ML20086C468
| ML20086C468 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/19/1974 |
| From: | Schwalje E Public Service Enterprise Group |
| To: | Knuth D US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086C466 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311280020 | |
| Download: ML20086C468 (4) | |
Text
sa i O pag e
Public Service Electric and Gas Cornpany 80 Park Place Newark, N.J. 07101 Phone 201/622-7000 November 19, 1974 Dr. Donald F.
Knuth, Director Directorate of Regulatory Operations 7920 Norfolk Avenue Bethesda, Maryland 20014
Dear Dr. Knuth:
FIRE AT EQUIPMENT HATCH CONTAINMENT NO. 2 NO. 2 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-311 On October 21, 1974 a verbal report was made to Region 1 3 Directorate of Regulatory Operations, advising of a fire which occurred approximately 11:20 p.m. on October 18, 1974 around the heavy equipment hatch at Reactor Containment of No. 2 Unit.
This report was in acecrdance with provision of 10CFR50.55(e).
On discovery of the fire, on-site personnel immediately notified fire-fighting units of Lower Alloways Creek which arrived on site approximately 11:47 p.m.
The fire was extinguished with water and the fire-fighting units left the site approximately 1: 30 a.m.
Burned in the fire was the wooden form constructed around the lower portion of the equipment hatch which was to be poured on Monday, October 21, 1974.
The temporary deck on the equipment pedestal and all the wooden supports outside the forms were burned and destroyed.
The wooden roof over the substation was burned and charred.
All the electrical cable s and extension cords coming from the substation under the pedestal going through the heavy equipment hatch into the containment were burned.
The cables did not burn or support combustion into the containment building itself.
The heavy equipment hatch steel frame, rebars and concrete in the area were subjected to various amounts of heat from the fire.
Special efforts were made by the fire department to cool the hatch and adjacent steel with spray water.
The heat caused some spalling of concrete at the hatch way under and on top of the heavy equipment pedestal platform.
Lead wires from strain gauge s coming through the poured concrete were damaged.
8311280020 741209 PDR ADOCK 05000311 S
PDR The Energy People p // 952001 I,~
O O
~
Dr. D.F. Knuth 2-11-19-74
/
A committee was formed October 21, 1974 to investigate the cause, the extent of damage, th6 loss and preventive measures.
No clear evidence indicating the cause of the fire has been found either by the investigating committee or the Insurance Company (NML).
However, po s sible causes may be conjectured from the following observation s:
a.
A check of the forms on the opposite side of the hatch which was unaffected by the fire revealed that the forms were very dry.
b.
Though all of the cables suffered varying degrees of damage, two (2) 110v lines were completely burned through.
c.
A strong wind was blowing through the area in front of the equipment hatch, intensifying any fire which may have started there.
There is a possibility that the two llov lines may have abraded against some metal (rebar, etc.),
causing a spark which ignited the forms.
It is also possible that a discarded, lighted cigarette may have ignited some materials.
As stated pre-viously, no conclusive evidence was found supporting either premise.
Following the inspection by the committee and Insurance Company on October 21, 1974, work was begun to clear the area of ' debris (burned forms, loose strongbacks, etc.), and to reinstall cablec and establish scaffolding for repairs and form work.
The Structural Division of the PSE&G Engineering Department, together.
with the PSE&G Energy Laboratory began their detailed investigation of the areas of the containment affected by the heat to ascertain if any structural damage had occurred on 0ctober 30, 1974.
The results of their findings to date are:
l l
Reinforcing Bars:
The reinforcing bars adjacent to the-equipment hatch were sub-ject to the greatest heat as was evidenced by the slight dis--
coloration of the bars.
Four (4) No. 9 bars in this area-vere selected for tensile tests to determine if they had been adversely affected by the heat.
The test bars were sele cte d on the basis of the following:
1.
According to eyewitness reports, they were in the areas of greatest heat and flame intensity.
I i
p,,.
}
d
'3-11-19-74
'Dr.
