ML19221B132
| ML19221B132 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-06.2.1., NUREG-75-87, NUREG-75-87-6.2.1., SRP-06.02.01.05, SRP-6.02.01.05, NUDOCS 7907120477 | |
| Download: ML19221B132 (9) | |
Text
e asc,4 NU REG-75/087 o
0 f "
~g
',g U.S. NUCLEAR REGULATORY COMMISSION i
i.
STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.2.1.5 MINIMUM CONTAINMENT PRESSURE 3.NALYSIS FOR EMERGENCY CORE COOLING SYSTEM PERFORM /NCE CAPABILITY STUDIES REVIEW RESPCNSIBILITIES Primary - Containment Systems Branch (CSB)
Secondary - Reactor Systems Branch (RSB) l I
AREAS OF REVIEW Following a loss-of-coolant accident in a pressurized water reactor (PWR) plant, the emergency core cooling system (ECCS) will supply water to the reactor vessel to reflood, and thereby cool the reactcr core. The core flooding rate is governed by the capability f of the ECCS water to displace the steam generated in the reactor vessel during the core reflooding period. For PWR plants, there is a direct dependence of core floodina rate on containnent pressure; i.e., the core flooding rate will increase with increasing containrent pressure. Therefore, as part of the overall evaluation of ECCS perfornance, the CSB reviews analyses of the nininum containrent pressure that could exist during the period of time until the core is reflooded following a loss-of-coolant accident to confirm the validity of the containment pressure used in ECCS perforrance capability studies. The CSB reviews the assumptions rude regarding the operation of ngineered safety feature heat renoval systems; the effectiveness of structural heat sinks within
~g '
tne conta inment to re ove energj from the containment atmosphere, and other heat rencval n
processes, such as steam in the containment mixing with ECCS water spilling from the break in the reactor coolant systen; and in the case of ice condenser containments, mixing with water fron melted ice that drains into the lower containment volume. The review is done for all PWR containment types, i.e., dry, subatmospheric, and ice condenser containments.
The RSB is responsible for determining the acceptability nf the mass and energy release data used in the minimum containment pressure analysis (sae SRP Section 6.3).
This infornation is derived from the applicant's evaluation of ECCS performance capability in accordance with Appendix K to 10 CFR Part 50.
It should be noted that the minimum containment pressure analysis done in connection with ECCS performance evaluation differs from the containment functionai performance analysis, i-U,at the conserv.tist and margins are take. in opposite directions in the two cases. Thus, the minimum containment pressure analysis required by the regulations USNRC STAND ARD REVIEW PLAN si 4.,.r
,i.a.......
,-,......................c..-................~.,,.~,,,...
.,.,*....ac e.,,he o,ic.....c o, n..cto, m.i...a....,.
.a.,b:...,,h......,.9.,uc.,io.... e.,vei 1,,
....,........s,............,...,~,...m...,,...,...c..........
1.. ~.,..
................~....,c,_,,,s..,,~....
....... ~,......
,w.3 n
.t.n..... e ps.n. h 61 b.
. p 4c.,fy,
.....pr.....
t
.cc.mm...f. C.mm.n,..nd 9. g.fl.C1 p le f.,m.,s.n end..p i.nc.
4 c........,,...,.....,..,,,....u.......1c........,......
)
.[
, j,f
.. o e amm
"" I 7 90712 0 4~77
for ECCS perfomance evaluation is not conservative with regard to peak ccntainment pressure in the event of a loss-of-coolant accident and cannot be used to determine the containment design basis.
II.
ACCEPTATCE CRITERIA Paragraph I.D.2 of Appendix K to 10 CFR Part 50 requires that the containment pressure used to evaluate the perfomance capability of a PWR energency core cooling systen not exceed a pressure calculated cor.servatively for that purpose.
The guidelines given below indicate the conservatism that analyses of the containment response to loss-of-coolant accidents should have for detemining the minimum containment pressure for ECCS perfomance capability studies:
1.
Calculatiors of the mass and eneray released during postulated loss-of-coolant accidents should be based or. the requirenents of Appendix K to 10 CFR Part 50 (Ref. 2).
2.
Brar.ch Technical Position CSB 6-1, "flinimun Containment Pressure ifodel for PWR ECCS Perfomance Evaluation," delineates the calculational approach that should be followed to assure a conservative prediction of the minimum containment pressure.
Ii. REVIEW PROCEDURES t
The review procedures described below are followed for the review of the minimum containment pressure analysis. The reviewer selects and emphasizes material from these l
piocedures as may be appropriate for a particular case. Portions of the review r y be carried out on a generic basis or by applying the results of previous reviews of sinilar plants.
The CSB reviews the analyses in the safety analysis report of the minimum containment pressure following a loss-of-coolant accident. The RSE confims the validity of the applicant's mass and energy release data. The CSB evaluates the conservativeness of the assumptions used by the applicar,t regarding the operation of containment heat renoval systens and the effectiveness of structural heat sinks, by comparing the applicant's calculational approach to the method outlined in Branch Technical Position CSB 6-1.
