ML19289F863
| ML19289F863 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/31/1979 |
| From: | Crews J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Sternberg D, Thompson D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| NUDOCS 7906200462 | |
| Download: ML19289F863 (10) | |
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Bachround Informat, ion and'Historl
'F*om Grev Book (Feb.19791 bI Licensee: Metropolitan Edison Company A/E:
Burns A Roe N5SS:
0&W Pressurized Water Reactor, 277? W (906MWE).
!nitial Crit.
3-28-78 Co.mercial Ops.
12-30-78 c350 lie of operation Containment isolation valves failed to close Spe.cific Ite:cs
'12-13-78 on an autmiatic test s.ignal due to an inoperable actuation logic relay.
NRC witnessed generator trip from 96% power.
' 12-P R-78 Routine turbine trip at 154 power.
'1-15-79 Condenser vacuum degraded (cause uaknown)
Closing turbine bypass valves, lif ting S/G reliefs. Both relief discharge bellows ruptured.
Operations resumed 1-31-79.
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}lednesda_y, fierch 28. 1979 c...
Whi. operating at 93*i power, a problem occurred in the
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4:00 a.m.
Loss of Feed feedwater polishing system-(full flow condensata demineralizers
/G "E 935 to remove condensate impurities to preclude their entry into p
S/G) causing S/G feedwater pumps to trip.
u The loss of feedwater flow to the 5/G caused a turbine cenerator Turbine Trip Si_p..
(Steam ficw/ feed flow mismatch).
StN m bypass valves opened to durrp steam to condenser (cutomatic ection).
u pen
( The resulting transient on the primqry systea ccused n RX Scrap
( reactor scram due to hich reactor ecclant oressure.
[ The resulting transient on the primary systea also caused a
'>zr. Itelie f Prassurizer then OP'"S-relief vulva on the pressurizer to open.
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y started relieving pressuriecr steam to the pressurizer relief tank (in containment).
(It is not clear if this relief stuck open or was manually opened by operator but the relief remained open after k
the high pressure transie,t was over.)
P7r. Relief Pressurizer relief tank overpressurized and through " Blew-Out Tank Vent 2 Disks" vented to the containment building.
Containment building pressure increased due to the venting Containment Frenure t of r. team inside containment.
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,f i RCGM-5(Saf ety injection TGbnitiM.csci.due,t,c.Mgh m..LS Safety N
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pressure (
4 psi).
240 002
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Safety injection started flow into the prirary at 1600 PSIG P7r Level 'f
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primary pressure pressurizer level was obs2rved increasing.
The steam driven auxiliary feedpump started and' fed water to S/G. -
A6r.. Eced Pump f Steam dump through the steam bypass valves to the turbine Harmal Core Peactor coolant Cooldown conde.nser provided cooldown of the reactor.
puw s were in operation and S/C's were being fed by the
( Au dliary Feed Pump (steam driven).
' As normal core cooling was established, and pressurt2cr level secured 5.I.
was increasing, the operator uent to reset on safety injection and secured safety injection pumpr..
Howev+r, it appears (there was that the pressurizer relief remained open.
(a h_igh water level in the pressuri7er.')
f t!ater from pressurizer relief valve vc ting to pressurizer Pzr. Relief relief tank flowed to reactor coolant drain tenk.
Tank m
Drain Tank (Within Containment).
(
f The resetting of safety injection allowed valves to open Urain Tank to to permit automatic pumping of reactor caclant drain tanks t
to holdup tanks in the auxiliary building.
( 240 003
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The oper ator appears also to have shut the tain steam isolation Shut MSIV valves. 'ihis action secured steam finw hnd to the condenser. This removed the normal s
, core cooling flow path La the heat sink.
Safety's Open The steam generator code safety's opened and casr.enced
. venting steam to atmosphere.
Due to the pressurizer relief operation pressuri7er level began Pzr. l.evel to rapidly drop.
Tube failure Dee to the pressure surges there also appears to be some S/G S damage to the primary to secondary boundry of 5/G B.
Tripped RCP' e.
? The loss of pressure required tripping of all reactor coolant pumps due to loss of on low NPSR.
4
( net positive suction head.
Vapor in
( The loss of primary system pressure continued unchecked Th. Legs.
resul ting, in vapor bubble formation in the loop Th legs.
(B & W plants have single pass vertical steen generators naking the Th leg the system high point.)
e 1oss of This tripping of reactor coolant pumps and subseauent vapor flatural 1 ck of the lh legs stopped all primary coolant flow to the Circu la tion Flow to S/G.
steam generators for heat removal purposes.
(The vapor
, formation in the Th legs blocked natural circulation).
