ML20066E146
| ML20066E146 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 01/15/1991 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20066E147 | List: |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM BVY-91-02, BVY-91-2, NUDOCS 9101180099 | |
| Download: ML20066E146 (6) | |
Text
{{#Wiki_filter:.. .= VERMONT YANKEE t NUCLEAR POWER CORPORATIONe Ferry Road. Brattleboro, VT 05301 7002 -{ ENGINE It OFFICE f ~ ~ ~ Sho MAIN STREET DOLTOh MA 01740 [508) 77D 6711 Proposed Change 162' January 15, 1991 United States Nuclear Regulatory Commission Document Control Desk -Washington, DC 20555 t
References:
(a) License No. DPR 20 (Docket No. 50-271) (b) NUREG 0737,. "TMl Action Plan," Item Ill.D 3.4 -j (c) Clarifbetion to NUREG 0737, TMI Action Plan, item Ill.D,3.4 ) (d) -Letter, FW 818, R.L. Smith (vYNPS) to D.G. Eisenhut-(NRC), " Submittal of Information on NUREG 0737,- Item. lit.D.3.4,_ Control Room Habitability," dated January 12, 1981 (e) Letter, NVY 80 22, D.B. Vassallo (NRC) to R.L Smith ~ (VYNPS), dated l February 24, 1982 (f) Regulation Guide 1.78, " Assumptions _ for Evaluat!ng the Habitability of a Nuclear Power Plant Control Room ' During-a Postulated Hazardous Chemical Release," June 1974 (g) NUREG 75/087, " Standard Review Plan" (h) " Technical Guidance for Hazard Analysis, Emergency Planning for Extremely _ Hazardous Substances," U.S. Environmental Protection Agoney, Federal Emergency Management' Agency, U.S. Department of Transportation, December 1987 1 (1) " Pocket Guide to Chemical Hazards," National Institute of Occupational Safety and Health, September 1985
Dear Sir:
Subject:
Proposed Change No.162. Toxic Gas Monitoring System Pursuant to Section 50.90 of the Commission's Rules and Regulstions, Vermont Yankee hereby proposes the following changes to Appendix-A of the Operating License. Proposed Change This proposed change eliminates the Technical Specification requirements for the Toxic Gas Monitoring System (TGMS). Revised - Pages 34a, 49c, 60b,. and : 66 are provided in to this submittal. l 0[ l 9101100099 910115 f jDR ADOCK 05000271 7 PDR [ J i a l-
i , VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission i January 15, 1991 Page 2 It is Vermont Yankee's intention that the TGMS, and the Botiled Gas Pressurizailon System (BGPS), will be completely deactivated and removed from service, and all references removed from associated documents following approval of this proposed change..In the case of the TGMS, all detectors and associated automatic protective actions will be disconnected. 11 should be noted that removal of the TGMS wl!I eliminate the automatic Initlation of the control room HVAC System into the Recirculation Mode. However, the ability for Control Room operators to manually place the HVAC System into the Recirculation Mode will remain. Reason for Chance The TGMS was installed to meet the Control Room habitability requirements of NUREG 0737, item 111,D.3.4 [ Reference (b)] for a postulated off site toxic chemical release. The TGMS samples Control Room HVAC intake alt for five tox'c gases and causes Control Room Isolation dampers to close and the Bottled Gas Pressurization System to initiate when gas concentratons reach predetermined setpoints. These automatic actions are designed to provide Control Room operators with at least two minutes to don breathing apparatus before the Control Room air reaches toxM limits. Since its instaliation, the TGMS has been an operational burden. The relatively frequent (several per operating cycle) occurrence of trouble alarms and spurious trips aro-a distraction to Control Room operators and reduce the effectiveness for the system in an actual emergency. These operational difficulties stem from the fact that the system requires use of sensitive instruments and very low actuation setpoints. Vermont Yankee has spent and continues to spend considerable resources on calibration, preventive maintenance, and corrective maintenance efforts to address these inherent difficuttles, Vermont Yankee believes that the TGMS only improves. Control Room habitability for certain very low probability events. We believe that this benefit is outweighed by the distractions and stresses that the system imposes on Control. Room operators and - by the costs of maintalning the system, Thus, Vermont Yankee submits this proposed Technical Specification change and justification for removal of the TGMS. Basis for Chance The basis for the Toxic Gas Monitoring System is NUREG 0737, Item lit.D.3.4, " Control Room Habitability." [ Reference (b) and (c)]. Vermont Yankee's original submittal on this item Reference (d) showed that the provisions of NUREG 0737, Item til.D.3.4 relating to Control Room habitability following a radiological release or an on-site chemical release were satisfied without the need for a TGMS (no TGMS existed at that time). The NRC SER for this item [ Reference (e)) co[Cluded that the criteria of NUREG 0737, item Ill.D.3.4 would be satisfied upon completion of modifications for a detection system which addresses potential off site chemical releases. Thus, the basis for the TGMS is the "off site" release portion of NUREG 0737, item Ill.D.3.4.