D.F. Knuth 2.
These bars were in the exterior layer and nearer to the flames than the interior 18S bars, and being smaller in diameter would have been heated to a higher temperature than the larger bars.
All the bars cut out in this-area and tested showed results above the specified 90,000 p.s.i. ultimate strength.
A sample No. 9 bar containing a cadweld splice was also cut out and tested and it also passed the 90,000 p.s.i.
ultimate strength requirements.
From these tests we are satisfied that neither the reinforcing bars or the cadweld splices have been adversely affected by the fire.
Reinforcing bars will be replaced where test sample s were taken.
Concrete:
Visual inspection of the concrete on the outside of.the con-tainment indicated surface spalling of the concrete over the areas subject to the direct heat of the flames.
The spalling did not appear very deep nor had the concrete undergone any_
change in color which would have indicated exposure.to extreme temperatures.
After the observations were made, the concrete-was chipped back in the spalled areas to sound hard concrete.
The amount of concrete removed varied from 1/2 inch to a maximum of about.
3 inches in some localized areas.
The soundness of the under-lying concrete was verified by means of a Swiss Hammer and a.
Windsor Probe which were previously calibrated using the con--
tainment concrete untouched by the fire.
Both devices' indicated that the compressive strength of the concrete under the spalled-areas was sound and exceeded the specified minimum strength of-3,500 p.s.i.
As the damaged concrete was limited to-the outer surface of the wall, we have concluded that the structural integrity of. the containment was not impaired.
The spalled areas will be repaired by bondin'g a=high strength-grout to the original concrete and finishing-it.off.to.the line-of-the original surface.
Equipment Hatch The portion of the equipment hatch tube that_is welded to the-
. liner ^ plate and_ projects inward forming part;of.the' containment' pressurefboundary was unaffected by the fire.. The paint._oncthe~
liner plate and' adjoining equipment-hatch 1 tube was.found'to_be_-
in perfect condition'showingrthat-the heat'from theLfire.did not penetrate-to.this area'and could not:have.affected the
~ integrity.of the containment.
^
.A
h o
O
-Dr.
D.F. Knuth 4-11 7h The paint on the lowe,r section of the tube projecting beyond the outside of the containment was burned.
No evidence of damage or warping from exposure to heat was observed.
As reinforcing bars adjacent to the tube and subject to greater heat suffered no loss of strength, we concluded that the much more massive tube was undamaged.
This part of the tube which projects outward from the containment is not part of the pressure boundary system.
A non-pressure tight head will be bolted to this end and serve only as a weather and missile shield.
Strain Gauges:
Some damage was done to the strain gauges located on the reinforcing bars around the hatchway.
We expect, however, to have fully 50 percent of these in working order.
This number is deemed adequate as Unit.No. 1 is fully instrumented to verify the design.
To summarize, we have from our investigation assured ourselves that the integrity of the containment has not been impaired as a result of the fire.
The repairs due to this fire are expected to be completed by mid-December 1974.
Since electrical sho rting may have caused this fire, new replace-ment electrical cables are being installed in steel conduit from the distribution cabinets to the interior of the containment as a preventative measure.
Communications and instructions between United Engineers & Constructors, Inc. Safety Department and on-site construction personnel will be improved to keep the former better informed on the status of fire-fighting equipment and pro-tection systems.
This should improve the availability of this equipment in times of emergency.
Detailed results of our tests and evaluations will be available at the plant site for your future inspection.
If you desire additional information on this subject, we will be-pleased to discuss it with you.
Very truly yours, if *
(. &
P E. N.
Schwalje Manager of Quality Assurance i
Engineering & Construction j
Department
[
CC Mr. J.
P.' O'Reilly l
King of Prussia, Pa.
, _ =
O G
FO M
tO E',j G=
N u,;
>~ ~a c3 Cn LAJ d
Y,*, t 3
~
LaJ Lu "3 O
g c ', t s.
Ld
'J N
,i o
?
r.
Z
....)
m A
e D
i I
l
,