B12020, Summary of Results of Haddam Neck Probabilistic Safety Study
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|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 03/31/1986 |
| From: | CONNECTICUT YANKEE ATOMIC POWER CO. |
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| B12020, NUDOCS 8604100286 | |
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Docket No. 50-213 B12020 Summary of the Results of the Haddam Neck Probabilistic Safety Study i
March,1986 8604100286 860331 4
PDR ADOCK 05000213 <
p one J
Summary of Results The Haddam Neck PSS calculated a mean value core melt frequency of 5.5 x 10-4 per reactor-year.
The core melt frequency is based on the internal initiators examined in the study which include anticipated transients, special initiators, as well as hypothetical design basis accidents. A summary of the dominant core melt sequences is provided in Table I.
The dominant core melt sequences involve a loss of high pressure recirculation during small-break and medium-break LOCAs. The high pressure recirculation system at Haddam Neck utilizes the charging system in conjunction with the residual heat removal system. The high pressure safety injection system is not currently used for high pressure recirculation. The charging system has only one injection path designed for use during recirculation, into Loop 2 cold leg.
Failure of the charging system results in loss of high pressure recirculation.
In addition to loss of high pressure recirculation due to random component failures, the Haddam Neck PSS considered the loss of recirculation due to a break in the charging injection path. If a small-or medium-break LOCA occurs in Loop 2 cold leg, connecting piping or in the charging line downstream of the check valves and is sized sufficiently to degrade the charging flow rate but not depressurize the system, high pressure recirculation will fail to perform its function and we have assumed its failure in this analysis.(l) The loss of high j
pressure recirculation either due to component failure or an adverse break size and location, has been identified as an important contributor to core melt frequency (14% of total core melt frequency).
In addition, sequences caused by the loss of offsite power and/or Motor Control Center-5 are also found to be significant.
Under general plant transients, consequential LOCAs resulting from an unisolated, stuck-open PORV are important contributors.
The remaining core melt sequences listed in Table I show that, besides those sequences already mentioned, no other single accident sequence dominates core melt frequency. The table also shows that containment heat removal is available for most of the core melt sequences. For the station blackout sequence, the availability of the diesel-driven fire pump for cantainment spray is an important consideration. The availability of containment heat removal is considered in the analysis as a means of maintaining containment integrity and as an active means of removing fission products to prevent large scale radioactive releases should core melt occur. The public risk impact of the dominant core melt sequences is reduced by having containment heat removal available.
A listing of the various initiating events and their contributions to the core melt frequency is presented in Table II. Small-break LOCA and loss of offsite power events are the largest contributors, representing 24.45 % and 22.45 %
respectively, of the calculated core melt frequency.
(1) The implications of this situation with respect to 10CFR50.72 and 50.73 are being evaluated separately and are the subject of separate correspondence.
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Table I DOMIWANT (XHIB El.T ACCIDEltT FRQUENCE3 CottTMtT.
FREQ./
$ OF IIOTRS FAILED lEST StirFORT SEQUENCE TE8A TOTAL C W RDOVAL ST5TEMS lESCRIPTION Includes Fallure INITIAT05 l.0TE Il 19.53 or Clierging
- Avell, High Pressure injeo.
Sysics Mone o
Small-Break Avall, Illgh Pressure LOCA Ilectreulation Falla 2.62E-5 4.78 Avell.
liigh Pressure Injeo.
o Avall, Adverse Break Sl e and Location 2.59E-7 0.05 Avell.
litch Pressure Injee.
o Falls Includag F ailure 2.70E-S 4.93 of Charging Avall.
litsh Pressure Injeo.
None o
Systee Hedlue-Avall,Illph Fressure Break LOCA Itectroulation Falls Avell.
5.16E-5 9.42 liigh Fressure injeo.
o Avall, Adverse Break Sl e and Loostion 2.55E-6 0.47 A vell.
High Fressure Injeo.
o Fstis Inclules f allin e 2.60E-5 4. 1 81 of Char ptrc Conseq. LOCA - Branch Avell.