4.' O. VERMONT YANKEE NUCLEAR POWER CORPORATION U,S. Nuclear Regulatory Coinmission January 15, 1991 Page 3 la its original approach to this item, Vermont Yankee provided the TGMS_ as an automatic-1 detection / isolation system in order to satisfy the deterministic criterla of Regulatory Guide 1,78 ~ Reference (f). NUREG 0737, item lil.D.3.4 Reference (c) makes reference to Regulatory Guide 1.78 as a source of guidance for. performing such evaluations. However, NUREG 0737, item lil.D.3.4 Reference (c) also makes reference to-Standard Review Plan (SRP), Section 2.2.3 ; Reference (g) as a source of guidance for such evaluations. SRP Section 2.2.3-establishes - probabilistic guidelines for Identifying design basis events. According to SRP Section 2.2.3, events which exceed these probabilistic guidelines must then-be addressed using the: deterministic methods of Regulatory Guide 1.78. i For this proposed change, Vermont Yankee uses the deterministic criteria of Regulatory i Guide 1.78 as screening criteria. For events which exceed these screening criteria, -the j probabilistic criterla of SRP Section 2.2.3 are applied. Application of these regulatory criteria i with the guldance provided by NUREG.0737, item Ill.D.3.4 Reference (c). 1, ' Analysis to Support' Removal of the Vermont Yankee Toxic Gas Monitoring l System," documents Vermont Yankee's analysis with respect to these regulatory criteria.. The-analysis is updated from the Reference (d) analysis with_ regard to the chemicals currently - shipped, the chemicals considered potentially toxic and the corresponding toxicity limits. The-results show that all chemicals satisfy the Regulatory Guide 1.78 screening criteria, with the exception of chlorine. For chlorine, the report shows that the frequency of an event leading to Control Room uninhabitability and subsequent fission product release is below the SRP Section 2.P.3 threshold for consideration as a design basis' event. Thus, the TGMS is not required to satisfy the provlMens of NUREG 0737, item Ill.D.3,4. Safety _ Evaluation The saf6ty analyses presented in Attachment 2 include both deterministic and probabillstic analyses. The deterministic analyses follow the general guidelines of: Regulatory Guide 1.78. Regulatory Gulde 1.78 guidance includes the following: a. A list o "some hazardous chemicals." 1 b. A " toxicity limit" for each chemical, c. Consideration of chemicals shipped within a five mile radius of plant. d. Consideration of chemicals shippeo more frequently than:10 times per year by truck and 30 times per year by rall. e. Methodology for calculating diffusion of a puff release, f
s VERMONT YANKEE NUCLEAR POWER CORPORATION - U.S. Nuclear Regulatory Commission j January 15, 1991 Page 4 The deterministic analyses presented in Attachment 2 follow the Regulatory Guide 1.78 methodology, with the exception of the list of chemicals and the toxicity limits. - A much more_ comprehensive list of chemicals, the EPA's list of Extremely Hazardous Substances (EHS), .I Reference (h), was used in this study, along with the Regulatory Gulde 1.78 list,'in order to identify potentially toxic chemicals. The-toxicity limits were based on the National Institute of Occupational Safety and Health (NIOSH) concentrations for "Immediately Dangerous to Life and-Health" (IDLH) Reference (1).- These values are generally higher than the Regulat.ory Guide _1.78 values, although the limited list of chemicals in Regulatory Guide 1.78 does not provide toxicity limits for all chemicals considered in' the analyals. Thu IDLH values are considered to be 1 consistent with the Regulatory Gulde 1.78' time frame of a two-minute exposure. Thus, Vermont- - i Yankee considers the deterministic analysis. presented in the ettached report to be -a. comprehensive analysis which is consistent with the general guidance and Intent of Regulatory - Gulde 1.78. The analysis results show that all chemicals except chlorine meet the deterministic screening criterla of either, 1. Toxic limits are not reached in the Control Room, or 2. . A two minute interval exists between the time a toxic chemical is detectable _by smell and the time the toxicity limit is reached. For chlorine, :he report presents-a probabWistic analysis of the frequency of a core damage event resulting from an off site _ chlorine release. The analysis acce.nts for = the transportation accident frequency, the effects of meteorology on plume dispersion, and on the plant response. The results show that the estimated frequency of such an event leading to core damage is orders of magnitude less than the SRP Section 2.2.3 guldeline of 1E.7 to 1E 6 por - year. Thus, this event is below tne threshold for consideration as a design basis event. The