deck Vent Pipes - Vent pipes are also welded to the fire suppression deck.aN cxtad 0:1. '.%
to; cu d: :: "'"?
'ri n
- 1 They.are provided to vent hot gases from.the region below the deck to the cell atmosphere to prevent the buildup of pressure below the fire suppression deck.
b*
y 3A.9.1.2.1.5 Insulation - Insulation is provided under the catch pan floor TL Mnd alongside the catch pan walls to protect the reinforced concrete struc-tbre from excessive temperature.
gyg g u,,;a,m Below the catch pan a g anular insulation mate ial (Mg0) is used in varying thickness to limit t e floor slab concrete emperature and to provide a vent path for the wat r vapor released by the heating of the
' structural concrete. A blanket equivalent) is attached to the% insulation (n':'dsilicate or the -
reinforced concrete walls behind the side. wall ~of the catch pan. A gap between the insulation and the catch pan side wall pemits the free themal expansion of the catch pan.
3A.9.1.2.1.6 Catch Pan Lip plate - To prevent liquid sodium from falling into the gap between the building concrete walls and the catch pan side walls, a continuous steel lip plate is provided along the perimeter of the catch pan.
The steel lip plate is welded to a plate embedded in the concrete wall and covers the gap between concrete and steel walls.
Li p plates are also provided to cover gaps between catch pan and embedments or penetrations anchored in the concrete floor slab.
3A.9.1.2.2 Open Catch Pans The open catch pans are similar to the catch pans decribed in Section 3A.9.1.2.1 except that they do not utilize a fire suppression deck.
Open catch pans utilize insulation under the catch pan floor but not along the side walls.
There is no substantial sedtp hu- ' ; in open catch pans since they are used where either the volu e of the spill is small or l
buu.c> up op
(
f/ utd #
3A.9-3
y"
(./,
~
equire:e.cn the liquid sodium can be conducted'through drains into catch pans with a.
fire suppression deck.
In open catch pans with drains, the catch pan floor is sloped toward the drains to facilitate draining.
A minimum slope of 1/8 to 1/4 inch per foot is used except for cells 244, 245 and 246 where the However horizontal drains (pen catch pan drains in most cells are vertical.
slope is 1/10"/ foot.
The o scuppers) are used in regions where vertical draining is not possible due to <the arrangement of the catch pan cells.
In a limite~d number of cells located above cells equipped with fire suppression decks, the sodium flows to the catch pan below through large lined openings passing through the ficor slab.
Some open catch pans are equipped with a grating to facilitate access for equipment maintenance.
6 3A.S.2 Design Evaluation,,'
r
~
3A.9.2.1 Sodium Spill Evaluation An evaluation of the consequences of a sodium /Nar, spill is provided in
)
RSAR Section 15.6.1.5.
The methods and criteria used 'for the evaluation of the. catch pan system are discussed in PSAR Appendix 3.8-C.
3A.9.2.2 Catch Pan System Analysis and Design The catch pan system is described in Sections.3A.9.1 and 9.13.2.2.-
.The Design Requirements, load Categcries, load Combinations, Stress and Strain Allowables, and Design Analysis procedures are given in PSAR Appendix 3.8-C.
Attachment D to Appendix 3.8-C gives the basis for the strain criteria and strain limits adopted for the cell liner system and utilized for the catch pan system under sodium spill accident conditions.
7 The catch pan plate has been designed for the loads and temperatures specified in Section 3.8-C, Attachment A.
The catch pan is designed as a l
free floating basin to collect DBA sodium /NaK spills.
The catch pan is free to expand under the themal loading of a DBA sodium spill thus minimizing the t
induced thermal stresses.
The major stresses in the catch pan are generated by the hydrostatic pressure of the sodium /NaK pool including the dynamic effects during an earthquake.
The hydrostatic seismic effects were calculated using Housner's theory (TID-7024; Nuclear Reactors and Earthquakes by T. H. Thomas et al. USAEC, August 1963).
The reduced strength of the catch pan plate due to sodium spill temperature conditions has been included based on Reference (6) of Section 3A.8.
l The fire suppression deck and fire suppression deck framing support f
l structure have been designed based upon typical panels and using beam i
i theory.
Seismic effects were considered based upon the applicable floor l
response spectra by using the appropriate seismic accelerations.
The I
reduction in steel strength with temperature was considered in determining the allowable stresses.
The catch pan is supported on granular insulation.
i Q.)- 9 4
,-n,
The. primary function of the insulation is to provide a themal barrier to prevent the degradation of the structural concrete slab supporting the catch pan under DBA sodium spill. conditions. The insulation also provides a uniform support for the catch pan plate while providing a vent path, through the voids in the granular matrix, for the release of water vapor generated during the heatup of the structural concrete.
Insulation is also provided, in some cases, along the perimeter of the catch pan to provide a thermal barrier to protect the structural concrete near the sodium pool.
The insulation is attached to the structural concrete and separated from the catch pan plate by an air gap to pemit the unrestrained growth of the floating catch pan.
3 -
3A.9.3 Testing For testing program see PSAR Section 1.5.2.8.
N 8
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INSULATION *
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e FIGURE 3A.9-1
of the sodiu. In the CVST at or below. 5 ppm.The system provid The cold trop used for this
(
44 service is separate from those used for reactor and primary loop sodium purification.,
/N55" A 44 sl and Processing kystem described in Section 9.3-2.
These two systems. operating together, provide the D
. Service (DHRS).
sodium temperature to approximatelThe DHR$ is sized to limit the average t
half hour after reactor shutdown. y 114DoF when the DHR$ 15 initiated one-pony motors are assumed operational.Under this condition, all primary pump When the DHRS is initiated twenty-four hours after shutdown, the average bulk primary sodiu l
59l on removal of the required reactor decsy heat by spent fuel within the EVST.
nerated heat load is approximately 11-1/2 MW, with DHR$ initiated o j
26 reactor shutdown.
9.1.3.1.2 Design Descrir, tion The EVST design and operating decay heat leads and sodium coolant outlet temperatures are given in Table 9.1-1.
other than the cooling system itself, are the storage ves i
{
tank and the internals. The internals 44-and support the spent fuel assemblies (contained in sodium-filled C permitting them to be satisfactorily cooled.
