ML19256E198
| ML19256E198 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/28/1979 |
| From: | Harold Denton, Stello V NRC OFFICE OF INSPECTION & ENFORCEMENT (IE), Office of Nuclear Reactor Regulation |
| To: | Gilinsky V, Hendrie J, Kennedy R NRC COMMISSION (OCM) |
| References | |
| NUDOCS 7910300070 | |
| Download: ML19256E198 (16) | |
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MEMORANDUM FOR:
Chairman Hendrie Commissioner Gilinsky
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" Commissione7 Kennedy ~
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Commissioner Bradford Commissioner Ahearne THRU:
Lee V. Gossick
' Signed)T. A.Rehm Executive Director (for Operations FROM:
Harold Denton, Director, Office of Nuclear Reactor Reg 0latior.
Victor Stel-lo, Jr., Director Office of Inspection and Enforcement
SUBJECT:
INCIDENT AT NORTH ANNA ON SEPTEMBER 25, 1979 By memorandum dated September 26, 1979, initial responses were provided to the-Commission's requests for information concerning the incidert at North Anna on September 25, 1979.
Additional information with regard to two of those requests is presente1 below:
1.
Reauest Provide a detailed chronology of the measures taken by the licensee and the NRC staff to notify appropriate state and Federal officials of this incident, and an analysis of how well the notification system functioned.
Response
A detailed chronology of the measures taken by the licensee and the NRC staff to notify appropriate officials is set forth in Enclosure 1.
An analysis of how well the system functioned is in progress.
2.
Reouest Assure that the Commissioners be kept informed of all new significant information on an on going basis.
Response
The sequence of events which occurred at North An a is described in Enclosures 2 and 3. covers reactor systems even s andeEnclosure 3 covers radiological release and monitoring events.
In.at lition, descriptions of the principal radiological events are given in Enc osure 4.
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, ;.c The informatica presented in these responses is preliminary and will be revised, corrected, <r supplemented as our knowledge of the incident and the circumstances surrounding it increases.
VictorStello,.4.Y'd'lY Harold Denton f' Director Director Office of Inspection Office of Nuclear and Enforcement Reactor Regulation 1224 306
ENCLOSURE 1 Personnel Notification and Action Event 6:09 a.m.
Reactor Trip Event,6:13 a.m.
Safety Infection from low pressurizer pressure.
6:13 a.m.
Control room operator calls On-duty supervisor, the North Anna Operating Supervisor, after plant trip.
Safety injection occurred while on phone.
The operating super-visor recommended MSIV closure.
Control room received call from IE Incident Response Center inquiring as to plant status, the caller was informed that the reactor was tripped and that a low-pressure safety injection has just been received.
(see response to item 2, Commission reply dated 9/27) 6:20 a.m.
The North Anna Station Manager, arrived on site, went to control room.
Safety injection was still in progress.
6:40 a.m.
The North Anna Superintendent of Operations, arrived on site and went to centrol rocm.
First reactor coolant pump had just been restarted.
6:50 a.m.
VEPCO Director of Nuclear Operations, notified of plant trip by the Station Manager.
[224307
b 6:55 a.m.
The Operating Supervisor arrived at the control room, got briefing, reviewed plant status.
Event,7:00 a.m.'
Auxiliary Building radiation monitor increased to 1000 times background.
Auxiliary Building evacuated.
7:05 a.m.
Auxiliary building air samples taken.
7:20 a.m.
The North Anna Health Physics Supervisor arrived and went to control room.
Reviewed radiological problems, proceeded to direct efforts by H. P. staff.
7:30 a.m.
Auxiliary building posted as an a.irborne radiation area,.
w 7:30 a.m.
Resident Inspector arrived at site.
7:50 a.m.
The Station Manager notified the NRC Resident Inspector of reactor trip and safety injection current status.
7:58 a.m.
Tr.e Resident Inspector notified a RONSB Section Chief, Region II of trip and scfety injection, plant status.
Proceeded to control rcom to assess plant status and obtain details of event.
8:00 a.m.
The Director of Nuclear Operations called plant management regarding status and plans for remaining shutdown and begin refueling outage or return to operations.
1224 308
8:20 a.m.
The VEPC0 Superintendent of Technical. Services, arrived in control room af ter visit to station services office.
Received briefing on way to control room.
Started reviewing reportability of event, dispatched engineer to gather information on it, checked on H P., chemistry activities; initiated an engineering evaluation of rapid cooldown of reactor coolant system due to safety injection.
Westinghouse contacted on this.
8:50 a.m.
The Resi~ dent Inspector called a Region II RONSB Section Chief to provide more details on event and plant status.
,The plan'.
'd been returned to no-load Tavg and was stable.
Event 9.00 a.m.
Auxiliary Building radiation monitor indicated background.
9:00 a.m.
The birector of Nuclear Operation informed station management of decision to remain down to begin outage.
