ML19351E552
| ML19351E552 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 12/04/1980 |
| From: | Hovey G METROPOLITAN EDISON CO. |
| To: | Jay Collins Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19351E556 | List: |
| References | |
| TLL-634, NUDOCS 8012100451 | |
| Download: ML19351E552 (6) | |
Text
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.e Metropolitan Edison Company I
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Post Office Box 480 y
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Middletown Pennsylvania 17057 f
Wnter's Direct Osal Nurrber w
December 4, 1980 TLL 634 TMI Program Office Attn:
Mr. John T. Collins, Deputy Director U. S. Nuclear Regulatory Commission c/o Three Mile Island Nuclear Station Middleto,wn, Pennsylvania 17057 t-
' dear Sib:
Three Mile Island Nuclear Station, Unit 2 (TMI-2)
Operating License No. DPR-73 Docket No. 50-320 EPICOR II Liner Evaluation Status Fo wa{d j herewith is the initial evaluation of the possibility of cor-rosion of EPICOR II liners, which corrosion might result in loss of full integrity of the liners with resultant leakage.
Also, included below is other information related to this subject.
It must be remembered that leakage of the liners would have only ve ry minimal consequences. This is because of the cumulative effect of several factors, such as:
o The free water content of each liner can be expected (based on extensive testing of the dewatering procedure) to be less than 1.5 gallons--possibly approaching zero.
Radioactivity of residual water, based on experience with the o
EPICCR I and II systems, is expected to be minimal.
o At worst, based on the attached evaluation, the loss of inte-grity, should it occur, would be only in the nature of pin-hole leaks. not a failure that might alter the structural integrity of the liner.
o The liners are stored in a high-integrity, massive structure with internal drains and a sump, that would confine any credible leakage, conducting liquid to the sump from which it esuld be removed for aporopriate handling and treatment.
Perusal of the attached evaluation report will, we believe, make it apparent that, for the parameter, which might contribute to the possibility of corrosion, the worst credible situation has been assumed.
Even so, with this assumption of the worst aggressive possible combina-tion of variables, it is concluded that only eight (8) of the sixty-five (65) liners studied might fail sooner than twenty-five (25) years.
Under the assumed conditions, these eizht liners might be perfora ed in some fifteen (15) to nineteen (19) months.
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e John T.1 Collins ~ TLL'634 However, it is very likely that the parameter that is the principal contributor to corrosion, the pH of water in llc liner, is not at
'all likely to be as low in these eight liners as was assumed. The material in the liners was selected and located with the intent of assuring that.the residual water would be over 5 pH.
Sampling of eight EPICOR I liners, in storage for up to one (1) year, showed that while the. final ef fluent from the liner was as low as 3.3 pH, in all liners, the pH of'the later sample was over 5.
It, therefore, seems that there is assurance that the '.ow pu values in the EPICOR II liners' effluent have not persisted, the pH has risen, and that corrosion rates are-less than those used in.the study.
Every-effort has been and continues to be made -to gain information 3
that would allow a more precise assessment of conditions existing in these liners.
Several programs such as:
(1) Sampling EPICOR II Liners, (2) More Exact Integrated Dose Calculation, (3) Exchange of Information with Epicor, Inc., and (4) Testing Results fro.n Various Resin Degrada-tion Studies, all pose as providing information that may improve the generalized assumptions made in these evaluations.
In addition to discussing and transmitting the evaluation report, this letter also discusses, below:
o-Resin integrated dose calculations o
Liner Sampling Program-o EPICOR II Liner Contingency Plans o
Liner Staging "odule METALLURGICAL EVALUATION REPORT A.
LINER INTERNAL ENVIRONMENT ASSESSMENT The internal environment of an EPICOR resin liner is based upon such variables as chemical, thermal, and radiation reactions.
All variables must be accounted for when determining the environment existing within a liner at any specified time. Various assumptions have been made in characterizing these reactions. A continuing effort is being made toward verifying these assumptions.
It is expected the liner sampling program, completion of the integrated dose calculation, and the exchange of information with Epicor, Inc., and the availability of Penn State, Georgia Institute of Technology, and Brookhaven Nati?nal Laboratory (BNL) testing results will assist in this effort.
'B.
LINER METALLURGICAL EVALUATION Following the categorization of the internal environment of the liners, a metallurgical evaluation was performed. This analysis included several assumptions while attemoting to determine when a liner might first be perforated.
