ML20236Y359

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Safety Evaluation Accepting Licensee Request to Modify Standby Liquid Control Sys Tech Specs,Per Requirements of ATWS rule,10CFR50.62.C.4.SALP Input Also Encl
ML20236Y359
Person / Time
Site: Pilgrim
Issue date: 07/22/1987
From:
Office of Nuclear Reactor Regulation
To:
Shared Package
ML20149B797 List:
References
FOIA-87-644 NUDOCS 8712110264
Download: ML20236Y359 (4)
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8 o NUCLEAR REGULATORY COMM'!iSiON W ASHINGTON, D. C. 20555 74 p

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACT 08' PEGULATION RELATING TO STANDBY LIQUID CONTROL SYSTEM BOSTON EDISON COMPANY PILGRIM NUCLEAR p0WER STATION DOCKET NO. 50-293 l

1.0 INTRODUCT!0N By letters dated May 29, July 8 July 15,1987, from R. G. Bird Boston Edison Company (BEco), to U. S. Nuclear Regulatory Comission, BECo proposed to change the Technical Specifications (TS) for Pilgrim. The changes address the use of boron, enriched in the isotope B-10, in the sodium pentaborate solution used in the Standby Liquid Control System (SLCS) in order to meet the requirements of the Anticipated Transient Without Scram (ATWS) Rule,10 CFR 50.62 paragraph (c)(4). The proposed changes are to TS Sections 3.4.A. 3.4.D. 4.4.A, 4.4.C.

Figure 3.4-1 and 2, Basis 3.4, 4.4 and Table 6.9.1 all associated with the SLCS.

2.0 EVALUATION The proposed TS changes for Pilgrim are intended to meet the requirements of the ATWS Rule, 10 CFR 50.62.C.4 The ATWS Rule requires that the SLCS be equivalent in control capacity to a system with an 86 gpm injection rate, using 13 weight percent unenriched sodium pentaborate solution, in a system with a 251 inch diameter reactor vessel. Of the several proposed approaches presented in the General Electric report, Reference 1, and approved in the NRC ,

evaluation, Reference 2 BEco has chosen to use enriched (in B-10) boron.

Using the calculation methods of Reference 1 results in a sinimum concentration of 8.42 weight percent sodium pentaborate when osing an enrichment of 54.5 atom percent B-10 and an injection of 39 gpm and a water mass of 507,850 pounds (227 inch vessel). The new limits are reflected in the revised T/S section 3.4.C.3 and Figure 3.4.1.

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i The temperature / concentration requirements of existing Figure 3.4.2 are no longer required because the curve extends down only to 9.4% sodium pentaborete concentration and is based upon naturally enriched sodium pentaborate. The proposed revised concentration limits, in proposed TS Figure 3.4-1. allow a raximum concentration of 9.22% enriched sodium pe.,taborate. At 9.22% enricted sodium pentaborate concentration, the teciperature requino to preclude sodiun pentaborate precipitation (with a 10*F margin) is 48'F; the centrolleo building temperatures provide assurance that it will be difficult for the SLCS solution to approach this limit, and system alarms provide operator notification of such a potential event. Because of the 10*F margin to potential sodium pentaborate precipitation at monitored concentration levels, the 48'F temperature limit provides equavalent protection to that considered in the original safety evaluation. The 48'F temperature limit, which is incluoed in the proposed TS, preempts the previous temperature - concentration curve provided in Figure 3.4.2. Accordingly, the staff finds the proposed TS Section 3.4.C.2 and deletion of Figure 3.4.2 to be acceptable.

Having selected the enriched boron option of compliance with the ATWS Rule, BEco, following an approved approach, has elected to have the sodium pentaborate formulated at the chemical vendor's facility. The boron enrichnent test will therefore be done prior to the acceptance for use en the site. Tte boron enrichment test also will be doce anytime boron is added to the solution and each refueling outage. If the enrichment level is less than 53.5 atom percent, a period of seven days is allowed to bring the boron enrichment into compliance. If at the end of the seven day period, compliance can not be assured, the license is required to submit a report, within seven days, to the NRC advising the licensee's plan to comply with the ATWS Rule. These are all acceptable procedures. They have been agreed upon as elements of an ,

appropriate approach for compliance with the ATWS Rule in discussions between the staff and industry (BWR Owners Grcup ATWS Committee, Ref. 3). The proposed changes in T/S Sections 4.4.C.4 and 3.4.D.1.2.3 to implement these procedures are acceptable.

3 The bases to technical specification 3.4. and 4.4 were revised to reflect the proposed changes. The revised bases are acceptable since it adequately explains the bases for the proposed requirements in the technical specifications.

3.0 CONCLUSION

S I

.BEco has requested TS changes for Pilgrim which would provide for the use of enriched boron in the SLCS to meet the requirements of 10 CFR 50.62.C.4. The approach selected by BECo and the associated TS are acceptable. The staff has concluoed, 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, and (2) such activities will be conducted in canpliance with the Commission's reguations and the issuance of this amendment will not be inimical to the comon defense and security or to the health and safety of the public.

REFERENCES

1. " Anticipated Transients Without Scram: Response to NRC ATWS Rule, 10 CFR 50.62", NEDE-31096-P, December 1985.
2. " Safety Evaluation of Topical Report (NEDE-31096-P) ' Anticipated Transients Without Scram: Response to ATWS Rule,10 CFR 50.62'", letter from G. Lainas (NRC) October 21, 1986.
3. Minute; of BWR Owner's Group infonnal meeting on April 1,1987 with NRC to discuss ATWS Technical Specification Bases, Bethesda, MD, April 3, 1987.

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EWCLOSURE 2 BOSTON EDISON COMPANY PILGRIM EUCLEAR POWER STATION SYSTEMATIC ASSESSENT OF LICENSEE PERFORMANCE functional Areas

1. Management Involvement in Assuring Quality.

Technical review of the subeittal indicates that the management rerfews are not satisfactory. In the submittal, Pilgrim Reactor Pressure lessel diameter was given as 218" instead of the actual diameter of 227".

Rating: Category 3

2. Approach to Resolution of Technical Issues from a Safety Standpoint.

! The licensee showed a general understanding of the technical issue amd used acceptable approaches.

Rating: Category 2

3. Responsiveness to NRC Initiatives The licensee responded favorably to NRC initiatives.

Rating: Category 2 4 Staffing (including management)

N/A

5. Reporting and analyses of reportable events N/A
6. Training and effectiveness and qualification N/A
7. Overall rating for functional area: 2

Reference:

NRC Manual Appendix 0516 - Systematic Assessment of Licensee Performance l

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