ML19220B321
| ML19220B321 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/22/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19220B317 | List: |
| References | |
| PP-750722, NUDOCS 7904250634 | |
| Download: ML19220B321 (5) | |
Text
9 3 ranch Technical Position CSB 6-4 CONTl.I:iMENT PURGING DURI';G Nori\\1. PLA'iT OPERATIONS A.
BACKGROUND This branch technical positice pertains to syste= lines which can provide an open path fro the contain=ent to the environs during nor=al plant operation; e. g., the purge anc vent lines of the contain=ent purge syste=.
It supple =ents the pcsition taken in S tandard Review Plan 6.2.4.
While the ccntain=ent purge syste= prceides plant opera:1er.a1 flexibility, its design cust consider the i=portance of =ini= icing the release of centainment at=osphere to the environs following a postulated loss-of-coo. ant accident. The ref o re, plant designs =uat not rely on _ts use on a routine basis.
The n eed for purging has not always been anticipated in the lesign of plant :, and therefore, design criteria for the containment pi'rge syste=
have i et been fully developed. The purging experience at operating plants varies considerably fro = plant to plant.
Some plants do not purge during reactor operation, so=e purge inter =ittently for short periods and so=e purge continuously.
The contain=ent purge systa= has been used in a variety of ways, for exa=ple, to alleviate certain operational proble=s, such as excess air leakage into the contain=ent fro: pneu=atic controllers, for reducing the airborne activity within the containnent to facilitate personnel access during reactor power operation, and for centrolling the contain=ent pressure, te=perature and relative humidity. However, the purge and vent lines provide an open path frc= the contain=ent to the environs. Should a LOCA occur during contain=ent purging when the reactor is at power, the calculated accident doses shvuld be within 10 CFR 100 guideline values.
The sicing o f the purge and vent lin es in =cs t plants has been based on the need cc control the con tain=ent at=osphere during refueling operations.
This need has resulted in very large lines penetrating 79042bO 6f
'id as
O e
-2_
the con tain=en t (about 42 inches in dia=e ter). Since these lines are nor= ally the only ones provided that wi.1 per=it sc=e degree of control over the containment at =c s phe re to facilitate personnel access, sc=e plants have used the: i ar con tain=ent purging during nor=al plant operation. Under such :cnditions, calculated accident doses could be s i gnifican t.
The refo re the use of these large contain=ent purge and vent lines should be restricted to ccid shutdown conditions mad refueling operations.
The design and use of the purge and vent lines should be based on the pre =ise of achieving acceptable calculated offsite radiological conse-quences and assuring that e=ergency core cooling (ECCS) effectiveness is not degraded by a reductica in the contain=ent backpressure.
Furge syste= designs that are acceptable for use on a non-routine basis during nor=al plan: cperation can be achieved by providing additional purge and vent lin es. The size of these lines should be li=1ted such that in the event of a loss-of-coolant accident, assu=ing the purge and vent valves are cpen and subsequently close, the radiological cense-quences calculated in accordance with Regulatory Guide 1.3 and 1.4 would not exceed the 10 CFR 100 guideline values.
Also, the =axi=u=
i=e for valve cl:sure should not exceed five seconds to assure that the purge and vent valves would be closed before the enset of fucl failures following a LCCA.
The size of the purge and vent lines should be about eight inches in dia=eter f or PWR plants.
This line size =ay be overly conservative frc= a radiclogical viewpoint for the Mark III 3RR plants and the HTGR plants because of centain=ent and/or core design f eatures. Therefore, larger line sizes =ay be j us tifie 1.
Ecwever, for any propcsed line size, the applicant zus t de=cnstrate that the radiological consequences follr:.ing a loss-of-ccolant accident would be within 10 CFR 100 guidelines values.
In s u==ary, the acceptability of a specific line si:e is a. function of the site =etec: ology, contain=ent des ign, and radiclogical source ter:
for the reac:or type; e.g.,
3WR, ?%R or HTGR.
Yk bb
@ 3.
3FMCH TECHNICM. POSIT!CN The syste= used to purge the contain=ent for the reac:or operational
= odes of peae r operation, s tartup, and ho t s t andby ;
i.e.,
the on-line purge sys ta=,
s!.ould be independent of the purge syste used for the reactor operational = odes o f ho t shutcown, cold shutdown, and refueling.
1.
The on-line purge syste should be designed in accordance with the following c:lteria:
a.
The perfor=ance and reliability of the purge system isolation valves should be consistent with the operability assurance progra= outlined in MI3 3 ranch Technical Position MIS-2, Pu=p and Valve Operability Assurance Progra=.
(Also see Standard
?.eview Plan 3. 9. 3. ) The design basis for the valves and ac:uators should include the buildup of contain=ent pressure for the LOCA break spectru=, and the purge line and vent line ficus as a functicn of ti=e up to and during valve closure.
b.
The nu=ber of purge and vent lines that =ay be used should be li=1:ed to one purge line and one vent line.
c.