I turntable has already been discussed in 9.1.2.1.The structural design of the 44
$9l be designed, fabricated and inspected in confo codes and standards (see Section 3.2) to provide a leak-proof containment ppropriate for the sodium coolant.
elevation so that normal fluctuations due to changes in temp number of stored components do not uncover the top of the CCP's in which the spent fuel is stored.
During off-nomal conditions. such as a leak or rupture in either the vessel or the cooling system, the vessel sodium out-side the CCP's cannot fall below the minimum safe level.
Thts level is defined as that below which fuel cladding temperatures would exceed the possible location within the storage vessel. The sodiu 44 The EVST sodium inlet lines contain antisyphon device cooling system leak from latering the vessel sodium below the minimum 44 safe level.
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'to cc:h cf the nore:1 EVST cooling loops. The DSP.S IcK 4
- expir.cion tcnk is isolt.ted end the EVST licR pump is incret. sed :
4:D tc Th2 covcr gas space in the two EVST Ic if.,
,J lc:r.403 gp: cch.g:nsion tcnts is cross-connected to equalize tank I;aK
.P.-
N. lev 01s.
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a 9.1.3.i.3' S-fe^r Cvelustion
=
b.
J TimEVST cooling ccpability can be provided by either of two iden-
'W@
ticiil, forced convection cooling circuits. each of which can removg 1803 ktf uhile c:aintaining a mtxictai EVST sodium outlet temperature of SS10 F.
y
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4
- In.!the 'cxtrcn:ly unlikely event' that the normal circuits are un-6 avail bic,. hut til.1 be remwcd throu2h a third independent (backup) natural A
conv:ctic:tecoling circuit. At 1603 Ltf this' backup cooling circuit will usintain (; die 2 tc";icrcturcs within the EVST below 775 Fv J
0 2
... "criticcl temp 2rature in a fuel assembly, from the standpoint s
Tha of safetys is tha.pg.k fuel cladding. temperature.
The normal and emargency Mt limits.croitM.,.n h-Table 9.1-2.
- f. j-g th:. tiia s;II.: 70:ik fuel cladding temScrature is approximately 1000F greater c'iua outict temperature sliora in Table 9.1-1.
Hence, no damate
'p to tha stcrcf fuc1 essemblies will occur.
T
.a j.
'}Thi' codas: and standards to which the EVST vessel and the sur-jly' roundinginrd-tank, are designed and. fabricated as ure that leakage of sodium till;)2 a.very le i probability event.
At the minimum level,
.j adequate coalir.giis' maintained with no temperature inceases from those
'j
.k-shorn in anblo19:14 Jput?tY f Yl'Y#b*
Er.cidof the~ three sodium cooling loops is designed against the
'q possibility-of ttiasn-mode failure.
Two pump suction lines are provided.
D.;
vithin the EVST'for, normal sodium circuit tio. 2.
The open end elevation P
of each is different,.one high, cne lort.
Each of the two lines is d
sep:rately valved c 9
loop, th icolation;xternally to the EVST.. After the initial fill of the I
vclva in the low suction line is locked closed and r: mains cloccd (except for periodic testing) throughout the plant life, i
This lou.tectica line is used onlyin the event of a major loop or vessel
- l 1
ngtura.cC ra pump suction line is provided within the EVST for normal coeling circuit !?o.1.
The open end elevation of this line is between
- 1 those fo6 circuit t{o. 2.
This line is valved externally to the EVST, and
'i is called c."t;ith" punp suction. line.
During normal system operation, one 3
l of the nort-1 cooling loops is operated using the "high" pump suction line, i
The suctica -line(s)' in the standby nore:1 loops are closed.
In the event
+
of a ns.idr fcilure i(rupture) of tha operating normal soditna cooling loop, the isolttion valvyin the pump suction line is closed by operator action from the centrol rdom, signalled by concurrent alarms, indicating low level l
.,. r.. ;
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\\i in the (V5T ad a sodium leak within the cooling loop cell.
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tion valve should not be closed the EVST sodium level could only b If the isola-to the (ht h) pump suction outlet within the tank.W 51 phoning from the 44 turn line fs prevented by an antistphon vent in this line if a failure of normal cooling loop occurs, as described previously, the
,44!
standby normal cooling circuit 44l its lower pump suction and increasing pump flow to thecan be immediately a j
i 400 gpm. A wok st$
pf"'** W n rate of y* ~s or o.teetr erfMtwf 16 mr IVS' l'CC' v
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be activated after the first loop has expertenced a fa (backup) circuit will be brought into operation.
vided within the EVST for the backup cooling circuit.One suction line is pro-The open end eleva '
j tion of this suct.fon line is below the lower section line of normal c circuit No. 2.
Flow back to the EVST is through the fill / drain line.
Siphoning from this return line is prevented because the entire back 44 loop is elevated above the sodium level in the EVST.
Failure of any component. In any can cause Icss of only the cfreutt in which it is located.of the sodium or NaK loo
?
44 minutes to provide essentfallystandby or backup cooling circuit ca The normal i
potential radiologfcal consequences of an extremely unlikely re 44 \\ 591 EVST sodium to an inerted cell is described in Sectio j
. electrical power are on the Class IEAll components of the normal sodi t
EVST cooling and reactor decay heat removal. power system, to ensure, continuous In the event of complete loss of external power to the plant, power to both of the normal cooling circ 44 is provided by the plant diesels.
Imediate activation of the ofesel-powered supply is not necessary for the EVST sodium pianps sinee' the sod volume within the EYST provides a heat sink to minimize sodlum tempe l
rise during loss of circulation.
mately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> beforg the maximum sodium temperature in th 1
44 i
the EVST reaches 600 f.
l NaK puros and airblast fansActivation of the emerge cy power supp 59 availability of DHRS for rea.ts reautred within % our, however,ly to the ctor decay heat remov 1.
to ensure the 44 natural draft heat exchanger.The only " active" component in the back 1
i 26 not require connection to the emergency power systemIt is operated man 44 Isolation of all of the cooling clated NaK loop) in separately shielded. Inerted cells precludes bo radioactive sodium fire paring the operability of the other.and the possibility of any failure in one loop in-o 1
k kend. 59 Dec. 1930 9.1-27
I 7
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10' OF Atlat sL ANKET RECton 10' OF FutL piGroet Fig.are at-12A EYST Sodiun and riozzle Elcsations i
9.1 8 4 A
9.3.1 Sodium and N_aK Receivine System 9.3.1.1 Design Basit This system provides the capability to receive and melt fresh.
