ML17191A797

Safety Evaluation Supporting Amends 163 & 158 to Licenses DPR-19 & DPR-25,respectively

ML17191A797
Person / Time
Site:	Dresden
Issue date:	10/24/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML17191A796	List: ML17191A795 ML17191A797
References
NUDOCS 9807220293
Download: ML17191A797 (6)

Text

UNITED STATES

• NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-G001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 163 JO FACILITY OPERATING LICENSE NO. DPR-19 AND AMENDMENT NO. 158TO FACILITY OPERATING LICENSE NO. PPR-25 COMMONWEALTH EDISON COMPANY QRESPEN NUCLEAR POWER STATION. UNITS 2 ANQ 3 DOCKET NOS. 50-237 AND 50-249

1.0 INTRODUCTION

By letter dated March 5, 1997, as supplemented October 3, 1997, Commonwealth Edison Company (ComEd, the licensee), submitted a license amendment to revise the Technical Specifications (TS) to remove the main steamline radiation monitor (MSLRM) - high reactor scram and the main steamline tunnel radiation -

high input to the main steamline isolation function. The proposed changes are a result of the Boiling Water Reactor Owners Group (BWROG) initiative to.

minimize inadvertent scrams and Main Steam Isolation Valve closure due to erroneous radiation monit?r actuation. The licensee referenced the licensing topical report NED0-31400 and provided supporting information as well as a description of the proposed changes and bases for their acceptability. The licensee's proposed changes are based t>nthe Octobfr 1981 BWR Owners' Group Licensing Topical Report NED0-31400 and NUREG-0800

• The licensee states that elimination of this trip function would result in reduced potential for unnecessary reactor shutdowns caused by spurious MSLRM trips and would increase plant operational flexibility without compromising plant safety.

- In NED0-31400, a reevaluation of the role of the MSLRM in the control rod drop accident (CRDA) analysis was performed, confirming that removal of the MSLRM scram/isolation features would not compromise CRDA consequences. The topical

_ report also evaluated the potential effect on occupational exposure in the event of a sudden release of radioactive material from the fuel and concluded that the elimination of the scram/isolation features would have no adverse effect.

1 NED0-31400A, *safety Evaluation for Eliminating the Boiling Water Reactor Main Steam Line Isolation Valve Closure Function and Scram Function of the Main Steam Radiation Monitor*.

2 NUREG-0800, Standard Review Pl an (SRP) 15.4. 9, ReviSion 2, July 198L 9001220293 911024 -

\\

'\\ :

. PDR ADOCK 05000237

~

p

• • -'*- ***---*--cc-- - * ------- ----~J~_QFL -r. _:_ ----~!

• *specifically, the licensee proposed the following changes for Units 2 and 3:

1.

Table 2.2.A-1, (Reactor Protection System Instrumentation Setpoints) -

Delete setpoint requirements for *Main Steam Line Radiation -High*

(i.e., Item 6 and note (c).

2.

Bases 2.2.A (limiting Safety System Bases)- Delete reference to *Main Steam Line Radiation -High.* (i.e., Item 6).

3.

Table 3*.1.A-1 (Reactor Protection System Instrumentation)- Delete paragraph 11Main Steam line Radiation - High* (i.e., Item 6 and Action 15).

4.

Table 4~1.A-1 (Reactor Protection System Instrumentation Surveillance Requirements)- Delete reference to 11Main Steam Line Radiation - High" (i.e., Item 6 and note (q)).

5.

Table 3.2.A-1 (Isolation Actuation Instrumentation) - Delete action statement reference to Main Steam Line Tunnel Radiation-High (i.e.,

Item 3.b, note (b) and note (g).

6.

Table 4.2.A-1 (Isolation Actuation Instrumentation Surveillance Requirements)- Delete Item 3.b, and note (d).

By letter dated October 3, 1997, ComEd provided additional information concerning the proposed amendment.

The additional information provided by ComEd did not change the initial proposed no significant hazards consideration determination.

