B12020, Summary of Results of Haddam Neck Probabilistic Safety Study
| ML20199L066 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 03/31/1986 |
| From: | CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | |
| Shared Package | |
| ML20199L056 | List: |
| References | |
| B12020, NUDOCS 8604100286 | |
| Download: ML20199L066 (12) | |
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Docket No. 50-213 B12020 Enclosure 1 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 l events are the largest contributors, representing 24.45 % and 22.45 % :
respectively, of the calculated core melt frequency. I (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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l Table I DOMIWANT (XHIB El.T ACCIDEltT FRQUENCE3 CottTMtT.
FAILED lEST FREQ./ $ OF IIOTRS SEQUENCE TE8A TOTAL C W StirFORT RDOVAL ST5TEMS lESCRIPTION Includes Fallure INITIAT05 Avell, l.0TE Il 19.53 or Clierging Mone o High Pressure injeo. Sysics Small-Break Avall, Illgh Pressure LOCA Ilectreulation Falla 2.62E-5 4.78 Avell.
o liigh Pressure Injeo.
Avall, Adverse Break Sl e and Location 2.59E-7 0.05 o litch Pressure Injee. Avell.
Falls Includag F ailure 2.70E-S 4.93 of Charging Avall.
None o litsh Pressure Injeo. Systee Hedlue- Avall,Illph Fressure Break LOCA Itectroulation Falls 5.16E-5 9.42 o liigh Fressure injeo. Avell.
Avall, Adverse Break Sl e and Loostion 2.55E-6 0.47 High Fressure Injeo. A vell .
o Fstis Inclules f allin e 2.60E-5 4 . 1 81 of Char ptrc Mone o Conseq. LOCA - Branch Avell. Systre Ceneral to ET23 FORT LOCA, Flant Illgh Fressure Injee Translent Avell, Rectro. Flow Falls 1.87E-6 C.34 o Conseq. t.0C4 - Branch Avall.
to ET23, Seal Fall.
LOCA, RC5 Depress.
Falls OR Avall, 5.9?E-T o.11 Recirculation Flow Falls i
Table I (Con't)
DOMINANT CORE del.T ACCit4HT SEQUENCES c0NTtwF.
Telt.an NEAT FREO./ s Or Surf 0nf SnooENCE NOTBS TEAR _ TOTAL. CMF DESCRIPTION. Af3OTAL INITIATOR SISTEtB 3.18E-5 2.15 Stuck c ren.
o Reactor Trip Falls Avall. Unisolat eJ topy/
Ceneral Branch to ET22, SRT durtra ATW3 Plant Manual Trip Falla, Transient Fressurl er Relief Falls OR 0.37 Emergency Foration Avall. 2.02E-6 Falls OR 0.21 Avall. 1.15E-6 Haln Feedwater Unavall, AFW Falls l.15E 5 2.10 ET26 is identi-LOSte o Bus 4 or 7 Avall or Avall. col to Et23. See Loss oF Falls, Conseq. LOCA Ef23 Offsite (DCleEACS eDC2+EAC9) Branch to ET26, Seal Power Failure LOCA, RCS Depress. Falla, OR 1.05E-5 8.92 HrSI Injee. Falls Avall.
OR 0.44 2.40E-6 Low Fressure Reelro. Avall.
Falla o AFW Falls, Fall to Avall. 2.45E-6 0.45 Recover Of fsite Power, Bleed and Feed Falle OR Avall. 9.02E-7 0.17 Long Term Cooling Falls slavail. t.ott-5 f.86 All o AFW Falla 5.25E-7 0.It Support Recover Power W/in. b)Unavall.
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.
FallSD ffEAT FREO./ $ OF Notr_1 SUrrORT SE(*JENCE REPOTAI.
TE8A Tuf tt. EW Sf37 EMS 1ESCRlrfl0N INITIATOR f.56 a) Avall. 8.StE.6 o AFW Falls 4.88E-7 0.09 Loss or Fall to Recover b) Unavail.
Offsite C' Fower within 30 Hin.
Power Recover Power within 100 Hin.