Since the assumptions are subject to change in the near future, the conclusions are also subject to change. The Attachment to-this letter is the study'from which these conclusions were reached.
As the internal environment of a liner is more accurately characterized, this metallurgical evaluation will be updated to present an actual vs.
a worst case condition.
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John'T. Collins -
'TLL 634 RESIN INTEGRATED DOSE Very general calculations of Integrated Dose have been made and reported to the NRC and Brookhaven National Laboratory (BNL) personnel. These calculations-were based on methods employed by Georgia Institute of Technology.1 As has been reported, these were considered preliminary until a more exact analysis had been completed.
i A method employing a computer code has now been developed and beach marked to actual liner radiat*,n surveys. A discussion of this method will now be forwarded to the..aC by December 18, 1980.
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EPICOR LINER SAMPLING PROGRAM J
One ef fort in progress that will significantly aid in more precisely defining the internal environment of an Epicor liner is the liner sampling program. Two recent meetings with NRC representatives have been held discussing the details of this program; therefore, the details are not provided herein.- An updated summary is discusse':
d i
A TMI SAMPLING PROGRAM The TMI Sampling Program is proceeding with a liquid and gas sample from prefilter' expected to be taken the latter part of December, 1980. The prefilter and its storage location were inspec*ed on November 21, 1980. A video tape of this inspection was mace. This inspection found the liner in excellent condition with nothicg unusual observed. A test of the liquid and gas sampling procedure is expected during the week of December 1,-1980, in the EPICOR II Chemical Cleaning Building. This test will verify the adequacy of the procedure. Some of the items which Meted /GPU are hoping to gain from this task are:
o Water Sample and Analysis 4
Gas Sample and Analys'is o
o Liner Gas. Pressure 4
o Internal and External Radiation Profile o
Thorough External Liner Inspection with Video Tape Assuming no problems are experienced with prefilter '16, prefilt er. 3 will undergo the same sampling program at a later date. A contingency
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i plan has been developed should a water sample not be withdrawn. This plan involves adding an organic material to the liner which would liberate resin water of hydration.
In this manner, this liberated water can then be removed from the liner by the underdrain system.
l This method allows. water sampling, with the added benefit of inerting a portion ofsche resin bed.
i IR. C, McParland, "The Effect of. Gamma Radiation on Ion Exchange Resins and Activated Charcoal",-Appendices A & B to Section 3 of TMI-II-RR-6, TMI Unit 2 Recovery Quarterly Progress Report to NRC for the Period-Ending March 31,'1980, Metropolitan Edison Company, Middletown, PA,-
.pp. 3-18 to 3-40, 1980.
L
e John T. Colline TLL 634 B.
DOE SAMPLING PROGRAM The DOE Liner Sampling Program has just recently gained full en-dorsement from the DOE and Meted /GPU. This program should have significant progress in the near future, especially since the TMI Program should provide hel-ful information related to liner handling and insnection methods. The DOE program is more inclusive than the TMI effort and will aid in characterizing the internal environ-ment of a liner and assessing the integrity of the liner.
Since NRC representatives have recently received a presentation on this effort, details are not provided herein.
However, it is requested the NRC reply to Meted /GPU letter, TLL 413, dated September 4, 1980, regarding a waiver for shipment of non-solidified Epicor liners.
Timely receipt of a waiver will remove an element of un-certain:y from this program that currently exists.
EPICOR II LINER CONTINGENCY P_LAN As discussed provicusly, a leak of a liner, even though it should occur, will have little consequence.
Even so, should it be decided that pre-ventive or corrective actions are warranted, Meted /GPU has been considering what action might be taken should a problem exist.
Two (2) alternative actions have been identified as follows:
A.
CHEMICAL ADJUSTMENT An investigation has been made into how the corrosiveness of resins might be adjusted by chemical means. This work has included contacting various resin experts as well as performing tests at TMI, GPU laboratory, and contractor facilities. This work involves adding an organic material to a resin bed. The resins chemically bind this material preferentially to the water of hydration, thereby liberating the water of hydration.
In this manner, the medium within the liner which allows for the transfer of ions during corrosive reactions would be replaced with a material that would fail to act as a transferring medium.
This action would make the bed essentially tnert by retarding corrosive attack. Liberated water would be re-moved by dewatering methods.