In certain cases, the CSB may perfom confimatory containment pressure response analyses using the CONTE?tPT-LT computer code. In these cases, containment pressure calculated by the CSB is compared to that used in the applicant's evaluation of the performance capability of the emergency core cooling system, to assure that an appropriately conservative value has been used. The CSB advises the RSB of the acceptability of the containment backpressure used in the LCCS perfamance evaluation.
IV.
EVALUATION FINDINGS The conclusions reached on completion of the review of this section are presented in SRP Section 6.2.1.
V.
REFERENCES
\\h/
T'.e reference for this section are listed in SRP Section 6.2.1.
Rev. 1 6.2.1.5-2
BRANCH TECHNICAL POSITION CSB 6-1 MINIMUM CONTAINMENT PRESSURE MODEL FOR PWR LCCS PERFORMANCE EVALUATION A.
BACKGROUND Paragraph I.D.2. of Appendix K to 10 CFR Part 50 (Ref.1) requires that the containment pressure used to evaluate the performance capability of a pressurized water reactor (PWR) emergency core cooling system (ECCS) does not exceed a pressure calculated conservatively for that purpose. it further requires that the calculation include the ef fects of operation of all installe d pressure-reducing systems and processes. Therefore, the following branch technical position has been developed to provide guidance in the performance of a minimum containment pressure analysis. The approach descriLed below applies only to the ECCS-related containment pressure evaluation and not to the containment functional capability evaluation for postulated design basis accidents.
B.
BRANCH TECHNICAL POSITION 1.
Input In forma t io n for Model a.
Initial Containment Internal Conditions The minimu11 containment gas temperature, minirum containment pressure, and naxinum humidity that may be encountered under limiting normal operating con-ditions should be used.
Ice condenser plants should use the raximum containment gas temperature.
b.
Initial Outside Containment Arbient Conditions A reasonably low ambient temperature external to the containment should be used.
c.
Centainrent Volume The maximum net free containrent volume should be used. This maximur volume should be determined from the gross containment volume minus me volumes of internal structures such as walls and floors, structural steel, r;ajor equip-nent, and piping. The individual volume calculations should reflect the uncertainty in the corponent volumes.
d.
Purce Supply _ and Exhaust Systems If purge systen operation is p oposed during the reactor operating modes of startJp, power operation, hot standby and hot shutdown, the system lines should be assured to be initially open.
2.
Active Hoat Sinks a.
Spray.and Fan Cool _inq Sys tems The operation of all engineered safety feature contaircent heat reroval systems operating at ravimun heat removal capacity; i.e., with all containment spray trains operatir; at raximum flow conditions and all emergency fan cooler units operating, should be assumed.
In addition, the minimun ter-perature of the 9
stored water for the spray cooling systen and the cooling water supplied to the f an coolers, based on technical specification limits, sh;u'd Le assumed.j d I
i 6.2.1.5-3 Rev. 1
Deviations from the feregoing will be accepted if it can be shown that the worst conditions regarding a single active failure, stored water temperature, and cooling water temperature have been selected from the standp3 int of the overall ECCS model.
b.
Containmen,. Steam Mixing With Spilled FCCS Water The spillage of suecooled ECCS waMr into the containment provides an additional heat sink as the subcooled ECCS waser mixes with the steam in the containment. The ef fect of the steam-water rixing should be considered in the containment pres-sure calculations, c.
Containt"ent Meam Mixir3 Wib Water fron Ice Pel t The water resulting from ice celting in an ice condenser containment provides an additional heat sink as the subcooled water nixes with the stean while draining from the ice condenser into the lower containment volume. The effect of the stear'-water nixing should be considered in the containment pressure calculations.
3.
Passive Heat Sinks a.
Identification The passive heat sinks that should t;e included in the containment evaluation model should be established by identifying those structures and components within the containment that could influence the pressure response. The kinds of structures and components that should be incluaed are listed in Table 1.
O Data on passive heat si :s have been ccapiled from previous reviews and have been used as a basis f the simplified nodel outlined below. This n'odel is acceptable for minimum containment presme analyses for construction permit dppliCations, and until such time (i.e., at the operating license review) that a complete identification of available heat 3;nks can be made. This simplified approach has also been followed for operating plants by licensees complying with Section 50.46(a)(2) of 10 CFR Part 50.
For s
.h cases, and for construction permit reviews, where a detailed listing of heat sinks withi: the containment of ten cannot be provided, the following procedure may be used to model the passive heat sinks within the containment:
(1) o e the surface area and thickness of the primary containment steel shell or steel liner and associated anchors and concrete, as appropriate.
(2) Estimate the exposed surface area of other steel heat sinks in accordance with Figure 1 and assure an average thickness of 3/8 inch.
(3) Model the internal concrete structures as a slab with a thickness of one foot and exposed surface of 160,000 ft2 The heat sink thernophysical properties that would be acceptable are shown in Table 2.
