ML19221A620
| ML19221A620 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/21/1979 |
| From: | INDUSTRY ADVISORY GROUP |
| To: | |
| References | |
| OSP-790521, TASK 113, TASK-113, NUDOCS 7905230454 | |
| Download: ML19221A620 (9) | |
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INFORMATION ON THE RELATIVE SAFETY OF ALTERNATE COOLING MODES C
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Safety requires the avail-COOLING MODE ability of the following Nat'l Bolling LP Conts
- 1) RC Pump 2)Cire.
3 )llP I S 4)Nat'l Cire, 5 ) RilR 3) Floc Offsite Power X
Nucleate Onsite Power X(?)
X X (?)
X I
X Steam Generator X
Non-leaking Steam Generator X
X Feedwater Flow X
X X
Stable core configuration Y.
X Control Room X
X X
Pump seal flow or Pump seal X
?
cooling water Nc,-leakage of Pit m p S c 31 s I
X RV seal X
X Sampling lines X
X Instrument lines X
X P.S.
Pressure -300 psi X
?
casc at Let down System X (?)
close it operab le close i t In-core Instrume tation X
X X
X X
o r saxe u p Closed Pressurizer Vent X
nake up needed X Valve Unbreached containment X
X Fire free containment X
X Upgraded RHR e csi.c-X Out of core instr.
X X
X X
X Keep subcooled
- P adiological Assessment Group to verify safety luo 035 7 905 23 0. g.y u
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RELATIVE SAFETY Safety:
Avoid H2 eIPlosion Criteria: Avoid release of fission producta to public Cool the core (avoid melting)
Process parameters should be available by measurement 1.
R.C.
Pump (greatest degree of safety)
Advantages a.
Effective cooling b.
Has the most back up options c.
Probably gives most core flew d.
Involves items normally used e,
We know its working Disadvantages a.
Adds to System as much heat as the core (or ore) o.
Requires off-site power c.
Requires highe'c pressure d.
Requires make-up pump 2.
Natural circulation with solid primary and solid secondary systems.
Advantages a.
Probably better heat transfer than HPIS will give b.
Still has quite a few options left c.
Gas evolution is less tnan with toiling natural circulation d.
Persits colder shut down at lower pressure than with R.
C.
Pumps Disadvantages a.
Effectiveness not verified either by analysis or test b.
Requires off-site power or jury-rig c.
Can't have bad leaks in primary system or needs considerable make up d.
Off-design mode
- 3. National Circula. ion with Nucleate boiling with secondary systen soli-Advantages a.
Probably gives better heat transfer than solid natural circulation in primary system.
b.
May permit jury-rigging to rely only on on-site
- power, c.
Is a logical sequence if solid primary system natural circulation doesn't work well.
Disadvantages a.
Cas evolution could be a probica, and could lead to blocking candy cane.
b.
Hay disturb core more than solid natural circulation y,
c.
Pressure maintenance required'in P S d.
Requires off-site p6wer e.
Has not been verified by analysis on test i66 036
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Relative Safety Page Two
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4.
HPIS Advantages a.
In principle, provides forced flow through core b.
Doesn't require secondary system.
c.
Requires only on-site power Disadvantages a.
Potential for by-passing core (via S.G.'s) needs to be studied b.
Keeps system at higher press than RHR c.
Vent, to the containment and adds to water volume in the containment 5.
RHR Advantages a.
h'a s designed to cool core for long term b.
Requires on site power only c.
It operates at relatively low pressure Disadvantages a.
High radioactivity in the coolant b.
Should be upgraded by providing more redundancy for long term cooling c.
Operability of containment valves in system not confirmed 6.
Containment Flooding Advantages a.
It is the last available resort to cool core.
b.
It is better thaa letting core melt in dry containment Disadvantages a.
Heat transfer capability is unconfirmed b.
Makes eventual clean up difficult because of large volume of water and because water will carry debris to points otherwise cleaner c.
Endangers process monitoring capability d.
Potential thermal shock problem if there are significant hot spots c.
1-oses sump valve, sump pump, reactor system drain tank pump, etc.
f.
This is most severe off-design use of component g.
If there is containment liner damage, there is possible leak path to public h.
It puts positive pressure on containment
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TAELE I 3
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.m gh Forms of Dreeners tien Sequence Importanc e Prob. bili t y-u-
i Loss of offsita powr 1
I A
B f
Loss of instrtr.entatic.a I
A A
l T. T. Core T/C's, hessn. cm fla.
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lr p essurizer level i..,
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- l Loss.of RC pumps B
A l
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B Can't open pressurizcr valve I
B A
Loss of pressurizer heaters I
C A
Loss of secondcry circulation IV B
B 1
l Let down valve stuck open I
B B
Loss of letdo system Y
B A
Nitrogen frcza accumulator I
B C
a cumulators stuck closed I
C C
Contairment breach i.
VI A
C Personnel mislocation A
A Human error possibility I
A A
H expl sion 2
I B
B Flooding containment VI A
B Failure of barrel check valves I
C C
Failure of R.Y. head seals III C
C Loss of incore instrumentation seal III B
C Fire in contair.w nt*
VI A
B Fire in auxiliary
- I A
B Fire in other areas
- A B
Air crash into plant I
A C
F1'oding c
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'A C
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e.m Foras'_of' tecsers tion Sequence Importance Probabi1ity z
ccolability degradation A
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tecking $/C. pctsu;g7 ed secondary VII g
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Fcreaticicf K A G 2
I C
A o
Failure of contairrent penetration VI A,.
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Evacustion of control rosa
- A C
Breach of waste syntaa (Site evac.)*
f A
B 1
Valve aligr.=ent errors I
A A
Loss of.11 A/C power I
A B
Iristrument/Se.pling line leak III B
B l
Ecron dilution.
I A
C
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B
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A B
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DEGRADATION SEQUENCE SRIGY
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OBJECTIVE identify rr[fkions to the planned cooling degradation sequence in the event of plant / system failures.
RESULTS
. A list of possible plcnt/ system failures is provided in Table 1.
Additionally, each failure has been annotated to indicate probability and consequence (importance).
These probability and importance designations range fra:n A t.o,C in descending order and are based en engineering judgetent of the group.
Each failure event has been considered relative to the need for revision of the reference sequence (Sequence I).
Sequences are identified by nte.ber in Table II.
IMPORTANT Four identified plant / system failure events deserve detailed and urgent consideration.
These are identified by
- in Table I.
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