ML19210B177
| ML19210B177 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/18/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19210B173 | List: |
| References | |
| NUDOCS 7911040105 | |
| Download: ML19210B177 (8) | |
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BRANCH TECHNICAL POSITION CSB 6-1 oo MINIMUM CONTA!!.'4ENT PRE 55URE MOCEL FOR PWR ECCS PERTOR.v.ANCE EVALUATION A.
BACKCROUND Paragraph I.D.2 of Appendix K to 10 CFR Part 50 (Ref.1) requires that the containment i
pressure used to evaluate the performance capability of a pressurized water reactor (P'.;R) emergency core cooling system (ECCS) not exceed a pressure calculated conservatively for that purpose. It further requires that the calculation include the effects of cperatien of all installed pressure reducing systems and processes. Therefore, the following trancn technical position has been developed to prov de guidance in the performance of rini un containment pressure analysis. The approach described below applies only to the ECCS-related containc.ent pressure evaluation and'not to the contain. ment functional capacility evaluation for postulated design basis accidents.
B.
RRANCH TECW;! CAL POSITICN 1.
Input Ir.for atien for Madel a.
Initial Contain ent Internal Conditions The minicun contain ent gas temperature, mininum containrent pressure, and naximum hunidity that may be encountered under limiting nort:al ocerating conditions should be used.
b.
Initial Outside Contain ent Arcient Coeditions A reascrably les ambient temperature external to the contair. Ont she;1d be ust).
c.
Contair ent Volure The eaxiran net free containment volume should be used. This raxi a free volume should be dctenmined from the gress containment volure minus tae scia es of internal structures such as walls and floors, structural steel, ra.'cr c:.i; ent, and piping. The individual voluma calculations shculd reflect the uncertainty in the component volux.es.
a 2.
Active Heat Sinks a.
Spray and Fan Cooling Systems The operation of all engineered safety feature containment heat removal systems operating at maximum heat removal capacity; i.e., with all containment spray trains operating at maximum flow cor.ditions and all emergency fan cooler units operating, should be assumed. In addition, the minimum temperature of the st0 red water for the spray cooling system and the cooling water supplied to the fan coolers, based on technical specification limits, should be assumed.
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Deviations f the foregoing will be accepted if it c ' ')e shown tnat the worst conditions regarding a single active fail re, stored water temperature, and cooling water temperature have been selected from the standpoint of the overall ECCS model.
b.
Contain.ent Stea,Mixino With Spilled ECCS Water ThespillageofsubcooledECCSwaterinto$hecontainmentprovid?sanadditional heat sink as the subcooled ECCS water mixes with the steam in the containment.
The effect of the steam-water mixing should be considered in the containrent pressure calculations.
g c.
Containrent Steam Mixing With Water from Ice Melt The water resulting from ice melting in an ice condenser contair. ment provides an additional heat sink as the subcooled water mixes with the steam while draining g
from the ice condenser into the lower containment volume. The effect cf the steam-water mixing should be considered in the containment pressure calculations.
3.
mssive Feat Sinks a.
Identification.
The passive heat sinks that should be included in the containrrnt evaluation model should be established by identifying those strue.ures and co7 enents within the containment that could influence the pressure response. The kinds of struc-tures and compenents that should be included are listed in Table 1.
)
Data on passive heat sinks have bcen compiled from previcas reviews and have
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been used as a basis for the simplified riodel outlined t.elow. This r: del is acceptable for minimum containment pressure analyses for constructicn per,it applications, and until such time (i.e., at the operating license ef vic'.J trat a complete identification of available heat sinks can bc rade. Tnis sir:lified approach has also been followed for o; crating plants b/ iicensees cc siy 4; with Section 50.46 (a)(2) of 10 CFR Part 50. Fcr such cases, and for ccnste :tica permit reviews, where a detailed listing of heat sinks within the cent 31* ent often cannot be provided, the following procedure may be used to model : e passive heat sinks within the containment:
(1) Use the surface area and thickness of the primary containment steel shell or steel liner and associated anchors and concrete, as apprceriate.
(2) Estimate the exposed surface arca of other steel heat sinks in ace:rdance with Figure 1 and assume an average thickness of 3/8 inch.
(3) Model the internal oncrete structures as a slab with a thickness of 1 foot 160,000 ft.2 and exposed surface of The heat sink therinophysical properties that would be acceptable are shown in
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Table 2.
