ML19262B074
| ML19262B074 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 11/16/1979 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML19262B069 | List: |
| References | |
| NUDOCS 7912110513 | |
| Download: ML19262B074 (10) | |
Text
9 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD IN THE MATTER OF
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COMMONWEALTH EDISON COMPANY
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Docket Nos. 50-295
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50-304 (Zion Station Units 1 and 2)
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Proposed Amendments to
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Increase Spent Fuel Storage
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Capacity (43 F.R.
30938)
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AFFIDAVIT OF TOM TRAMM I, TOM TRAMM, of lawful age, being first duly sworn, upon my oath certify that the statements contained in the attached pages and accompanying exhibits are true and correct to the best of my knowledge and belief.
Wh.fW SUBSCRIBED AND SWORN TO before me this / _,a day ofNovember, 1979.
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Notary Public My commission expires / C'.'
19 /.
/
7 912110 $2 1532 205
AFFIDAVIT OF TOM R.
TRAMM My name is Tom R.
Tramm, I am employed by Common-wealth Edison Company as Project Engineer for Zion Station.
My education, background ael work experience were outlined in the testimony I gave in this proceeding in June 1979.
Because of observed cracking in low pressure type 304 stainless steel piping systems the NRC's Inspection and Enforcement Bulletin IE 79-17, issued July 26, 1979, called for inspection and nondestructive examination of safety-related stainless steel piping that contains stagnant or essentially stagnant, oxygenated, borated water.
On October 29, 1979 the NRC issued revision 1 to IE Bulleting 79-17, which among other things more clearly defined the systems to be inspected.
Although Zion's spent fuel pool is not considered stagnant, it does c'7tain oxygenated, borated water and there is type 304 stainless steel present.
As discussed in my previous testimony the spent fuel pool is lined with 3/16" thick type 304 stainless steel sheets that are welded together and to anchors embedded in the concrete pool structure.
The pool cooling system contains welded type 304 stainless steel piping and other unwelded type 304 compo-nents such as heat exchangers, pumps and valves.
1532 206
The fuel assemblies stored in the pool have top and bottom nozzle assemblies cast from type 304 stainless steel.
There is also stainless steel in the rod control cluster (" spider") assemblies, the burnable poison rod assemblies and the control rods.
However, the spider assemblies and attached control rods are removed in the reactor core during refueling and re-used in new fuel assemblies.
They are nc ' present in the spent fuel stored in the pool, except in tne unusual case of a full core discharge.
There are some burnable poison rod assemblies within the stored spent fuel assemblies, but they, like the spider assemblies and attached control rods, play no structural role.
The present fuel racks are fabricated entirely from type 304 stainless steel plate, bar, angles, and sheet with welded connections.
The proposed racks will also be made of welded type 304 stainless steel sheet, bar, and plate.
These new racks will also contain Boral.
The proposed fuel racks contain structural weld joints of two basic types.
Each spent fuel storage tube has a full-penetration weld which runs from top to bottom along one side of the 0.105" stainless steel outer sheath of the tube.
This weld is made prior to the final forming process in which the inner and outer stainless steel sheaths with the boral plates in the middle are squeezed together 1532 207
and made square.
The dotted line on the attached sketch (Exhibit 1) indicates the apprc~' mate location of the full-penetration weld.
There is a similar full-penetration weld which runs from top to bottom along the inside sheath but this is not a structural weld and therefore has no safety significance.
In addition, fillet welds are used on these racks to attach the tubes to joining strips and to the base plate, which supports the entire array of tubes.
Fillet welding is also used to join some components of the base plate.
The attached cross section sketch (Exhibit 2) shows how the fuel storage tubes are joined with continuous fillet welds using long flat narrow joining strips.
The operating environment for these welded type 304 stainless materials is not severe.
The water in the pool itself is not considered stagnant, temperatures are low, water chemistry is good, and operating pressures are low.
The term " stagnant" was not orignally defined in I.E.
Bulletin 79-17, nor is it a technical engineering term.
However, on October 29, 1979 the Staff issued revision 1 to I. E.
Bulletin 79-17, which states:
For this review, the term " stagnant, oxygenated borated water systems" refers to those systems serving as engineered safeguards having no normal operating functions and contain essen-tially air saturated borated water where dynamic flow conditions do not exist on a continuous basis. 1532 208
The water in the spent fuel pool constantly circu-lates due +
the operation of the spent fuel pool cooling system and natural convective heat transfer around the stored spent fuel essemblies.