Mone o
Systre Ceneral to ET23 FORT LOCA, Flant Illgh Fressure Injee Translent Avell, Rectro. Flow Falls 1.87E-6 C.34 Conseq. t.0C4 - Branch Avall.
o to ET23, Seal Fall.
LOCA, RC5 Depress.
Falls OR Recirculation Flow
- Avall, 5.9?E-T o.11 Falls i
Table I (Con't)
DOMINANT CORE del.T ACCit4HT SEQUENCES c0NTtwF.
Telt.an Surf 0nf SnooENCE NEAT FREO./
s Or NOTBS SISTEtB DESCRIPTION.
Af3OTAL TEAR _
TOTAL. CMF INITIATOR Stuck c en.
o Reactor Trip Falls Avall.
3.18E-5 2.15 r
Unisolat eJ topy/
Ceneral Branch to ET22, SRT durtra ATW3 Plant Manual Trip Falla, Transient Fressurl er Relief Falls OR Emergency Foration Avall.
2.02E-6 0.37 Falls OR Haln Feedwater Avall.
1.15E-6 0.21 Unavall, AFW Falls ET26 is identi-Bus 4 or 7 Avall or Avall.
l.15E 5 2.10 col to Et23. See LOSte o
Loss oF (DCleEACS Falls, Conseq. LOCA Ef23 Offsite eDC2+EAC9)
Branch to ET26, Seal Power Failure LOCA, RCS Depress. Falla, OR HrSI Injee. Falls Avall.
1.05E-5 8.92 OR Low Fressure Reelro. Avall.
2.40E-6 0.44 Falla o AFW Falls, Fall to Avall.
2.45E-6 0.45 Recover Of fsite Power, Bleed and Feed Falle OR Long Term Cooling Avall.
9.02E-7 0.17 Falls All o AFW Falla slavail.
t.ott-5 f.86 Support Recover Power W/in. b)Unavall.
5.25E-7 0.It Systees 30 Hirutes,liigh (Comb. of Fressure Injection Losses of Falls DC. AC, Serv. Water i
l Table I (Con't)
TADIR 6.3-5 letINANT CORE El.T ACCIDENT SEQUENCFS CDNTMff.
ffEAT FREO./
$ OF FallSD Notr_1 SUrrORT SE(*JENCE TE8A Tuf tt. EW Sf37 EMS 1ESCRlrfl0N REPOTAI.
INITIATOR o AFW Falls a) Avall.
8.StE.6 f.56 Loss or Fall to Recover b) Unavail.
4.88E-7 0.09 Offsite C'
Fower within 30 Hin.
Power Recover Power within 100 Hin.
High Pressure Injeciton Falls o AFW Available a) Avall.
9 05E-6 f.65 Fall to Recover b) Unavall.
- 5. lie-7 0.09 within IS Hinutes, Recover Power within 8 Hours, High Pressure Injection Falls AFW Avallable Avell 5.78E-7 0.88 o
Fall to Recover rover within 15 Min, Fall to Recover within 8 Hours onantitled using AFW Avellable, Fall Avell.
2.00E-5 3.65 results or EACge o
EAC9 to Recover rever Section 4.3 12 (Station within 15 Hin, Fall Blackout) to Recover Fower within 8 ffours
8 s
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Table I (Con't)
DevilWANT CORE ELT ACCIDENT SEQUENCES CONT 991T.
FAILED ffEAT FREQ./
$ OF NOTE 3 SUFFORT SEQUENCE SYSTEMS DESCRIFT10lt Rett)fAI.
TEAR _ TUT At, CW INITIATOR ET26 is ident.
o Conseq. LOCA -
Avall.
2.89E-6 0.53 to E121. See Loss of Branch to ET23, ET 2)
Offstte Seal Failure LOCA, Power RCS Depres. Falls OR Low tressure Avalt.
9 13E-7 0.17 Rectro. Falls OR Avall.
4.69E-7 0.09 litsh Pressure Injection Fatts LOSF'HCC5 o Fall to Recover Avail.