Problems observed during trip and safety injection reviewed further.
10: 40 a. m.
Region II informed IE Headquarters / Field Coordination of the event.
10:50 a.m.
The Resident Inspector related additional information to his Section Chief; activity levels, plans for shutdown, excessive cooldown rate.
1224 309
_u -
4 11: 00 a.m.
Region II initiated the transmittal of Preliminary Notification PN0-II-79-1 to H Street, Maryland National Bank Building, Phillips Building and East-West Towers.
Transmittal completed at 11:20.
11:00 a.m.
Commonwealth of Virginia (Bureau of Radiation Health) was informed by Region II.
11:15 a. m.
A second contact was made with Commonwealth of Virginia by Region II to correct PN statement on news release.
11:45 a.m.
JE Field Coordination informed IE Technical Programs.
12:00 p.m.
Additional exchange of information between Technical Programs and Region II.
12:15 a.m.
Technical Programs briefed the Director of Inspection and Enforcement.
12:15 a.m.
Field Coordination informed the NRR Chief of Operating Reactors Branch 1.
12:30 p.m.
Region II informed NRR Licensing Project Manager.
12:45 p.m.
Technical Programs informed Nuclear Reactor Regulations.
1224 310
1: 00 p.m.
IE Deputy Director notified Congressional Affairs between 10:00 a.m. and 1:00 p.m.
1:00 p.m.
Region II, also, informed NRR Chief of Operating Reactors Branch 1.
1: 00 p.m.
VEPC0 notified County administrations of Lousia and Spotsylvania Counties.
1:15 p. m.
NRC Operations Center was manned.
1: 30 p.m.
,NRC Operations Center obtaineu status of plant fr,m Resident Inspector.
1: 30 p.m.
The NRC Operations Center notified the following persons of the event:
Chairman's Technical Asristant Executive Director fsr Operations Commissioner Bradford's Technical Assistant Commissioner Ahearn's Technical Assistant Commissioner Gilinsky Director of Nuclear Reactor Regulation 2:29 p.m.
NRC Operations Center obtained status of plant from VEPC0 Vice President.
) ). A.
9 5-2:30 p.m.
NRC Operations Center reached Commissioner Kennedy's Technical Assistant.
,2:54 p.m.
VEPCO.Vice President and the Plant Manager discussed the event and plans with the NRC Operations Center.
VEPC0 agreed to put the plant in the cold shutdown mode per normal procedures and to issue a press release.
3:00 p.m.
VEPC0 notified Commonwealth of Virginia Office of Emergency Services.
4:07 p.m.
b'hite House Situation Room was notified.
4:15 p.m.
Director, IE, called Governor's Office 4:57 p.m.
Commonwealth of Virginia informed of PN supplement.
7:30 p.m.
DOE was briefed.
1221 312
ENCLOSURE 2 SEQUENCE OF REACTOR EVENTS Much of the following'information was taken from the data acquisition system.
Because of system limitations, the times given are approximate.
0544 Reactor power was at 78%.
A tube rupture in the drain cooler for low pressure feedwater heater 58 caused drain cooler dump valve LCV-SD-1248 to cycle.
The valve apparently failed clored causing extraction steam condensate to back up irto the feedwater heater.
0609 The turbine tripped on high nigh level in feedwater heater 58.
The reactor tripped because of the turbine trip.
The main steam dump
'alves ope'ned automatically to reduce the reactor coolant temperatur_e below the no-load setpoint which is 547 F.
One of the main steam dump valves failed in the open por,ition causing the reactor to cool down rapidly below 547 F.
0610 The low pressurizer pressure alarm actuated at 2022 psig.
The temperature in loop 2 af the reactor cooling system was 537 F, 100 below the saturation temperature.
At least one bank of pressurizer heaters actuated and an auxiliary feedwater pump started.
0611 Pressurizer pressure was 1901 16psig.
The temperature of the reactor coolant system cold leg was 533 F, 94 below the saturation temperature.
Condensate pump 1C tripped.
Main feedwater pump C tripped because of low condensate pressure.
Steam generator low level alarms actuated.
122.;
313
0612 The temperature of the reactor coolant system cold leg was 522 2 F.
The level in the volume control tank was low at 17%.
0613 Safety injection initiated automatically because of a low pressurizer pressure signal, the low pressurizer level signal had been previously administratively tripped based on IEB 79-06A.
The event resulted in a decrease in pressurizer level below the trip setpoint.
Pressurizer level was at 0.2% and the alarm setpoint is at 9%.
0614 The reactor coolant system cold leg temperature was 507 3 F.
0615 High pressure safety injection pump B started.
The low pressure safety injection pumps started.
Main feedsater pump A tripped because of the safety injection signal.
0617 Pressurizer level was at 9.4%.
0615 Pressurizer pressure was at 2161 5 psig.
0619 Main steam trip valves had been closed to stop steam dump.
Steam pressure was 596 psig.