' solidified sodium, delivered to the site in tank cars or drves, and transfer the sodium to primary and intermediate storage vessels. System capacity is based on moltout and drain of an 80.000-1b capacity tank car in 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.
Tha system r.:ceives and transfers to storage all Nak used in the
- All fresh sodium and NaK wi.11 be filtered prior to stora nents used for sodium transfer will not be used for NaK transfer.ge. Compo-The system also provides the capability to rereve sodium and NaK from plast systems for off-sit,e disposal, 9.3.1.2 DesignDescrAtton This system consists of a tank car oil heating station for meltout of sodium tank cars, a clam shell heater for melting drums of sodium. transfer piping and valves, and filters for cleanup of fresh sodium or Nat. The piping and filters for the NaK are on a portable rig, and independent of the sodius system.
Both systems are shown on Figure 9.3-1.
Transfer of sodium and NaK to system storage vessels is by gravity flow.
(
9.3.1.3 Destan Evaluation i
The Sodium and NaK Receiving System components are designed to accepted industrial and nuclear standards to insure structural integrity and operational reliability. The components, applicable design code and class, f
plus their seismic category are Itsted in Table 9.3-1.
s.s et u s e u, A11[p ping, valv%and filters of the sodium and NaK es Receiving ystem are con,struction fres Type 304 stain r-450'F and 150 F respectively.The design temperatures for the soditas The design pressure for both sodium and NaK components of the receiving station is full vacuum to 20 psig.
i W
l 9.3-la Amend. 40
\\
July 1977 Cos.1995
y
(
opriatoornecessaryc$rictt9recalvings:diunc0 cite, i
sp rergancy planninguring loading.
with local offletals Q
be taken to consider an outsid fire Gl s The system monitored for external leaks of liquid metal by I
s leak detection devices.
gg This system for handling the incoming fresh sodium and NaK does not present any radiological haaards, nor is it involved in any way with
[
i reactor safety. Portable sodium carbonate fire extinguishers and person-nel protective equipment is'provided by the Sodium Fire Protection System for protection against potential sodium or NaK fires that can occur during i
loading and un1 The cells containing system storage
}
vessels are equ,oading operations.
ipped with permanently installed fire protection equipment as describesi in Section 9.13.2. 4 -
2 9.3.1.4 Tests and Inspection
^
a Prior to'use. leak checks will be made and instrumentation and preheat capability will be checked according to specific procedures. The system filters will be tested to assure that no blockage exists.
I J
9.3.I.5 _ instrumentation Requirements Instrumentation and controls (I&C) are provided for operation, performance evaluation and diagnosis of the Sodium and NaK Receiving System. These functions are re i
full range of normal operation. quired for off-normal, as well as for the Details of the I&C for the Na and NaK
-)
receiving system are shown in Figure 9.3-1.
r 58l46I Temperatures and the tank car sodium level are measured to monitor system status during operation.
l.eak detection sensors are strategically located to alert the operator of a break in the system in order that correction action t
may be taken. Table 9.3-4 indicates planned location of leak detection sensors.
No automatic control instrumentation is required for this sub-system as all operations are manual. 0This subsystem is non-nuclear and i
operated at peak temperatures of N400 F.
Therefore, commercial grade in-strumentation is adequate to monitor subsystem performance. After initial i
transfer of sodium and NaK into the plant, the system will be inactive at I
ambient temperature except during actual transfer operations.
I l
9.3.2 Primary Na $torage and Processing 9.3.2.1 Design Basis l
1 This system provides primary sodium purification (cold trapping),
provides storage for the sodium used in the reactor vessel, the PHTS loops, and the EVST, mitigates the change in reactor vessel sodium level and accow modates thermal expansion and contraction of primary sodium.
This system, working in conjunction with the EVS Sodium Processing System, also provides a means of removing reactor cecay heat in the event of loss of all the steam l
l i
generators.
i N
ry
{ }
q 1o, i.g conditi na t J i m nea. to,1..t 11guld metal leadin ur n
,1..to,,,.qo 4.3-1
~
Specific syste, design basis are as follows:
a.
Primary sodium purification - limit the oxygen content to 2.0 gpm and the hydrogen content to 0.2 gpm, and maintain the tritium content within limits which will satisfy plant radiological release criteria.
b.
Primary sodium storage - provide on-site storage capacitf suffIclent to permit anticipated maintenance on plant systems.
Total storage capacity is provided to permit complete drainage of the reactor vessel and loop piping to the first high point.
This capacity wilI accommodate the above, tne 3 PHTS 1. oops or the EVST, but not simultaneously.
c.
Reactor level control - provice the capability during alI plant operating conditions to maintain the reactor vessel sodium level below the reactor head reflector plate.
d.
Primary sodium expansion - accommodate thermal expansion of primary sodlum from 4000F to PHTS structural design 0
0 temperatures of 1015 F hot leg and 765 F cold leg.
e.
Reactor decay beat removal - system sizing is based on limitingtheaveragebulkprimarysodiumtemperatureto approximately 1140 F when the DHRS is initiated one-half hcur af ter reactor shutdown, c?" ;:: p.-
,T ;., y m..r y;.-
=t e r-s.
cre- + ? :::P.
With DHRS Initiated twenty-four hours'after reactor shutdown, system size will maintain the average bulk primary sodlum temperature below 900 F, ;!i :n pr' r, p=p pen n. - wra o.. uy.
9.3.2.2 Desian Descr!otion The Prirrary Sodium Storage and Processing System consists of the following components:
a.
Primary Sodium Overflow Vessel b.
Primary Sodium Makeup Pumps (2)
)
c.
In-Containment Primary Sodium Storage Vessel d.
Ex-Containment Primary Sodium Storage Vessels (2) l -
e.
Primary Sodium Cold Traps (2) f.