Each of the spent fuel pool cooling pumps is designed to pass an amount of water equal to the entire pool volume through a heat exchanger every five hours and une of these pumps is nearly always operating.
Therefore, I do not consider conditions in the pool to be stagnant or essentially stagnant.
There are two loops in the spent fuel pool cooling system.
The water in the loop which is operating is of course constantly flowing.
The water in the other loop is not.
Recirculation is periodically switched to the inactive loop to equalize wear on the system. Generally this is done at least twice per year.
Although the spent fuel pool cooling system is not considered one of the " engineered safeguards systems" which must be inspected according to I.E.Bulletin 79-17, as limited by Revision 1,I/ both loops would be termed " stagnant" by the Bulletin definition, since t..ey do not experience continuous flow all the time.
An exception is the pipe I discussed in the June hearings which returns water to the pool.
This pipe serves both loops and therefore experiences continuous flow.
~1/
The spent fuel pool cooling system is identified as an " Auxiliary System" rather than an " Engineered Safety Feature" in the Zion FSAR.
1532 209 Finally, there is no convective flow path within the spent fusi storage tube walls so any water inside the stainless steel sheaths is expected to be stagnant.
In addition, low pool temperature minimizes corrosion rates. Typically the Zion spent fuel pool tempera-ture is 70'F and it seldom exceeds 85'F, even during re-fuelings.
These observed temperatures are lower than the temperatures discussed in the June hearings with respect to pool boiling, but those were calculations based on very conservative assumptions and on FSAR values which were themselves conservative.
The observed temperatures reflect the fact that Lake Michigan is a very cold lake.
Pool water chemistry is controlled by demineralization to minimize corrosion.
Although complete profiles of the ionic content of pool water are not routinely performed at Zion, chloride ion content is measured periodically and is generally below.5 ppm.
These temperature and chloride values are consistent with the typ cf.i PWR values reported by Dr. Johnson in Aucachment B to his prepared testimony (Tr. 1057).
Dissolved oxygen cannot be controlled in an open pool.
The oxygen level was recently measured to be 7.4 ppm.
In the past, oxygen level measurements in similar systems at the plant have ranged between 1.5 and 7.5 ppm.
In the event that cracks occur the consequences can Le described as follows.
1532 210 f
As discussed in my previous testimony, all leakage through the pool liner is collected and processed for recycle in the plant.
Further, pool level monitoring instruments and sight glasses would show leakage indicating deterioration of the liner welds.
Liner weld cracking therefore poses no probitm.
Cracks in tra spent fuel pool piping are considered both by the NRC Staff and by Commonwealth Edison to be of no safety significance.
Such weld cracks would probably have been detected by means of the nondestructive examination program undertaken in response to I&E Bulletin 79-17 and outlined in the testimony of Robert Shannon.
Moreover, even if pipe failure should occur redundatit pool cooling systems would make repair of most pipes possible without interruption of normal cooling.
No pipe break can lead to pool draining.
Finally, as described in my previous testimony a variety of alternate water sources are available if the spent fuel pool cooling system become completely unavailable.
Stainless steel is not used in the fuel assemblies to contain fuel or fission products.
The only structural welds involving stainless steel are those which join the top nozzle assembly to the zircalloy control rod guide tubes. If these structural welds were to fail the worst consequence would be that the top nozzle would pull off during transfer 1532 211
of a fuel assembly, causing the rest of the assembly to be dropped.
The consequences of a fuel assembly ' op accident were described in some detail in the hearings in June.
The relatively light weight of the top nozzle assembly and the inherent strength of the zircalloy control rod guide tubes, the zircalloy fuel rods and inconel spacers in the fuel assemblies ensures that any weakening of the elds which join the top nozzle assembly to the zircalloy control rod guide tubes would not lead to the crushing or collapse of the assembly unless the assembly is dropped.
The structural welds in the proposed racks are important because their integrity is assumed in the analyses of the response of the racks to postulated seismic events.
This cor.cern is addressed by Dr. Staehle in his affidavit.
On an unrelated matter, in the June hearings I informed the Board that there was a leak in one of the Component Cooling System heat exchangers which was scheduled for repair in the Fall 1979 refueling outage.
To bring you up to date, that outage is now taking place and repairs are being made.
I am confident that the leak will be eliminated.
1532 212 4
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