A major concern with this procedure is the possibility of releasing the bound radioisotopes.
A test was performed on a resin column previously used for verification of the Epicor resin mixes for processing the 'B' Reactor Coolant Bleed Tank (RCBT). The column used for the test was scaled and loaded with resins similarly to a prefilter.
250 mE of 'B' RCBT water was passed through this column dewatered by draining. The organic material visibly dried the resins. The liberated water contained -
only very low concentrations of radioisotopes indicating the radio-isotope to resin bond was not altered significantly.
The details of this option and exact material selection have not been made, however, this option offers significant advantages.
B.
ADDITIONAL LINER BARRIER PROGRAM A second contingency plan involves placing the carbon steel liner into a container made of more corrosion resistant material. This container will provide an additional protective barrier to liquid loss around the sides and bottom of the liner.
An engineering package will be developed for this option.
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John T. Collins TLL 634 LINER STAGING MODULE EPICOR liners have been stored since removal from service. Two (2) items of interest are discussed below:
A.
MOVEMENT OF LINERS Liners in the Interim Liner Staging Area have been moved to the A and/or B Liner Staging Module at the rate of two (2) per week.
This rate has been constant over the past few weeks and should remain constant bearing adverse weather conditions.
It is of note that some of the oldest EPICOR II liners have already been moved.
For example, prefilters 1, 2, 3, 4, and 5 have been successfully moved. No irregularities or unusual conditions were noted or experienced during these evolutions.
B.
STAGING MODULE SUMP WATER The 'A' and
'B' Liner Staging Modules share a common sump.
This sump collects liquids entering individual module cells or leakage directly into the sump. Design of the modules was intended to preclude rain water introduction, however, it has been observed the sump level increases slightly during rain. The sump water has been recently analyzed by both TMI and offsite laboratories.
This analysis has shown the presence of Tritium at a concentration of 3 X 10-5 uc/ml and Cesium 137 at 2 X 10-8 uc/mt. For comparison, the NRC limits (10 CFR Part 20) for these isotopes in water dis-charge to restricted r.reas are, for Tritium, 3 X 10-5 uc/mL and Cesium, 2 X 10-5 uc/m2, many times higher than found in the sump.
Four (4) possible scenarios have been identified which could explain how these isotopes entered the sump.
1.
One or more liners may well have been externally contaminated when in service. While in storage, changing humidity and temperature conditions could cause condensation resulting in the washing of this contamination to the sump.
2.
One or more liners may have been perforated releasing free standing water existing in the liner. This liquid would have been collected in the sump.
3.
The heat generated by the deposited curies could cause a vaporization of the water of hydration of the resins. This vaporization could carry radioisotopes with it.
Knowing the liners release gases at approximately 2 PSI these radio-isotopes could be released from the liner, then condensed in the storage cell. This condensation would be collected in the sump.
(While liners do not leak with up to 18 psig water pressure, they have been found to leak air through the threaded connections at 2 psig).
4.
As resins break down due to chemical and radiation interraction gases are liberated.
Although the gases themselves may not necessarily be radioactive, they could carry radioisotopes with them. These radioisotopes could be released from the liner and collected in the sump, similarly to method 3.
e John T. Collins TLL 634
.he precise mechanism has not been identified nor has any credible method been excluded.
However, as the Interim Liner Staging Area is emptied, the storage cells are being studied with respect to contamination of the cells. To date, no contamination has been detected in the cells once containing resin liners.
There is not, at present, any reason to believe a liner is leaking. To the contrary, both the above-described and attached metallurgical evaluation and the studies of the Interim Liner Staging Area lead to the conclusion that the source of the comtamination in the sump is other than a perforated liner.
Action is in progress to minimize further the introduction of rain water into the sump.
The sump will be pumped dry and any additional liquid introduction will be closely monitored.
It is premature to draw any conclusions concerning the low levels of contamination in the Staging Module Sump Water. Meted /GPU recognizes the importance of identifying the source of this contamination at the earliest possible date.
The NRC will be kept advised of our activities in this regard.
The above up-dates the NRC on current activities at TMI-2 related to EPICOR II liner integrity. We will continue to keep you informed.
Sinqerely,
,/
j bf G. K. Hovey Vice-President and Director, TMI-2 GKH:RIN: dad Enclosure cc:
Bernard J. Snyder