ML20056D267
| ML20056D267 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 08/04/1993 |
| From: | Warembourg D PUBLIC SERVICE CO. OF COLORADO |
| To: | Joseph Austin NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| P-93080, NUDOCS 9308110197 | |
| Download: ML20056D267 (3) | |
Text
.
.k
^
I h Public Service *
=;.";1 16805 WCR 191/2; Platteville, Colorado 80651 August 4,1993 Fort St. Vrain Unit No.1 P-93080 U. S. Nuclear Regulatory Commission ATrN: Document Control Desk Washington, D. C. 20555 ATTN:
Mr. John H. Austin, Chief Decommissioning and Regulatory Issues Branch Docket No. 50-267
SUBJECT:
Supplemental Information for Proposed Amendment to Decommissioning Technical Specifications
REFERENCES:
1.
PSC Letter, Crawford to Austin, dated May 7,1993 (P-93045) 2.
PSC Letter, Crawford to Weiss, dated January 9,1992 (P-92014)
Dear Mr. Austin:
This letter provides additional information in support of the proposed revision to the Fort St. Vrain (FSV) Decommissioning Technical Specifications that1was submitted via Reference 1. This information is submitted in response to questions raised during a July 21,1993 telephone conversation between Public Service Company of Colorado (PSC) and Mr. Clayton L. Pittiglio, the NRC Project Manager for Fort St. Vrain.
In. Reference 1, PSC proposed a revision to the Design Features of the FSV Decommissioning Technical Specifications that would allow use of a push-rod device to remove seven core outlet thermocouple assemblies underwater. The main reason for this request was to reduce worker radiation exposures during thermocouple removal. The NRC requested additional information regarding (1) the magnitude of the dose savings that would result from this thermocouple removal method, and (2) the worker exposures that would result in the event of a seal failure on the push-rod shaft.
l
()'
w3 9308110197 930804 Q
PDR ADOCK 05000267 p
PDR g2 p
--x_
P-93080 August 4,1993 i g the 23 person-Rem would be saved by remov next Page 2 an analysis PSC estimates that approximately s opposed to removing them d
trations. This estimate is base on pport ing contractor for radiation protection sul proj thermocouples underwater aPrestressed Concrete Reacto timated that the thermocouple remova i
of up to performed by PSC's decommiss on hours, with working area neld dose rates removal.
services, SEG, Inc. This analysis es to 10 mrem /hr for underwater i n the require approximately 1000 person-e determined, taking into considerat o 5000 mrem /hr for external removal and up 25 i volved. These effective dose rates Within these fields, effective dose rates werdura d on these Rem /hr for underwater removal. Based ouple removal project is estimatel 2 person-Rem f mrem /hr for external removal and 2 n:
t rnal removal, and approximate y in worker doses conditions, toe core outlet thermoc i
approximately 25 person-Rem for ex eter removal represents
'nderwater removal, so that underwa device, the maximum
,pproximately 23 person-Rem.
of the shaft seals on the push-rod (Reference 1).
would encounter is less than 2 gpmworker do 1 vent of a total failure ter leak rate that workers lt in a
^!culated that this leak would resu d 2.5 curies of cobsit-60 i ts dation of the leak would require 20 m nu e,
ld water radionuclide N water includes 100 curies of tritium an d
tions), and tion, swallowing 10 ml of water, an e toinhalation, skin absorp contributors.
d to evaluate the methodology that PSC previously u (Reference
'e of the push-rod shaft seals is boun eimmersion tude 932 mrem for a 10 minute H. Holmes Mrmation, please contact Mr. M.
k
~
P-93080 August 4,1993 Page 2 PSC estimates that approximately 23 person-Rem would be saved by removing the thermocouples underwater as opposed to removing them externally through the Prestressed Concrete Reactor Vessel penetrations. This estimate is based on an analysis performed by PSC's decommissioning contractor for radiation protection support services, SEG, Inc. This analysis estimated that the thermocouple removal project would require approximately 1000 person-hours, with working area field dose rates of up to 5000 mrem /hr for external removal and up to 10 mrem /hr for underwater removal.
Within these fields, effective dose rates were determined, taking into consideration the duration and location of the specific tasks involved. These effective dose rates are 25 mrem /hr for external removal and 2 mrem /hr for underwater removal. Based on these conditions, the core outlet thermocouple removal project is estimated to involve approximately 25 person-Rem for external removal, and approximately 2 person-Rem for underwater removal, so that underwater removal represents a net savings in worker doses of approximately 23 person-Rem.
In the event of a total failure of the shaft seals on the push-rod device, the maximum shield water leak rate that workers would encounter is less than 2 gpm (Reference 1).
PSC has calculated that this leak would result in a worker dose of 5 mrem, assuming that:
Isolation of the leak would require 20 minutes, Shield water includes 100 curies of tritium and 2.5 curies of cobalt-60 a
(which is approximately 100 times current shield water radionuclide concentrations), and Dose is due to inhalation, skin absorption, swallowing 10 ml of water, and external dose contributors.
This calculation uses the same methodology that PSC previously used to evaluate the dose that a worker would receive from an accidental fall into the shield water (Reference 2). The 5 mrem dose from failure of the push-rod shaft seals is bounded by the doses evaluated in Reference 2, which include 932 mrem for a 10 minute immersion in shield water containing 500 curies of tritium.
If you have any questions regarding this information, please contact Mr. M. H. Holmes at (303) 620-1701.
Sincerely, 0 TY /&tt&wf~ Director Don W. Warembourg Decommissioning Program i
\\
P-93080 August 4,1993 Page 3 DWW/SWC cc:
Regional Administrator, Region IV Mr. Ramon E. Hall, Director Uranium Recovery Field Office Mr. Robert M. Quillin, Director Radiation Control Division Colorado Department of Health l
i
,