Inmates at Lorton Reformatory's Central Facility returned to their jobs yesterday, ending a three-week work stoppage at the institution that climaxed last week with a riot in which guards shot 13 inmates.

Corrections Department spokesman LeRoy Anderson said that about 500 inmates assigned to prison industries ended their strike and returned to work at Lorton's laundry, license plate, furniture repair and print shops. He said the inmates accepted a proposal designed to end the stoppage that was first made by the corrections department but rejected by inmates almost two weeks ago.

The attempted transfer on Sept. 23 of five inmates believed to be leaders of the strike led to a riot by about 300 other striking inmates who prevented removal of the five from the institution. Guards fired tear gas to quell the riot, and when the inmates charged a small group of guards, seven officers armed with shotguns fired into the crowd of inmates, wounding 13, authorities said.

"I'm not going to discuss cause-and-effect relationships," Anderson said, "but I think it's safe to assume that the shootings had a chilling effect" on the strike.

After the riot, 17 alleged strike leaders were transferred to another institution, Anderson said, which also "had an effect" on the prisoners' decision to return to work yesterday. The 17 are being held at the D.C. Jail pending their acceptance at a federal prison, he said.

The inmates stopped work Sept. 9, complaining of low wages, poor medical and food services, and a variety of lesser complaints, Anderson said.

The resolution of the work stoppage, he said, "was not like dealing with a conventional labor-management dispute. Even though they're called negotiations, we don't negotiate with inmates. We listen to them."

Anderson said that, though the proposal that ended the strike was put into writing, there is no signed agreement with the inmates.

He said the agreement includes:

*A 10 percent inmate wage increase for fiscal year 1986, which begins today. The previous base pay ranged from 31 cents to 84 cents an hour.

*A 5 percent raise for those who have been in the same job category for more than a year, effective today.

Annual physical examinations.

*A review of the prison menu to ensure variety.

*A visit by a "company representative" to inmates in the furniture repair shop to explain the dangers of paint thinners and other solvents used there.

*Placement of a cover on a food canteen truck to ensure that food does not spoil, and extending the truck's stay at the institution from one to two hours a day.

*A new day and time for issuance of clothing and linen.