High Pressure Injeciton Falls a) Avall. 9 05E-6 f.65 o AFW Available 5. lie-7 0.09 Fall to Recover b) Unavall.
within IS Hinutes, Recover Power within 8 Hours, High Pressure Injection Falls Avell 5.78E-7 0.88 o AFW Avallable 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
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Table I (Con't)
DevilWANT CORE ELT ACCIDENT SEQUENCES CONT 991T.
FAILED ffEAT FREQ./ $ OF SEQUENCE NOTE 3 SUFFORT TEAR _ TUT At, CW DESCRIFT10lt Rett)fAI.
SYSTEMS INITIATOR 0.53 ET26 is ident.
Avall. 2.89E-6 to E121. See o Conseq. LOCA -
Loss of Branch to ET23, ET 2)
Offstte Seal Failure LOCA, Power RCS Depres. Falls OR 0.17 Avalt. 9 13E-7 Low tressure Rectro. Falls
- OR 0.09 Avall. 4.69E-7 litsh Pressure -
Injection Fatts Avail. 7.69E-6 1.40 LOSF'HCC5 o Fall to Recover (DCl+EACS, tlCC-5. AFW Avail.,
DC2eEAC9) Frisary Integrity Fatts Avail 3 80E-6 0.69 o Fall to Roeover HCC-5, AFW Falla 0.89 Not Evaluated
-- 4.90E-6 Using Event free Unisolated None o Unisolated LOCA in Letiown Line 1.0C4 he Letdown Line Mot Evatustad 2.80E.7 0.05 Using Event free Interfacing Nons o Interfaatng Systems --
/
LOCA Systems LOCA Mot Evaluated s
-- 2.70E.7 0.05 Using Ever.t Tr ee None o Catastrorhia Reactor Cata- Vessel Rupture strophie Reactor Vessel Rupture 7
Table I (Con't)
DOMINANT CORE PEl.T ACCit'ENT SEQUENCTS CDNTP0ff.
FAILED FREO./ $ Or SEQUENCE REAT Noir.1 SuFFORT TEAR . TUTAL CIW' IESCRIFTIDW BEPDTAL INITIATOR 315 FEM 5 6.70E-6 1.22 Loss oF HCC-5 o Fall to Recover Avall.
HCC-5, Af W Avallable, HCC-5 Frimary Integ. Falls Avail. 7. 30E-6 1.3) o Fall to Recover HCC-5 AfW Falls Avalt. 4.2TE-6 0.78 o NCC-5 Recovered AFW Avallable, Frimary Integ. Falls, Bleed and Feed Falls, OR Avall. 4.0(E-7 0.07 Long Term Cosling Falls f.58E-6 0.29 Total Loss of IC DC1'DC2e o HCC-5 Recovered, Avail. is Not Recow.
HCC-5 Frimary Integ. Falls, 356 results in l Bleed and Feed Falta Loss of toth OR f.59E-6 0.29 semi-vital and AfW Falls, Avall. yltat Instrumtn.
Bleed and Faed Falta 4.97E-6 0.98 o Fall to Recover Avall.
HCC-5, AFW Available.
Frimary Intes. Falla 5.0 tE 6 0.91 o Fall to Recover Avall.
HCC-5. AFW Fatts 1.62E-5 2.96 Loss oF DCteDC2 o Primary Intes. Falls, Avail.
DC Sus t Bleed and Feed Falls 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 FPEO./ 5 0F Sit 0UENCE ffEAT +
SUFFORT TERR TUT At. CW DESCRIFTION RE90TAl.
INITIATOS ST5 TEM 5 5.35E-6 0.98 Loss of Mone o AFW Falls Fall Avail.