Makeup Pump Drain Vessel 1
g.
Interconnecting Piping and Valves h.
Primary Sodium OverfIow Heat Exchanger I
l 9.3-3 l
Amend. 64 Jan. 1982 l
l l
t l
pump maintenance can be accomplished af ter shutdown and Isolation of he f ailed pump from the system.
The pump la deelned, the cell atmosphere changed to alr, and the necessary precautions taken vin respect to radioactivity, to allow pump repair.
Two liquid-cooled sodlim cold traps, errenged In parallel, are included in a bypass on the reactor makeup return line to provide sodlum purification. Each and 600'F (reactor hot standby temperature). trap is rated at 60 gpm at norm Our 'ng nors,al plant operation, one trap is le use and the second is In standby. A.Ithough both traps can be operated, a single trap is suf ficient to remove entirlpated oxygen 3nteska3e and mcIntain the oxygen content below 2 ppe.
The concentration at triflum in the primary sodlum is also maintained et a lov 46 level by cold trap operation. Operation of one primary cold trap, cer.bined i
with he trittim dif f usion through Me IHX to thi Intermediate system maintains 46l the tritium content of the primary sodlum at less than 3tl T/gm Na, l
During a shutdown for fuel handling, both cold traps ma?
y be operated, if necessary, to provide a maximum cleanup flow of 160 gpm. The total capacity is designed to provide for removal of potential oxygen Inteakage during fuel handling rapidly enough so that no additional plant downtime (over and above
' trap (s)that required for fuel handling and normal startup) is required.
46 Flow to %e is controlled by throf tle valves in the outlet from ea-h trap.
Electromagnetic flow meters are provided to monitor flow through each pump and each cold trap.
System arrangement also permits independent cold trapping of s'odlus In the overflow vessel or In the In-conf alnment primary sodlum storage vetsel during shutdown situations, when makeup to the reactor is not required.
pumps, which can also take suction from these vessels, are used for theseThe makeup operations.
b.
Circuit Doer _ation During Reactor Decay Heat Removal _ - The overflow and '
' " ~
makeup circuit is designed to provide reactor decay heat removal la the event of loss of all the steam generators in the Intermediate heat transfer system. Operation during this mode is referred to as the Otract Heat Removal Service (DHRS).
Switchover to this mode of operation is accomplished rewotely from the control room.
i DHR$ components are subjected, durIng plant service, to numerous reactor During a scram, primary sodium temperature decreases.
The resultant scr ams.
contraction of coolant lowers the sodlum level within the reactor, and the sodium overflov is laterrupted. The makeup pumps continue to operato, transferring sodlum In the overflow vessel back to the reactor vessel until the sodlum overflor resumes at a Ic.er tenperature - approximately 6004.
The primary cold trap lifettme is estimated to be 13 years.
This tra However,p will be too radioactive to permit hands-on maintenance.
steel shielding has been provided around this trap to expedite the replacerent operations. The procedure for primary cold trap replacement is as follows. partially dgain the sodlum and NaK while maintaining '
a terperature of 300-400 F, remove all heater power and allow the remaining sodium to freeze, cutand cap weld the sodium and NaK lines cut the electrical leafds. unbolt the supports pull the I trap by crane from the cell, and place it in storage provided in[w g _ j fg 3
plant.
.{3, y p ma
l Table 9.3-7 l
DESIGN TEMPERATURES AND PRESSURES
- Na and NaK Receiving System Primary Cold Trap NaK Cooling System ~-
Sodium Piping and Fresh Sodium Filters 450 F, 20 psig All Components 6500F, 100 psig 0
NaK Piping and Fresh NaK Filters 1500F, 20 psig Intermediate Sodium Processing System Primary Na Storage and Processing System Cold Trap, Economizer Overflow Vessel 900 F,15 psig and Pumps 7750F,-225'psig 0
Makeup Pumps, Cold-Trap 9000F,100 psig Overflow Heat Exchanger 6500F,100 psig
' Cold Trap Crystal 11zer '7500F, 225. psig. '
0 IC Vessel, Makeup Pump Drain Vessel 650 F, 50 psig and Connecting Piping EC Vessel 4500F, 50 psig Piping PHTS Drain from 51A/81 Interface 10150F, 200 psig Piping, Normally Opera-to " Spec. Change" ting Cold Trap Circuit -
PHTS Drain From " Spec. Change" (incl. stand by trap 0
to Second Isolation Valve 650 F,.200'psig and drain lines to-Overflow Line and Makeup Pump first isolation 0
valve) 775 F, 225 psig Suction Line - from OV to isolation Valves on Pump Suction Line 9000F,15 psig Balance of Makeup Circuit 9000F,100 psig Between IHTS Loops and.
All Other Piping 6500F,100 psig First Isolation
~
0 Valve 775 F, 325 psig EVS Processing System Cold Trap (including piping thereof) 7000F,100 psig All Other Drain 800 F, 100 psig Piping 7000F, 100 psig.
0 EVST Backup Sodium Cooler Piping EVST NaK Storage Vessel 4
1500F, 50 psig NaK Drain Piping from Loop Isolation Valve to Storage Vessel 1500F, 100 psig 0
All Other Components and Piping 650 F,100 psig i
0
- All System 81 components designed for full vacuum at 450 F
/
9.1-20d 1
- Ir.:. :.i'.;r.t cc Ch c trtr.:fc: b:.b:::: t!.c EYST stdica cooling lee and t: : r:Citn t.cor:.;c vcotels is prcycated by b:o r.orr.011y clo:cd iwittica v:1v:.1 fr. :c:ic: bet'. acn tha stor; 2 v:ssel.nd ec:h fill cnd 6 cin connt:.t.:6 to ti a ecolir.2 losps cc th;:::a in Figure 9.3-3 t
IntMrtcat th:.:fte of sedica to cr.d from the Ei'5T itself, via
?
its dr5tn lir.'; (fr:a t's b:tt:a of tha brcIxp redium eccler). is pro-E' vinted by c th..r.d t _::,1 pic:o in tha dre.in lina. Once the EVST is filledr th2-sr:n -picca-is recoved end the rcr.nining pipa ends sealed by flang:s, to ricr:nt :cidantel drain %2. The removed section is i
physically lecttd hiEh taough so thct cny sodium leak at the flanged f
joint ctr.:*.0t.ddn the EVST belott a le' ei v.hich would inte.:rfere with t
v the coolinterfrtca.-
4,)
9.3.2.3 UUP..m D.rltr.* t.i en Th; c5tc$ cr.in nGIcFe c'esig.6d to accepted indUstnai t.r.a r,ec1ctr ste.ri:-d to insure structercl intc;rity cnd oparctionci reli:bility.' Ti:2 cc:,.:n.r.ts, cppitecblo dcsir.n coda and c16ss, plus tt.cir scisr'c crtq:ry. tra liste.d in Tcbic 9.3-1. c
/.11 r:. tc.cf t!.~. system tre tc.cnitor:d by leak detection devices, with alcrc; fc.dctc: Lien of external lockcce frca piping and compon2nts.