2.0 EVALUATION The licensee referenced General Electric (GE) Topical Report NED0-31400 in support of its request to eliminate the MSLRM scram and group isolation functions. In the topical report, GE analyzes a CRDA where the main steamline..

high radiation isolation is eliminated. The resulting radiological ~xposures are small fractions of 10 CFR Part 100 limits. The topical rrport received staff approval in a safety evaluation (SE) dated May.15, 1991

• The MSLRM consists of ionization chambers that monitor for ganuna radiation* at points external to the main steamlines.

In the event of a high radiation level, which is indicative of fuel failure, the MSLRM provides.a scram signal and a close signal to the Main Steam Isolation Valves (MSIV) and other Group I isolation valves. The MSLRM was designed to provide an early indication of gross fuel cladding failures. The original intent of this monitor was to mitigate the releases of the detected fuel failure by measuring gross ganuna radiation from the main steamlines downstream of the outboard MSIV.

These 3 Memorandum from R. W. Houston to W. T. Russel, "SEP Review of Dresden-2,*

December 14, 1981 *

• scram arid. isolation signals limit releases to the environment and mitigate the radiological effects of the fuel cladding during a CRDA to well within the limits of 10 CFR 100.11.

The only design basis accident in which either the MSLRM scram or MSIV isolation functions are taken into consideration 1s the CRDA.

To be consistent with Section 15.4.~ of the Standard Review Plari (SRP), all of the postulated radioactive material is assumed to be released to the condenser.4nd turbine before the isolation occurs. Hence, th~ automatic isolation resulting from the MSLRM signal provides no benefits, since the resultant dose

~

consequences from the control rod accident will remain unchanged.

Ho~ever,

• __

for Dresden, the dose analysis does rely on the operator tripping the mechanical vacuum pumps within 15 minutes after receiving the high-high.alarm from the MSLRM.

In a May 15, 1991, Safety Evaluation (SE) on NED0-31400A, the staff concluded that removal of the MSLRM trips that automatically shut down the reactor and close the MSIV was acceptable and that Licensing Topical Report, NED0-31400A, may be referenced in support of an amendment request as long as the following three conditions were met:

1.

The applicant demonstrates that the assumptions with regard to input values (including power per assembly, X/Q, and decay times) that are made in generic analysis bound those for the plant, The licensee provided a comparison of the key input parameters and the dose assessment assumptions between the Dresden design basis and the NED0-31400A analysis assumptions. The comparison shows that on an overall basis, the

• Dresden dose analysis is bounded by the NED0-31400 analysis. The licensee's

. analyses calculated the doses for the 0-2 hour to the exclusion area boundary

. (EAB) to be 0.91 rem to the thyroid and 0.07 rem to the thyroid for the low population zone (LPZ).

These doses are well within the SRP acceptance criteria of 10% of the values in 10 CFR 100.11 or 30 rem for the thyroid dose~

The NEDD analysis did not include tonsideration of the open drain and sample lines; however, their contribution to the overall dose analysis is insignificant *

. By letter dated October 3, 1997, the licensee provided additional information conc~rning the assumption with regard to input values used in the Dresden plant-specific evaluation, for power per assembly and decay times. The licensee stated in the letter that the specific values used in the Dresden analysis for.power per assembly and decay times are bounded by the generic analysis.

The turbine gland seal condenser release path was analyzed by the licensee.

This release path is specific to Dresden Station and was not considered in the BWROG NED0-31400A analysis, and was analyzed as an additional release path not automatically isolated during a CRDA.

For the turbine gland seal condenser path, all the noble gases and iodine reaching the gland seal condenser are assumed to be released to the environment. This assumption is conservative

• with respect to the iodine since no washout and plate out is assumed.

The release from the turbine gland seal condenser is conservatively treated as a ground level release, even though it discharges through the plant stack. The calculated doses from the turbine gland seal condenser were added to the thyroid and whole body doses calculated for each of the two scenarios, and the resulting total releases were well within the limits of 10 CFR 100.11.

The staff finds that the 11ce.nsee's analysis compares favorable with its evaluation and meets the applicable requirements of Condition 1 and is, therefore, acceptable.

2.

The applicant includes evidence (implemented or proposed operating procedures, or equivalent corrmitments) to provide reasonable assurance that increased significant levels of radioactive material in the main steamlines will be controlled expeditiously to limit both occupational doses and environmental releases, and In the response to Condition 2, the licensee has in place the Offsite Dose Calculation Manual (ODCM), a Radiation Protection Program, including an as low as reasonably achievable (ALARA) program, and a Radiological Environmental Monitoring Program.