The sice of the purge mad vent lines should not exceed about eight inches in dia=eter unicss detailed justification for larger line sites is provided.
d.
The contain=ent isolation provision-, for the purge syste= lines should =eet the standards appropriate to engineered safety features; i.e.,
quality, r edundan cy, testability and other appropriate criteria.
e.
Instrumentation and con:rol syste=s provided to isolate the purge sys te= lines should be indepen dent and actuated by diverse parameters;
- e. g., contain=ent pressure, safety injection actuation, and contain=ent radiation level.
If energy is required to close the valves, at least two diverse sources of energy shall be provided ei:her of which can affect the isolation f"n C: icn.
f.
Purge systa= isola: ion valve closure ti=es, includin g his tru=en tation delays, should not axceed five seconds.
g.
Provis ions should be =ade :o ensure that isolation valve closure will not be preven:ed by debris wnich could potentially becoce entrained in tae escaping air and s tea =.
'ia 3kiost
kx1 d$~h o
-~
'S
~~
t '
p qs
'W Y
- 4,,Nk V
IMAGE EVALUATION TEST TARGET (MT-3) 1.0
?'2 "25
, g, y=2 r3 9 l,l
$'N u
a 1.25 1.4 l 1.6 i
4 6"
$?%
/f
- s 4%
+ y 5,,,,,y,,
egh e y,,
3 o
+,
N
/
' go
$$ kk((y 44{4'/h
%f
%x
\\
IMAGE EVALUATION NY TEST TARGET (MT-3) 1.0 "25
- n2 o' n l'; : n b "; [lL2A I,I g
a
!11 1.25 IA lll l.6 1,l EL=E 6"
s e %,Y h7f
- DV
.-sp
$b h
,/
"<f':;S>/>},;
oy 5,
p%e
///o e
~
N'N\\ /
[ g,
91
/
,y 6
\\
7 t'++
sq%+4 TEST TARGET (MT-3) 1.0
.?'"?24
~32
','l 2 2 1K-l; ;33 t
'a l 2.0 l.I L
==
i!M l.25 1.4 lt1.6-_
,1 4
6" d
%lb/ %,h,,
Q4 4,p? '~l4 c
' op,,,,,
g
,3%
,+
fy G, & ' 'g, o+y a
/
f:'?,'
fff
%)
% <?
IMAGE EVAL.UATION TEST TARGET (MT-3) 1.0 3
e ra2 q22
', ' ;3 6
['
l,l bb
.m M
11.25 1.4 ll 1.6 l
==
u 6
A4
<$ e4 e
b, so#2, /sr/
- w,,
N q
s, x'Q s
s
- s' O
4 y
y
d,f'?e
$0 "IN'?h'Iq) i'
/p//
/
,s
- $d7*
%d*9 TEST TARGET (MT-3) 1=0 T. P L21---
t.
b"
! "36i IRS ll u
48=
ll 1.25 i 1.4 l i.6 ll l-6"
- \\
m?{??>y+6
$?.h,sh 4
v
,p
.e, p 0
'$ w g
s
6
-4_
2.
The purge syste should not be relied on for te=perature and huaidity centrol within the con:ain=ent.
3.
Provisiens should be =ade to =ini:i:e the need for purging of the centainment by providing contain=ent at=osphere cleanup sys tens within the containment.
4.
Provisions should be =ade for testing the availability of the isolatien function and the leakage rate of the isolation valves, individu. ally, during reactor operardon.
5.
The follcwing analyses should be perfor=ed to justify the centain=ent purge sysca: design:
An analysis of the radiological consequences of a loss-of-coolant a.
accident.
The analysis should be done for a spectru: of break sizes, and the instru=entation and setpoints that will actuate the vent and purge valves cicsed should be identified. The source ter= used in the radiological calculations should be based en a calculation under the ter=s of Appendix K to deter =ine the extent of fuel f ailure and the cenec=itant release of fission products, and the fission product activity in the pri=ary coolant. A pre-ex'. sting iodine spike should be censidered in determining pri= mi coolant activity. The volu=e of contain=en in which fission products are =ixed should be justified, and the fission products frc= the above sources should be assu=ed to be released through the open purge valves during the =aximum interval required for valve closura.
The radiological consequences should be within 10 CFR 100 guideline values.
b.
An analysis which de=enstrates the acceptability of the provisions
=ade to protect structures and saf ety-related equip =ent; e.g.,
f ans, fil:crs and ducrwork, ' cated beycnd the purge systa=
isola: ion valves agains: less of function frc= the environ =ent created by the escaping air and s team.
c.
An analysis of the redue:1cn in the centain=ent pressure resulting f rc= the partial loss of centainment at=osphere during the accident f or ECCS backpressure deter =ination.
E- 00(
3_
d.
n e allewable Aeak rates v.,
.'e urge and vent isolacion valves e
should be specified for the spectrt:m of design basis pressures and flows against which the valves nust close.75-067