Safety injection was reset.
Charging pump (HPI) B was tripped.
0620 Reactor coolant system cold leg pressure was 2314 psig.
0621 Pressure in steam generator 2 was 596 psig.
Feedsater pump C was started.
1224 314
0623 Net volume of water charged into the reactor coolant system in the preceding 10 minutes was 2564 gallons.
0625 Auxiliary feedwater pumps 3A and 3B were stopped.
0627 The power operated relief valve cycled to limit the pressure rise in the reactor coolant system.
Letdown to the chemical and volume control system was -initiated.
0628 Pressurizer pressure was 2340 psig.
Steam generator 3 pressure was 612 psig., _
0629 Reactor coolant pump 1B was started.
Auxiliary pressurizer spray was initiated.
0631 Pressurizer level was 63%.
0639 Pressurizer power operated relief valve was closed.
0648
.'ae relief valve on the volume control tank lifted, thus transferring reactor coolant to the high level waste drain tank and releasing dis-solved noble gases to the auxiliary building via the waste system vent.
An incorrectly connected vent line allowed venting directly to the auxiliary building.
122 J:
315
ENCLOSURE 3 Radiologi 31 Seouence of Events Date Time Item Results 9/23 0730 Reactor Coclant Sample I-131-3.9 E-2 uc/cc 9/25 0000-0400 Auxiliary Bldg. Air Samples No significant activity 0609 Reactor Trip
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% 0700 Auxiliary Building Air Increased to ^- 1000 times Monitors Increase background - returned to background by 0900 S 0700 Evacuated Auxiliary Building Two people 0705-0710 Auxiliary Building Air 100-150 times NPC Samples 0720-0803 Auxiliary Building Vent Sample Result.c 133 Vent A Xe
- 2.0 E-5 uc/cc Xe 35 - 9.6 E-6 uc/cc 1
2, Xe*"" - 1.0 E-5 uc/cc
- i221, 316
Vent B Xe
- 1.0 E-5 uc/cc 0830-1430 Auxiliary Building Air Noble gas activity Samples
< 10% MPC by 1030 0940 Reactor Coolant Sample I-131-8.IE-2 uc/cc 1400 Containment Entry ano Air Activity - 240 x MPC Sample (not unusual for operating PWR facility) 1600 Reactor Coolant Sample I-131-1.4E-1 uc/cc N1700 South Fence Line TLDs Changed No exposures above background 12L24 317
ENCLOSURF 4 RADIOLOGICAL EVENTS Radioactivity Released From the Plant Tha vent stacks and process vent were continuously monitored by the installed monitoring system for noble gas and particulate activity during the transient.
Continuous cartridge collection sampling systems for iodine were in operation.
Noble gas monitors increased about a factor of 200 over ambient, returning to ambient levels by 0900.
All monitor systems remained operational and on scale throughout the release.
In addition, grab samples were' collected from the auxiliary building vents.
Based on an analysis of th'ese samples, it is estimated that approximately 7.5 curies _
of noble gases (pr.imarily Xe-133) were released over a period of three hours.
No iodine activity was detected in the samples.
The release aolounted to approximately 0.1 percent cf,ne applicable license limit.
(i.e., 0.1% of the maximum allowable instantaneous release rate)
Offsite Radiolooical Iroact During the period of release the wind was blowing from the North to the South.
Using site meteorological data, the dispersion factor (X/Q) at the site boundary was 4 /10-6.sec/m.
Based on a total estimated release of 7.5 curies over a three hour period, the dosa to an individual at the site boundary would be less
~
than.01 millirem Fourteen (14) TLDs at the site boundary were pulled subsequent to the transient and showed no exposures above background.
1224 318
Plant Personnel Exposure No significant personnel exposures resulted from the transient.
A total of five plant personnel were involved with the evacuation and re-entry of the auxiliary building.
(Two people had to be initially evacuated.) The maximum radiation dose received by any single plant personnel was 10 millirem as measured by pocket dosimeters.
The TLDr of the five personnel involved were read with the following results for the exposure periods involved:
~
Personnel Total Dose Exposure Period A
157 mrem Sept.
B 71 mrem Sept.
C 17 mrem July /Aug/ Sept D
13 mrem Sept.
E 3 mrem 10-26 Sept.
2.adioactivity Evaluation - In Plant Shortly af ter reactor trip, air samples of the auxiliary building indicated
. Xenon at approximately 100-150 times MPCs.
Levels reduced to less than 10 per-cent of MPC, by 1030.
71' 71O lLLb Jl /
_ 3-Primary coolant samples showed only slight increases in iodine concentrations which are expected to cccur foll.owing a reactor trip.
In' plant area direct radiation monitors and direct radiation surveys showed no significant increase above normal levels.
m e
- 1227, 320
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