Tha s#~
CI
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9.3-7a kmnd -[
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Oct.. LG Dr.
A.
6
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instrumentation also will determine the occurrance of internal leakage from one part of the system to another, and alert the operator so the systems can be shut down for maintenance or repair.
Those cells which house the Primary Sodium Processing System will be inerted during system operation and during all periods while a potential Na spill could otherwise result in potential off-site radiological release excess of 10CFR20 limits.
The Primary Sodium Storage and Processing System is connected to the reactor by the overflow and the makeup return lines.
The nozzles for these lines are located near the top of the reactor; so that', in the extremely unlikely event of a line failure, there would be very little sodium lost from the reactor, and reactor cooling would not be affected.
35]
All of the system except for the ex-containment storage vessels are located in the RCB, in cells which provide shielding, an inerted atmosphere, and tornado protection.
When it is necessary to store sodium from the Primary Heat Transport System in the ex-containment vessels, it is radioactively decayed for approxi-mately 10 days before it is transferred to the ex-containment vessels.
All components of the overflow and makeup circuit (wh'ich may be required for removal of reactor decay heat) are designed as Seismic Class I
(
components.
The makeup pumps are connected to the emergency power supply in order to insure operation during decay heat removal.
MMC Theworstin-containmentacNdentforthein-containmentprima@
(sodium storage tankJthat can be postplated)for th's system is rupture of the Fovert low vesse4which could dump OfM, Hic gal. of primary sodium into the cell. This accident is discussed in Section 1;;.G.
i.
G.S.
o The possible plugging of the overflow line is not considered a
.i credible event, because it is an 81n. and 6 in. line, normally flowing at 46 150 gpm, with the line sloped to the overflow vessel at 1/2 to 3/4 in./ft.
The sodium is main'tained at a low oxygen content (2 ppm or less) which, combined with the high temperature, keeps oxides from building up in the line.
If somehow the line we*e plugged, the reactor sodium level would slowly rise, until highlevel alarms initiated operator action to shut down the plant.
Shutdown lowers the reactor sodium level, and no safety aspects are involved.
9.3.2.3.1 Analysis of Loss of Cold Trap Cooling In the event cooling is interrupted on the PHTS cold trap and sodium flow continues, the sodium temperature in the crystallizer will rise rapidly and approach the inlet temperature, which will be up to 8800F.
The consequence would be dissolution of the solid sodium-oxide (Na2 ) and solid sodium hydride 0
(NaH).
i36 Amend. 46 Aug. 1978 9.3-8
Dissolution of Nap 0 and NaH W-If the PHTS were clean (s2 ppm oxygen and s0.2 ppm hydrogen) and the first cold trap were filled with Na20 and NaH, the interruption of cooling on h
the cold trap without simultaneously cutting off sodium flow could cause a F
maximum release of oxygen and hydrogen to the system by dissolution.
The hot scdium continuing to flow into the uncooled crystallizer would raise its tem-L perature rapidly and cause the Na20 and NaH to go back into solution.
i The time available to take corrective action (e.g., to shut off r
sodium valves and flow into the cold trap) depends on the rate of dissolution.
Calculations were made of the time required to dissolve the. entire contents of the first PHTS cold trap as a function of the sodium temperature in the crystallizer.
Table 9.3-5 shows how this time changes significantly with temperature.
It shows that there is some minimum temperature required for all of the Na20 or NaH to be completely dissolved.
Below this temperature, tne system would reach saturation with Na20 or NaH after a long time of recirculation through the trap, and the traps would contain a residue of solid Na20 or NaH.
g3 P
The first cold trap has been estimated to contain 13 v/oq(volume percent Na20 and 87 v/o N-H at end-of-life, which is after about M years of full-power operation.
Table 9.3-5 shows that it would take 2.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> with 8000F sodium flowing at 60 gpm to redissolve alt the Na;0 while it would take 7.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to redissolve all the hydrogen.
If the sodium were 4500F, it would take 138 hours0.0016 days <br />0.0383 hours <br />2.281746e-4 weeks <br />5.2509e-5 months <br /> to dissolve all the Na2, but only 25.4% of the NaH would be 0
dissolved after a long time (theoretically approaching infinity).
Conclusion There is on the order of at least an hour available to the operators to take corrective action following loss of cold trap cooling before enough oxide or hydride can be dissolved from the cold trap to raise their concentrations in the PHTS to saturation levels.
Assuming that the sodium flow valves were closed within hours af ter loss of cooling (, no poten-tial for plugging any part of the PHTS would exist. Above 4400F PHTS sodium temperature), the oxygen could not reach saturation even if all Na90 were redissolved or flushed from the cold trap.
Above 555vF, the hydroaen could not reach saturation even if all NaH were redissolved.
i 46 Safety related instrumentation will indicate and alarm a cold trap high temperature condition to the operators to assure remote manual 46 l closure of the cold trap isolation valves. This will prevent dissolution of enough hydride or oxide to preclude safe cooldown to refueling con-ditions.
Even assuming instrumentation failure and no operator action at all, the dissolved oxide and hydride will remain in solution in the coolant both during reactor operation and following shutdown to hot standby condition.
Consequently, operation of the cold trap cooling l
system is not a safety function and the system should be considered a non-safety class.
However, the primary cold traps are connected to the reactor coolant boundary through double automatic isolation valves.
