ML19309B580
| ML19309B580 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/07/1980 |
| From: | Wilson R METROPOLITAN EDISON CO. |
| To: | Jay Collins NRC - TMI-2 OPERATIONS/SUPPORT TASK FORCE |
| References | |
| TLL-108, NUDOCS 8004040325 | |
| Download: ML19309B580 (2) | |
Text
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j-Metropolitan Edison Company I[y Q IF jE j- [1- (Jj Post Office Box 480 j
e Middletown, Pennsylvania 17057 717 944-4041 Wnter's Direct Dial Number March 7, 1980 TLL 108 TMI Support Attn:
J. T. Collins, Deputy Director U. S. Nuclear Regulatory Commission c/o Three Mile Island Nuclear Station Middletown, Pa.
17057
Dear Sir:
Three Mile Island Nuclear Station, Unit II (TMI-2)
Operating License No. DPR-73 Docket No. 50-320 TS-27 Funi-Decay Heat Removal System Filter Status This letter is to document the status of the MDHR filter and provide technical bases upon which we have concluded that no changeout of the MDHR "One Shot" filter is technically required.
Tne Pall Trinity Filter, as described in the MDHRS spec, is considered a "One Shot" filter.
The filter housing (welded shut to contain radioactivity) is not replaceable and the cover is welded closed to eliminate leakage and spread of contaminants.
The "One Shot" principle is designed to remove initial debris from the process water during the first 30 to 60 minutes of system operation. Af ter initial debris ( > 10 microns) collection, the filter is to be isolated and bypassed by remotely operated isolation and full flow bypass valves.
This full flow bypass will be used for all future system operation.
Specific flow velocities in the 36" hot leg (to the indigenous DH System interface) and in the other large piping will be so low that particulate entrainment during long term operation is expected not to occur.
(i.e., 2 pumps 0100 gpm each, velocity in 36" hot leg is.06 ft/sec; one pump @ 115 gpm, velocity in 36" hot leg is.036 ft/sec.)
- s..
The primary intended function of the MDHR filter is to initially protect the MDHR pump seals against a startup surge of particulate material.
For long term operation, the pump seals are independently protected by Borg-Warner Cyclone separators.
Our judgement is that long term operating velocities will be so low as to preclude particulate entrainment in the fluid stream.
In addition, the SOHR pump seals have been protected from particulates by cyclone separators, and dual mechanical seals are incorporated in the MDHRS pumps. We have spoken with users of essentially identical pumps under basically similar conditions f.tetropottan Ec. son Company is a f.' ember of the General Pub 5C Ut'! t.es System 800A040 325
March 7, 1980 i
b (t T. Collins TLL 108 6
and have concluded that the pump design which we have is sound.
Further explanation of pertinent facts are as follows:
During the process of designing the }dni-Decay Heat Removal System, a single element "One Shot" filter was added to the HDHR System upstream of the pumps and heat exchangers because of the potential presence of debris in the FOHR drop line.
This debris would potentially be laying on the gate of DH-V1 and DH-V171, and on the horizontal portion of the RCS hot leg.
The potential debris is assumed to be highly radioactive and is assumed to be of sufficient mechanical hardness that it could have adverse effect on the MDHR pump seals. Additionally, Borg-Warner ceparators were procured and installed, one on each pump, to ensure protection of the seal faces during all phases of pump operation including initial system operation.
The latter items were the system designer's intended fulfillment of a self imposed requirement to protect the pump's mechanical seals, which are dual - Dura Metallic seals, Type PTO.
The filter assembly, added for initial particulate surge protection, was initially designed to be a removable inline type.
However, concerns regarding the spread of radioactive contamination during filter changeout resulted in a modification, endorsed by the NRC in a meeting held in October, to weld closed the here-to-before accessible filter cartridge container.
The filter assembly consists of a Pall Trinity filter housing, the top of which is welded closed with flanged inlet and outlet connections, fitted into a lead shielded cart on wheels.
Based on the above, we conclude there is no requirement to agree to provide changeout of the FOHR filter.
Sincerely, Kl R. F. Wilson j
j i
O Director, TMI-II i
q RFW:SDC: hah cc:
R. H. Vollmer