ML20024B453
| ML20024B453 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/05/1979 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| TASK-*, TASK-GB GPU-2526, IEB-79-05A-02, IEB-79-5A-2, NUDOCS 8307080776 | |
| Download: ML20024B453 (5) | |
Text
=...
G90 252A P
UNITED STATES NUCLEAR REGULATORY CCMISSICN
, dr OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 APRIL 5, 1979 IE Bulletin 79-05A NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT Description of Ciret.ustances:
4 Preliminary information received by the NRC since issuance of IE Bulletin 79-05 on April 1,1979 has identified six potential human, design and mechanical failures which resulted in the core damage and radiation releases at the Three Mile Island Unit 2 nuclear plant.
The information and actions in this supplement clarify and extend the original Bulletin and transmit a preliminary chronology of the TMI accident
~
through the first 16 heurs (Enclosure 1).
1.
At the time of the initiating event, loss of feedwater, both of the auxiliary feedwater trains were valved out of service.
2.
The pressurizer electromatic relief valve, which opened during the initial pressure surge, failed to close when the pressure decreased below the actuation level.
(
3.
Following rapid depressurization of the pressurizer, the pressurizer r
level indication may have led to erroneous inferences of high level in the reactor ecolant system.
The pressurizer level indication apparently led the operators to prematurely terminate high pressure injection flow, even though substantial, voids existed in the reactor coolant system.
4.
Because the containment does not isolate on high pressure injection (HPI) initiation, the highly radioactive water frcm the relief valve discharge was pumped out of the centainment by the automatic initiation of a transfer pump.
Tnis water entered the radioactive waste treatment system in.the auxiliary building where some of it overficwed to the floor.
Outgassing frcm this water and discharge through the auxiliary building ventilation system and filters was the principal source of the offsite release of radioactive noble gases.
5.
Subsequently, the high pressure injection system was intermittently operated attempting to control primary coolant inventory losses through the electrcmatic relief valve, apparently based on pressurizer level indication.
Due to the presence of steam and/or noncondensible voids elsewhere in the reactor coolant system, this led to a further reduction'in primary coolant inventory.
h e307080776 7904o5 DR ADOCK 05000 9
.i IE Bulletin 79-05A April 5, 1979 Page 2 of 5
~
6.
Tripping of reactor coolant pumps during the course of the transient, to protect against pump damage due to pump vibration, led to fuel damage since voids in the reactor coolant system prevented natural circulation.
Actions To Be Taken by Licensees:
For all Babcock and Wilcox pressuris:ed water reactor faciliti'es with an operating license (the actions specified below replace those specified in IE Bulletin 79-05):
1.
(This item clarifies and expands upon item 1. of IE Bulletin 79-05.)
In addition to the review of circumstances described in Enclosure 1 of IE Bulletin 79-05, review the enclosed preliminary chronology of the TMI-2 3/28/79 accident. This review should be directed tcward understanding the sequence of events to ensure against such an accident at your facility (ies).
2.
(This item clarifies and expan$ upon item 2. of IE Bulletin 79-05.)
Review any transients similar to the Davis Besse event (Enclosure 2
/
of IE Bulletin 79-05) and any others which wentain similar elenents 5
fr'om the enclosed chronology (Enclosure 1) which have. occurred at your facility (f es).
If any significant deviations frcrn expected performance are identified in your review, provide details and an analysis of the safety significance together with a description of i
any corrective actions taken.
Reference may be made to previous information provided to the NRC, if appropriate, in responding to this item.
3.
(This item clarifies item 3. of IE Bulletin 79-05.)
Review the actions required by your operating procedur.as for coping i
with transients and accidents, with particular attention to:
Recognition of the possibility oi' forming voids in the primary -
a.
coolant system large enough to compronise the core cooling.
capability, especially natural circulation capability.
b.
Operator action required to prevent the formation of such
. voids.
c.
Operator action required to enhance core cooling in the event such voids are famed.
(
e
--.-,----,-,_e_,---
g,-,-
e--
=- -, ~, - me
---a e
IE Bulletin 79-05A ApriT 5, 1979 Page 3 of 5 (This item clarifies and expands upcn item 4. of IE Bulletin 79-05.)
4.
Review the actions directed by the operating procedures and training instructions to ensure that:
Operators do not override automatic actions of engineered a.
safety features.
b.
Operating procedures currently, or a'e revised to,*specify r
that if the high pressure injecticn (HPI) system has been automatically actuated because of low pressure conditten, it must remain in operation until either:
(1) Both 1cw pressure injection (LDI) pumps are in cperation and ficwing at a rate in excess of 1000 gpm each and the situation has been stable for 20 minutes, or (2) The HPI system has been in operation for 20 mhnutes, and all hot and cold leg temperatures are at least 50 degrees belcw the saturation temperature for the existing RCS pressure.