7.69E-6 1.40 (DCl+EACS, tlCC-5. AFW Avail.,
DC2eEAC9)
Frisary Integrity Fatts o Fall to Roeover Avail 3 80E-6 0.69 HCC-5, AFW Falla Not Evaluated 4.90E-6 0.89 None o Unisolated LOCA in Using Event free Unisolated Letiown Line 1.0C4 he Letdown Line Mot Evatustad Interfacing Nons o Interfaatng Systems 2.80E.7 0.05
/
Using Event free LOCA Systems LOCA Mot Evaluated Catastrorhia Reactor 2.70E.7 0.05 s
Using Ever.t Tr ee None o
Cata-Vessel Rupture strophie Reactor Vessel Rupture 7
Table I (Con't)
DOMINANT CORE PEl.T ACCit'ENT SEQUENCTS CDNTP0ff.
FAILED SuFFORT SEQUENCE REAT FREO./
$ Or Noir.1 INITIATOR 315 FEM 5 IESCRIFTIDW BEPDTAL TEAR. TUTAL CIW' Loss oF HCC-5 o Fall to Recover Avall.
6.70E-6 1.22 HCC-5, Af W Avallable, HCC-5 Frimary Integ. Falls o Fall to Recover Avail.
- 7. 30E-6 1.3)
HCC-5 AfW Falls o NCC-5 Recovered Avalt.
4.2TE-6 0.78 AFW Avallable, Frimary Integ. Falls, Bleed and Feed Falls, OR Long Term Cosling Avall.
4.0(E-7 0.07 Falls Total Loss of IC DC1'DC2e o HCC-5 Recovered, Avail.
f.58E-6 0.29 is Not Recow.
HCC-5 Frimary Integ. Falls, 356 results in l
Bleed and Feed Falta Loss of toth OR semi-vital and AfW Falls, Avall.
f.59E-6 0.29 yltat Instrumtn.
Bleed and Faed Falta o Fall to Recover Avall.
4.97E-6 0.98 HCC-5, AFW Available.
Frimary Intes. Falla o Fall to Recover Avall.
5.0 tE 6 0.91 HCC-5. AFW Fatts 1.62E-5 2.96 Primary Intes. Falls, Avail.
Loss oF DCteDC2 o Bleed and Feed Falls DC Sus t OR Long Term Cooling Avati.
5.GPE-6 0.95 Falls
Table I (Con't)
ImHINANT COW. M f.T ACCIDt'NT SN74.NCF3 EX)MTMif.
Fi! LED SUFFORT Sit 0UENCE ffEAT FPEO./
5 0F
+
INITIATOS ST5 TEM 5 DESCRIFTION RE90TAl.
TERR TUT At. CW Loss of Mone o AFW Falls Fall Avail.
5.35E-6 0.98 to Recover tFW, Feedwater Bleed and Feed Fatts OR Long Term Cooling Avall.
1.48E-6 0.27 Falls o Conseq. LOCA -
Avail.
3.60E-6 0.66 Branch to ET23, FORV t.0CA,tilgh Fressure injee. Avait, Illgh Fressure Rectro.
Fatts o Fall to Trip (ATW5)
Avall.
1.35E-6 0.25 Branch to ET22, Manual Trip Falta, Fressuriser RelleF Fatts OR Emergency Boratton Avail.
2.31E-7 0.0%
Falls None o Low Fressure Injee.
- Avall, 8.06E-5 f.47 Large Avall, t.ow Fressure Preak
' Recirculation Falls
- LOCA o Low Fressure Injee.
Avail.
3 05E-6 0.56 Falls f
9 i
t
Table I (Con't)
TADI.E 6.3-5 DOMINANT CORE N:1.7 ACCIDENT SEQXNCES CONTHlf.
FAILED SUFFORT SEQUENCE ltEAT FREO./
3 0F INITISTOS STSTEMS DESCRIPTI0li NEmTAL TEAR ftTI AL CW NOTF3 o Lou Fressure Injee.
