ML20077S154

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Application for Amend to License DPR-40,revising Specs 2.22 & 3.1 to Delete Requirements for Toxic Gas Monitoring Sys
ML20077S154
Person / Time
Site: Fort Calhoun Omaha Public Power District icon.png
Issue date: 01/09/1995
From: Gates W
OMAHA PUBLIC POWER DISTRICT
To:
Shared Package
ML20077S152 List:
References
NUDOCS 9501230317
Download: ML20077S154 (8)
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b BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION In the Matter of )

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Omaha Public Power District ) Docket No. 50-285 (Fort Calhoun Station )

Unit No. 1) )

APPLICATION FOR AMENDMENT 0F OPERATING LICENSE I

Pursuant to Section 50.90 of the regulations of the U. S. Nuclear Regulatory Commission ("the Commission"), Omaha Public Power District, holder of Facility Operating License No. DPR-40, herewith requests that the Technical  ;

Specifications set forth in Appendix A to that License be amended to delete the -

requirements for the Toxic Gas Monitoring System. l The proposed changes in Technical Specifications are provided in  !

Attachment 3 to this Application. A Discussion, Justification and No Significant Hazards Consideration Analysis, which demonstrates that the proposed changes do not involve a significant hazards consideration, is appended in Attachment 1. The proposed changes in specifications would not authorize any change in the types or any increase in the amounts of effluents that will be released, or a change in the authorized power level of the facility.  ;

WHEREFORE, Applicant respectfully requests that Specifications 2.22 and 3.1 of Appendix A to Facility Operating License No. DPR-40 be amended in the form attached hereto as Attachment 3.

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.2-l A copy of this Application, including its attachments, has been submitted to the Director - Nebraska State Division of Radiological Health, as required by 10 CFR 50.91.

OMAHA PUBLIC POWER DISTRICT j By #- M l Vice President Subscribed and sworn to before me this 9 day o n a u. , 1995.

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U.S. fluclear Regulatory Commission LIC-94-0258

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i ATTACHMENT 1 l

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M DISCUSSION, JUSTIFICATION AND NO SIGNIFICANT HAZARDS CONSIDERATION DISCUSSION The Omaha Public Power District (0 PPD) proposes to revise the Fort Calhoun Station (FCS) Unit No. 1 Technical Specifications (TS) to delete requirements for the Toxic Gas Monitoring System (TGMS) as contained in TS 2.22 and TS 3.1, Table 3-3, item 29. Currently the TGMS is required to be operational in all operating modes to monitor the fresh air supply to the control room. The TGMS .

samples for six toxic gases and automatically switches the control room HVAC to

  • the recirculation mode when gas concentrations reach predetermined setpoints.

This automatic action was designed to provide the control room operators adequate protection from a toxic chemical accident. For additional protection, operators are required to don self contained breathing apparatus (SCBA).  ;

The T;MS was installed to meet the control room habitability requirements of NUREG-0737, Item III.D.3.4 " Control Room Habitability," for a postulated toxic chemical release. NUREG-0737 references Regulatory Guide 1.78, which uses r deterministic criteria, as one source of guidance for performing evaluations on toxic hazards. The original submittal approved for FCS (Reference 2 of Attachment 2) followed the guidance of RG 1.78 and identified six potential chemical hazards from on or off-site sources (Chlorine, Hydrochloric Acid, Sulfuric Acid, Hydrofluoric Acid, Hydrazine, and Ammonia). To ensure control '

room habitability following an accidental release of one of these chemicals 0 PPD committed to install a TGMS.

Subsequent to the original submittal, potential on-site sources of chemical releases which required the TGMS for detection have been r(moved (i.e.,

chlorine, hydrogen fluoride) or will be removed in the near future (sulfuric acid). In addition, the remaining on-site and off-site sources have been re-evaluated following Section 2.2.3 cf the Standard Review Plan (SRP), which uses  ;

probabilistic criteria for identifying potential hazards. NUREG-0737 references ;

Section 2.2.3 of the SRP as another acceptable method for identifying design  !

basis toxic hazards. Following this guidance, it has been concluded that the TGMS is not necessary as it only improves control room habitability for certain very low probability events.

Since its installation, the TGMS has been a maintenance burden. 'The maintenance i difficulties arise from the fact that the system requires the use of very  ;

sensitive instruments and very low actuation setpoints. OPPD has spent and  ;

continues to spend significant resources on calibration, preventative '

maintenance, and corrective maintenance activities to ensure continued operation of the TGMS. This effort has been increased recently due to the original I equipment manufacturer discontinuing its 10 CFR 50 Appendix B program which will require OPPD to either replace the TGMS or commercially dedicate replacement components.

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The benefit of improved control room habitability is outweighed by the associated maintenance costs and the distractions the system imposes on the control room operators in ensuring that the TGMS remains operable. Thus, it is proposed that TS 2.22 and 3.1, . Table 3-3, item 29, be deleted. It is OPPD's intention that if the proposed changes are approved, the TGMS would be completely deactivated. The removal of the TGMS will eliminate the automatic initiation of the control room HVAC recirculation mode. However, the ability to i manually place the HVAC system into the recirculation mode will be retained.

JUSTIFICATION To justify removal of the TGMS, the deterministic criteria of RG 1.78 were used as screening criteria. For events which exceeded these screening criteria, the probabilistic criteria of SRP Section 2.2.3 were applied. Application of these >

regulatory criteria is consistent with the guidance provided by NUREG-0737, and with the Safety Evaluation Report for Vermont Yankee's Technical Specification Amendment No. 132 (Docket 50-271, supporting Amendment to Facility Operating >

License No. DPR-28, dated October 24,1991). .