If 50 degree subcooling cannot be maintained after HPI cutoff, the HPI shall be
)
reactivated, Operating procedures currently, or are revised to, specify c.
that in the event of HPI initiation, with reactor coolant pumps (RCP) cperating, at least one RCP per iccp shall remain operating.
d.
Operators are provided additional infor=atien and instructions to not rely upon pressurizer level indication alene, but +4 also examine pressurizer pressure and other plant parameter indications in evaluating plant conditions, e.g., water inventory in the reactor primary system.
5.
(This item revises item 5. of IE Bulletin 79-05.)
Verify that emergency feedwater vr.1ves are in the open position in accordance with item 8 below.
Also, review all safety-rela +ad valve positions and positioning requirements to assure that valves are positioned (open or closed) in a manner to ensure the proper operation of engineered safety features.
Also review related procedures, such as those for maintenance and testing, to ensure that such valves are returned to their correct positiens folicwing necessary manipulaticns.
.3 4
y,m
,,_-,.m
,r,,--,y,ir-,
,.-,y-y-.
- E IE Sulletin 79-05A April 5, 1979 Page 4 of 5 6.
Review the containment isolation initiatien design and procedures, and prepare and implement all changes necessary to cause containment isolation of all lines whose isolation does not degrade core' cooling capability upon autccatic initiation of safety injection.
7.
For manual valves or manually-operated motor-driven valves which could defeat or ccepremise the flew of auxiliary feedwater to the steam generators, prepare and implement procedures which:
a.
require that such valves be locked in their cerrect position; or b.
require other similar positive positien controls.
8.
prepare and implemen't immediate'ly procedures which assure that two independent steam generator auxiliary feedwater flow paths, each with 100% ficw capacity, are operable at any time when heat removal frcm the primary system is through the steam generators. When two inde-pendent 100% capacity ficw paths are not available, the capacity shall be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant shall be placed in a cooling mode which does not rely en steam generators for cooling within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
When at least one 100% capacity ficw path is not available, the reactor shall be made suberitical within ene hour and the facility placed in a shutdown cooling mode which does not rely on steam generators for cooling within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or at the maximum safe shutdewn rate.
9.
(This item revises item 6 of IE Bulletin 79-05.)
Review your operating modes and procedures for all systems designed to transfer potentially radioactive gases and liquids out of the primary containment to assure that undesired pumping of radioactive liquids and gases will not occur inadvertently.
In particular, ensure that such an occurrence would not be caused by the resetting of engineered safety features instrumentation.
List all such systems and indicate:
a.
Whether interlocks exist to prevent transfer when high radiation indication exists, and b.
Whether such systems are isolated by the containment isolation signal.
?.'.'
~
IE Bulletin 79-05A April 5, 1979 Page 5 of 5
?&
10.
Review and modify as necessary your maintenance and test procedures to ensure that they require:
a.
Verification, by inspection, of the operability of redundant safety-related systems prior to the removal of any safety-related system frem service.
b.
Verification of the operability of all safety-related systems when they are returned to service following maintendnce or testing.
c.
A means of notifying inv0ved rea.ctor operating personnel whenever a safety-related system is removed frem and returned to service.
- 11. All operating and maintenance personnel should be made aware of the extreme seriousness and consequences of the simultaneous blocking of both auxiliary feedwater trains at the Three Mile Island Unit 2 plant and other actions taken during the early phases of the accident.
12.
Review your prcmpt reporting procedures for NRC notification to assure very early notification of serious events,
'i For Babcock and Wilcox pressurized water reacter facilities with an operating license, respond to Items 1, 2, 3, 4.a and 5 by April 11, 1979. Since these items are substantially the same as those specified in IE Bulletin 79-05, the required date for response has not been changed.
Respond to Items 4.b through 4.d, and 6 through 12 by April 16, 1979.
Reports should be submitted to the Director of the appropriate NRC Regional Office and a copy should be forwarded to the NRC Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Washington, CC 20555.
Fcr all other reactors with an operating license or construction permit, this Bulletin is for information purposes and no written response is required.
i Approved by GAO, B 180225 (R0072); clearance expires 7-31-80.
Approval was given under a blanket clearance specifically for identified generic prcblems.
Enclosures :
f 1.
Preliminary Chronology of TMI-2 3/38/79 Accident Until Core Cooling Restored.
1 2.
List of IE Bulletins issued in last 12 months.
r m
,,, _ _ _ _ _ _ _ _ _.