- Avall, f.0 3E-6 0.19 Large Avall, Lou Fressure Preek Rectre. Avall, Two LOCA Fath Rectre. Falls Steamline None o Conseq. SCTR-Branch
- 2. 36E-6 0.43 Release path out side Con.
to ET24, Illgh Pressure lainment Break Injection Avall, Loop Downstream lsolation Falls NRV Isolation of Feed /
Avall.
5.18E-6 0.9%
Failure to Isolate results o
Stenelines Fall, in Loss of SG Bleed and Feed Falls Cooling OR.
Long Term Cooling
- Avell, l.17E-6 0.28 Falla High Pressure Injeo.
- 5. 35E-6 0.98 Fath Outside Steam Mone o
Containment Avall, Feed / Steam Generator Lines Isolated, 30 Tube Cooling Avall, RCS Rupture Depressortration Falla, Lnop Isolation Falls o High Pressure Injeo. Avall.
8.97E-7 0.16 Avall, Feed / Steam 7
Lines Isolated,!;0 j
Cooling Falls, Loop Isolation Available 1
a
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Table I (Con't) tiOHINANT CORE WI.T ACCIttNT SR5fENCrJ CONTP9fT.
FREO./
J OF NOTRS FAILED flEAT SUFFORT SEQUENCE TEAR _ TOTAL OF item 3tAL Sf37 Del I*SCRIFT10st
_I5111410R 5.50E-T 0.10 Reactor Trip Falls Avell.
o Steam Loop Isolation Aval!
Cenerator Tube RCs i.evel Rupture 5 77E-6 t.05 Recovery A11res-Avell.
Charging Falls, sed as Slee4 and None o
Unisolated 50 Cooling Avall, Feed RCF 5eal (HFW or AF2 Avall)
Leak RCS Level Recov. Fall OR 1.89E-6 0 35 Avall.
Long Term Cooling Falla Results in t oss 6.18E-6 f.13 oF SG Cooling Feedline Isolation Avell.
None o
Main Falls, Bleed and Feedline Feed Falls Break OR 2.93E-7 0.05 Avail.
Long Tena cooling Avall.
7.72E-7 0.14 Feeditna isolation o
Avell, 30 Cooling Falls (tF2 + AF3 Fall)
Bleed and Feed Fatta 4.82E-4 87.9 TOTALt i
. s.
Table II CORE MELT FREQUENCIES BY INITIATORS
$E DESCRID ION cv rRED'JENCI SN nP PEFCEf" CO'TE BLTION ET03 Small-Break LOCA 1.34E-4 24.45 i
ET12 Loss of Offsite Power 1.23E-4 22.85 ET02 Medium-Break LOCA S.13E-5 14.84 ET09 General Plant Transient 5.34E-5 9.74 ET18 Loss of MCC-5 3.36E-5 6.13 ET20 Loss of DO Bus 1 2.94E-5 5.36 ET10 Total Loss of Main 1.36E-5 2.48 Feedwater ETC1 Large-Break LOCA 1.22E-5 2.23 ET06 Steamline Break Down-1.10E-5 2.01 stream of NRV ET04 Steam Generator Tube 1.04E-5 1.90 Rupture ET08 Unisolated RCP Seal B.45E-6 1.54 Leakage ET07 Main Feedline Break 7.48E-6 1.36 ET05 Steamline Break Upstream 7.00E-6 1.28 of NRV ET16 Insufficient Flow of 5 93E-6 1.08 Service Mater V, V1 LOCA Outside Containment 5.45E-6 99 ET19 Total loss of DC Power 4.46E-6
.81 r.T17 Loss of Control Air 3.40E-6
.62
~
ET11 Loss of DC Bus 2 2.66E-6 48 ET21 Loss of Semi-Vital AC 1.~t?E 6 J
l TOTAL 5.4BE-4 100 i
(
l Includes Station Blackout (EI 15), LOSP and Loss of MCC-5 (ET13), LOSP and Loss of one Energency Bus (ET14).
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