240'004 6
s At this point, it appears the vapor bubble enisrged 'nto Uncovered Reactor
- Core, the reactor vessel uncovering at least partially the upper I, core.
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f The decay heat generation then could have decaged clad Clad Failare
, integrity.
Pelease of Fission ( Fission products released by clad failure then vented through the still open pressurizer relief to the o
n t,
, pressurizer relief tank and then to both (1) the inside l of containment via the rupture disks on the pressurizer relief tank and (P.) tu. the reactor coolant drain tank
( within the containment building.
Fission Products (With the safety injection system in reset, the automatic pumping of the reactor coolant drain tank to tht holdup u
u ng.
tank in the auxiliary building (previous :y described) t continued.
Holdup tank As an inadequate number of holdup tanks was on the line to receive the volume of water transferred ircin the reactor A
dg.
coolant drain tank, the holdup tank overficwed to the floor I( of the Auxiliary Building.
Spill to Atmos, t' This released fission products to a flow path to atmosphere via Auxiliary Building ventilation.
( Aux, Oldg. Ventilation ft system contains HEFA and ch;2rcoal filters.)
+
240 '005 6
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Prinaiy to
.Another flow pat' of fission products to at=csphere was 0".fa primary to secondary to atmosphere by means of the tube to 9
[ damage to B steam generator and the operation of code (safaty'stoatmosphere.
Cooling by
[ At this time, the cooling of the core was attempted by O]g""d use of the letdown und charging system. This proved to g
q be inadequate due to blockage of filters in the letdown
- system, I
s Selection of At this point, there were several methods available for core Cooldown Method.
cooldown:
(1) Lepressurize the primary system and recirculate water from the containment sump to the primry via
/ Lhe safety injection (low pressure) system, or (2) Pressurize L the reactor coolant system to collapse the vapor bubble-;
in the coolant loops, start a reacter coolent pump and line up to dump steam to the condenser. The second method (the normal cooldown procedure)was selected by the licensee.
-..aW d 3:30 p.m.
Fadnesday,flarch 28, 1979 Bubble was collapsed in a reactor coolant loop hot leg.
Natural circulation flow was established. Pressurizer level
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has been brought into the range of level indication and some heaters are in operation.
Plans are to cooldown at 3"F/hr until the decay heat removal system (RHR) can be placed in operation at 350 PSIG and 350"F.
240 006.
4 3:00 a.a.
Thursday. Marph 29, 1979_
Primary syste:n pressure 850 PSI at 250"F.
1 P.eactor coolant pump in opera' ion to A steam generator (3 steam generator isolate,d)
Lining up to pump Aux. Building water to containment-sw.:p and place polly on Aux. Building floor to cover spill. Additional holdup tanks lined up to receive water.
Refueling water storage tank at approxicately the 22 ft.
level out of approx. 50 ft, Containment sump level indicators are pegged high.
Cooldown has continued since 1:00 3.m. at 1/2*F/ hour.
5:45 p.m.
RHR in service. Water pumped f-ani Aux. Bldg. Ficor to Containrcent.
-y-240 003 W
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a Off Site
!!arrisburg Airport (
? miles frota Plant) 17 mR/hr Rac?ation.
Harrisburg area (
10 miles away) 0.33 cP./hr detectable
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16 miles from Plant (7:30 a.m.1
' Currently radiation levels have returned to naar background l evel s.
Across River (East of Plant), I-131 10'8 cCi/cc detectable (low level)
One milk sample, I-131 Plant Radiation:
Control Room 4 mR/hr Control Room, airborne activity masks in use (non-essential personnel evacuated)
=..
North Cate Max 70m /hr o
Aux. Bldg. (lower le.vels) 8-92/hr Containment Bldg.
Conflicting information (one monitor'in dome shows 6,000 R/hr, another detector near incore monitors shows 500-600mR/hr).
240 008
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4
- 9 Friday, March 30, 1979 8:00 a.m.
Aux. Bldg. water removed to containment.
Primary 100J psi; 275" by in core thermocouples. Attempt to cool down by dumping system secured due to low steam pressure.
Presently the decay heat removal path is injection of 110 by high pressure safety injection, and draining via 2power operated pressurizer relief to containment.
Do not intend to utilize RilR cooldown at this time.
Surveys of island on Thursday showed less than 2mR/hr.
(Found 131}
no Sample taken on primar ' via letdown sample line Thursday a.m.
100 mi read 1000 R on contact 1 mi sent to Bettis.
Uncontrolleg Release While venting makeup tank to waste. gas ovorpressurized vent header and popped relief (time unknown; 2 min to several hours)
(Evacuation of vicinity of site possible if vented for several hours.)
__ - 3) -
240 009 i