Existing procedures for responding to high radiation alarms from MSLRM and offgas initiate actions through Emergency Operating Procedures (EOP) which ensure that significant levels of radiation in the main steamlines (MSL) are controlled expeditiously to limit both occupational doses and environmental releases. Dresden's radiation protection, chemistry*

operating, EOP and the ODCM will be revised as necessary to incorporate specific considerations to change isolation of the main steamlines from an automatic to a manual function. Thus, any significant increase in the levels of radioactivity in the MSL will continue to be promptly controlled to limit effluent releases and on~site occupational exposure.

The licensee has conunitted to review the Dresden Operation Annunciator and General Abnormal Conditions Procedures and revise them as required to ensure operator action to limit occupational doses and environmental releases prior to implementation of the proposed amendment.

The commitment has also been included in Appendix B to the license. Based on a review of the licensee's commitment, the staff has determined that Condition 2 has been satisfied.

3.

The applicant standardizes the MSLRM and offgas radiation monitor alarm setpoint at 1.5 times the nominal nitrogen-16 (N-16) background dose rate at the monitor locations, and corrmits to promptly sample the reactor coolant to determine possible contamination levels in the plant reactor coolant and the need for additional corrective actions, 1f either the MSLRM or offgas radiation monitors or both exceed their alarm setpoint.

In response to Condition 3, the licensee has committed to change the setpoints for the MSLRM and offgas radiation monitor alarms to 1.5 times the normal full power N-16 background (with hydrogen addition) dose rates prior to implementation of the amendment. This commitment has also been included in

. (I>

y

• Appendix B *Of the 1 icense. Either of these alarms will trigger entry into a procedure which will require a reactor coolant sample to be obtained and.

analyzed.* The offgas radiation monitor alarm is also set to help ensure that effluents are maintained ALARA in accordance with the ODCM.

Based on a review of the licensee's commitment, the staff has determined that Condition 3 has been satisfied.

The staff perfonned an independent analysis to determine plant conformance with the criteria that the CRDA is expected to result in radiological consequences less than 10% of the part 100 guidelines even with conservative assumptions.

In its analysis the staff utilized the assumptions contained in SRP Section 15.4.9. The staff computed the offsite doses for Dresden Unit 2 and 3 using the assumptions described in Table 1 and NRC's ACTICODE computer code. The resulting CRDA calculated values are listed below.

ASSUMPTIONS USED FOR CALCULATION RADIOLOGICAL CONSEQUENCES parameters Power level Number of Rods Perforated Number of Rods Melted Number of Rods In-Core Power Peaking Factor Condenser Leak Rates (%) day

• 2561.

850 0

45612 1.5 1.0 Fraction of fission product inventory release to coolant:

Iodines, percent 50 Noble gases, percent 100

• Receptor Point Variables Exclusion Area Boundary CEABl Atmosphere Relative Concentration, X/Q (sec/m3) 0-2 hours

• 2.6E-4 Low Population Zone CLPZ)

Atmosphere Relative Concentration, X/Q (sec/m3) 0-8 hours

.l.lE-5 Thyroid Poses EAB-0.26 rem LPZ-0.41 rem Based on the review of the licensee's application and safety analysis, the staff concludes that there are no adverse safety implications associated with removal of the MSLRM scram and MSIV closure function since the licensee has provided reasonable :assurance that the offsite radiation exposure levels are within the ac~eptance criteria of Section 15.4.9. of the SRP and well within the 10 CFR Part 100 guidelines. The staff concludes that the proposed changes

• ,-fo eliminate the reactor scram and MSIV isolation requirements assdchted with the MSLRM are acceptable.

3.0 STATE CONSULTATION

In accordance with the Commission's regulations, the I111no1s State official was notified of the proposed issuance of the amendments.

The State official had no convnents.

4.0 ENVIRONMENTAL CONSIPEBATION The amendments.change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (62 FR 19141). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51~2l(b), no environmental impact statement or environmental assessment need be prepared in connection.with the issuance of the amendments.

5.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public.will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: J. Minns G. Golub Date: October.24, 1997

.~*.

-~