ML20070M045
| ML20070M045 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/13/1991 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-91-28, NUDOCS 9103210025 | |
| Download: ML20070M045 (2) | |
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VERMONT YANKEE NUCLEAll POWER CORPORATION BVY 91-28 a-A -
Ferry Road. Brattleboro, VT 05301-7002 ENGINEE I OFflCE
$80 sAIN STREEl l
00L10N M A 01740
($019 775e4711 March 13,1991 U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Attn: Document Control Desk
References:
a)
License No. DPR 28 (Docket No. 50 271) b)
Letter, VYNPC to USNRC, BVY 91001, Response to inspection Report 50 271/90-13, dated 1/4/91 c)
Letter, USNRC to VYNPC, NRC Inspection Report 50 271/90 13, dated 12/5/90 De. Sir:
Subject:
Supplemental Response to inspection Report 50-271/90 13 This letter is intended to clarify an epparent misunderstanding regarding unresolved item 90-13-02 which was initially identified in Reference c). During inspection 50 271/91 10, dlacussion with D. Chawaga and P. O'Connell revealed that our original responso apparently did not address the main issue of the unresolved item. The fobowing is intended to clarify our responso and confirm our plans to implement the requireo changes to our bloassay program.
Referemco b) described in detall the assumptions we made for concluding the event was an Inhalation event and why we determined that the analysis of the actual exposure was conservative.~ However, our discussion of item B in Refere1ce c) of the unresolved llom, the air breathing rate germane to an MPC-hour calculation, did riot proclsely address the inspector's concerns. Vermont Yankee used data from ICRP.23 and ICRP 30 as well as air sample data in our original analysis but did not specifically perform an MPC-hour calculation. Instead, wo used a methodology which calculated the Derived Air Concentration (DAC) ard incorrectly assumed that DAC-hours corresponded to MPC hours. As the NRC pointed out, the rollance on such data' coupled with our assumption that DAC-hours roughly equate to Mi>C hours can lead to a situation where an intak; could exceed 2 MPC hours in one day or 10 MPC hours in one week and therefore the dose may potentially not be properly assessed, as required by 10CFR20.103. This lack of a proper MPC hour calculation is attributable to a lack of a formr.'
procedural process of evaluation. Such a procedure would require this assessment and then
' define the proper calculation.
Our misdirected response to this item [ Reference b)] was due to a misunderstanding of the intent of the specific NRC concern. Although we apologize for the misunderstanding and therefore lack of an accurate response to this unresolved Itam, we assure you that our Intentions were to develop a clear procedure, including the appropriate check of MPC hours.
The particular event which was central to this finding has been analyzed by the Yankee Atomic Environmental Lab and reported as an intake of 0.082 DAC-hours which compata to 2.37 MPC hours, thus, clearly showing the mismatch between DAC-hours and MPC-hours.
9103210025 910313 PDR ADOCK 05000271 M O/
O PDR j
VERMONT YANKEE NUCLEAR POWER CORPORATION t
U.S. Nuclear Regulatory Commission March 13,1991 Page 2 To correct this weakness in our program, we willimplement procedural changes to ensure that a programmatic assessment of all positive bloassays is performed in accordance with accepted models and reg::latory requirements.
This will be completed by May 1991.
Additionally, an extensive review is being performed to ensure that a proper MPC hour calculation is documented for past events. This will be completed by June 15, 1991.
It is our understanding that the concerns regarding the methodology used to assess the type and quantity of Intake, as discussed in items A and C of the report [ Reference c)] are resolved.
We trust that the Information provided adequately addresses your concerns; however, should you have any questions or desire additional information, please do not hesitate to contact uS.
Very truly yours, Vermont Yankee Nuclear Power Corporation
/
~
R J", t /rf Warren P. Murphy Senior Vice President, Operations
/dm cc:
USNRC Regional Administrator, Region l USNRC Resident inspector, VYNPS USNRC Project Manager. VYNPS
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