%0 Amend. 46 Aug. 1978 9.3-8a
cf 160 pgm). The total maximum heat transferred from two traps is approx-46 imately 270 kW. The NaK flow through each trap is regulated by a control valve and a temperature sensing element in each col.d trap.
NaK volumetric changes in the system due to temperature variations are accomodated within the -EYS M P rp:r: M-tir' ::nn:ded to th: hi ;hi pc'-t :f th: cyc t ~-
t primavg cold trap kjak. skorage Wsse. }.
A diffusion cold trapr100:ted en the celd !:;; cf the M P 100p -
(oxide removal). (See %ure 9. 5-4)is provided for system cleanup bet:: r the M:M ::cler 3rd 'S 9:K pr The NaK loop is taken up to a near isothemal condition at 600*F and circulated for processing by the NaK diffusion cold trap during ini-tial cleanup, following maintenance operations, or at any other time when maximum cleanup capability is required to reduce the impurities which may have accumulated in the loop. Heat is provided by the pump.
9.3.4.3 Design Evaluation The Primary Cold Trap NaK Cooling System components are designed to accepted industrial and nuclear standards to insure structural integrity and operational reliability. The components, applicable design code and class, plus their seismic category are listed in Table 9.3-1.
Des 8n bpdur 3 cd preures cne pes
- rd,k.%3-2 e
The NaK Cold Trap CooTing System is a nonradioactivo system.
The failure of the system causes shutdown of the associated cold trap which would, after some period of time, require an orderly plant shutdown, but would create no safety problems.
y The system is monitored by leak detection devices for both inter-nal and external leaks with alanns to alert the operator to take corrective action.
The pressure of the NaK in the cold trap cooling system is maintained higher than that of the sodium in the primary cold traps in order to insure in-leakage of NaK rather than out-leakage of radioactive sodium. The NaK is compatible with the primary coolant and NaK inleakage will have no deleterious effect on reactor operation and safety. The immediate result of a NaK-to-sodium leak will be an abnormal decrease in both NaK level and cover gas pressure in the Na storage vessel.
Both level and pressure are monitored and provided with high and low alanns for leak detection (high level indicates a Dowtherm-to-NaK leak).
Due to a low reserve head in the tank, a large leak will stop due to loss of suc-tion head, and this will also be detected by low flow alarms on system flow meters and high temperature alarms on the pump. Upon indication of a leak, the operating cold trap will be immediately isolated to minimize the NaK in-leakage. The cold trap will be solidified, removed, and replaced.
l The NaK storage vessel is a vertical vessel in order to maximize the change in NaK level for a given change in inventory, thus enhancing the capability of the level indicator and alarm to sense and detect relatively small leaks. A realistic estimate of NaK inleakage, prior to cold trap isolation, would be 25 gallons or less. A more accurate estimate will be
)
l made when system arrangement and component designs are finalized.
3
,1 t
9.3-H Amend. 46 l
Aug. 1978 l
l l
j The system also provides the capability to (1) fill the IHTS loops and l3J[2) purify sodium in the dump tanks, independe i
tem) l permit transfer of sodium from one dump tank to another.
9.3.5.2 Design Descriotion The Intennediate Sodium processing System provides purification of t
the sodtm in each of the three IHTS loops.
The system does not provide for storage of the IHT5 sodium.
tanks, which are part of the Steam Generator system.This capability is pro The Intemediate Sodium Processing System does provide the capability of transferring sodium into the loops from the dump tanks.
The same piping network allows the filling of each dump tank with fresh sodium from tank cars gr drums at the sodium receiving i
station.
through the same fill Itnes. Sodium removal from the tanks'into tank cars can be acci i
i The system includes the following components:
Intemediate Sodium Cold Trap Peps I
a.
b.
Intemediate soditan Cold Traps Interconnecting Piping and Valves i
c.
Refer to Figure g.3-5 for the P&lD and Figures 1,2-8 and 1,2-22 for layout and arrangement.
\\
Each of the three IHTS loo cation system consisting of a pump,ps is provided with a separate purtft-i A single trap per ! HTS loop is sufficient to remove antic and piping.
pated oxygen and hydrogen inleakage and to limit these impurities to a maximum of 2 and 0.2 ppm. respectively.
50 cold traps maintain the tritium level in the intermediate sodium at 0 01 In addition. the intermediate utiT/gm Na by effectively trapping about g85 of the tritium which enters the system by diffusion through the !HX.
i 5010.016 C1/ day, diffuses through the steam generators and enters t Most of the remaining trittum.
i 46 system.
The Intemediate Sodium processing System is also dump tanks such that the sodium in the dump tank may be processe system.
sodium from the dump tanks into the loops with a sm 46 gas pressure being maintained on the dump tanks.
transferred from one dump tank to another by gas pressure.an also c i
Sodium c be The IHIS cold trap lifetime is regeneration process is adopted.
a* 3.25 yr unless a.
The procedure for re.
placement of the crysfaltigee it. A g. A. //
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c.3.5.h 1 li-EM1v: tion 1
h.a In's.rc: dict 6 $$d.D Prc:ening System com.c:..nts tro de:ica:d to ac:gt i:.CSrici and nu:1c.c ttend:rde to insurc structural fr.tc2rity rt.'.:O n 1 rdic.hility. T!;a cer.p:n:nts, cpplictble desita ccde cnd ander:G;;t ci t.ss,
tl.dts'.isr.ic cti.ct. cry cro lirtt.d ht Tcbic 9.3-1. Fany.
G.1le. t.5-?.
n T!.a cyctc is monitored by le k d'nv co.ctection devices, with alarm for t
ssn w so.A yecceav.:e arc.
o tem [oem I
dete:tica lcf cnternc1 lechtga from piping tnd components.
' 4 r
' Tl.Y.Intcic; dicto Sodium Processin? Systei is a nonredio:ctive i
systc'. *TELt-2 fd11ure in a purification circuit is censidered the test tig.ift:ttt cvent, be:cuco it ultir:stely ccuses less of the IHTS loop The loss of fluid i::ald b2 sicnticd Ly the level i
to n.M:3 f t it.c:.m::ted.
i it.fic:ter: ca tha' IlfiS lcop cup.nsica terk. cnd operators could immdictcly -
isoltto t!.o puriftettica circuit (rc ste controlled isoittien valves).