Attachment 2, " Analysis to Support Removal of the Fort Calhoun Toxic Gas Monitoring System," documents the analysis with respect to these regulatory ,

criteria. The analysis was updated from that approved by Reference 2 of l Attachment 2, with regard to potential chemical hazards in the vicinity of FCS, I the chemicals considered potentially toxic, and the corresponding toxicity limits. The off-site sources evaluated included those that are, or are expected to be, used at nearby locations in appreciable quantities. The results show that all chemicals satisfy the RG 1.78 screening criteria, with the exception of I ammonia, carbon dioxide, sulfur dioxide, and chlorine. For the chemicals not I meeting the criteria of RG 1.78, the probability of a 10 CFR 100 fission product releas'e is acceptable since the frequency of an event leading to the lack of control room habitability is well below the threshold for consideration as a design basis event in accordance with SRP Section 2.2.3. Thus, the TGMS is not required to satisfy the provisions of NUREG-0737, Item III.D.3.4.

The analysis presented in Attachment 2 includes both deterministic and probabilistic analyses. The deterministic analyses follow the general guidance of RG 1.78 and include the following:

1. A list of hazardous chemicals
2. A toxicity limit for each chemical
3. Consideration of chemicals shipped or stored within five miles of FCS
4. Consideration of chemicals shipped more frequently than 10 times per year by truck and 30 times per year by rail
5. Methodology for calculating dispersion of a puff release.  !

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The deterministic analysis follows RG 1.78 methodology with the exception of the list of chemicals and the toxicity limits. A more comprehensive list of chemicals, the EPA's list of Extremely Hazardous Substances, was used in the analysis along with the RG 1.78 list in order to identify potentially toxic chemicals. The toxicity limits (except for Carbon Dioxide) were based on the National Institute of Occupational Safety and Health (NIOSH) concentrations for "Immediately Dangerous to Life and Health" (IDLH) which is referenced by the EPA list for acute toxicity limits. Although the limited list of chemicals in RG 1.78 does not provide toxicity limits for all chemicals considered in the analysis, the IDLH values are considered to be consistent with the RG 1.78 time frame for a two minute exposure. Thus, OPPD considers the deterministic analysis presented in the attached report to be a comprehensive analysis which I is consistent with the general guidance and intent of RG 1.78. The analysis results show that all chemicals except for ammonia, sulphur dioxide, carbon dioxide, and chlorine meet the deterministic screening criteria of either:

1. control room concentrations never reach toxic limits, or
2. there is at least two minutes between the time that the toxic gas is detectable by smell by the operating crew and the time the toxic limit is reached.

For chemicals that did not meet the above screening criteria, the analysis presents the results and methods for a probabilistic analysis to determine the frequency of a conditional core damage event resulting from an off-site chemical release (on-site chemicals were screened out by deterministic analysis). The I analysis accounts for the transportation, pipeline, and off-site storage 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 guideline of IE-7 to IE-6 per year. Thus, toxic gas events are well below the threshold for consideration as a design basis event.

The results of this analysis, as summarized in Attachment 2, demonstrate that the NUREG-0737 requirements for control room habitability following an on-site or off-site toxic chemical release are met without the need for a TGMS.

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BASIS FOR NO SIGNIFICANT HAZARDS CONSIDERATION:

The proposed changes do not involve a significant hazards consideration because operation of Fort Calhoun Station Unit No. 1 in accordance with these changes would not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated.

The previously evaluated accidents affected by this change are the on-site and off-site toxic chemical releases. These events have been re-evaluated for this proposed change and have been shown to meet the applicable regulatory screening criteria. The deterministic analyses performed show that the guidelines of Regulatory Guide 1.78 for control room habitability are met for on-site and most off-site chemicals. On-site chemical sources originally present when the toxic gas monitoring system was installed have been removed from site or determined not to exceed the deterministic analysis screening requirements. For those off-site chemical releases which did not meet the deterministic screening criteria a probabilistic analysis was perfsrmed. The probabilistic analysis performed in support of this proposed change shows that the probability of an off-site chemical release leading to 10 CFR 100 consequences is orders of magnitude less than the SRP 2.2.3 guidelines. These results show that there is no significant increase in the probability or consequences of any accident previously evaluated.

(2) Create the possibility of a new or different kind of accident from any previously analyzed.

Only events involving chemicals for which the TGMS provides an automatic detection / isolation function are affected by this change. As stated above, the potential events involving these chemicals have been re-evaluated using the appropriate regulatory guidance and shown to satisfy either the deterministic screening criteria of RG 1.78, or to be probabilistically insignificant compared to the guidelines of SRP Section 2.2.3. These results show that the proposed change will not create the possibility of a new or different kind of accident from any previously evaluated. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously analyzed.

(3) 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 III.D.3.4. The analysis provided to support this proposed change follows the regulatory guidelines of RG 1.78 and SRP Section 2.2.3, as specified in NUREG-0737, Item III.D.3.4. The analysis shows that the applicable regulatory criteria are met and the proposed changes do not involve a significant reduction in a margin of safety.

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Therefore based on the above, it is OPPD's position that this proposed amendment does not involve a significant hazards consideration as defined by 10 CFR 50.92 and the proposed changes will not result in a condition which significantly i alters the impact of the Station on the environment. Thus, the proposed changes ,

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meet the eligibility criteria for categorical exclusion set forth in 10 CFR '

t 51.22(c)(9) and pursuant to 10 CFR 51.22(b) no environmental assessment need be prepared.

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