ML20137H274

Forwards Evaluation of Residual Radionuclide Source Term at Trojan NPP at Start of Decommissioning (1994)

ML20137H274
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	06/28/1996
From:	Short S External (Affiliation Not Assigned)
To:	Feldman C NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20137H228	List: ML20137H223 ML20137H274 ML20137H284 ML20138E754
References
FRN-59FR43200, RULE-PR-20, RULE-PR-30, RULE-PR-40, RULE-PR-50, RULE-PR-51, RULE-PR-70, RULE-PR-71, RULE-PR-72, RULE-PR-MISC SECY-97-046A-C, SECY-97-46A-C, NUDOCS 9704020117
Download: ML20137H274 (2)

Text

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- P3cdic Northvest Natianai L.aborr >

June 28,1996 Dr. Carl Feldman Radiation Protection and Health Effects Branch Division of Regulatory Applications Office of Nuclear Regulatory Research U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Cari:

Enclosed with this letter is a copy of Dave Robertson's evaluation of residual contamination at the Trojan Nuclear Power Station. This letter report provides the following: 1) an assessment and update of the radionuclide source term and composition presently existing at 'l rojan,2) a comparison of this source term and composition with predicted values contained in the original PWR decommissioning assessment report (NUREG/CR-130),3) a review of the environmental radiological conditions at Trojan, and 4) an evaluation of the recently observed low-level tritium contamination of the Trojan containment building concrete. The major conclusions of this study are as follows:

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1) The updated radionuclide sourr term cetimate is in reasonably good agreement with the original predicted values in NUREG/CR-130 considering the many uncertainties associated with such estimates. This result gives credibility to the decommissioning conclus. ann in NUREG/CR-130.

2) A comparison of the radionuclide composition of the primary systems and the neutron activated reactor internal components between the original NUREG/CR-130 prediction and that measured in 1994 by Trojan staff are quite good. This suggests that the conclusions reached in NUREG/CR-130, and its update NUREG/CR-5884, with respect to dose impacts and remediation costs are still valid.

3) There is no sigaificant residual radionuclide contamination of the environs surrounding the Trojan plant and there has been no observed radioactive contamination in the l

groundwater (including tritium).

f Telephone (509)375-2868 m Fax (509)375M17 m e-mail sm shon@pnl. gov l

I Baneue Boulevara e P 0. Box 999 s RicNand. .. A 99352 9704020117 970331 PDR PR MISC 59FR43200 PDR ,

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1 Dr. Carl Feldman i

June 28,1996

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4) The observed low-level tritium contamination in the containment building concrete

! (2 to 3 orders of magnitude above background levels) is still somewhat of a mystery,  ;

although there are conceivable mechanisms to explain its presence, it does not appear to be an artifact of sampling (coring) contamination, since new coring equipment was used.

It is entirely possible that the contamination resulted from diffusion of the tritium through ,

the steel liner. Trojan staffindicated that during reactor operating periods the containment atmosphere did have significant levels of airbome tritium, some of which would be expected to diffuse through the steel. De. pite the higher than background levels of tritium contamination in the concrete, howes er, the levels are still below the acceptable residual contamination criteria and therefore should not be an issue for decommissioning.

Please call Dave Robertson (509-376-5664) or myselfif you have any questions on this letter report.

Sincerely, l

/ s

// >

St - ort, P.E.

Engineer Systems and Risk Management Department Enclosure 1

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