T:.is cv g t i:E: d cr.uso loss of onc IllTS Toep beccuce of the inchility to
[
c; int:.in rc g ired iurity 1cvols, but the plant cculd contir.ua to operate t
3 losps at a rcduccd poear icvel.
Powar outage to all e n t!.2 o C. c. tt:
prps. cr 1 css of ccoling to all cold traps, may cause plant shutdoun.
l tut e: id. dt centtitute a scroty problem.
t 9.3.5.
Te 5ts t:id'Inrcc:tions I'
I.c.h ch::hs will ba cade on the system prior to filling with
~.;
1 sodit:1.. Ir.strenantation and prehtat captbility will be checked prior to socica. fill..according to sp2cific procedures.
Following sodium fill, j
the systsn' pill be operationally tested.
4 9.3.5.5. IInstrueentation Recuirements,
i:
Ir$trumentation and controls (I&C) are provided for operation, perforr:.r..0 cvaluation, and diagnosis of the Intemedicte Sodium Processing Syste.a. 'E.tra functions are required for off-normal, as well as for the full rcnce of nom:1 operation. Details of the 1&C for the subsystem are The sha:n in tha pipir.2 cnd instrum ntttion diagram, Figure 9.3-5.
follct:ing I;C is rce,uired to ensura safe o;:eration of, and to prevent exter.st:c.dt age to, tha Interm2diate Sodiem Processing System.
Tempertures and loop flow c.easuremants are provided for all Critical temperatures and flows are systes.tc conttor their status.
alarr:d tc alcrt the cperator to off-normsl operations. All EM pumps ara maasure:r. ants and winding coolant loa provided 1:ith winding temperature:These macsuramants are alcrmad for the off-normal cc f
fic,i irdettion.
and inter. :hed to automatically shutdo.n the pump to prevent dtmaging it.
I i
Cifferential pressure sensors and flow naters are provided to alert the c crctor to i:: ible plugaing of the cold traps or insufficient cold trsp fic..
f..i C.2 b:.ilo.:s setl valves cro providad with leak detcetors, as 1
indicttci r. Tsbic 9.3-4 All valv:s are provided 4.7 kcend.
- .5 9.3-14
?.n--WNe f
e... g.. u l':-1.. M ::~.-
U y-W;C -
l
TACLE S.13-9 SPILL PARAMETERS Total Max. Flow
- Potential 0[II I
Rate 5p111 Vol?*
Cell (gpm)
(9,j3 (gal)
Reactor Service Buildingt 3rd Loop NDHX 332 44 730 730 EVST NaK Storage 350 1
1500 1500 Vessel EV5T Exp. Tank 352A 44 430 430 EV5T Exp. Tank 353A 44 480 480 j
Pipeway 354 44 440 440 Pipeway 355 44 440 440 Steam Generator Buildinott Reaction Prod.
207 1100 35200 35200 Tank No. 1 Reaction Prod.
208 1100 28400 28400 Tank No. 2 Reaction Prod.
209 1100 39600 39600 Tank No. 3 Ex. Cont.Na 211 50000 Tank Rupture Storage Vessel 3oooo
(-
Valve Gallery 211A 4 0000 -
Steam Gen. Loop No. 1 224/
1100 35200 35200 244 Steam Gen. Loop No. 2 22S/
1100 28400 2B400
-245 Steam Gen. Loop No. 3 226/
1100 39600 39600 246 18 Pipe cell 227 1100 35200 35200 Loop No. 1 IB Pipe Cell 228 1100 28400 28400 Loop No. 2 IB Pipe tell 230 1100 39600 39600 Loop No. 3 INTS Shield 231 1100 26600 26600 Cell Loop No. 1 IHTS Shield 232 1100 28800 28800 Cell Loop No. 3 IHTS Pipe Chase 248 1100 22100 22100 Loop No. 2 IHTS Pipe Chase 251 1100 20200 20200 Loop No.1 IHTS Pipe Chase 252 1100 19800 198'00 Loop No. 3
- Design basis leak
- See General Arr gg.
gg,g7 g
ma
9 9
occident analyses.
Included in the basis and discussed in PSAR f
section 11.1.5 la e design limit of 100 ppb (parts per billion)
(.
for plutonium content of the primary coolant.
2.
Retention, fellout, plateout, and agglomeretton of sodlum aerosol in cells or buildings, ehose design does not include specific safety features tg accomplish that f unction are not accounted. for in the analysts.. Neglecting these factors (en assumption that all'of the aerosol is evallable for release to the atmosphere) leads to over-prediction of potential off-site exposure.
3.
No credit for non-safety related fire protection systems is taken.
O 4.
Dispersion of aerosol released to the nimosphere was calculated 8
' utlllzing the conservative atmosphere dIlvtlon factors (X/Q) applicabla to ' discrete flmo Intervals provided in Table 2.3-38 (the 95th Percentile Values).
Guldance provided in NRC Regulatory Guide 1.145 was followed in calculating the X/Q values.
Detailed descriptions of.the str.ospheric dilution factors estimates are provided in Section 2.3.4 5.
Fallout of the serosol during transit do'wnwind was noglected.
6.
The cells will be structurally designed 10 molntain their Integelty under the accident temperatures and pressures and the weight of the spilled sodium.
For radiological calculations, no
[
credit is taken for cell atmosphere leak tightness.
\\.
7.
The, cell liners, catch pans, and catch pan fire suppression decks-are designated as Engineered Safety Features and will have design temperatures equal to or greater 1han 1he sodium spill icmperatore, thus confining the sodium spill, f l l l oc cel l s ' ' ' ' ' ' ' " ' "
" 'lkesul ti ng f rom a leak In a_h 8.
f e r ' ;.- ic. _ h l '.,.. ',i
...m
. 2,, : ll.'
^3 - Inerted a
sodlum or NaK pipe /componont in the cell producing the worst case
- g Nb "4
spill /ternperatur e condli f on.
The leak is based on a Moderate 9
Energy fluid System break (1/4 x pipe diametur x pipe thickness) es def f nod in branch technical position MEB3-1 with the sodlum or NaK system operating at 11s maximum normal operating 1cnporeturc and pressure.