147 240 Rev. 1
- 6. 2.1. 5 -4
Applicants should provide a detailed list of passive heat sinks, with apprc-l priate dimensions and properties.
b Heat Transfer Coef ficients The following conservative condensing heat transfer coefficients for heat transfer to the exposed passive heat sinks during tha blowdown and post-blowdown phases of the loss-of-coolant accident should be used (s~
Figure 2):
(1) During the blowdown phase, assume a linear increase in the condensing transfer coefficieat from h
=8 Btu /hr-fts "F, at t = 0, to a peak initial value four times greater than the maximum calculated condensing heat trrisfer coefficient at the end of blowdown, using the Tagami correlation (Ref. 2),
0.6c, h
= 72.5
)
where h
= maximum heat transfer ccefficient, Btu /hr-ft "F
2 ma Q
= primary coolant energy, Btu V
.= net free containment volure, ft i time interval to end of t sdown, sec.
t
=
g (2,
During the long-term post-blowdown phase of the accident, characterized by low turbulence in the containment atmosphere, assume condensing heat transfer coefficients 1.2 tirres greater than those predicted by the Uchida data (Ref. 3) and given in Table 3.
(3) During the transition phase of the accident, between the end of blowdown and the long-term post-blowdown phase, a reasonably conservative exponential tr ansition in the condensing heat transfer coef ficient should be assumed (See Figure 2).
The calculated condensing heat transfer coefficients based on the above method should be applied to all exposed passive heat sinks, both retal and concrete, ar,d for both painted and unpainted surfaces.
Heat transfer between adjoining materials in passive heat sinks should be based i the assumption of no resis tance to heat flow at the material interfaces. An example of this is the containrent liner to concrete interface.
\\q1 24\\
- 6. 2.1. 5 -5 agy, j
(4) Variations from the above guidelines may be found acceptable if the overall LCCS performance evaluation nodel rosul+s in an acceptable peak calculated fuel cladding terperature.
C.
REFERENCES 1.
10 CFR 550.46, " Acceptance Criteria for Energency Core Cooling Systems for Light Water Nuclear Power Reactors," and 10 CFR Part 50, Appendix K, "ECCS Evaluation Models."
2.
T. Tagami, " Interim Report on Safety Assessment and Facilities Establishment Project in Japan for Period Ending June 1965 (No.1)," prepared for the Natic,lal Reactor Testing Station, February 28, 1966 (unpublished work).
3.
H. Uchida, A. Oyama, and Y. Toga, " Evaluation of Post-Incident Cooling Systems of Light-Water Power Reactors," Proc. Third International Conference on the Peaceful Uses of Atomic Energy, Volume 13, Session 3.9, United Nations, Geneva (1964).
4 Schmitt, R. C., Bingham, G. E., and Norberg, J. A., " Simulated Design Basis Accident Tests of the Carolinas Virgiaia Tube Reactor Containment - Final Report," IN-1403, Idaho Nuclear Corporation, December 1970.
O it7 242 t
Rev. 1
- 6. 2.1. 5 -6
TABLE 1 IDENTIFICATION OF CONTAIhMENT HEAT SINKS 1.
Containment Building (e.g., liner plate and external concrete walls, floor, sump, and linear anchors).
2.
Containment Internal Structures (e.g., internal separation walls and floors, refueling pool and fuel transfer pit walls, and shielding walls) 3.
Supports (e.g., reactor vessel, steam generator, pumps, tanks, major components, pipe supports, and storage racks) 4.
Uninsulated Systems and Corponents (e.g., cold water systems, heating, ventilation and air conditioning systems, pumps, motors, fan coolers, recombiners, and tanks) 5.
Miscellaneous Equipment (e.g., ladders, gratings, electrical cables, trays, and cranes)
TABLE 2 HEAT SINK THERM 0FHYSICAL PROPERTIES S'
Specific Thermal Density Heat Conductivity fia teri al lb/ft3 Btu /lb 'F Btu /hr-ft "F Concrete 145 0.156 0.92 Steel 490 0.12 27.0 TABLE 3 UCHIDA HEAT TRANSFER COEFFICIENTS Mass Heat Transfer Mats Heat Transfer Ratio Coefficient Ratio Coef ficient
.ibair/lbstead (Btu /hr-ft;-F')
(lb air /lb steam)
(B /hr-ft -F )
(
2 50 2
3 29 20 8
2.3 37 18 9
1.8 46 14 10 1.3 63 10 14 0.8 98
,)
}kf C
7 17 0.5 140 5
21 0.1 280 4
24 6.2.1. 5 -7 Rev. 1
E Figure 1 Area of Steel Heat Sinks Inside Containment 5_
4
<C 1
G
% ~.,
cn m
a+
3
~
%S cn a
M*
5o 2
.5 1
1 I
i 1
2 3
4 6
3 Containment Free Volume, x 10 ft U
N N
_P-P-6 9
9
Figure 2 Condensing lieat Transfer Coefficients for Static Heat Sinks E
c>
h
=4xh
.y max Tagami t
g linear l
m u
stag) e.025(t-tP)
N L.
2 I
h=h
+ (h
-h stag max p
m h
t l
a 2
=
E h
= 1 2 ^- h
.-a 5
l stag Uchida E
O I
I t
Time P
l l
Iblowdown reflood I
1 I
I 5'
p N
N P
LD