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 Avail. 2.31E-7 0.0%
Emergency Boratton Falls o Low Fressure Injee. Avall, 8.06E-5 f.47 Large None Avall, t.ow Fressure Preak ' Recirculation Falls
- LOCA o Low Fressure Injee. Avail. 3 05E-6 0.56 Falls f
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Table I (Con't)
TADI.E 6.3-5 DOMINANT CORE N:1.7 ACCIDENT SEQXNCES FAILED CONTHlf.
ltEAT FREO./ 3 0F SUFFORT SEQUENCE ftTI AL CW NOTF3 NEmTAL TEAR STSTEMS DESCRIPTI0li INITISTOS o Lou Fressure Injee. Avall, f .0 3E-6 0.19 Large Preek Avall, Lou Fressure Rectre. Avall, Two LOCA Fath Rectre. Falls 0.43 Release path o Conseq. SCTR-Branch -- 2. 36E-6 Steamline None out side Con.
Break to ET24, Illgh Pressure lainment Downstream Injection Avall, Loop NRV lsolation Falls 0.9% Failure to Isolation of Feed / Avall. 5.18E-6 o Isolate results Stenelines Fall, in Loss of SG Bleed and Feed Falls Cooling OR .
Long Term Cooling Avell, l.17E-6 0.28 Falla
- 5. 35E-6 0.98 Fath Outside Steam Mone o High Pressure Injeo. --
Containment Generator Avall, Feed / Steam Lines Isolated, 30 Tube Rupture Cooling Avall, RCS 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 a
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Table I (Con't) tiOHINANT CORE WI.T ACCIttNT SR5fENCrJ CONTP9fT .
FAILED flEAT FREO./ J OF NOTRS SUFFORT SEQUENCE item 3tAL TEAR _ TOTAL OF Sf37 Del I*SCRIFT10st
_I5111410R 5.50E-T 0.10 o Reactor Trip Falls Avell.
Steam Loop Isolation Aval!
Cenerator Tube RCs i.evel Rupture 5 77E-6 t.05 Recovery A11res-o Charging Falls, Avell.
None 50 Cooling Avall, sed as Slee4 and Unisolated Feed RCF 5eal (HFW or AF2 Avall)
Leak RCS Level Recov. Fall OR 1.89E-6 0 35 Long Term Cooling Avall.
Falla Results in t oss Avell. 6.18E-6 f.13 oF SG Cooling None o Feedline Isolation Main Falls, Bleed and Feedline Feed Falls Break OR 2.93E-7 0.05 Long Tena cooling Avail.
7.72E-7 0.14 Avall.
o Feeditna isolation Avell, 30 Cooling Falls (tF2 + AF3 Fall)
Bleed and Feed Fatta 4.82E-4 87.9 TOTALt i
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Table II CORE MELT FREQUENCIES BY INITIATORS cv rRED'JENCI SN nP PEFCEf" CO'TE BLTION l
$E DESCRID ION 1.34E-4 24.45 ET03 Small-Break LOCA i 1.23E-4 22.85 ET12 Loss of Offsite Power S.13E-5 14.84 ET02 Medium-Break LOCA 5.34E-5 9.74 ET09 General Plant Transient 3.36E-5 6.13 ET18 Loss of MCC-5 2.94E-5 5.36 ET20 Loss of DO Bus 1 1.36E-5 2.48 ET10 Total Loss of Main Feedwater 1.22E-5 2.23 ETC1 Large-Break LOCA 1.10E-5 2.01 ET06 Steamline Break Down-stream of NRV Steam Generator Tube 1.04E-5 1.90 ET04 Rupture B.45E-6 1.54 ET08 Unisolated RCP Seal Leakage Main Feedline Break 7.48E-6 1.36 ET07 Steamline Break Upstream 7.00E-6 1.28 ET05 of NRV 5 93E-6 1.08 ET16 Insufficient Flow of Service Mater LOCA Outside Containment 5.45E-6 99 V, V1 4.46E-6 .81 ET19 Total loss of DC Power
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Loss of Control Air 3.40E-6 .62 r.T17 2.66E-6 48 ET11 Loss of DC Bus 2 ET21 Loss of Semi-Vital AC 1.~t?E 6 J l
i TOTAL 5.4BE-4 100
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l Includes Station Blackout (EI 15), LOSP and Loss of MCC-5 (ET13), LOSP and Loss of one Energency Bus (ET14). l
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