results of this safety analysis demonstrate that the NUREG 0737, Item lil.D.3,4 requirements for Control Room habitability following an off site toxic chemical release can be met without the need for-a TGMS. 1 This proposed change has been reviewed by 'the Vermont; Yankee Plant Operations Review Committee and the Vermont Yankee Safety and Audit Review Committeei Sianificant Hazards Consideration 'The standards used to arrive.at a determination that a request for amendment involves no significant hazards consideration are included in the Commission's regulations (10CFR50.92) which state that the operation of the facility in accordance with the proposed amendment would not: (1) Involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility of a new or different kind-of-accident from any accident previously evaluated, or (3) involve _ a significant _ reduction in -a margin' of safety. In addition, the Commission has provided guidance in the pactical app!! cation of these criteria in 51FR7751, dated March 6,1986; The discussion below addresses each of theso three criteria and demonstrates that the proposed amendment involves no significant hazards considerations.
- ~. .. --. ~... a VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission January 15 1991 Page 5 1. The proposed amendment will not involve a significant-increase in the probability - or consequences of an accident previously evaluated. The only_ previously-evaluated accidents affected by this change are off-site toxic chemical releases. These events have been_ re evaluated for this proposed change and _have been shown to meet the applicable regulatory criteria. The probabilistic analysis done In support of this proposed _ change shows that the probability of anl off site chlorine release leading to 10CFR100 consequences In orders of magnitude less s than the SRP Section 2.2.3 guidelines.- The deterministic analyses performed; show that the deterministic guidelines of Regulatory Guide 1.78 for Control Room Habitability are met for all other chemicals. These-results show that there is no - significant increase in the probability or consequences of any accident previously-evaluated, 2. The proposed amendment will not create the possibility of a new or different kind: i of accident from any accident _ previously evaluated. Only events _involvingi ' chemicals for which the TGMS_ provides an automatio detection / isolation function-are affected by this change. As stated above, the potential events involving these chemicals have been re-evaluated using appropriate regulatory guidance and shown either to satisfy the dete.ir.inistic screening guidelines of Regulatory Guide 1.78, or to be probabilistically Insignificant compared to the guidelines of SRP Section-r 2.2.3. These results show that this change will not create the possibill_ty of a new l or different kind of accident from any accident previously' evaluated. 3. The proposed amendment will not-involve a significant reduction in a margin of safety.' The margin of safety Is-defined by the regulatory basis for -the existing TGMS, namely NUREG 0737, item lil.D.3.4. The analysis provided to support this proposed change follows the regulatory guidelines of Regulatory Guide 1.78 and SRP Section 2.2.3, as_ specified in-NUREG 0737, item Ill.D.3.4, :This analysis shows that the appilcable regulatory criteria are met, hence this proposed change does not reduce a margin of safety. - Based on the above, we have _ determined that this change --does not constitute. a significant hazards consideration as. defined in 10CFR50.92(c), Schedule of Chanoe. The revised pages will be incorporated into the Technical Specifications -as soon as possible following receipt of NRC approval. I L 1
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- VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission -
January 15,.1991 Page 6 / We trust this submittal is acceptable; however,= should you have any questions, please conMet us, -Very truly yours, =i VERMONT YANKEE NUCLEAR POWER CORPORATION - W - Warren P. Mur y. Senior Vice Pr sident, Operations WPM /ss cc: USNRC Regional Administrator Region I USNRC Resident Inspector VYNPS t USNRC Project Manager - VYNPS 4 VT Department of Public Service STATE OF VERMONT -). ) a OF WINDHAM COUNTY ) Then personally appeared before me, Warren P. Murphy, who,1being duly sworn, did state that he is Senior Vice President, Operations of Vermont Yankee Nuclear Power Corporation,. that he is duly authorized to execute _and file the foregoing document In the name and on the-behalf of and that the statements therein are true-to the best of his knowledge and belief, Judi /Ai Harris . Notary Public My ommission Expires February 10, 1991 16 1 %4$ 4 .}}