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At the ope
'ng license stage, applicants should prr7e a detailed list of passive heas' sinks, with apcropriate dimensions and peoperties.
b.
Heat Trsnsfer Cocfficients The following conservative condensing heat transfer coefficients for heat trantfer to the exposed passive heat sinks during the blowdown and post-blowd:s.n phases of the loss-of-coolant accident should be used (See Figure 2):
(1) During the biswdown phase, assume a linear increase in the condccring heat ini W =8 Stu/hr-ft
- r at t = 0, to a peak transfer ccefficient fro h i
~ lue four times greater than the maxinum calculated condensing hcat trans-va fer coefficient at the end of blowdo.n, using the Tagami correlatien (Ref. 2),
0,62 h,,= 72.5 -f e
y where h
= ma i~ rum heat transfer ceefficient Stu/hr-ft
- F
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Q
= primary coolant energy Stu V
= net fica containnent volu: e, f t t
= time interval to end of blo.d:wn, sec.
p (2) During the long-tern post-blowdown phase of the accident, charac*erized by low turbulence in the contain. ment atrosphere, assu a condensing rest transfer coefficients 1.2 tir.cs greater than those predicted by the Uchida data (Ref. 3) and given in Table 3.
(3) During the transitipn phase of the accident, betwee1 the end of bit. e n and the long-terr. Post-blowdown phase, a reascnably Con?ervative ex;orential transition in the condensing heat transfer coefficient sk.ould i 0 assured (see Figure 2).
The calculated condensing heat transfer coefficients based on the at:ve rete d should be applied to all exposed passive heat sinks, both rcetai :nd ct" crete, and for both painted and unpainted surfaces.
Heat transfer between adjoining raterials in passive heat sinks should be based on the assumption of no resistance to heat flow at the matcrial interfaces. An example of this is the containment liner to concrete interface.
C.
REFERE"C E_S_
l.
10 CFR 550.46, " Acceptance Criteria for Emergency Core Cooling Systems for Light ater Nuclear Power Reactors," and 10 CFR Part 50, Appendix K. "ECCS Evaluation Models."
2.
T. Tagami, " Interim Report on Safety Asselsments and Facilities EstaD115hrent Project in Japan for Period Endinn June 1965 (No.1)," prepared for the National React-Testing Station February 28, 1966 (unpublished work).
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3.
H. Uchida. A. Oyar.
and Y. Toga, " Evaluation of Post-Incidc
'coling Systems of Light-Water Power Reactors," Proc. Third International Conference on the Pe.ceful Uses of Atomic Energy, Volume 13. Session 3.9 United Nations, Geneva (1964).
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TABtE 1 o
k IDENTIFICATION OF CONTA!'iMENT HEAT SINKS Containment Builoing (e.g., liner plate and external concrcte walls, floor, and sump, and 1.
lineranchors).
Containment Internal Structures (e.g., internal separation walls and floors, refueling 2.
pool and f uel transfer pit walls, and shielding malls).
I Supports (e.g., reactor vessel, steam generator, pumps, tanks, major com;cnents, pipe 3.
supports, and storage racks).
Uninsulated Systems and Components (e:g., cold water systems, heating, ventilation, and 4
air conditioning systems, pumps, motors, fan coolers, recombiners, and tants).
Miscellaneous Equipment (e.g., ladders, gratings, cicetrical cabic trays, and crar.es).
5.
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TABLE 2 NEAT $1NK THERM 0 PHYSICAL PROPERTIES Specific Themal Densi}y Heat Conductivity M_aterial Ib/ft Btu /lb *F Btu /hr.ft *F Concrete 145 0.156 0.92 I
Steel 490 0.12 27.0
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TABLE 3 UCHIDA HEAT TRANSFER COEFFICIENTS Mass Heat Transfer Mass Heat Transfer i
Ratio Coefficignt Ratia Coef ficipqt I
(1b air /lb steara)
(Btu /hr ft 'F)
(1b air /lb steam)
(Btu /hr-ft
'F) l 50 2
3 29 20 8
2.3 37 18 9
1.8 46 14 10 1.3 63 10 14 0.8 98 7
17 0.5 140 5
21 0.1 280 4
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Figure 1 Area of Steel IIcat Sinks Inside Contni:tment 5-O
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f Containment Free Volume, x 10' ft tn C'
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LeJ Revised 12/74
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