9.
Tho only crodit for operator action In mitt etion of postulated 0
sodium spills is shutdown of the Na overflow system makeup pumps 30 minutos after pl6nt scram for a postulated leak in the Primary Heat Transport System (see section 15.6.1.4).
i e
/ f. r. - L A del U A/u. n.
10.
The analysis of postulated liquid metal fires in air-filled cells
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does not include reaction of the liquid metal with postulated water released from concrete. The validity of this approach is presently being vertfled in conjunction with the large scale modium fires test program discussed in Section 1.5.2.8 of the PSAR.
If the test program does not support the present ana1ysIs approach, the appropriate ef fects of water release from concroie will be included in subsequent onelyses.
Table 15.6-1 provides a summary of the inittel conditions for each fire considered and the maxleum off-site dose as a percentage of the 10CFR100 guideline limits. As the table Indicates, a large margin exists between the potential off-site doses and 10CFR100.' A discussion of the pressure /
temperature transient for tech event is provided in the following sections; In no,cose do the fires result In conditions beyond the design capabilty of the cell /bullding.
The Project is assessing the Impacts of a design basis NeK spill in the Reactor Service Building end will provide the results 4e 4he44dA when the assess nts are completed. 7t,. a.erces/, fe/
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15.6-2a Amen (. 73
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.15.6.1.3 Failure of an Ew-contalement Primarv sodium stormon Tank I
15.6.1.3.1 Idontiffeetion of Unuaos and Aceidont DauerIetf an t
The two ex-containment primary sodium storage tanks are located in a cell l
(cell 211) on the lowest level of the Intermediate Bay of the Stoem Generator i
Building.
These tanks will be used to store primary sodium only In the event i
maintenance requires the complete drainage of more than 1 PHTS loop or the EVST or maintenance:Is required in cell 102A.
The postulated accident is the i
cceptete f ailure of one of the tanks, when f ull, which results in the complete l
i spill of the contained sodlum to the cell floor.
This postulated accident is extremely uniIkely, j
O When the ex-containment sodium tanks are f ull of Ilquid sodium, access to the tank cell is prohibited due tot the sodium activity and the cell la closed and 2 and the free volume of the cell is 55.700 ftg area is approximately 2400 ft Inerted (~250 ).
The cell floo 2
The floor of the cell is protected with a Engineered Saf ety Feature steel catch pan, 3/8 Inch thick.
The sides of the catch pan extend vertically upward to a height such that the maximum potential spill volume can be saf ety contained within the catch pan, j
For conservatism, the postulated accident is assumed to occur near the end of i
l plant life (30 years) when the radioactive content of the primary sodlum has potentially reached its peak.
A minimum of 10 days decay time, in-l containment, is required prior to charging an ex-containment storage tank, to Insure substantial decay of No-24 l
89 eTD U$ M i
Ol The postulated accident results In the spill of G,000 gellons (,00,000 lbs.)
of 450 F sodlum to the cell floor.
This spill represents 100% of the 0
contained volume of one of the two tanks and is an extremely conservative l
upper bound.
The total postulated spill is contained by the catch pan.
15.6.1.3.2 Annfvsis of Effacts and Consecuences The consequences of this postulated event were determined as follows:
The spilled sodlum reacts with the available oxygen 12%) In the a.
cell, burns and releases 27% of the Na 0 formed as airborne 2
particles (Reference 3).
l b.
The radioisotope concentrations in the aerosol are the same as j
the initial concentrations In the sodlum, Itedloactl*ve decay during the accident is neglected, c.
d.
No credit for retention, plate-out, o settling of the aerosol in l
either the ex-contalnment storage tank or the Steam Generator Building was taken, it was conservatively assumed for redlological evaluations that all the aerosol generated during l'
,l combustion was released directly to the environment.
Fallout of the aerosol during transit downwind was neglected.
e.
SDFIRE-ll analysis of the fire in the Inertad cell Indicates that canbustion Amend. 64 15 6-8 Jan. 1982 69:91 G21/W3T
9.1 - 12 Comment Provide additional justification why the Fuel Handling Cell cooling system and boundary are not safety related.
Response
Off-site doses from a combined argon cooling system failure and cooling grapple blower failure with a bare core assembly in the FHC are enveloped by the accident in PSAR Section 15.5.2.3 and the RSB fuel handling accident margin source term.
Therefore safety related FHC equipment is not required to support the safety analysis of PSAR Chapter 15.
The RSB HVAC system described in PSAR 9.6.3 is designed to mitigate the consequences of an RSB fuel handling accident margin source term.
This margin source term is a 20kw fuel assembly with a release of 100% of fission product inert gases, 100% of halogons,1% of other fission products and 1% of Pu.
The off-site doses from this fuel handling accident margin source term are:
Site Boundary Dose 0-2 hr Whole Body 1.27 Rem Thyroid 64 Rem Lung 2.4 R2m Bone 1.3 Rem Low Population Zone Dose 0-30 day Whole Body
.57 Rem Thyroid 25 Rem Lung 1.1 Rem Bone
.81 Rem On site doses from the above PHC accident have been evaluated to confirm that operator action can be taken in the RSB to further mitigate this accident and to operate other equipment.
For a 15kW bare assembly in the FHC, the RSB would have to be evacuated or breathing apparatus donned approximately 10 min after a loss of argon cooling system plus failure of the FHC cooling grapple blower.
Dose to an operator with breathing j
' apparatus in the FHC gallery would be.43 Rem in the first hour, 1.2 Rem in the second hour and the dose rate will not exced 1.65 Rem /hr.
For a 6kW bare assembly in the FHC, the RSB would have to be evacuated or breathing apparatus donned approximately ~30 min after a loss of the argon cooling system plus failure of the FHC cooling grapple blower.
Dose rate to an operator with breathing apparatus in the FHC operating gallery will not exceed 1 mrem /hr.
Even upon the loss of offsite power, actions could be taken to return the fuel assembly to the core component pot by remote-manual operation of the FHC crane.
The above dose rates will allow this effort to continue until the fuel assembly is in a core component pot where it can be left unattended.
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